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Abstract

Estuaries are subjected to multiple anthropogenic stressors, which have additive, antagonistic or synergistic effects. Current challenges include the use of large databases of biological monitoring surveys (e.g. the European Water Framework Directive) to help environmental managers prioritizing restoration measures. This study investigated the impact of nine stressor categories on the fish ecological status derived from 90 estuaries of the North East Atlantic countries. We used a random forest model to: 1) detect the dominant stressors and their non-linear effects; 2) evaluate the ecological benefits expected from reducing pressure from stressors; and 3) investigate the interactions among stressors. Results showed that largest restoration benefits were expected when mitigating water pollution and oxygen depletion. Non-additive effects represented half of pairwise interactions among stressors, and antagonisms were the most common. Dredged sediments, flow changes and oxygen depletion were predominantly implicated in non-additive interactions, whereas the remainder stressors often showed additive impacts. The prevalence of interactive impacts reflects a complex scenario for estuaries management; hence, we proposed a step-by-step restoration scheme focusing on the mitigation of stressors providing the maximum of restoration benefits under a multi-stress context.

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... One way to measure RF usefulness is the usage of the pseudo-R 2 coefficient that comes from the cross-validation process, at an "out-of-bag" error level, and measures only the performance of the learning phase (Breiman, 2001). Although this coefficient has been used in several environmental studies, some researchers are aware that pseudo-R 2 cannot be assessed as a true forecast (Large et al., 2015;Teichert et al., 2016;Thomas et al., 2018). Therefore, in this study, we have chosen to compare the raw data from an automated system to the output of the machine learning model, using the coefficient of determination (R 2 ). ...
... Moreover, we used an individual conditional expectation (ICE) plot (Goldstein et al., 2015), to identify if the interactions created during the learning phase are comparable with the real biological mechanisms. These ICE plots are an improvement on the partial dependence plot (PDP) used several times in previous scientific studies on phytoplankton and water environments (Cutler et al., 2007;Derot et al., 2020;Friedman et al., 2001;Roubeix et al., 2016;Teichert et al., 2016). The PDP highlights the marginal effect between a selected predictor and the target signal (Friedman, 2001). ...
... The results of this study indicate that the forecast performance of the RF model increases with increasing sampling frequencies. In addition, it should be noted that although some other studies in similar fields have used the pseudo-R 2 to measure the performance of the RF model, the authors are aware that the coefficient does not assess the true forecast (Large et al., 2015;Teichert et al., 2016;Thomas et al., 2018). Thus, we split our dataset between a learning part and a test part (Fig. 3), and used the Pearson coefficient to measure the forecast performances. ...
Article
In aquatic ecosystems, anthropogenic activities disrupt nutrient fluxes, thereby promoting harmful algal blooms that could directly impact economies and human health. Within this framework, the forecasting of the proxy of chlorophyll a in coastal areas is the first step to managing these algal blooms. The primary goal was to analyze how phytoplankton bloom forecasts are impacted by different sampling frequencies, by using a machine learning model. The database used in this study was sourced from an automated system located in the English Channel. This device has a sampling frequency of 20 min. We considered 12 physicochemical parameters over a six-year period. Our forecast methodology is based on the random forest (RF) model and a sliding window strategy. The lag times for these sliding windows ranged from 12 h to 3 months with four different sampling times until 1 day. The results indicate that the optimal forecast was obtained for a 20 min time step, with an average R² of 0.62. Moreover, the highest values of fluorescence were predicted when the water temperature was approximately 11.8 °C. Consequently, we demonstrated that the sampling frequency directly impacts the forecast performance of an RF model. Furthermore, this kind of model can recreate interactions that closely resemble biological processes. Our study suggests that the RF model can utilize the additional information contained in high-frequency datasets. The methodology presented here lays the foundation for the development of a numerical decision-making tool that could help mitigate the impact of these algal blooms.
... Therefore, this assumption is relevant to many approaches to marine spatial CIA. That is, all approaches fundamentally assume that cumulative impact scores and ecosystem condition are related in some predictable, usually linear, way Brown et al., 2014;Teichert et al., 2016). However, a linear relationship with CIA scores is likely to be unrealistic, due to the many examples of tolerance thresholds and unpredictable ecosystem state shifts (Kraberg et al., 2011) as well as non-additive stressor interactions (Stockbridge et al., 2020). ...
... Grey shading shows 95% confidence intervals: (a) Percent cover (index ranges from 0 to 100), (b) Habitat structure index (HSI; index ranges from 0 to 100), (c) Seagrass quality index (SQI; index ranges from 0 to 1). Teichert et al., 2016), namely that cumulative impact score is representative of ecosystem condition. We did this by collecting empirical data on seagrass condition through video transects and comparing these to cumulative impact scores for the same locations generated in a previous study (Jones et al., 2018), which used the widely applied method proposed by Halpern et al. (2008). ...
... The key assumption that ecosystem condition is related to modelled cumulative impact scores in a predictable, negative way is critical to established CIA methodologies (Halpern and Fujita, 2013;Teichert et al., 2016). However, our findings show there is little to no relationship between cumulative impact scores and seagrass ecosystem health in our study area based on three different indices for measuring seagrass condition. ...
Article
Full-text available
Human activities put stress on our oceans and with a growing global population, the impact is increasing. Stressors rarely act in isolation, with the majority of marine areas being impacted by multiple, concurrent stressors. Marine spatial cumulative impact assessments attempt to estimate the collective impact of multiple stressors on marine environments. However, this is difficult given how stressors interact with one another, and the variable response of ecosystems. As a result, assumptions and generalisations are required when attempting to model cumulative impacts. One fundamental assumption of the most commonly applied, semi-quantitative cumulative impact assessment method is that a change in modelled cumulative impact is correlated with a change in ecosystem condition. However, this assumption has rarely been validated with empirical data. We tested this assumption using a case study of seagrass in a large, inverse estuary in South Australia (Spencer Gulf). We compared three different seagrass condition indices, based on survey data collected in the field, to scores from a spatial cumulative impact model for the study area. One condition index showed no relationship with cumulative impact, whilst the other two indices had very small, negative relationships with cumulative impact. These results suggest that one of the most commonly used methods for assessing cumulative impacts on marine systems is not robust enough to accurately reflect the effect of multiple stressors on seagrasses; possibly due to the number and generality of assumptions involved in the approach. Future methods should acknowledge the complex relationships between stressors, and the impact these relationships can have on ecosystems. This outcome highlights the need for greater evaluation of cumulative impact assessment outputs and the need for data-driven approaches. Our results are a caution for marine scientists and resource managers who may rely on spatial cumulative impact assessment outputs for informing policy and decision-making.
... Although not overcoming these constraints, several human pressure indices have been proposed for estuarine ecosystems, some being used for evaluating the response of fish communities, as was done within the scope of the European Water Framework Directive (e.g. Vasconcelos et al. 2007, Lepage et al. 2016, Teichert et al. 2016). ...
... The use of fish-based multimetric indicators allows coverage of different facets of communities at different levels of organisation (molecular, physiological, individual or population), while considering a wide variety of anthropogenic stressors on water quality, habitat quality and cascade effects on fish (Minier et al. 2015). The choice of the metrics to be used in the indicator, the specificities due to the geographical region, the sampling strategy and the explanation of the variance due to anthropogenic pressures remain complex steps in the construction of an indicator (Teichert et al. 2016). In addition, not all species or taxonomic levels have the same capacity to answer questions about the health of the system (Bortone et al. 2005). ...
... While resources for environmental conservation are usually restricted, the co-occurrence of multiple stressors is a challenge for ecosystem management where priorities are defined through mitigation actions. In such situations, disentangling the effects of multiple stressors is a preliminary requirement in order to focus restoration efforts on the dominant anthropogenic stressors and their impacts (Feld et al. 2016, Teichert et al. 2016. The complex relationships between the ecological response and stressors can lead to unexpected or ineffective management outcomes (Paine et al. 1998), especially when non-linear and interactive settings are involved (Hewitt et al. 2016, Samhouri et al. 2017). ...
... Although not overcoming these constraints, several human pressure indices have been proposed for estuarine ecosystems, some being used for evaluating the response of fish communities, as was done within the scope of the European Water Framework Directive (e.g. Vasconcelos et al. 2007, Lepage et al. 2016, Teichert et al. 2016). ...
... The use of fish-based multimetric indicators allows coverage of different facets of communities at different levels of organisation (molecular, physiological, individual or population), while considering a wide variety of anthropogenic stressors on water quality, habitat quality and cascade effects on fish (Minier et al. 2015). The choice of the metrics to be used in the indicator, the specificities due to the geographical region, the sampling strategy and the explanation of the variance due to anthropogenic pressures remain complex steps in the construction of an indicator (Teichert et al. 2016). In addition, not all species or taxonomic levels have the same capacity to answer questions about the health of the system (Bortone et al. 2005). ...
... While resources for environmental conservation are usually restricted, the co-occurrence of multiple stressors is a challenge for ecosystem management where priorities are defined through mitigation actions. In such situations, disentangling the effects of multiple stressors is a preliminary requirement in order to focus restoration efforts on the dominant anthropogenic stressors and their impacts (Feld et al. 2016, Teichert et al. 2016. The complex relationships between the ecological response and stressors can lead to unexpected or ineffective management outcomes (Paine et al. 1998), especially when non-linear and interactive settings are involved (Hewitt et al. 2016, Samhouri et al. 2017). ...
Chapter
This chapter addresses the use of fish as indicators of environmental health. The main anthropogenic pressures impacting estuarine fishes are reviewed, as well as the main types of responses by fishes at different levels of biological organisation. Fishes have been widely used to assess estuarine health through different methodological approaches, namely comparisons with historical data or reference conditions, experimental approaches, environmental impact or risk assessment methods, as well as qualitative or quantitative indicators and models. A large number of multi‐metric indices based on fish have been proposed and are routinely used in environmental assessments, although to disentangle natural variability from anthropogenic pressures in a multi‐stress context of global change is still a major challenge.
... Although still a major stressor and activity in many regions globally (see Cowley et al. 2022), estuarine fisheries in Europe no longer pose a major threat to fish communities and come well behind pollution and physical destruction of habitats in terms of anthropogenic pressure (Teichert et al. 2016). Nevertheless, the recent use of modern electronic tools such as high-resolution echo sounders, high-precision GPS and radar have considerably improved the efficiency of fishing compared to 10-15 years ago, and this should raise questions about the sustainability and the necessary supervision of fishing activity in estuaries. ...
... They have demonstrated high performance to select relevant environmental parameters explaining the fish spatial distribution such as time of the year, the year, the distance to estuarine mouth, dissolved oxygen, turbidity, water temperature, salinity and depth (Fodrie & Mendoza 2006, Froeschke & Froeschke 2011. They also provide powerful insights to investigate interactive effects between environmental stressors to identify which restoration benefits can be expected from mitigation measures (Teichert et al. 2016). This has been well demonstrated by Archambault et al. (2018) in their spatially structured age and stage-based hierarchical Bayesian model. ...
Chapter
This chapter presents the causes of physical and ecological degradation of estuaries in relation to human activities and climate change. The direct and indirect effects of degradation on ecosystem services and fish are listed, as well as the key questions that need to be answered in order to undertake rehabilitation and restoration actions. Ecohydrology and ecoengineering are indispensable tools to be mobilised alongside a variety of models to guide actions in favour of habitat and whole estuary functioning. Finally, several examples of restoration are presented to move from theory to practice. The restoration of estuaries has often become essential to ensure sustainable fish communities and requires a holistic view of the problems and a coordination of efforts to ensure the success of the actions undertaken.
... In addition to these widely reported, and direct, ecological impacts of coastal urbanisation on species, assemblages and ecosystems, there are also a myriad of indirect consequences for many species which result from significant changes to the physical features of the seafloor (Waltham and Connolly 2011;Munsch et al. 2017). The terrain of estuaries and coastal waters has been modified widely via the combined effects of dredging, trawling, nourishing, armouring and mining operations, and these structural changes likely have consequences for both coastal biodiversity and ecosystem functioning (Rochette et al. 2010;Teichert et al. 2016;Bolam et al. 2021). ...
... mangroves, seagrasses, saltmarshes, rock bars, sandbars, log-snags, channels), which provide a variety of high-relief terrain features that support diverse fish assemblages Henderson et al. 2019). Estuaries are, however, also focal points for coastal development and human recreation, and the combined effects of urbanisation, fishing and dredging fragment natural ecosystems and modify seafloor terrain (Teichert et al. 2016;Amorim et al. 2017). The ecological consequences of landscape modification have been well documented and include changes to the composition of estuarine floral and faunal assemblages, reductions in the diversity of fish and invertebrates, as sensitive specialist species are replaced by generalist taxa that can capitalise on opportunities provided in urban habitats, and variation in the rates of important ecological functions Mayer-Pinto et al. 2018;Olds et al. 2018). ...
Article
Full-text available
Context Landscape modification alters the condition of ecosystems and the structure of terrain, with widespread impacts on biodiversity and ecosystem functioning. Seafloor dredging impacts a diversity of flora and fauna in many coastal landscapes, and these processes also transform three-dimensional terrain features. The potential ecological significance of these terrain changes in urban seascapes has, however, not been investigated. Objectives We examined the effects of terrain variation on fish assemblages in 29 estuaries in eastern Australia, and tested whether dredging changes how fish associate with terrain features. Methods We surveyed fish assemblages with baited remote underwater video stations and quantified terrain variation with nine complementary metrics (e.g. depth, aspect, curvature, slope, roughness), extracted from bathymetry maps created with multi-beam sonar. Results Fish diversity and abundance were strongly linked to seafloor terrain in both natural and dredged estuaries, and were highest in shallow waters and near features with high curvature. Dredging, however, significantly altered the terrain of dredged estuaries and transformed the significance of terrain features for fish assemblages. Abundance and diversity switched from being correlated with lower roughness and steeper slopes in natural estuaries to being linked to features with higher roughness and gentler slopes in dredged estuaries. Conclusions Contrasting fish-terrain relationships highlight previously unrecognised ecological impacts of dredging, but indicate that plasticity in terrain use might be characteristic of assemblages in urban landscapes. Incorporating terrain features into spatial conservation planning might help to improve management outcomes, but we suggest that different approaches would be needed in natural and modified landscapes.
... C'est ainsi que des caractéristiques comme la perte d'habitat, perte de zone intertidale, la poldérisation, l'endiguement, la modification de la bathymétrie ou de la topographie générale, les interférences avec le régime hydrologique (l'entrée des ports, les quais, les jetées, les épis, les chenaux dragués) ou encore le littoral affecté par des activités humaines ont été utilisées dans un indice de pressions anthropiques (Lepage et al., 2016b). D'autres travaux consistant à vérifier les interactions entre les différentes pressions et à évaluer les pressions auxquelles il serait intéressant de répondre en priorité ont montré que les pressions hydromorphologiques se classent en sévérité d'effet juste après la qualité chimique de l'eau et l'oxygène dissous (Teichert et al., 2016). ...
... Dans le but d'appréhender la complexité des interactions entre les différents types de pressions d'origine anthropique s'exerçant sur les indicateurs d'état écologique, des modèles innovants permettant d'évaluer les effets indirects des pressions comme les modèles en équations structurelles (Villeneuve et al., 2018) ou les random forest (Teichert et al., 2016) Élargir les outils de modélisation à des approches probabilistes pour construire des analyses de risque Un numéro spécial (57 S1) de la revue Freshwater Biology a été consacré en 2012 aux réponses des communautés aquatiques aux actions de gestion dans les bassins versants. Page et al. (2012) y plaidaient pour ne pas se contenter de simples relations doses/réponses pour la gestion de systèmes aussi complexes et divers que les milieux aquatiques et préconisaient un recours à des analyses probabilistes de risque pour bien prendre en compte les nombreuses incertitudes. ...
Book
Full-text available
Since 2004, Irstea, the French research institute of science and technology for environment and agriculture was deeply involved for the developpement of research programs aiming to build the toolbox necessary for the implementation of the European Water framework directive in France. This book presents a synthesis of all these programs, explaining the divers aspects of the scientific and technical contribution from the Institute and its researchers and engineers, and in wich way these approaches have made progressing the kwnoledge on ecological assessment in a broad view.
... In addition to these widely reported, and direct, ecological impacts of coastal urbanisation on species, assemblages and ecosystems, there are also a myriad of indirect consequences for many species which result from significant changes to the physical features of the seafloor (Waltham and Connolly 2011;Munsch et al. 2017). The terrain of estuaries and coastal waters has been modified widely via the combined effects of dredging, trawling, nourishing, armouring and mining operations, and these structural changes likely have consequences for both coastal biodiversity and ecosystem functioning (Rochette et al. 2010;Teichert et al. 2016;Bolam et al. 2021). ...
... mangroves, seagrasses, saltmarshes, rock bars, sandbars, log-snags, channels), which provide a variety of high-relief terrain features that support diverse fish assemblages Henderson et al. 2019). Estuaries are, however, also focal points for coastal development and human recreation, and the combined effects of urbanisation, fishing and dredging fragment natural ecosystems and modify seafloor terrain (Teichert et al. 2016;Amorim et al. 2017). The ecological consequences of landscape modification have been well documented and include changes to the composition of estuarine floral and faunal assemblages, reductions in the diversity of fish and invertebrates, as sensitive specialist species are replaced by generalist taxa that can capitalise on opportunities provided in urban habitats, and variation in the rates of important ecological functions Mayer-Pinto et al. 2018;Olds et al. 2018). ...
Article
Landscape modification alters the condition of ecosystems and the complexity of terrain, with consequences for animal assemblages and ecosystem functioning. In coastal seascapes, dredging is routine practice for extracting sediments and maintaining navigation channels worldwide. Dredging modifies processes and assemblages by favouring species with wide trophic niches, diverse habitat requirements and tolerances to dredge-related eutrophication and sedimentation. Dredging also transforms the three-dimensional features of the seafloor, but the functional consequences of these terrain changes remain unclear. We investigated the effects of terrain modification on the functional diversity of fish assemblages in natural and dredged estuaries to examine whether dredging programs could be optimised to minimise impacts on ecological functioning. Fish assemblages were surveyed with baited remote underwater video stations and variation in functional niche space was described using species traits to calculate metrics that index functional diversity. Terrain variation was quantified with nine complementary surface metrics including depth, aspect, curvature, slope and roughness extracted from sonar-derived bathymetry maps. Functional diversity was, surprisingly, higher in dredged estuaries, which supported more generalist species with wider functional niches, and from lower trophic levels, than natural estuaries. These positive effects of dredging on functional diversity were, however, spatially restricted and were linked to both the area and orientation of terrain modification. Functional diversity was highest in urban estuaries where dredged channels were small (i.e. <1% of the estuary), and where channel slopes were orientated towards the poles (i.e. 171–189°), promoting both terrain variation and light penetration in urban estuaries. Our findings highlight previously unrecognised functional consequences of terrain modification that can easily be incorporated into dredging programs. We demonstrate that restricting the spatial extent of dredging operations and the orientation of dredged channel slopes, wherever this is practical, could help to limit impacts on ecosystem functioning and productivity in urban seascapes.
... Ainsi, les deux dernières décennies ont vu l'émergence de nombreuses études visant à évaluer les effets combinés des stress sur les organismes, en vue de se rapprocher des conditions naturelles et d'améliorer notre compréhension des phénomènes actuels (i.e. crise de la biodiversité) (Anacleto et al., 2018;Bowen et al., 2006;Bruder et al., 2017 Heath et al., 1994;Lange et al., 2018;Liess et al., 2016;Mantyka-Pringle et al., 2014;Petitjean et al., 2019a;Teichert et al., 2016;Townsend et al., 2008). ...
... Parmi ces 42%, environ 60% des réponses aux stress multiples sont représentées par des interactions antagonistes ou synergiques ( Fig. 40; . Ainsi, l'une des préoccupations actuelles majeure est d'améliorer les connaissances des effets combinés des stress sur l'intégrité et l'état de santé des organismes aquatiques afin d'améliorer les actions de conservation des populations Teichert et al., 2016). ...
Thesis
Full-text available
Dans le milieu naturel, les poissons sont exposés à une multitude de facteurs de stress biotiques et abiotiques, mais leurs interactions sont encore mal connues. La hausse des températures et la contamination par les éléments trace métalliques (ETMs) sont des sources importantes de stress pour les poissons. Les parasites ont également des effets sur la physiologie de leur hôte, mais sont rarement considérés en tant que facteurs de stress. Ces trois facteurs de stress agissent via des voies physiologiques communes (immunité, stress oxydant, métabolisme) et sont donc susceptibles d'interagir de manière complexe (e.g. antagonisme, synergisme). De plus, il existe souvent une grande variabilité des réponses entre échelles biologiques, des molécules aux populations. Notamment, l'historique d'exposition des populations de poisson dans leur milieu naturel pourrait conditionner leur capacité de réponse au stress. La prise en compte de ces deux niveaux de variabilité (i.e. interactions entre stress et entre échelles d'organisation) représente donc un verrou scientifique majeur pour mieux comprendre les effets des stress multiples sur les populations de poissons d'eau douce. Cette thèse vise donc à évaluer les effets combinés de facteurs de stress abiotique (i.e. température, ETMs) et biotique (i.e. challenge immunitaire provoqué par le parasitisme) sur les réponses des poissons d'eau douce via une approche multi-échelles. Afin de remplir ces objectifs, le Goujon (Gobio occitaniae) a été utilisé comme espèce modèle dans le cadre de trois approches méthodologiques : (i) une approche transversale de terrain visant à comparer l'état de santé de population de poissons le long des gradients de stress ; puis, (ii) des expérimentations en conditions contrôlées afin de distinguer les effets des différents facteurs de stress simples dans différentes populations sauvages ; enfin (iii) une expérience de translocation réciproque (i.e. encagement sur le terrain) entre sites contaminés et peu contaminés afin de tester l'adaptation locale des populations. Les résultats montrent que les stress simples ont des effets importants aux échelles biologiques fines et induisent la mise en place de stratégies métaboliques de compensation : les poissons investissent dans les défenses immunitaires et antioxydantes, avec une réduction des réserves énergétiques. De plus, les ajustements comportementaux (i.e. activité de nage, recherche de nourriture) sont particulièrement importants sous stress simples, et permettent d'ajuster l'acquisition d'énergie ce qui limite les effets sur la survie et la croissance. Au contraire, les stress multiples ont peu d'effets aux échelles moléculaires et cellulaires, mais provoquent des réponses complexes à l'échelle individuelle, ce qui se traduit par des effets antagonistes sur le comportement et des effets négatifs sur la survie et la croissance. Ces résultats suggèrent que sous stress multiples, les capacités de réponse des poissons pourraient être dépassées, menant ainsi à une stratégie de conservation, avec des effets délétères sur la fitness. Cependant, les réponses observées étaient fortement variables selon la population considérée. [...]
... The individual conditional expectation (ICE) plots, which are an improved version of the partial dependence plot (PDP), enables the interpretation of the interactions between the predictors created by the RF model during the learning phase (Friedman et al., 2001;Goldstein et al., 2015). These numerical tools allowed us to find some similarities between the learning phase interactions and biological processes (Cutler et al., 2007;Derot et al., 2020;Roubeix et al., 2016;Teichert et al., 2016). To categorize the cyanobacteria into some intensity classes, we used a clustering algorithm called K-means based on machine learning (Hartigan and Wong, 1979). ...
... Notably, they used the pseudo-R² to validate their forecasts (Breiman, 2001). However, several studies, including this one, know that the coefficients cannot be accessed directly as a true forecast because the pseudo-R² measures the goodness-of-fit during the learning phase (Large et al., 2015;Teichert et al., 2016;Thomas et al., 2018). Our results can use the R² from the test part instead of the learning phase. ...
Article
The development of anthropic activities during the 20th century increased the nutrient fluxes in freshwater ecosystems, leading to the eutrophication phenomenon that most often promotes harmful algal blooms (HABs). Recent years have witnessed the regular and massive development of some filamentous algae or cyanobacteria in Lake Geneva. Consequently, important blooms could result in detrimental impacts on economic issues and human health. In this study, we tried to lay the foundation of an HAB forecast model to help scientists and local stakeholders with the present and future management of this peri-alpine lake. Our forecast strategy was based on pairing two machine learning models with a long-term database built over the past 34 years. We created HAB groups via a K-means model. Then, we introduced different lag times in the input of a random forest (RF) model, using a sliding window. Finally, we used a high-frequency dataset to compare the natural mechanisms with numerical interaction using individual conditional expectation plots. We demonstrate that some HAB events can be forecasted over a year scale. The information contained in the concentration data of the cyanobacteria was synthesized in the form of four intensity groups that directly depend on the P. rubescens concentration. The categorical transformation of these data allowed us to obtain a forecast with correlation coefficients that stayed above a threshold of 0.5 until one year for the counting cells and two years for the biovolume data. Moreover, we found that the RF model predicted the best P. rubescens abundance for water temperatures around 14°C. This result is consistent with the biological processes of the toxic cyanobacterium. In this study, we found that the coupling between K-means and RF models could help in forecasting the development of the bloom-forming P. rubescens in Lake Geneva. This methodology could create a numerical decision support tool, which should be a significant advantage for lake managers.
... This index is used as a measure of the total pressure (urban land use, agriculture, rivers, industries) to assess the relationship between assessment methods (usually, phytoplankton, macroalgae and macroinvertebrates) and environmental pressures (Camp et al., 2015;Pinedo et al., 2015;Torras et al., 2016). The problem with this kind of index is that it is not always clear which pressure is responsible for an observed response and, consequently, in cases of failure to achieve good status, it is not clear which pressures should be addressed (Carvalho et al., 2019;Lemm et al., 2019), although in some cases the analyses are successful in disentangling the effects of different pressures in the ecological status in transitional waters fish (Teichert et al., 2016). On the other hand, such approaches are reasonably successful at detecting a departure from good ecological status and, thus, at minimizing the risk of a "false negative" due to the absence of an appropriate pressurespecific metric. ...
... In this case, the effects of different pressures can be disentangled using these different modules Böhmer et al., 2004). In all other cases, relationships only provide general answers to pressure combinations, and hydromorphological and physicochemical supporting elements have to be used to detect the cause and suggest restoration measures (see Teichert et al., 2016). ...
Article
Full-text available
The European Union has embarked on a policy which aims to achieve good ecological status in all surface waters (i.e. rivers, lakes, transitional and coastal waters). In theory, ecological status assessment methods should address the effects of all relevant human pressures. In this study, we analyze the degree to which methods European countries use to assess ecological status tackle various pressures affecting European waters. Nutrient pollution is by far the best-covered pressure for all four water categories. Out of total of 423 assessment methods, 370 assess eutrophication and pressure-specific relationships have been demonstrated for 212 of these. “General degradation” is addressed by 238 methods, mostly validated by relationships to combined pressure indices. Other major pressures have received significantly less effort: hydromorphological degradation is assessed by 160 methods and pressure-specific relationships have been demonstrated for just 40 of these. Hydromorphological pressures are addressed (at least by one BQE) only by 25% countries for coastal waters and 70–80% for lakes and transitional waters. Specific diagnostic tools (i.e. single-pressure relationships) for hydromorphology have only been developed by a few countries: only 20% countries have such methods for lakes, coastal and transitional waters and less than half for rivers. Toxic contamination is addressed by 90 methods; however, pressure-specific relationships have been demonstrated for just eight of these. Only two countries have demonstrated pressure-specific acidification methods for rivers, and three for lakes. In summary, methods currently in use mostly address eutrophication and/or general degradation, but there is not much evidence that they reliably pick up the effects of other significant pressures such as hydromorphology or toxic contamination. Therefore, we recommend that countries re-examine: (1) those pressures which affect different water categories in the country; (2) relevant assessment methods to tackle those pressures; (3) whether pressure-response relationships have been developed for each of these.
... Although still a major stressor and activity in many regions globally (see Cowley et al. 2022), estuarine fisheries in Europe no longer pose a major threat to fish communities and come well behind pollution and physical destruction of habitats in terms of anthropogenic pressure (Teichert et al. 2016). Nevertheless, the recent use of modern electronic tools such as high-resolution echo sounders, high-precision GPS and radar have considerably improved the efficiency of fishing compared to 10-15 years ago, and this should raise questions about the sustainability and the necessary supervision of fishing activity in estuaries. ...
... They have demonstrated high performance to select relevant environmental parameters explaining the fish spatial distribution such as time of the year, the year, the distance to estuarine mouth, dissolved oxygen, turbidity, water temperature, salinity and depth (Fodrie & Mendoza 2006, Froeschke & Froeschke 2011. They also provide powerful insights to investigate interactive effects between environmental stressors to identify which restoration benefits can be expected from mitigation measures (Teichert et al. 2016). This has been well demonstrated by Archambault et al. (2018) in their spatially structured age and stage-based hierarchical Bayesian model. ...
... Finally, many freshwater systems are subjected to multiple types of pollution and degradation. Therefore, tackling one specific stressor may have unexpected or even negative outcomes due to complex interactions with other stressors (Jackson et al. 2001;Nõges et al. 2016;Teichert et al. 2016). ...
... Our results do not only confirm the importance of nutrients but also illustrate the complex nature of the various stressors affecting riverine systems (Jackson et al. 2016;Teichert et al. 2016). Furthermore, improving hydromorphological and more specifically riverbed quality to a 'very good' standard seems unfeasible as many rivers have been heavily modified. ...
Article
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The European Union adopted the Water Framework Directive (WFD) in the year 2000 to tackle the rapid degradation of freshwater systems. However, biological, hydromorphological, and physico-chemical water quality targets are currently not met, and identifying successful policy implementation and management actions is of key importance. We built a joint species distribution model for riverine fish in Flanders (Belgium) to better understand the response of fish communities to current environmental policy goals. Environmental covariates included physico-chemical variables and hydromorphological quality indices, while waterway distances accounted for spatial effects. We detected strong effects of physico-chemistry on fish species’ distributions. Evaluation of fish community responses to simulated policy scenarios revealed that targeting a ‘good’ status, following the WFD, increases average species richness with a fraction of species (0.13–0.69 change in accumulated occurrence probabilities). Targeting a ‘very good’ status, however, predicted an increase of 0.17–1.38 in average species richness. These simulations indicated that riverbed quality, nitrogen, and conductivity levels should be the focal point of policy. However, the weak response of species to a ‘good’ quality together with the complexity of nutrient-associated problems, suggest a challenging future for river restoration in Flanders.
... For transitional waters, and specifically for lagoons, methods based on fishes are still under validation. Potential methods rely on the use of multi-metric indices that take into account the fish assemblage as a whole, and supplementary information (e.g., environmental parameters and human activities) to evaluate anthropogenic pressures acting on the lagoon [40][41][42]. ...
Article
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Mediterranean coastal lagoons are increasingly affected by several threats, all concurrently leading to habitat degradation and loss. Methods based on fish for the assessment of the ecological status are under implementation for the Water Framework Directive requirements, to assess the overall quality of coastal lagoons. Complementary tools based on the use of single fish species as biological indicators could be useful as early detection methods of anthropogenic impacts. The analysis of skeletal anomalies in the big-scale sand smelt, Atherina boyeri, from nine Mediterranean coastal lagoons in Italy was carried out. Along with the morphological examination of fish, the environmental status of the nine lagoons was evaluated using a method based on expert judgement, by selecting and quantifying several environmental descriptors of direct and indirect human pressures acting on lagoon ecosystems. The average individual anomaly load and the frequency of individuals with severe anomalies allow to discriminate big-scale sand smelt samples on the basis of the site and of its quality status. Furthermore, a relationship between skeletal anomalies and the environmental quality of specific lagoons, driven by the anthropogenic pressures acting on them, was found. These findings support the potentiality of skeletal anomalies monitoring in big-scale sand smelt as a tool for early detection of anthropogenic impacts in coastal lagoons of the Mediterranean region.
... Or, de par leur emplacement stratégique et en raison de leur productivité, les estuaires ont été fortement anthropisés au cours des deux derniers siècles (Sheaves et al., 2015). D'intenses modifications ont été apportées à la structure des habitats, afin de tisser les trames socio-économiques des territoires (Teichert et al., 2016). Un cas particulièrement intéressant dans le contexte français est l'estuaire de la Seine. ...
... Estuaries are coastal ecosystems characterized by a high biological diversity and productivity across latitudes [1]. However, despite their ecological and economic importance, estuaries are increasingly altered by anthropogenic impacts that modify biogeochemical cycling and ecosystem services (e.g., fisheries, water quality; [2,3]). Currently, coastal eutrophication is a pervasive environmental problem that alters the complex functional and structural properties of estuaries across fertility and salinity gradients [4][5][6][7][8]. ...
Article
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The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (exponential model; R2 = 0.46; RMSE = 4.8, p < 0.0001). The statistical model replicated [Chl-a] spatial patterns across the BB complex. This work shows the utility of high-frequency continuous Chl-a fluorometry sampling coupled with L8/OLI image analysis to increase the frequency and number of field data sets to assess water quality conditions at large spatial scales in highly dynamic deltaic regions.
... The response of coastal watersheds to any management intervention is multifaceted and complex (Duarte et al., 2015;Teichert et al., 2016), however QNMs allow us to examine these impacts across multiple recovery objectives in one framework. Our scenarios represent the social-ecological system of Puget Sound under different proposed development interventions and hypothesized system behaviorsthe basis for which are previously-developed recovery plan documents (https://www. ...
Article
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Population growth and the associated transformation of landscapes is a major management challenge for coastal ecosystems. Coastal conservation and management should be guided by social, cultural, economic, and ecological objectives, but integrative decision support tools appropriate for complex ecosystems remain underutilized. Evaluating alternative policies for objectives that span the interconnected terrestrial, freshwater, and estuarine habitats along coastlines is limited by the lack of appropriate quantitative tools and available data. We employed qualitative network models (QNMs) to evaluate multi-benefit outcomes of potential management interventions to address population growth and development using a case study of Puget Sound-a large, urbanized fjord-type estuary in Washington, U.S.A. With input from regional scientists and stakeholders, we developed a base conceptual model of the links among human stressors and ecosystem components across the terrestrial-freshwater-estuarine gradient of a generalized Puget Sound watershed. We simulated scenarios representing alternative strategies for accommodating human population growth, namely new development outside of urban centers versus redevelopment (densification) within urban centers, and characterized the responses of multiple recovery objectives and ecosystem stressors for each scenario. Of the urban redevelopment scenarios, reducing stormwater runoff and increasing green infrastructure provided the most favorable outcomes. On rural lands, limiting new development to existing transportation corridors and iincreasing floodplain and riparian habitat extent concomitant with new development produced similar outcomes. Moderate levels of coordinated interventions on both urban and rural lands had favorable outcomes for more ecosystem objectives compared to either moderate intervention applied separately. This study demonstrates the value of qualitative tools for cross-habitat evaluations of possible futures in complex ecosystem-based management systems. Magel CL and Francis TB (2022) Evaluating ecosystem-based management alternatives for the Puget Sound, U.S.A. social-ecological system using qualitative watershed models.
... The inclusion of fish as a Biological Quality Element (BQE) in the implementation of the Water Framework Directive (WFD) 2000/60 [18] has added further interest, especially for transitional waters [19][20][21][22]. The proposed methods for the assessment of the ecological status of transitional waters, based on fish as BQE, rely on the use of multi-metric indices that take into account the fish assemblage of the lagoon as a whole, and supplementary information to evaluate anthropogenic pressures acting on the lagoon [23,24]. Nevertheless, the approach based on the use of a single fish species as a biological indicator remains valid [25], and can rely on the use of fish condition, health and contamination patterns. ...
Article
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The evaluation of past and present anthropogenic impacts affecting the ecological quality status of transitional ecosystems is crucial from the perspective of protecting them from further deterioration, and to evaluate remediation and restoration measures. Contamination patterns of thick-lipped grey mullet from two Mediterranean coastal lagoons within a protected area in Italy were assessed and compared in order to evaluate their overall quality status and to collect information that can provide useful feedback on management choices aimed at enhancing environmental quality and biodiversity conservation. The quality status of the two lagoons was evaluated by an environmental assessment methodology based on indicators of direct and indirect human pressures, while a broad range of analyses were carried out to determine the presence and concentration of persistent organic pollutants (POPs) and metals in fish muscle tissue. A good quality status resulted for both lagoons, and an overall limited anthropogenic impact in the surrounding area. This could account for POPs and metal contamination levels found in mullet, although limited, and relating to their patterns. The overlap of results achieved with the two evaluation approaches can provide support for management choices in Mediterranean lagoon environments, especially for those committed to the protection and conservation of biodiversity.
... Machine learning is frequently being applied as a data exploration tool for identifying relationships among variables in large ecological datasets. Data mining techniques such as treebased methods, support vector machines, and Bayesian inference are more effective at uncovering relationships within large complex datasets than traditional statistical modeling procedures (Hochachka et al. 2007;Teichert et al. 2016). For example, machine learning has been used to predict how biodiversity will shift with climate change (Baltensperger and Huettmann 2015), which is an emerging theme in tidal marsh ecology research . ...
Article
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Over the last 20 years, innovations have led to the development of exciting new technologies and novel applications of established technologies, collectively increasing the scale, scope, and quality of research possible in tidal marsh systems. Thus, ecological research on marshes is being revolutionized, in the same way as ecological research more generally, by the availability of new tools and analytical techniques. This perspective highlights current and potential applications of novel research technologies for marsh ecology. These are summarized under several themes: (1.) imagery — sophisticated imaging sensors mounted on satellites, drones, and underwater vehicles; (2.) animal tracking — acoustic telemetry, passive integrated transponder (PIT) tags, and satellite tracking, and (3.) biotracers — investigation of energy pathways and food web structure using chemical tracers such as compound-specific stable isotopes, isotope addition experiments, contaminant analysis, and eDNA. While the adoption of these technological advances has greatly enhanced our ability to examine contemporary questions in tidal marsh ecology, these applications also create significant challenges with the accessibility, processing, and synthesis of the large amounts of data generated. Implementation of open science practices has allowed for greater access to data. Newly available machine learning algorithms have been widely applied to resolve the challenge of detecting patterns in massive environmental datasets. The potential integration on digital platforms of multiple, large data streams measuring physical and biological components of tidal marsh ecosystems is an opportunity to advance science support for management responses needed in a rapidly changing coastal landscape.
... This method has been widely applied in ecology (Breiman, 2001;Cutler et al., 2007) and more recently in freshwater fisheries studies to predict fish abundances and species responses to environmental alterations (e.g. Vezza et al., 2015;Ward et al., 2014) and to assess and predict the effects of restoration and management actions (Cochran-Biederman et al., 2015;Flanagan & Richardson, 2010;Teichert et al., 2016). RF is a statistical ensemble method based on the combination of a multitude of decision trees, which is used to determine the mean prediction of the individual trees (Breiman, 2001). ...
Article
Effective protection of migratory fish requires long‐term conservation encompassing active restoration and management measures with follow‐up studies. The main findings of long‐term (1995–2019) monitoring of anadromous and potamodromous brown trout Salmo trutta in the River Bidasoa are presented. The main aims were evaluating trout number and median migration date changes, and assessing the effects of management (closures, size limits and quotas, fish stoking) and connectivity measures (fishways and weir removals). Results showed an increasing trend in upstream migrants and decrease in migration dates (earlier migrations). Effects of overlapping measures were difficult to differentiate and were affected by environmental conditions. Statistical analysis demonstrated that fishing closures (2008–2011) and fishway construction (2008) were of great importance, whereas the effect of fish stocking (2003–2012) was variable and unclear. The unexpectedly short‐term effect of three weir removals (2014–2016) may have been due to unusually high discharges in March, affecting the recruitment during previous years.
... Addressing these interacting drivers of change jointly and understanding how they affect different ecosystem components and ecosystem functioning are important to natural resource managers (Planque et al., 2010;Hidalgo et al., 2011;Giakoumi et al., 2015;Halpern et al., 2015;Feld et al., 2016). Since the review by Crain et al. (2008), studies analyzing the cumulative and interactive effects of drivers of change have moved from species-level research to ecosystem-level research (e.g., Micheli et al., 2013;Feld et al., 2016;Schinegger et al., 2016;Teichert et al., 2016;Mach et al., 2017;Lercari et al., 2018;Ramírez et al., 2018). Nevertheless, a deep understanding of the cumulative effects of drivers of change is often impossible when analysts rely only on statistical analyses of empirical data, which hampers a comprehensive prediction of responses to multiple drivers and, thus, the proper mitigation of cumulative impacts of multiple drivers on marine ecosystems and restoration projects (Segurado et al., 2018). ...
Article
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The marine ecosystem off British Columbia (BC), Canada, has experienced various changes in the last two decades, including reduced lipid-rich zooplankton biomass, increased marine mammals, and deteriorated commercial fisheries, particularly those targeting pelagic species such as Pacific Herring (Clupea pallasii). Understanding how stressors interactively and cumulatively affect commercially important fish species is key to moving toward ecosystem-based fisheries management. Because it is challenging to assess the cumulative effects of multiple stressors by using empirical data alone, a dynamic, individual-based spatially explicit ecosystem modeling platform such as Object-oriented Simulator of Marine Ecosystems (OSMOSE) represents a valuable tool to simulate ecological processes and comprehensively evaluate how stressors cumulatively impact modeled species. In this study, we employed OSMOSE to investigate the cumulative effects of fishing, plankton biomass change, and marine mammal consumption on the dynamics of some fish species and the BC marine ecosystem as a whole. We specifically simulated ecosystem dynamics during the last 20 years under two sets of scenarios: (1) unfavorable conditions from the perspective of commercial fish species (i.e., doubling fishing mortality rates, halving plankton biomass, and doubling marine mammal biomass, acting individually or collectively); and (2) favorable conditions with the three factors having opposite changes (i.e., halving fishing mortality rates, doubling plankton biomass, and halving marine mammal biomass, acting individually or collectively). Our results indicate that, under unfavorable conditions, the degree to which species biomass was reduced varied among species, and that negative synergistic and negative dampened effects were dominant under historical and doubled fishing mortality rates, respectively. Under favorable conditions, species biomasses did not increase as much as expected due to the existence of complex predator-prey interactions among fish species, and positive synergistic and positive dampened effects were prevailing under historical and halved fishing mortality rates, respectively. The Frontiers in Marine Science | www.frontiersin.org 1 September 2020 | Volume 7 | Article 565699 Fu et al. Cumulative Effects, Fishing, Productivity, Predation ecosystem total biomass and the biomass to fisheries yield ratio were found to be good ecological indicators to represent ecosystem changes and track the impacts from the multiple drivers of change. Our research provides insights on how fisheries management should adapt to prepare for potential future impacts of climate change.
... As in previous works, our results corroborate the idea that stressor's interactions seem to have different impacts at the organism-and population levels when compared to impacts caused by isolated stressors [68][69][70]. Therefore, the use of models such as the present one, capable of integrating several factors of stress and predict their short-and longterm effects on organisms is crucial to assess the temporal variations of natural populations and support decision-making regarding mitigation measures and the sustainable management of populations and ecosystems. ...
Article
The seaweed Gracilaria is not only relevant to the functioning of coastal ecosystems as it also has an important economic value particularly linked to agar extraction. Climate change is expected to affect the production of marine macrophytes and hence their related processes. Baring this in mind, our aim was to develop a numerical model capable of predicting variations on Gracilaria sp. growth and standing stock under climate change scenarios, including temperature rise (RCP2.6 and RCP8.5), hypersalinity and enhanced nitrogen (N) runoff. Single- and multiple-stressor simulations were run to check for possible interactions amongst different stressors and the resulting impacts on Gracilaria sp. growth. Results indicate that the effects of isolated and combined stressors on Gracilaria sp. standing stock differ. The tested temperature rise scenarios induced decreases of 29% (RCP2.6) and 57% (RCP8.5) on the red algae biomass, with more severe effects under the highest emission scenario (RCP8.5), which were related to enhanced algal respiration, decomposition and grazing pressure. Seasonal hypersalinity caused a reduction of 35% on the net productivity of Gracilaria sp., while the simulated N runoff increase (25%) had no effect on the annual biomass of Gracilaria sp. Contrarily to the moderate effects of single-stressors, multiple-stressor scenarios had severe impacts on Gracilaria sp. annual standing stock with reductions > 90%, pointing out to the occurrence of synergistic effects of temperature and salinity on the production of Gracilaria sp. Overall, these results indicate that within the next decades, the interaction of different environmental stressors will pose significant constraints to the production of Gracilaria sp. on natural systems with subsequent effects to therein associated ecological services.
... Coastal and estuarine ecosystems are increasingly exploited, polluted, and their biodiversity is decreasing (IPBES, 2019). Moreover, pollution has been identified as one of the main factors affecting the ecological quality of these areas, especially by altering their nursery function (see for instance Fonseca et al., 2014;Gibson, 1994;Nunes et al., 2014;Teichert et al., 2016). The effect of pollution in these habitats is such that, in Europe and especially in France, fish-based indicators of the ecological quality of transitional waters are particularly calibrated to respond to water contamination (Courrat et al., 2009;Delpech et al., 2010;Pasquaud et al., 2013). ...
Article
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Studying adverse effects of chemical pressure on aquatic ecosystems needs a comprehensive knowledge of bioaccumulation mechanisms of pollutants in biota to predict internal concentrations, especially for Persistent Organic Pollutants (POPs). However, the large variability of responses in measured POP concentrations requires explicit consideration of both individual variability and environmental influences. Dynamic Energy Budget (DEB) theory provides a rigorous and generic conceptual framework for tackling these questions in a relevant mechanistic way. In the present study, parameterisation and calibration of previous DEB models for Solea solea were revisited in order to accurately represent the full life cycle with an original emphasis on larval stage, metamorphosis, reproduction rules and sexual differences. We first improved calibration thanks to the use of the estimation procedure developed by the DEB network coupled with a broad compilation of data from literature. Then, we validated this set of parameter estimates on independent datasets of i) individual monitoring of larval growth in controlled food conditions from a novel experiment, and ii) juvenile and adult growth, and female fecundity, from a natural population. Finally, we combined the DEB model developed in the present paper with we used a simple toxicokinetic (TK) model from literature. This TK model was also combined to a previous DEB model and was used to reproduce the mean trajectories of a growth and contamination dataset. We applied the same TK model with our DEB model considering inter-individual variability in food availability. This application highlighted the need to accurately consider inter-individual variability in ingestion to correctly estimate growth and contamination variability. The present work is the first step in the development of a mechanistic TK model that will be used in a companion paper for investigations of juvenile sole sensitivity to warming, nursery quality and prey contamination, in highly fluctuating estuarine environments.
... The number of species representing MJ (105) and MM (53) in the present study was much higher than that reported earlier. Similarly, MM and MJ dominated in terms of the number of individuals over ES in contrast to the pattern in temperate estuaries (Lobry et al., 2003;Franco et al., 2008;Selleslagh and Amara, 2008;Selleslagh et al., 2009Selleslagh et al., , 2010Teichert et al., 2016). We compiled available qualitative data on species diversity in estuaries along the western coast of India (Bijukumar and Sushama, 2000;Bhat et al., 2012;Roshith et al., 2013;Asha et al., 2015;Johny, 2016;Deepashree et al., 2017;Sreekanth et al., 2017;Bhakta et al., 2018) and described the guild structure. ...
Article
The structure of fish guilds was analysed in four tropical monsoonal estuaries, namely Zuari, Mandovi, Terekhol, and Kali, along India’s western coast. The fish were sampled from 2017 to 2019 both temporally and spatially: temporally in three seasons, named with reference to the monsoon as before (February–May), during (June–September), and after (October–January) the monsoon and spatially from the upper, middle, and lower stretches of the estuaries. The composition of fish guilds was similar for the four estuaries but varied with the season and the location (gradient). The dominant guilds consisted of marine species, both juveniles and seasonal migrants, and carnivores and omnivores.
... These systems mostly form attractive and strategic locations that are preferred by humans for inhabitation, settlement, and for undertaking several types of anthropic activities. Owing to the ideal geographical features, estuaries are highly preferred locations for the establishment and development of large urban centers to facilitate industrial, marine, port, aquaculture, and agricultural activities (Elliott and Whitfield, 2011;Teichert et al., 2016). However, the estuarine systems are highly fragile biologically, with considerable biological diversity that has attracted their use for breeding purposes and as a tropic site for rearing several freshwater and marine species. ...
... Given the lack of accurate data and knowledge regarding the interactions between the impacts on receptors, this could not yet be incorporated. However, given the complexity and local variability of the interactions between additive, synergistic and antagonistic pressures (see Teichert et al., 2016 for definitions), it may not be possible for these to be incorporated into a single, generic methodological framework that can be used by the different industries, in different regions. In addition, the CEA does not discriminate between the seabed habitat types but identifies the 'seabed' as a single receptor. ...
Article
The assessment of the cumulative impacts of multiple human activities is an increasingly important yet complex part of managing the marine environment. Despite this, as yet, there is no consistent approach to considering these in assessments and/or management (e.g. environmental impact assessment, marine spatial planning). Current and previous approaches to the assessment of cumulative impacts have limitations and shortcomings e.g. double counting of impacts or avoiding, complicating and confounding impacts, which need to be addressed to allow for pragmatic decisions to be made. Here, an innovative, practical approach to marine CIA is presented that considers the three dimensional nature of the marine environment, and the spatial and temporal effects-footprints likely to occur during the lifetime of a development. The new approach is tested within a GIS platform and shows an effective visual representation for decision makers, managers and policy makers on which to base their decisions. While showing potential, the approach indicates the need to incorporate temporal data and assessing temporal trends. Despite this limitation, the tool markedly improves on previous approaches due to the national and practical application, and the incorporation of 3D nature of pressures and receptors.
... Courrat et al., 2009 ;Delpech et al., 2010 ;Pasquaud et al., 2013). Il apparaît ainsi que la contamination chimique est un des principaux facteurs responsable de la dégradation de l'état écologique des zones estuariennes (Delpech et al., 2010 ;Pasquaud et al., 2013 ;Teichert et al., 2016). Plusieurs travaux réalisés en milieux côtiers (Munschy et al., 2011 ;Bodin et al., 2007 ;Loizeau et al., 2001a,b) et fluviaux (Lopes et al., 2011) sur des contaminants organohalogénés hydrophobes ont permis de mettre en évidence des phénomènes de bioamplification le long de la chaîne trophique. ...
Thesis
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Les estuaires sont des écosystèmes aquatiques particulièrement soumis au changement global et notamment à la pollution par de nombreux xénobiotiques pouvant présenter un risque écotoxicologique et sanitaire. En toxicologie environnementale et en évaluation des risques la bioaccumulation est un processus fondamental car elle contrôle les doses internes de toxiques potentiels. Or les flux de contamination et de décontamination des organismes dépendent de processus internes (e.g. nutrition, croissance) eux-mêmes dépendant des conditions environnementales (e.g. température, nourriture) qui peuvent être affectées par le changement global.Dans ce contexte, cette thèse se propose de décrire, dans un cadre de modélisation mécaniste, les processus de bioaccumulation de deux familles de polluants organiques persistants (POP) halogénés potentiellement toxiques et bioaccumulables, aux propriétés physico-chimiques contrastées : les polychlorobiphényles (PCB, composés historiques fortement lipophiles) et les substances perfluorées (PFAS, composés émergents amphiphiles). Ce travail se focalise sur l’estuaire de la Gironde dont la fonction de nourricerie est fondamentale pour de nombreuses espèces de poissons marins dont la sole commune (Solea solea), souvent utilisée comme indicatrice de la qualité des nourriceries côtières et estuariennes.Pour permettre de tenir compte des fluctuations des conditions environnementales sur la bioaccumulation, dans la première partie de ce travail, j’ai développé un modèle de toxicocinétique(TK) couplé avec un modèle mécaniste bioénergétique basé sur la théorie DEB (Dynamic Energy Budget). Ce modèle DEB a été paramétré pour la sole commune et calibré pour chaque sexe (package DEB tool). Il permet de prédire les principales évolutions des fonctions physiologiques d’intérêt en bioaccumulation (ingestion, croissance, reproduction...), tout au long du cycle de vie d’un individu, en fonction de conditions environnementales dynamiques. Le modèle TK développé a été complexifié par l’ajout d’un flux d’élimination de contaminants, non considéré dans les précédents modèles DEB-TK.La calibration des paramètres toxicocinétiques (TK) du modèle, pour 4 congénères de PCB, est basée sur une méthode innovante de prise en compte de la variabilité individuelle d’ingestion, appliquée à une expérimentation de contamination de juvéniles de sole via leur nourriture. Ce travail a montré que même en tenant compte de l’ingestion de chaque poisson, l’assimilation efficace de contaminant était très variable et corrélée aux taux de lipides des individus. Dans une seconde partie, ce modèle a été appliqué aux conditions in situ de l’estuaire de la Gironde. Il a permis de mettre en évidence la forte influence de la composition du régime alimentaire sur la variabilité de l’âge à la maturité sexuelle et de la contamination des soles pour les deux familles de contaminant étudiées. La confrontation des prédictions du modèle aux mesures de contaminants dans les juvéniles de sole de l’estuaire a permis de calibrer les paramètres TK du composé majeur de chaque famille dans l’environnement (CB153 et PFOS). Cette calibration a conduit à deux constats dans le cadre de l’évaluation du risque : (1) un manque de connaissances pour extrapoler les calibrations de paramètres TK en conditions contrôlées vers les conditions naturelles ; (2) la différence d’erreur d’évaluation du risque liée à l’utilisation des mêmes paramètres TK «les plus pessimistes » quels que soient les composés. Enfin, des scenarios prospectifs simples ont été développés pour illustrer ces résultats et les possibles applications du modèle développé.In fine, ces prédictions de la contamination, de la croissance et du développement des soles pourront être reliées, lors de travaux ultérieurs, à des effets potentiels sur les fonctions physiologiques de la sole (modèles DEBtox), et aux conséquences sur la dynamique des populations de soles (e.g.modèles matriciels de population).
... Meta-analyses (e.g., Crain and others, 2008) are helping researchers to understand the prevalence of additive, synergistic and antagonistic interactions, while statistical approaches are helping to identify the presence and nature of non-additive interactions (e.g., Teichert and others, 2016). In addition, there have been significant advances in the handling of uncertainty in assessments (e.g., Rochet and others, 2010;Foster and others, 2014;Gissi and others, 2017) and some progress in defining thresholds and reference points to use in assessments, though they can be somewhat subjective as they are defined by societal objectives (e.g., Samhouri and Levin, 2012;Large and others, 2015;Samhouri and others, 2012;. ...
... For instance, in Canada and New Zealand, overfishing and aquaculture development have made it more difficult to sustain Indigenous Peoples' fisheries [12,13,111]. The cumulative effects of ongoing environmental damages [14,15], as well as the ongoing effects of colonization and continued dispossession of land and sea [13,[16][17][18], further compromise the long-term relationships of Indigenous Peoples to their territories. These combined effects are in some cases leading to loss of culture and lifestyle, language, identity, health, self-determination, traditional ecological knowledge, sense of place and belonging as well as indirect economic losses [13,19,20]. ...
Article
The biodiversity crisis is paralleled by a decline in the ability of Indigenous peoples to practice traditional livelihoods, cultures and languages. The world’s oceans and coastal communities face such threats, prompting increasing interest in establishing conservation measures. Systematic conservation planning (SCP) is a structured approach to establish conservation measures with clearly defined objectives, such as protected areas. Many Indigenous peoples are resurging to reclaim and protect some of their traditional lands and revitalize their cultures as rights holders. SCP goals and Indigenous goals could thus align. This research documents the Indigenous-led marine conservation planning process of the Songhees Nation to reclaim and assert stewardship around the Tl’ches archipelago near Victoria, Canada. We compare the Songhees marine conservation planning approach to SCP approaches. The Songhees approach showed similarities to SCP in the initial scoping phase of the marine conservation planning, in the review and compiling of existing data prior to the collection of data as well as the focus on focal species. The Songhees approach to marine conservation planning also differed from SCP as it included one zone only, did not involve any other stakeholders, and tried to account for the whole social-ecological system in one process step. This research provides useful insights and a guidance to help interested Indigenous communities worldwide to conduct their own marine conservation planning.
... In intensive aquaculture, farmed sh are frequently exposed to stressors such as crowding and handling, which in uence health and welfare, and can threaten aquaculture sustainability [8,9]. In natural settings, sh populations are increasingly Page 3/29 becoming subjected to multiple anthropogenic stressors, which threaten their sustainability [10][11][12]. ...
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Background: The welfare of farmed fish is influenced by numerous environmental and management factors. Fish skin is an important site for immunity and a major route by which infections are acquired. The objective of this study was to characterize bacterial composition variability on skin of healthy, diseased and recovered Gilthead Seabream (Sparus aurata) and Barramundi (Lates calcarifer). S. aurata, which are highly sensitive to gram-negative bacteria, were challenged with Vibrio harveyi. In addition, and to provide a wider range of infections, both fish species (S. aurata and L. calcarifer ) were infected with gram-positive Streptococcus iniae, to compare the response of the highly sensitive L. calcarifer to that of the more resistant S. aurata. All experiments also compared microbial communities found on skin of fish reared in UV (a general practice used in aquaculture) and non-UV treated water tanks. Results: Skin swab samples were taken from different areas of the fish (lateral lines, abdomen and gills) prior to controlled infection, and 24, 48 and 72 hours, 5 days, one week and 1 month post-infection. Fish skin microbial communities were determined using Illumina iSeq100 16S rDNA for bacterial sequencing. The results showed that naturally present bacterial composition is similar on all sampled fish skin sites prior to infection, but the controlled infections (T1 24 h post infection) altered the bacterial communities found on fish skin. Moreover, when the naturally occurring skin microbiome did not quickly recover, fish mortality was common following T1 (24 h post infection). We further confirmed the differences in bacterial communities found on skin and in the water of fish reared in non-UV and UV treated water under healthy and diseased conditions. Conclusions: Our experimental findings shed light on the fish skin microbiome in relation to fish survival (in diseased and healthy conditions). The results can be harnessed to provide management tools for commercial fish farmers; predicting and preventing fish diseases can increase fish health and welfare, and enhance commercial fish yields.
... Though this research supports previous findings, the novelty in our approach is that it elicits empirical affirmations of associations between LULC and estuarine biotic health, which were previously based on anecdotal information (Beger et al., 2010;Stoms et al., 2005;Thrush et al., 2004). Whereas previous studies quantified effects of anthropogenic stressors on estuarine health/condition (e.g., Miller et al., 2018;Teichert et al., 2016), our study also quantified the linkage between natural land covers and estuarine biotic health. Establishing a quantifiable link between all land-cover types (anthropogenic and natural) and estuarine health is a critical step in systematically valuing implications of land conservation to estuarine environments. ...
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The composition of land‐use/land cover (LULC) in coastal watersheds has many implications for estuarine system ecological function. LULC can influence allochthonous inputs and can enhance or degrade the physical characteristics of estuaries, which in turn affects estuaries’ abilities to support local biota. However, these implications for estuaries are often poorly considered when assessing the value of lands for conservation. The focus of research regarding terrestrial and estuarine interfaces often evaluates how LULC may stress estuarine ecosystems, but in this study we sought to understand how LULC may both positively and negatively influence estuaries, using measures of observed biotic richness as proxies for estuarine function. We investigated the influence of LULC on estuarine biotic richness with Bayesian hierarchical models, using multiple geospatial datasets from 33 estuaries and their associated watersheds along the Gulf of Mexico coastal region of the United States. We designed the hierarchical models with observed species richness of three functional groups (i.e. pelagic fishes, forage fishes, and shrimp) from fishery‐independent trawl surveys as response variables. We then set salinity and water temperature as trawl‐specific covariates, and measures of influence from six LULC classes as estuary‐specific covariates, and allowed the models to vary by estuary, trawl program, salinity, and temperature. The model results indicate that observed richness of each functional group is both positively and negatively associated with different LULC classes, with estuarine wetlands and forested lands demonstrating the strongest positive influences on each functional group. The results are generally consistent with past studies and the modeling framework provides a promising way to systematically quantify LULC linkages with the biotic health of estuaries for the purposes of potentially valuing estuarine implications of land conservation.
... Stressors with relatively high effects scores and moderate likelihoods of increasing in prevalence over the next decade included poor water quality and bycatch. Although improved water quality has enhanced salmon stock status in many English rivers over the last 50 years (Mawle and Milner 2003), concerns about the impacts of poor water quality on the passage of smolts and adult salmon through estuaries exist (Hugman et al. 1984), especially given the potential for synergistic effects in combination with other stressors including climate change (Teichert et al. 2016). Measures to alleviate poor water quality impacts have been implemented under the EU's Water Framework and Marine Strategy Framework Directives, which aim to safeguard the good ecological status of aquatic ecosystems (EC 2000(EC , 2008(EC , 2017. ...
Article
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Atlantic salmon Salmo salar is a socio-economically important anadromous fish species that has suffered synchronous population declines around the North Atlantic over the last five decades. Reduced marine survival has been implicated as a key driver of the declines, yet the relative importance of different stressors causing mortality at sea is not well understood. This review presents a synopsis of the principal stressors impacting Atlantic salmon in estuarine and marine environments. It also applies a semi-quantitative 2-D classification system to assess the relative effects of these stressors on English salmon stocks and their likely development over the next decade. Climate change and predation were identified as the biggest threats at present and over the next decade. Poor water quality and bycatch were classified as relatively high impact stressors, but with a lower likelihood of becoming more prevalent in the future due to available mitigation measures. Other, less influential, stressors included tidal barrages, artificial light at night, impingement in power-station cooling waters and thermal discharges, pile-driving noise pollution, invasive non-native species, electromagnetic fields, salmon mariculture, and tidal lagoons. Salmon fisheries exploitation was not regarded as an important stressor currently because effective exploitation rate controls have been implemented to substantially reduce fishing pressure. Future research priorities include addressing knowledge gaps on expanding stressor impacts from climate change, predation, renewable energy developments, and artificial light at night. Local management actions directed towards improving freshwater and estuarine habitats to maximise ecosystem resilience to stressors and minimise their cumulative impacts are recommended.
... Large estuaries are impacted by interactive and cumulative effects among endogenic stressors (water pollution, coastal urbanization, flow changes, intertidal loss, eutrophication) and exogenic unmanaged stressor (e.g., warming waters linked to climate change). These stressors are seriously affecting the ecological quality of transitional waters and particularly their fish communities (Elliott et al. 2015;Teichert et al. 2016). Resident fish species that experience the estuarine environment throughout their life are more responsive to the local interaction of stressors, than non-resident fish using estuaries during a specific life stage (Teichert et al. 2017). ...
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The main objective of this study was to improve our knowledge on the responses of fish populations to multistress (diffuse pollution and warming waters) in estuaries. Adult flounders were caught in two estuaries in the Eastern English Channel: the heavily polluted Seine estuary vs the moderately contaminated Canche estuary. Fish samplings were conducted in January just before the reproduction period, and in July when gonads were at rest. The overall rise in coastal winter water temperatures detected over the Channel impairs the flounder’s phenology of reproduction in the two estuaries, inducing a delay of maturation process and probably also spawning. The higher liver histopathology index in Seine vs Canche could be the consequence of the fish exposition to a complex cocktail of contaminants in a strongly industrialized estuary. Higher levels of neurotoxicity, gill lipid peroxidation, and liver EROD activity were observed in Seine vs Canche. Furthermore, a possible impairment in mitochondrial metabolism was suggested in the Seine flounder population. We confirmed in this study the potential role of two membrane lipids (sphingomyelin and phosphatidylserine) in the resistance towards oxidative stress in Seine and Canche. Finally, we suggest that the Seine flounder population (and possibly the connected Eastern English Channel flounder populations over the French Coast) could be seriously impacted in the future by multistress: higher winter temperatures and chemical contamination.
... (3) Random forest is a statistical ensemble learning method for classification, regression and other tasks based on the combination of a multitude of decision trees (Figure 15), which is used to determine the mode (classification) or mean prediction (regression) of the individual trees (Breiman, 2001). This method has been widely applied in ecology (Breiman, 2001;Cutler et al., 2007) and more recently in freshwater fish studies to predict fish abundance and species response to environmental (Vezza et al., 2015;Ward et al., 2014) as well as to assess and predict the effects of restoration and management actions (Cochran-Biederman et al., 2015;Flanagan and Richardson, 2010;Teichert et al., 2016). Moreover, random forest can capture the over-dispersion or zero-inflation inherent in count data (Garcia-Marti et al., 2019), allow freedom from normality and homoscedasticity assumptions and does not require previous data transformation or a separate test set for cross-validation as it is performed internally during the run (Breiman, 2001). ...
Thesis
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Many fish species need to move between different habitats in order to complete their life cycles. As a result, migration responds to internal and external factors, with environmental variables, such as river flow and thermal regimes, acting as the main stimuli for the onset and maintenance of migratory behavior in freshwater fish. Moreover, river fragmentation and anthropogenic alterations on these variables (e.g. river regulation) may have strong impacts on fish populations, which could be aggravated by future projections of climate change and increasing water demand. Thus, to assess these impacts and define mitigation measures, it is vital to understand fish movement patterns and the environmental variables affecting them. Native Iberian fish fauna presents the greatest European percentage of endemism, characterized by a low number of families, with most species belonging to the Cyprinidae family. The most representative species from this family are barbels and nases, for example, the Iberian barbel and the Northern straight-mouth nase. However, scarce information exists regarding the ecological requirements of these endemic species during their upstream migration. Another important family in the Iberian Peninsula, in terms of recreational fishing and ecological traits, is the Salmonidae, the brown trout being one of the most representative salmonids worldwide. Although this species has been deeply studied, most available research has been focused on anadromous populations, and studies in the south of its natural distribution are still scarce. The present thesis aims to cover some of these research gaps regarding upstream migration patterns of Iberian barbel, Northern straight-mouth nase and brown trout (both potamodromous and anadromous ecotypes), as well as to determine the environmental conditions which trigger these movements. In addition, this information is used to evaluate the effect of human impacts and assess the effect of mitigation measures on these species. In order to achieve this, the long-term movement data of these three species in four different locations of the Iberian Peninsula (Porma River (León), Tormes River (Salamanca), Marín River (Navarra) and Bidasoa River (Navarra)) were gathered, analyzed and discussed. In all the studied cases, data were collected in fishways, since they are mandatory points of passage during upstream migration. Survival analysis techniques were used to study median migration dates and patterns. Subsequently, random forest regression was used to evaluate the influence of environmental variables on the number of captures, develop models that can predict when upstream movements were more likely to occur, evaluate different scenarios of river discharge and water temperature and assess the possible effects of management and restoration actions. The long-term monitoring is an essential tool, not only for identify population changes, migration patterns and cues, but also for the evaluation of the overall effect of changes in the parameters involved in the migration and assessing the effects of mitigation measures. Therefore, continuous monitoring studies are necessary to define adaptive strategies and reliable management plans to ensure the conservation of Iberian freshwater fish.
... Standardised lists of pressures and impacts are given in Elliott et al. (2017), Koss et al. (2011) and Robinson & Knights (2011). Cumulative impact matrices are given in Eassom & Church 2013, Teichert et al. (2016 and Marine Scotland (2012), and Lonsdale et al. (2020) describe a Geographical Information System (GIS)-based method for cumulative assessments in estuaries. ...
Chapter
This chapter details the governance and management of estuarine fish ecology, habitats and fisheries, whereby the governance in turn covers the policies, administrative bodies and legislative instruments. It uses case studies predominantly from North America, Europe, Australia, New Zealand, South Africa and Japan but other areas are mentioned where possible. It describes the management and legal approaches to the means of controlling human activities and the way in which management also has to include economic, technological, societal and cultural aspects. In addition, because of the inherent importance of connectivity, the chapter emphasises that the management of estuarine habitats, fish and fisheries also depends on the management of catchments and the adjacent sea areas where these affect estuaries.
... Oyster reefs support resident species, positively influence abundance and size of transient fish, and are known for their production of ecosystem services including shoreline protection, wave attenuation, improved water clarity, linking trophic levels (TLs), and creation of physical structure , Coen et al. 2007, Gregalis et al. 2009, Loch et al. 2020. However, oyster reefs are vulnerable to anthropogenic stressors due to their proximity to human development, and their areal extent has decreased greatly over time (Zu Ermgassen et al. 2012, Teichert et al. 2016. As oyster reefs are of critical importance to mitigate threats facing coastal ecosystems, their restoration has the potential to increase fish diversity and abundance and the production of associated ecosystem services , Coen et al. 2007, Gittman et al. 2016. ...
Article
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Essential fish habitat is critical for foraging, breeding, or as refugia. As such, restoration of these habitats has the potential to increase the diversity and abundance of fishes. Here, we explored how fish communities responded in the first 12-24 mo following oyster reef restoration. Study sites included 8 restored reefs plus 4 live and 4 dead reefs as controls. Oyster reef metrics (e.g. density, height, thickness) and fish abundance and diversity metrics were quantified, including species richness, Shannon diversity, Simpson’s diversity, and Pielou’s evenness. Species composition was explored further to identify indicator species and assess habitat preferences. Patterns of fish community diversity and species composition were compared to oyster reef metrics to discern what oyster reef characteristics best predict fish diversity. Results showed that intertidal oyster reefs were structurally restored and shifted from resembling negative control reefs to positive control reefs within 12-24 mo. Across all treatment types, oyster shell height and reef thickness were the best predictors of fish diversity. However, at the fish community level, assemblages at restored reefs were similar to those at positive and negative controls. Species-level analyses suggest treatment types have unique indicator species, including Chilomycterus schoepfi (striped burrfish) for dead reefs, Lutjanus synagris (lane snapper) for restored reefs, and Gobiosoma robustum (code goby) for live reefs. This work suggests fishes can be used as higher trophic level indicators of restoration success, and ecosystem-based approaches, such as habitat restoration, can restore essential fish habitat, thus benefiting fish communities while moving coastal ecosystems toward sustainability.
... Random Forest and Boosted Regression Trees) are increasingly used in ecological studies (Elith et al., 2008), including those on multiple stressors effects (e.g. Hewitt et al., 2016;Kotta et al., 2017;Ceccarelli et al., 2020), they rarely distinguish among interaction types (Teichert et al., 2016). Multiple linear regression on the other hand can identify stressor interaction types from the direction and magnitude of estimated model coefficients (e.g. ...
Article
To enable environmental management actions to be more effectively prioritized, cumulative effects between multiple stressors need to be accounted for in risk-assessment frameworks. Ecological risk and uncertainty are generally high when multiple stressors occur. In the face of high uncertainty, transparent communication is essential to inform decision-making. The impact of stressor interactions on risk and uncertainty was assessed using generalized linear models for additive and multiplicative effect of six anthropogenic stressors on the abundance of estuarine macrofauna across New Zealand. Models that accounted for multiplicative stressor interactions demonstrated that non-additive effects dominated, had increased explanatory power (6 to 73 % relative increase between models), and thereby reduced the risk of unexpected ecological responses to stress. Secondly, 3D-plots provide important insights in the direction, magnitude and gradients of change, and aid transparency and communication of complex stressor effects. Notably, small changes in a stressor can cause a disproportionally steep gradient of change for a synergistic effect where the tolerance to stressors are lost, and would invoke precautionary management. 3D-plots were able to clearly identify directional shifts where the nature of the interaction changed from antagonistic to synergistic along increasing stressor gradients. For example, increased nitrogen load and exposure caused a shift from positive to negative effect on the abundance of a deposit-feeding polychaete (Magelona). Assessments relying on model coefficient estimates, which provide one effect term, could not capture the complexities observed in 3D-plots and are at risk of mis-identifying interaction types. Finally, visualising model uncertainty demonstrated that although error terms were higher for multiplicative models, they better captured the uncertainty caused by data availability. Together, the steep gradients of change identified in 3D-plots and the higher uncertainty in model predictions in multiplicative models urges more conservative limits to be set for management that account for risk and uncertainty in multiple stressor effects.
... Previous works have presented coupled process-based modeling and empirical models [86], random forest models [87], probabilistic ERA frameworks with prevalence plots [88] and others [89] to tackle the impact of multiple stressors in aquatic systems. The present work adds up to this by introducing an approach that, in addition to prioritizing stressors, also highlights the most sensitive trophic groups to the tested stressors and provides clues on how direct and indirect effects transfer across the food web. ...
Article
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Due to non-linear interactions, the effects of contaminant mixtures on aquatic ecosystems are difficult to assess, especially under temperature rise that will likely exacerbate the complexity of the responses. Yet, under the current climatic crisis, assessing the effects of water contaminants and temperature is paramount to understanding the biological impacts of mixtures of stressors on aquatic ecosystems. Here, we use an ecosystem model followed by global sensitivity analysis (GSA) to prioritize the effects of four single emerging contaminants (ECs) and their mixture, combined with two temperature rise scenarios, on the biomass production of a NE Atlantic estuary. Scenarios ran for 10 years with a time-step of 0.1 days. The results indicate that macroinvertebrate biomass was significantly explained by the effect of each single EC and by their mixture but not by temperature. Globally, the most adverse effects were induced by two ECs and by the mixture of the four ECs, although the sensitivity of macroinvertebrates to the tested scenarios differed. Overall, the present approach is useful to prioritize the effects of stressors and assess the sensitivity of the different trophic groups within food webs, which may be of relevance to support decision making linked to the sustainable management of estuaries and other aquatic systems.
... In relation with the interaction types, we found an overall prevalence of antagonisms over synergisms, which was consistent across four out of six of the most studied pairwise stressor combinations. These results are in line with previous freshwater meta-analyses (Birk et al., 2020;Jackson et al., 2016;Teichert et al., 2016;Manuel Villar-Argaiz et al., 2018) and contrast with the higher prevalence of synergisms found in marine ecosystems (Crain et al., 2008;Przeslawski et al., 2015;Manuel Villar-Argaiz et al., 2018). Disturbance regime, microevolutionary selection and the evolutionary abiotic context might explain the prevalence of antagonisms in freshwaters. ...
Article
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Freshwater ecosystems are exposed to an increasing number of stressors, challenging their biomonitoring and management. Despite recent advances in multiple-stressor research, regional-scale assessments in areas with high freshwater biodiversity and increasing anthropogenic pressure are urgently needed. We reviewed 61 studies focused on freshwater individuals, populations and communities from the Iberian Peninsula to (i) quantify the frequency of experimental approaches used (manipulative, observational), aquatic systems, biological organization levels, and types of organisms and modelled responses, (ii) identify key individual stressors and the frequency of significant positive (increase in response magnitude) and negative (decrease) effects and (iii) determine types of interacting stressors and the frequency of their combined effects. Our dataset comprised 409 unique responses to 13 types of individual stressors, 34 stressor pairs and 12 high-order interactions (3- and 4-way). We found a higher prevalence of manipulative (85 %) respect to observational studies, and a greater focus on lotic systems (59 %) and heterotrophic organisms (58 %). The most studied stressors were nutrient (Nutr), thermal (Therm), hydrologic (Hydr), ultraviolet radiation (UVR), toxic (Toxic) and salinity (Sal) stress and land-use pressure. Individual stressors showed a higher proportion of negative (34 %) than positive effects (26 %). Nutr × UVR, Toxic × Toxic, Therm × Toxic, Hydr × Toxic, Sal × Therm, and Nutr × Therm were the most studied stressor pairs. Non-interactive (50 %) and interactive responses (50 %) were balanced. Antagonistic effects (18 %) were slightly more common than synergisms (15 %), reversal or opposing (13 %) and high-order interactions (4 %). Such proportions varied within experimental approaches, biological organization levels and organism types. Our findings are helpful to manage certain stressor combinations in Iberian freshwaters. Further efforts in Iberian multiple-stressor research should be directed to (i) intensify the study of lentic systems, (ii) explore more observational data, (iii) autotrophic organisms and (vi) biodiversity-ecosystem functioning responses, and (v) cover a wider range of stressors and (vi) more complex interacting stressor scenarios.
... Further, driver strength can vary with time and its environmental context, and new drivers may emerge. For example, the impact of anthropogenic drivers such as nutrient pollution, overexploitation, and introduced species can vary in the presence of each other (Segner et al., 2014;Teichert et al., 2016), as well as due to mitigation efforts, human population shifts, and/or technological advances (Jenny et al., 2020). These considerations require accounting for a wide array of potential drivers at multiple timescales when seeking to understand how, when, and why ecosystems have varied through time. ...
Article
Understanding environmental driver-response relationships is critical to the implementation of effective ecosystem-based management. Ecosystems are often influenced by multiple drivers that operate on different timescales and may be nonstationary. In turn, contrasting views of ecosystem state and structure could arise depending on the temporal perspective of analysis. Further, assessment of multiple ecosystem components (e.g., biological indicators) may serve to identify different key drivers and connections. To explore how the timescale of analysis and data richness can influence the identification of driver-response relationships within a large, dynamic ecosystem, this study analyzed long-term (1969–2018) data from Lake Erie (USA–Canada). Data were compiled on multiple biological, physical, chemical, and socioeconomic components of the ecosystem to quantify trends and identify potential key drivers during multiple time intervals (20 to 50 years duration), using zooplankton, bird, and fish community metrics as indicators of ecosystem change. Concurrent temporal shifts of many variables occurred during the 1980s, but asynchronous dynamics were evident among indicator taxa. The strengths and rank orders of predictive drivers shifted among intervals and were sometimes taxon-specific. Drivers related to nutrient loading and lake trophic status were consistently strong predictors of temporal patterns for all indicators; however, within the longer intervals, measures of agricultural land use were the strongest predictors, whereas within shorter intervals, the stronger predictors were measures of tributary or in-lake nutrient concentrations. Physical drivers also tended to increase in predictive ability within shorter intervals. The results highlight how the time interval examined can filter influences of lower-frequency, slower drivers and higher-frequency, faster drivers. Understanding ecosystem change in support of ecosystem-based management requires consideration of both the temporal perspective of analysis and the chosen indicators, as both can influence which drivers are identified as most predictive of ecosystem trends at that timescale.
... Most human activities in the marine environment are concentrated around the coast. These, combined with coastal development, place pressures on coastal environments (Teichert et al., 2016). ...
Technical Report
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The known effects of marine sediment on New Zealand’s 87 seabird species and 47 shorebird species were discussed in this report. Knowledge gaps were also highlighted.
... Usually, methods for the calculation of the cumulative pressure effects integrate pressures without weighting the pressure effect (Ban et al., 2014;Korpinen et al., 2021). In other cases, weightings are applied to the sensitivity of the ecosystem components at risk (Halpern et al., 2015;Stelzenmüller et al., 2018;Galparsoro et al., 2021), but very few, if any, consider the additive, synergistic or antagonistic effects of multiple pressures in biodiversity importance risk (Piggott et al., 2015;Teichert et al., 2016), which are also not included in the double evaluation methodology. In this sense, the method in the Bay of Biscay could be adapted to provide a weighting factor for each human activity, based on its potential to impact the environment, as well as its temporal incidence (e.g., constant, punctual, concentrated in certain season, etc.). ...
Article
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The EMOD-PACE project, funded by the European Commission, aimed to promote international ocean governance between EU and China. One of the objectives of EMOD-PACE is to compare European and Chinese modelling approaches for ecosystem vulnerability assessment. In particular, our objective was to test the applicability of the Chinese evaluation approach of resource-environment carrying capacity (MRECC) and spatial development suitability (abbreviated as "double evaluation") to a European sea (the Bay of Biscay), in the context of marine spatial planning. The methodology involves three different steps: (i) an evaluation of areas of ecological importance, which includes species and habitats (i.e., biodiversity protection) and coastal characteristics; (ii) assessment of current marine development and utilization; and (iii) an ecological risk identification and the evaluation of the MRECC, by intersecting results from (i) and (ii). After collating information for 31 species of interest (fish, reptiles, mammals and birds), seven habitats (seagrass, seaweeds, saltmarshes, fish spawning areas, tidal flats, estuaries and unique habitats), marine protected areas and eight current human activities performed at sea (aquaculture, ports, ocean energy facilities, shipping, aggregate extraction and dredging, fisheries, military areas and tourism and recreation), they were aggregated and intersected (ecological data vs. human activities), and the ecological risk was determined. Since the total area covered by Marine Protected Areas and areas of high ecological importance is 135,372 km 2 , the available carrying capacity for development of marine activities within the Bay of Biscay is 229,266 km 2. When we apply weighting to the calculation of the ecological importance and human activities, the high importance areas increase and the available carrying capacity decreases by 0.2%, to 228,637 km 2. In this work we demonstrate that the Frontiers in Marine Science Chinese double evaluation approach can be adapted and applied to a European sea, but to obtain more accurate results, and more extensive application to different areas are needed. Also, we have identified essential improvements, including better information for a number of species and habitats; more robust methods to identify biodiversity priorities; additional fish life-story traits; include future human activities; risks posed by multiple activities; and use appropriate weights through a stakeholder consultation.
... After their planktonic stage, a large variety of marine fish and crustaceans settles in coastal and estuarine nurseries where shallow waters provide favourable growth conditions and shelter against large predators (Beck et al., 2001). However, these areas are subject to intense human modifications, including eutrophication, cattle grazing, urban development or harbour activities, which have caused dramatic changes in estuarine structure and functioning (Lafage et al., 2021;Lotze et al., 2006;Teichert et al., 2016a). For example, habitat loss and fragmentation remain a major threat for fish juveniles, particularly due to the erosion, and human induced vegetation shifts, of intertidal areas that provide shelter and food resources (Cattrijsse and Hampel, 2006;Laffaille et al., 2000;Teichert et al., 2018a). ...
Article
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Life-history trait expression not only depends on the current environmental constraints, but also on the past ones that shaped traits expressed earlier in life. Such an effect, named carry-over, can occur in fish nursery grounds when juvenile performances after settlement are influenced by their larval traits in combination with conditions experienced in nurseries. To date, the impacts of environmental and human stressors on post-settlement traits have been assessed, but independently from larval traits, so that the contributions of environmental versus carry-over constraints remain unquantified. Here, we used a reconstructive approach based on otolith microstructure to investigate how carry-over and environment affect life-history traits of the European seabass, Dicentrarchus labrax. In the northeast Atlantic Ocean, seabass juveniles were collected in six French estuarine nursery areas with contrasted environmental conditions (water temperature, salinity, food availability, and anthropogenic impacts), and five of their life-history traits across ontogenetic stages were measured (pelagic growth, larval duration, size at settlement, post-settlement growth and body condition). Piecewise structural equation model emphasized the strong co-variation of larval traits in response to food availability and temperature in the pelagic environment, stressing that fast growing larvae are characterized by shorter pelagic larval duration, but larger size at recruitment. However, the magnitude of carry-over effects greatly varied between traits, revealing that larval trait impacts on post-settlement traits remained minor as compared to the nursery environment. In estuarine nurseries, our findings suggest that resource allocation results from a trade-off between somatic growth and energy storage. Fish juveniles exposed to anthropogenic stress or risk of food limitation tended to predominantly invest in storage, whereas individuals in favourable conditions allocated their resources in somatic growth. These findings highlight the importance of heterogeneity in pelagic and nursery environments in understanding trait variations and population dynamic of estuarine dependent fish.
... In intensive aquaculture, farmed fish are frequently exposed to stressors such as crowding and handling, which influence health and welfare, and can threaten aquaculture sustainability [8,9]. In natural settings, fish populations are increasingly becoming subjected to multiple anthropogenic stressors, which threaten their sustainability [10][11][12]. Stress-mediated impairment of immune function has been widely described in cultured and wild fish, and is associated with an increased susceptibility to disease [13][14][15]. Mucosal immune response plays a crucial role in the course of the infection and includes healthy and dynamic microbial communities [16][17][18][19]. ...
Article
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Background The welfare of farmed fish is influenced by numerous environmental and management factors. Fish skin is an important site for immunity and a major route by which infections are acquired. The objective of this study was to characterize bacterial composition variability on skin of healthy, diseased, and recovered Gilthead Seabream (Sparus aurata) and Barramundi (Lates calcarifer). S. aurata, which are highly sensitive to gram-negative bacteria, were challenged with Vibrio harveyi. In addition, and to provide a wider range of infections, both fish species (S. aurata and L. calcarifer) were infected with gram-positive Streptococcus iniae, to compare the response of the highly sensitive L. calcarifer to that of the more resistant S. aurata. All experiments also compared microbial communities found on skin of fish reared in UV (a general practice used in aquaculture) and non-UV treated water tanks. Results Skin swab samples were taken from different areas of the fish (lateral lines, abdomen and gills) prior to controlled infection, and 24, 48 and 72 h, 5 days, one week and one-month post-infection. Fish skin microbial communities were determined using Illumina iSeq100 16S rDNA for bacterial sequencing. The results showed that naturally present bacterial composition is similar on all sampled fish skin sites prior to infection, but the controlled infections (T1 24 h post infection) altered the bacterial communities found on fish skin. Moreover, when the naturally occurring skin microbiota did not quickly recover, fish mortality was common following T1 (24 h post infection). We further confirmed the differences in bacterial communities found on skin and in the water of fish reared in non-UV and UV treated water under healthy and diseased conditions. Conclusions Our experimental findings shed light on the fish skin microbiota in relation to fish survival (in diseased and healthy conditions). The results can be harnessed to provide management tools for commercial fish farmers; predicting and preventing fish diseases can increase fish health, welfare, and enhance commercial fish yields.
Article
Human pressures on ecosystems from landscape transformation and harvesting can result in changes to body size and functional traits of affected species. However, these effects remain very poorly understood in many settings. Here we examine whether and how fishing and the attributes of coastal seascapes can operate in concert to change the body size and functional traits of the giant mud crab, Scylla serrata; a prized fisheries species. We captured 65 legal sized (> 15 cm carapace width) male giant mud crabs from 13 estuaries in southeast Queensland, Australia. These estuaries span a wide range of fishing and catchment landscape transformation intensity. We made a total of 9000 external morphometric measurements in the study. There was a distinct effect of estuarine landscape context on body size, with the largest individuals captured from systems with bigger inlets and lower extent of intertidal flats. Variation in functional traits was most often associated with variation in fishing pressure and human population size in the catchment. Crabs from areas with less commercial fishing pressure and lower human populations in the catchment had the largest chelipeds. We also found effects of urbanisation (negative correlations), intertidal flats (inconsistent effects) and mangrove extent (positive correlations) on the size of some functional traits. Our results show that human pressures can have sublethal effects on animals in estuaries that alter body size and functional traits. These phenotypic responses might have consequences for the fitness and ecological roles of targeted species, and the yields of fisheries catches.
Article
The catch of Corbicula japonica is one of the top three in Japan's inland water fisheries. Most of the Japanese fishing stock of this bivalve comes from Lake Shinji. Since the 1980's the catch of this species declined drastically with strong inter-annual variation. New recruitment and poor growth of the clams were thought to be the main reasons for this decline. This bivalve has a poor transportation ability after the settlement. Therefore, it is also important to know their suitable habit that is affected by multi interacting parameters of water qualities and sediments. In order to get a better understanding of their habitat, we used machine learning models to test abiotic limiting factors. The database that we used in our study included 337 sampling stations with 7 physicochemical variables and the Corbicula japonica counting which was divided into two size categories: small (shell length < 4 mm) and large (shell length ≥ 4 mm). Due to their low self-transportation ability, their survival is primarily influenced by the site environment, such as water quality and sediment conditions. To extract physicochemical thresholds that directly impact these clam populations, we applied a coupled methodology based on a random forest model and partial dependence plots. We highlighted that the use of three different populations groups for each size category, allowed us to significantly increase the accuracy of our model to predict groups. Moreover, our results show that the three most influential predictors were, in order of importance, the water depth, ignition loss of the bottom sediments and silt clay (diameter ≤ 0.063 mm) content of the bottom sediments; with, respectively, the following physicochemical limitations for the preferable habitat: 4 m, 10% and 45%. These limitations are based on the thresholds that we extracted from the coupling between a Random Forest model and the partial dependence plots. Our findings emphasize that this coupled methodology has the advantage of being able to manage the zero values of population and give graphical interpretation of the limiting environmental factors. Consequently, the results that we presented here clearly demonstrate a further step towards comprehension of the inter-annual variations in the fishery resources of Corbicula japonica after accounting for the impact of new recruitment. In addition, this kind of numerical tool could help the local government to manage the clam's population by restoring and conserving the water quality and sediment conditions of the lake.
Chapter
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Due to the high infection rate, lack of vaccine and cure, COVID-19 has affected most countries of the world. Nigeria Centre for Disease Control (NCDC) has done an excellent job of updating Nigerians on the reported cases and sensitising the populace on appropriate measures and precautions for self-protection. In this paper, the current and potential implications of COVID-19 on energy and environment research in Nigeria were discussed. The potential for positive environmental consequences of the lock-down due to the COVID-19 pandemic is highlighted. The paper expressed scepticism on the long-term positive environmental implications of the pandemic. For research in energy and environment, there is lack of access to labs, psychological hindrance of working from homes, lack of stable electricity and internet connections at homes. This is a call to indigenous researchers in energy and environment research to embrace the opportunities in process modelling and simulations to advance their research.
Chapter
Estuarine ecosystems are important habitats for many fish species. Large-scale patterns of estuarine fish communities can be affected by geographical factors, such as water temperature and latitude, which either limit or allow fish dispersal, and/or by environmental factors that select locally adapted species. Furthermore, increased human activity has also altered fish diversity through the modification of estuarine environments. In this study, we used environmental DNA metabarcoding to study a large-scale pattern of estuarine fish communities across 26 watersheds in the Japanese Archipelago, and assessed the effects of geographical, environmental, and anthropogenic factors in structuring these communities. Of the 197 fish species detected, 40 species were red-listed by the Japanese Ministry of Environment and seven were alien. Non-metric multidimensional scaling showed that both latitude and water temperature affected river mouth fish communities. Although other anthropogenic factors were not found to affect these communities, the bank artificialization rate was influenced. Furthermore, the relationship between the fish community and ocean currents was weak. The number of red-listed fish affected fish community structures, whereas that of alien species did not. The numbers of red-listed fish were negatively correlated with the bank artificialization rate and the rate of tetrapod formation. These findings provide useful information that may be used to conserve estuarine ecosystems.
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a b s t r a c t We present a modelling framework that combines machine learning techniques and Geographic Infor-mation Systems to support the management of an important aquaculture species, Manila clam (Ruditapes philippinarum). We use the Venice lagoon (Italy), the first site in Europe for the production of R. philip-pinarum, to illustrate the potential of this modelling approach. To investigate the relationship between the yield of R. philippinarum and a set of environmental factors, we used a Random Forest (RF) algo-rithm. The RF model was tuned with a large data set (n = 1698) and validated by an independent data set (n = 841). Overall, the model provided good predictions of site-specific yields and the analysis of marginal effect of predictors showed substantial agreement among the modelled responses and available ecolog-ical knowledge for R. philippinarum. The most influent environmental factors for yield estimation were percentage of sand in the sediment, salinity, and water depth. Our results agree with findings from other North Adriatic lagoons. The application of the fitted RF model to continuous maps of all the environmen-tal variables allowed estimates of the potential yield for the whole basin. Such a spatial representation enabled site-specific estimates of yield in different farming areas within the lagoon. We present a pos-sible management application of our model by estimating the potential yield under the current farming distribution and comparing it to a proposed re-organization of the farming areas. Our analysis suggests a reduction of total yield is likely to result from the proposed re-organization.
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Many services provided by coastal and marine ecosystems are in decline. Awareness of these declines and the need to improve existing management has led to a shift toward ecosystem-based approaches to marine management and conservation, both in the US and elsewhere. Marine ecosystem-based management (EBM) involves recognizing and addressing interactions among different spatial and temporal scales, within and among ecological and social systems, and among stakeholder groups and communities interested in the health and stewardship of coastal and marine areas. We discuss some overarching principles of marine EBM and highlight key challenges facing implementation. We then recommend ways in which natural and social scientists can advance implementation of ecosystem-based approaches in the oceans by addressing key research needs, building interdisciplinary scientific capacity, and synthesizing and communicating scientific knowledge to policy makers, managers, and other stakeholders.
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Large, S. I., Fay, G., Friedland, K. D., and Link, J. S. 2013. Defining trends and thresholds in responses of ecological indicators to fishing and environmental pressures. – ICES Journal of Marine Science, 70: 755–767. Both fishing and environmental forces can influence the structure of marine ecosystems. To further understand marine ecosystems and to implement ecosystem-based fisheries management (EBFM), an evaluation of ecosystem indicators is warranted. In this context, it is particularly important to identify thresholds where fishing and environmental pressures significantly influence ecological indicators. We empirically determined numerical values of environmental forces and fishing pressure that significantly altered the response of ecological indicators for the Northeast Shelf Large Marine Ecosystem. Generalized additive models predicted a non-linear relationship for each pressure–response pairing. With this smoother, 95% confidence intervals (CI) for estimated first and second derivatives for each relationship were determined via parametric bootstrap. A significant trend or threshold was noted when the CI for the first or second derivative was greater or less than zero, delineating the level at which pressure variables influence the rate and direction of ecosystem indicator responses. We identify reference levels where environmental forces and fishing pressure result in ecosystem change by collectively examining the responses of multiple ecological indicators. Individual indicators showed unique responses to pressures, however, similar values for the pressures were associated with significant changes for multiple indicators. These reference levels establish a foundation for implementation of EBFM.
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The ability to understand and ultimately predict ecosystem response to multiple pressures is paramount to successfully implement ecosystem-based management. Thresholds shifts and nonlinear patterns in ecosystem responses can be used to determine reference points that identify levels of a pressure that may drastically alter ecosystem status, which can inform management action. However, quantifying ecosystem reference points has proven elusive due in large part to the multi-dimensional nature of both ecosystem pressures and ecosystem responses. We used ecological indicators, synthetic measures of ecosystem status and functioning, to enumerate important ecosystem attributes and to reduce the complexity of the Northeast Shelf Large Marine Ecosystem (NES LME). Random forests were used to quantify the importance of four environmental and four anthropogenic pressure variables to the value of ecological indicators, and to quantify shifts in aggregate ecological indicator response along pressure gradients. Anthropogenic pressure variables were critical defining features and were able to predict an average of 8-13% (up to 25-66% for individual ecological indicators) of the variation in ecological indicator values, whereas environmental pressures were able to predict an average of 1-5 % (up to 9-26% for individual ecological indicators) of ecological indicator variation. Each pressure variable predicted a different suite of ecological indicator's variation and the shapes of ecological indicator responses along pressure gradients were generally nonlinear. Threshold shifts in ecosystem response to exploitation, the most important pressure variable, occurred when commercial landings were 20 and 60% of total surveyed biomass. Although present, threshold shifts in ecosystem response to environmental pressures were much less important, which suggests that anthropogenic pressures have significantly altered the ecosystem structure and functioning of the NES LME. Gradient response curves provide ecologically informed transformations of pressure variables to explain patterns of ecosystem structure and functioning. By concurrently identifying thresholds for a suite of ecological indicator responses to multiple pressures, we demonstrate that ecosystem reference points can be evaluated and used to support ecosystem-based management.
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The potential for complex synergistic or antagonistic interactions between multiple stressors presents one of the largest uncertainties when predicting ecological change but, despite common use of the terms in the scientific literature, a consensus on their operational definition is still lacking. The identification of synergism or antagonism is generally straightforward when stressors operate in the same direction, but if individual stressor effects oppose each other, the definition of synergism is paradoxical because what is synergistic to one stressor's effect direction is antagonistic to the others. In their highly cited meta-analysis, Crain et al. (Ecology Letters, 11, 2008: 1304) assumed in situations with opposing individual effects that synergy only occurs when the cumulative effect is more negative than the additive sum of the opposing individual effects. We argue against this and propose a new systematic classification based on an additive effects model that combines the magnitude and response direction of the cumulative effect and the interaction effect. A new class of “mitigating synergism” is identified, where cumulative effects are reversed and enhanced. We applied our directional classification to the dataset compiled by Crain et al. (Ecology Letters, 11, 2008: 1304) to determine the prevalence of synergistic, antagonistic, and additive interactions. Compared to their original analysis, we report differences in the representation of interaction classes by interaction type and we document examples of mitigating synergism, highlighting the importance of incorporating individual stressor effect directions in the determination of synergisms and antagonisms. This is particularly pertinent given a general bias in ecology toward investigating and reporting adverse multiple stressor effects (double negative). We emphasize the need for reconsideration by the ecological community of the interpretation of synergism and antagonism in situations where individual stressor effects oppose each other or where cumulative effects are reversed and enhanced.
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1. Introduction Aquatic biological standards, established in law, can be an effective mechanism to promote restoration and ensure the ecological sustainability of aquatic resources (Adler, 2003; Hering et al., 2010). Several countries around the world have established legislation or policies to promote the restoration and maintenance of aquatic ecosystems (CWA, 2006; ANZECC, 2000; EC, 2000). However, the effectiveness of such policy initiatives depends upon the technical clarity of ecological goal statements, and the political clarity of intent that is written into the law. The United States Clean Water Act, for example, states a long-term, national objective to ''restore and maintain the . . . biological integrity of the Nation's waters'' (section 1251). However, the Act does not define the ecological components, or attributes, that constitute biological integrity. Neither does the Act recommend scientific methods to measure the condition of aquatic biota. Rather, the U.S. Clean Water Act delegates the technical implementation of the
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There is an increasing need in assessing ecological quality and integrity of estuaries and lagoons. This chapter shows the most recent efforts in assessing individual biological elements (from phytoplankton to fishes), together with the integrative tools developed in different geographical areas worldwide. However, reducing complex information from multiple ecosystem elements to a single color or value is a substantial challenge to marine scientists, and requires the integration of different disciplines (chemists, engineers, biologists, ecologists, physics, managers, etc.), to reach agreement on the final assignment of ecological status. Hence, in the near future, emphasis needs to be directed at understanding the complexities of estuarine system functioning rather than simplifying and scaling down the system into smaller components.
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Following widespread deterioration of coastal ecosystems since the 1960s, current environmental policies demand ecosystem recovery and restoration. However, vague definitions of recovery and untested recovery paradigms complicate efficient stewardship of coastal ecosystems. We critically examine definitions of recovery and identify and test the implicit paradigms against well-documented cases studies based on a literature review. The study highlights a need for more careful specification of recovery targets and metrics for assessing recovery in individual ecosystems. Six recovery paradigms were identified and examination of them established that partial (as opposed to full) recovery prevails, that degradation and recovery typically follow different pathways as buffers act to maintain the degraded state, and that recovery trajectories depend on the nature of the pressure as well as the connectivity of ecosystems and can differ between ecosystem components and among ecosystems. A conceptual model illustrates the findings and also indicates how restoration efforts may accelerate the recovery process.
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There is increasing interest in the resilience of marine and estuarine populations, communities and ecosystems, and their rapid change when stresses reach some threshold or tipping point. Current research on thresholds is altering our understanding of these systems, the processes by which they change, and our approach to their management and restoration. In this Theme Section conceptual, modeling, and empirical studies explore threshold dynamics in marine coastal systems in a variety of habitats and across different scales. The contributions provide a window on present research, highlight some of the issues being debated, and point to some of the potential applications of threshold dynamics to resource management issues.
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Many services provided by coastal and marine ecosystems are in decline. Awareness of these declines and the need to improve existing management has led to a shift toward ecosystem-based approaches to marine management and conservation, both in the US and elsewhere. Marine ecosystem-based management (EBM) involves recognizing and addressing interactions among different spatial and temporal scales, within and among ecological and social systems, and among stakeholder groups and communities interested in the health and stewardship of coastal and marine areas. We discuss some overarching principles of marine EBM and highlight key challenges facing implementation. We then recommend ways in which natural and social scientists can advance implementation of ecosystem-based approaches in the oceans by addressing key research needs, building interdisciplinary scientific capacity, and synthesizing and communicating scientific knowledge to policy makers, managers, and other stakeholders.
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Conservation of aquatic resources requires management of both fishing effort and the mosaic of habitats used by nekton that sustain fisheries production. Within this context, “environment” is viewed as the sum of die abiotic and biotic surroundings, including habitat and other organisms, whereas, “habitat” is viewed as the localized structured component that acts as a template of organization and attractor for nekton. Although there is much debate, it is generally believed that nekton survival depends upon approaching their physiological optima first and then behaviorally searching out the appropriate life-stage-dependent habitat. Deviation from die optimal environment increases mortality and/or decreases production. This conceptual view possesses both dynamic (physical-chemical) and stationary (structural) components. Young estuarine-dependent nekton respond hierarchically to environmental conditions which will “deliver” them into the optimal nursery zones within the landscape leading to higher survival, growth, and production. Variability in climatic conditions coupled with large-scale El Niño-Southern Oscillation (ENSO)/LaNiña events influence recruitment and can shift the position of the dynamic component such that it either does not overlap the stationary component or does so infrequently and only to a small degree. Under these conditions, habitat is considered a limiting factor when these two components are spatially/temporally uncoupled or when access to the structural component is lost due to development or other anthropogenic impacts. For example, habitat alteration due to bulkheading/filling eliminates or reduces access to intertidal salt marshes, which are vital to estuarine ecosystem processes. Additionally, these anthropogenic activities also lead to habitat fragmentation, a change in the spatial arrangement of important habitats along the estuarine axis, and potentially to shifts in the source/sink balance of the estuary. These changes can alter ecosystem health, dynamics, and ultimately productivity. Understanding linkages between these components of the environment is important to aquatic management. The focus of this article is to present a conceptual model that links the environment-habitat mosaic with production, and to illustrate the impact of habitat loss on estuarine productivity. This approach is valuable for 1) predicting the outcome of perturbations, 2) development of a better understanding of the linkages between components of the environment, and 3) providing a basis for future research using a more holistic approach.
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Global stressors, including climate change, are a major threat to ecosystems, but they cannot be halted by local actions. Ecosystem management is thus attempting to compensate for the impacts of global stressors by reducing local stressors, such as overfishing. This approach assumes that stressors interact additively or synergistically, whereby the combined effect of two stressors is at least the sum of their isolated effects. It is not clear, however, how management should proceed for antagonistic interactions among stressors, where multiple stressors do not have an additive or greater impact. Research to date has focussed on identifying synergisms among stressors, but antagonisms may be just as common. We examined the effectiveness of management when faced with different types of interactions in two systems - seagrass and fish communities - where the global stressor was climate change but the local stressors were different. When there were synergisms, mitigating local stressors delivered greater gains, whereas when there were antagonisms, management of local stressors was ineffective or even degraded ecosystems. These results suggest that reducing a local stressor can compensate for climate change impacts if there is a synergistic interaction. Conversely, if there is an antagonistic interaction, management of local stressors will have the greatest benefits in areas of refuge from climate change. A balanced research agenda, investigating both antagonistic and synergistic interaction types, is needed to inform management priorities.