Article

Rapid biogeographical plankton shifts in the North Atlantic Ocean

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Abstract

Large-scale biogeographical changes in the biodiversity of a key zooplankton group (calanoid copepods) were detected in the north-eastern part of the North Atlantic Ocean and its adjacent seas over the period 1960–1999. These findings provided key empirical evidence for climate change impacts on marine ecosystems at the regional to oceanic scale. Since 1999, global temperatures have continued to rise in the region. Here, we extend the analysis to the period 1958–2005 using all calanoid copepod species assemblages (nine species assemblages based on an analysis including a total of 108 calanoid species or taxa) and show that this phenomenon has been reinforced in all regions. Our study reveals that the biodiversity of calanoid copepods are responding quickly to sea surface temperature (SST) rise by moving geographically northward at a rapid rate up to about 23.16 km yr−1. Our analysis suggests that nearly half of the increase in sea temperature in the northeast Atlantic and adjacent seas is related to global temperature rises (46.35% of the total variance of temperature) while changes in both natural modes of atmospheric and oceanic circulation explain 26.45% of the total variance of temperature. Although some SST isotherms have moved northwards by an average rate of up to 21.75 km yr−1 (e.g. the North Sea), their movement cannot fully quantify all species assemblage shifts. Furthermore, the observed rates of biogeographical movements are far greater than those observed in the terrestrial realm. Here, we discuss the processes that may explain such a discrepancy and suggest that the differences are mainly explained by the fluid nature of the pelagic domain, the life cycle of the zooplankton and the lesser anthropogenic influence (e.g. exploitation, habitat fragmentation) on these organisms. We also hypothesize that despite changes in the path and intensity of the oceanic currents that may modify quickly and greatly pelagic zooplankton species, these organisms may reflect better the current impact of climate warming on ecosystems as terrestrial organisms are likely to significantly lag the current impact of climate change.

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... an has been absorbing a large part of the surplus heat added to the climate system (Figure 1.8). This gradual uptake of heat could translate into sudden and stepwise shifts in marine ecosystems instead of gradual change over the years, due to the thermal thresholds in the marine environment that often manifest themselves as abrupt ecosystem shifts (Beaugrand et. al., 2009). Over 99 % of all organisms on Earth are ectothermic, making them susceptible to fluctuations of temperature, and hence, to global warming (Atkinson, 1994). Temperature is assumed to be a basic factor, ruling the physical environment (e.g. viscosity), limiting physiological processes (e.g. oxygen delivery within the organism) and bioche ...
... physiological processes (e.g. oxygen delivery within the organism) and biochemical reactions (e.g. enzyme activity), and finally determining growth and developmental rates of living organisms (Richardson, 2008). Temperature also has a substantial impact, directly and indirectly, on species interactions such as competition, predation and mutualism (Beaugrand et. al., 2009;Kordas et. al., 2011). A shift in temperature, either on a latitudinal or a seasonal scale, can modify these interactions between species and result in a changed ecosystem composition (Halsband-Lenk et. al., 2002). From a food web point of view, primary production by the smallest plankton is expected to increase in the warmer waters, but ...
... As a consequence, temperature often has striking impacts on virtually all life processes from a molecular scale to the entire pelagic ecosystem scale and from plankton to higher trophic levels (Beaugrand and Kirby, 2010;Beaugrand et al., 2009). ...
Thesis
Oceans and seas are often perceived as the last wilderness on the planet. However, anthropogenic actions are already impacting these ecosystems, ranging from the coasts and the sea surface to the open ocean and the deep sea floor. Marine ecosystems are currently affected by multiple human activities, such as eutrophication, overfishing, the introduction of non-indigenous species, the contamination by hazardous chemicals and (micro)plastics, etc., in addition to climate change, leading to impaired environmental conditions. Evidence is growing that these changing environmental conditions have negative effects on the biodiversity and functioning of marine food webs. Due to their rapid responses to environmental variation, planktonic organisms are used as bio-indicators of ecosystem changes. With the need for better understanding the impact of a changing environment on zooplankton communities, zooplankton monitoring programs have been carried out in the marine environment globally since the early 20th century. Most zooplankton monitoring studies focus mainly on variability in biodiversity and biomass. However, this approach is hindered by challenges in the identification, which is time-consuming, complicated and requires biological expertise. A combination of new technologies and techniques, together with classical in situ and laboratory studies, could improve our understanding of such biodiversity patterns by assessing the health and physiology of marine plankton. In this thesis, we aimed to apply molecular methods to investigate spatiotemporal patterns in zooplankton dynamics, as well as to investigate the influence of environmental variation and stressors on these dynamics.
... L'augmentation de la concentration atmosphérique de ce gaz à effet de serre est fortement corrélée à l'augmentation des températures atmosphériques (Thomson, 1997). Cette hausse des températures se répercute également en milieu océanique (Beaugrand, 2009, Figure 4), engendrant notamment le ralentissement de la circulation méridienne de retournement (Zickfeld et al., 2007) et le phénomène d'acidification des océans (Cao et al., 2007). Le réchauffement et l'acidification des océans, la diminution de la concentration en oxygène dissous, et les variations de l'approvisionnement en nutriments se répercutent déjà sur la répartition et l'abondance de la faune et de la flore marines dans les zones côtières, en haute mer, et dans les profondeurs océaniques (IPCC, 2019). ...
... De plus, dans la région de la mer de Bellingshausen et de la péninsule Antarctique, la période d'eau libre a augmenté de trois mois en 2010-2011 comparé à 1979-1980 ; tandis que la durée de la période d'eau libre a diminué de plus de deux mois dans la partie ouest de la mer de Ross (Stammerjohn et al., 2012). Source : Beaugrand, 2009. ...
... Global change triggers extensive abiotic modifications in the ecosystems, impacting a broad range of species (Beaugrand, 2015;Sequeira et al., 2019a). In the oceans, current and predicted non-exhaustively modifications include eutrophication (Vasas et al., 2007), acidification (Cao et al., 2007), rising temperatures (Beaugrand, 2009) and a change in the meridional overturning circulation (Zickfeld et al., 2007). Polar ecosystems are especially vulnerable (Clarke et al., 2007;Constable et al., 2014;Parkinson, 2004), with some substantial consistent changes occurring in the Arctic (Comiso et al., 2008;Johannessen et al., 2004;Lewis et al., 2020;Nghiem et al., 2007), and modifications with contrasted trends occurring in the remote Southern Ocean (Holland et al., 2019;Stammerjohn et al., 2012;Turner et al., 2015). ...
Thesis
Because time-series relative to foraging ecology, environmental parameters and population trends are scarce, few studies focused on the mechanisms linking oceanographic variables with the foraging behaviour and breeding success in marine top predators. This PhD thesis aims to assess the effects of inter-annual environmental conditions and individual strategies on the foraging ecology and breeding success of the southern elephant seal (Mirounga leonina), a key species of the Southern Ocean. The simultaneous analysis of stable isotopes and tracking-diving time-series highlighted that the foraging habitats, as well as the diving- and foraging behaviour of female seals, remained stable over the last fourteen years. This thesis also revealed a consistency in the utilization proportion of the Antarctic and sub-Antarctic foraging habitats. The body condition of female seals tend to improve less when they exploit the latter habitat, and the corresponding weaning mass of their pups, considered as a proxy of the breeding success, was globaly higher but tended to decrease over the study period. A difference in habitat quality was detected between the areas located east and west of the Kerguelen archipelago, with the area located west providing higher foraging and breeding success. Moreover, a structuration in foraging habitat and breeding success was highlighted between two colonies (i.e. breeding sites) located at Kerguelen Island. Despite consistency in the behaviour of female seals, an overall improvement in body condition was assessed over the study period. Combined with a global decrease in δ13C values, this result suggests that some modifications are occurring in the food webs of the Southern Ocean.
... De plus, dans la région de la mer de Bellingshausen et de la péninsule Antarctique, la période d'eau libre a augmenté de trois mois en 2010-2011 comparé à 1979-1980 ; tandis que la durée de la période d'eau libre a diminué de plus de deux mois dans la partie ouest de la mer de Ross (Stammerjohn et al., 2012). Source : Beaugrand, 2009. Les séries temporelles de données existantes, couplées à divers scénarios prédictifs, ont permis d'estimer que l'océan Austral est susceptible de subir de nombreux changements au cours des prochaines décennies (voir Constable et al., 2014 pour une synthèse bibliographique ; Figure 5). ...
... Global change triggers extensive abiotic modifications in the ecosystems, impacting a broad range of species (Beaugrand, 2015;Sequeira et al., 2019a). In the oceans, current and predicted non-exhaustively modifications include eutrophication (Vasas et al., 2007), acidification (Cao et al., 2007), rising temperatures (Beaugrand, 2009) and a change in the meridional overturning circulation (Zickfeld et al., 2007). Polar ecosystems are especially vulnerable (Clarke et al., 2007;Constable et al., 2014;Parkinson, 2004), with some substantial consistent changes occurring in the Arctic (Comiso et al., 2008;Johannessen et al., 2004;Lewis et al., 2020;Nghiem et al., 2007), and modifications with contrasted trends occurring in the remote Southern Ocean (Holland et al., 2019;Stammerjohn et al., 2012;Turner et al., 2015). ...
... Ce phénomène pourrait avoir des répercussions importantes sur la population d'éléphants de mer de l'archipel de Kerguelen, mais l'analyse d'une plus longue série temporelle est nécessaire afin de déterminer si la tendance détectée persiste. En effet, des résultats contradictoires avaient été obtenus au cours d'une étude couvrant la période2006-2009 (Authier et al., 2012b, mais il est à noter qu'au-delà des différentes périodes d'étude considérées, les modèles de mélange de l'étude citée ont été réalisés sur la masse au sevrage des jeunes, tandis que le modèle de mélange élaboré dans les présents travaux a été appliqué aux valeurs de δ 13 C. De plus, c'est le succès reproducteur d'une femelle à l'échelle de son existence (« lifetime reproductive success »), et donc l'ensemble de ses évènements de reproduction, qui déterminera la persistance d'une stratégie au sein de la population.La masse au sevrage est susceptible d'impacter la dynamique de population, au travers du recrutement au sein de la population reproductrice, vers l'âge de quatre ans(Clausius et al., 2017a;McMahon et al., 2017). Cependant, 40 à 60% des jeunes meurent au cours de leur premier voyage en mer(Cox et al., 2020), et plus que la masse au sevrage, la survie individuelle(McMahon et al., 2000b) est un facteur clé impactant le recrutement des ...
Thesis
En raison du manque de séries temporelles associant écologie en mer, paramètres océanographiques, et trajectoires démographiques, peu d’études se sont intéressées aux mécanismes reliant conditions océanographiques, succès alimentaire à l’échelle des trajets en mer, et succès reproducteur associé chez des prédateurs marins. Le présent travail de thèse propose de déterminer l’effet de la variabilité interannuelle des paramètres environnementaux, ainsi que des stratégies alimentaires individuelles, sur l’écologie alimentaire et le succès reproducteur d’une espèce emblématique de l’océan Austral : l’éléphant de mer du sud (Mirounga leonina). Grâce à l’étude de séries temporelles d’isotopes stables du carbone et de l’azote, ainsi que de données de télémétrie, cette thèse a mis en évidence que les zones d’alimentation, ainsi que le comportement de plongée et de recherche alimentaire de femelles éléphants de mer, ont très peu évolué au cours des quatorze dernières années. Cette thèse a également révélé une relative stabilité des stratégies alimentaires antarctique et subantarctique, et que la condition corporelle des femelles se nourrissant en zone subantarctique tend à diminuer au cours du temps, tout comme la masse au sevrage de leurs jeunes, considérée comme un proxy du succès reproducteur. Une différence de qualité entre les habitats situés de part et d’autre de l’archipel de Kerguelen a également été mise en évidence, révélant que l’habitat situé à l’ouest de l’archipel semble plus profitable aux femelles éléphants de mer en termes de succès alimentaire. En outre, une structuration des stratégies d’approvisionnement a été mise en évidence entre deux sites d’étude localisés sur l’archipel de Kerguelen. Malgré une constance du comportement des éléphants de mer, une augmentation globale de leur condition corporelle a été mise en évidence au cours de la période d’étude, qui, cumulée à une diminution continue de la signature isotopique en δ13C, suggère que des changements non négligeables sont en train d’opérer au sein des réseaux trophiques de l’océan Austral.
... It is now widely acknowledged that there was a period of hydroclimatic change during the twentieth century, manifested in significantly higher sea surface temperatures, which dramatically altered planktonic ecosystems in the Northeast Atlantic (Beaugrand, 2004;Edwards et al., 2006;Philippart et al., 2011;Nohe et al., 2020). This warming of the oceans has continued, and in only 40 years, there has been a significant shift in plankton and fish communities (Beaugrand et al., 2002(Beaugrand et al., , 2009Choquet et al., 2017;Nohe et al., 2020). By the end of the twenty-first century, the Intergovernmental Panel on Climate Change (IPCC) climate projections indicate a mean increase in the sea surface temperature of between 0.73 °C to 2.58 °C (IPCC, 2019). ...
... Temperature has been linked to the abundance and geographical distribution of Calanus spp in the North Atlantic (Barnard et al., 2004;Bonnett et al., 2005;Choquet et al., 2017). Thus, as regions warm or cool, we can expect dramatic changes in the abundance and dominance of different copepod species (Beaugrand et al., 2002(Beaugrand et al., , 2009Richardson & Schoeman 2004;Choquet et al., 2017;. ...
... (Dutz, 1998;Collumb & Buskey, 2004;Prince et al., 2006;Costa et al., 2008). Therefore, in Chapter 4, adult female A. tonsa were exposed to (Beaugrand et al., 2002(Beaugrand et al., , 2009Beaugrand, 2012;Chivers et al., 2017;Murphy et al., 2020), and evidence of how climate change affects planktonic species is growing, particularly in terms of increased ocean temperature and ocean acidification (George & Harris, 1985;Costello et al., 2006;Edwards et al., 2006;Mayor et al., 2007Mayor et al., , 2012Cripps et al., 2014). Direct effects of warming and acidification to copepods include changes in physiology and behavior that can alter growth (McFeeters & Frost, 2011;Doan et al., 2019), body size (Escribano & Mclaren, 1992;Garzke et al., 2015;Sommer et al., 2016), reproductive output Mayor et al., 2012;Weydmann et al., 2012), naupliar development , and survival (Sommer et al., 2007;Kroeker et al., 2010;Cripps et al., 2015). ...
Thesis
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Copepods form an important link between phytoplankton and higher trophic levels. Several species of phytoplankton, including dinoflagellates of the genus Alexandrium, produce neurotoxins commonly known as paralytic shellfish toxins (PSTs). The toxins from harmful algae (HA) may impact copepod survival, eeding, and fitness by acting as a feeding deterrent and/or by causing physical incapacitation. However, copepods may be able to overcome these toxic effects and/or become tolerant to toxicity by partial metabolism. Published information on how HA affect survival, feeding and other physiological processes in opepods are difficult to compare due to the different concentrations of HA used as food, the level of toxins in the food, and the various responses measured on different copepod species from different locations. Very few experiments have examined how HA toxins influence the survival, feeding and fecundity of copepods within UK waters. This thesis aims to address this knowledge gap whilst also choosing organisms of wider geographical relevance. This study examined the effects of a toxin-producing dinoflagellate, Alexandrium catenella, on two physiologically different copepods: Acartia tonsa, a pelagic coastal copepod that is found in the UK and other coastal waters including Northern & Southern America and Australia, and Calanus helgolandicus, which is spread across the North East Atlantic with high numbers on the European shelf and in oceanic waters. In Chapter 3, short-term (24 h) survival and feeding experiments revealed that adult female A. tonsa can survive exposure to field-recorded bloom concentrations of toxic A. catenella. Survival only decreased when exposure levels exceed reported environmental concentrations by two orders of magnitude. The lethal median concentration (LC50) was 12.45 ng STX eq L−1. Ingestion rates were higher when offered A. catenella in the absence of alternative prey, potentially suggesting compensatory feeding. A. tonsa actively selected non-toxic Rhodomonas sp. over toxic A. catenella when offered a mixed diet. Chapter 4 demonstrated that the survival of female A. tonsa is not affected by prolonged (10 days) exposure to toxic A. catenella. However, additional feeding and egg production experiments suggested that whilst A. tonsa can obtain enough energy from ingesting toxic A. catenella to survive, it suffers reproductive impairment when feeding on this prey alone. In Chapter 5, C. helgolandicus showed a decrease in feeding rate when feeding on toxic A. catenella compared to when feeding on the non-toxic congener, Alexandrium tamarense. On the other hand, the egg production and hatching success rates were not affected by the relative abundance of toxic A. catenella and non-toxic A. tamarense in diet, suggesting they may have used biomass reserves to sustain egg production. Body toxin analysis of C. helgolandicus showed they may bioaccumulate toxins in their bodies; however, the retention efficiency was very low. Full toxin profiles for A. catenella, including 8 to 12 PSTs, are presented in all experiments. This study furthers our understanding of PST-producing HA-copepod interactions, and how they may be affected by the increased frequency and magnitude of HA blooms.
... In the north-east Pacific, there is a decrease in zooplankton community abundance during warm events, and a change from communities dominated by cool-water indicator species towards warm-water indicative communities, extending the range of these species poleward. The large carrying capacity of boundary currents means that warm-water species are carried rapidly into environments where previously their survival would not have been possible, with cool-water associated species displaced even further north (Gregory et al., 2009) or moving deeper into the water-column (Richardson, 2008). This snap-shot study on the effects of an extreme rise of temperature should encourage further analysis of the dynamics of Southern Hemisphere zooplankton population responses to warming, and the bottom-up controls this variability is likely to exert on higher-trophic levels. ...
... Due to the known influence of temperature on the distribution of plankton (Richardson, 2008;Gregory et al., 2009), the four response variables were modelled against temperature using univariate linear models. Following this, full models were constructed using a broader suite of environmental variables that characterised the oceanography of the region. ...
Thesis
The land-sea interface provides some of the world’s most valuable and biodiverse habitats, despite being exposed to anthropogenic pressures. Marine predators which cross this interface are particularly vulnerable, with human activities in coastal zones diminishing both the quality and availability of suitable breeding and foraging areas. These predators are constrained to forage in smaller oceanic regions while rearing young on-land, therefore their reproductive success is intrinsically linked to the productivity of nearshore waters. Changing environmental conditions, as a direct and indirect consequence of climate change, can alter the structure, distribution and community composition of lower-trophic level prey. In order to predict the response of ecosystems to this change, and to changes as a result of extreme events such as marine heatwaves (MHW), an in depth understanding of the links between environmental factors, prey-field dynamics and predator behaviour is needed. The continental shelf to the south-east of Tasmania is a hotspot of biodiversity, where seasonal productivity supports a large and diverse array of marine birds and mammals. However, this region is also subject to rapid environmental change, being situated within the south-east Australian climatic-hotspot. Due to the intensification and increasing southward penetration of the East Australian Current (EAC), a major western boundary current running from the sub-tropical Coral Sea to the south-east coast of Australia, warming is occurring at an accelerated rate. Quantifying how prey-field dynamics respond to these changing environmental conditions, and the flow-on effects to the behaviour of apex predators, formed the main objective of this study. Surveys were conducted over a three-year period (2015-2018), during which a prolonged marine heatwave (MHW) event occurred that increased water temperatures of the entire western Tasman Sea by a mean of 2.9°C above climatology for 251 days. To develop an integrated understanding of ecosystem dynamics through a period of high environmental variability, zooplankton prey-field dynamics, fish school presence, little penguin (Eudyptula minor) foraging behaviour, and the distribution and abundance of key bird species were analysed in relation to local environmental factors. Zooplankton community composition and abundance were examined in relation to environmental drivers. Generalised additive models (GAMs) indicated a significant decrease in community abundance during the MHW, with a shift in species assemblages away from temperate species and towards EAC-associated species. The size structure of the zooplankton community was also analysed using the normalised biomass size spectra (NBSS). The NBSS is an effective way to demonstrate the variability present in a community, in terms of gains and loss of energy through respiration, predation and mortality. It can also be indicative of changes to the equilibrium of a community. Strong seasonality was detected in the results, with temperature, current velocity and mixed-layer depth being significant drivers of variability in the NBSS. These lower trophic level dynamics were linked to the behaviour of top predators through a detailed case study of the at-sea habitat preference of little penguins breeding in south-east Tasmania (n=13). Tracking was conducted over two summer periods, in 2016 during the MHW, and in 2018 under cooler and more stable environmental conditions. Habitat models (species distribution models) were developed to asses spatial distribution patterns and examine the bio-physical factors influencing foraging trips at fine-scale. Regions of higher sea-surface temperature gradients and cooler than average temperatures were found to increase the probability of penguin presence. The predictability of little penguin habitat-use according to prey-type was also assessed by including covariates for the general distribution of resources in the region; e.g. total zooplankton abundance, and the abundance of Australian krill (Nyctiphanes australis), which forms part of little penguin diet. Little penguin foraging areas were more influenced by the distribution of Australian krill than by general zooplankton abundance. The response of local predators to changes in bio-physical parameters were measured by modelling the distribution of 10 species of seabirds using boosted regression trees. Key species ranged from small planktivores, such as the common diving petrel (Pelecanoides urinatrix), to albatross (family Diomedeidae). Therefore, to encompass the range of prey that underpins the distribution of these species, biological covariates included zooplankton biomass, and the presence (and absence) of fish schools (determined using hydro-acoustics during surveys). Seabird species were separated into feeding groups using multivariate analysis and modelled separately to reveal potential drivers for each group. Despite different biological predictors influencing the distribution of different groups, sea surface temperature was found to explain the greatest amount of variation across all feeding groups. This influence is thought to be prey-mediated, as both biological covariates tested exhibited negative correlations with increasing SST. Through considering the complex links which exist between predators, their prey and the physical environment, this study produces new insights into the potential effects of extreme events. Further, it improves our understanding of how general warming trends affect prey structure and the possible flow-on effects for predators. Modelling the distribution of apex predators enables the identification of important foraging regions with favourable bio-physical characteristics. We highlight how detailed assessments of ecosystem and environmental interactions can be pivotal to informing the effective management of these vulnerable and biodiverse ecosystems into the future.
... Given the large population sizes, extensive distribution patterns, high standing genetic diversity, and short generation times of marine zooplankton in general, adaptive responses to even weak selection may be expected as the loss of variation due to genetic drift should be negligible (Peijnenburg & Goetze, 2013). While some plankton communities show rapid range shifts and phenological changes in response to ocean warming (Beaugrand et al., 2009(Beaugrand et al., , 2014Hays et al., 2005), we only have limited understanding of the potential for evolutionary responses of marine zooplankton to future conditions (Dam, 2013;Peijnenburg & Goetze, 2013). ...
... To gain further insight into the nature and drivers of dispersal barriers in the open ocean, as well as to identify signals of selection across the genome, a broader range of ecological observations and in-depth analyses of genome-wide diversity in zooplankton will be necessary (Bucklin et al., 2018;Choo et al., 2020;Choquet et al., 2019;Gagnaire et al., 2015). This is important because marine zooplankton are key players in pelagic food webs and useful indicators as rapid responders to environmental variation and climate change (Beaugrand et al., 2009). Shelled pteropods could be particularly suitable model organisms to gain insight into the evolutionary potential of marine zooplankton and to deepen our understanding of speciation processes in the open ocean for a number of reasons. ...
Article
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Pteropods, a group of holoplanktonic gastropods, are regarded as bioindicators of the effects of ocean acidification on open ocean ecosystems, because their thin aragonitic shells are susceptible to dissolution. While there have been recent efforts to address their capacity for physiological acclimation, it is also important to gain predictive understanding of their ability to adapt to future ocean conditions. However, little is known about the levels of genetic variation and large‐scale population structuring of pteropods, key characteristics enabling local adaptation. We examined the spatial distribution of genetic diversity in the mitochondrial cytochrome c oxidase I (COI) and nuclear 28S gene fragments, as well as shell shape variation, across a latitudinal transect in the Atlantic Ocean (35°N–36°S) for the pteropod Limacina bulimoides. We observed high levels of genetic variability (COI π = 0.034, 28S π = 0.0021) and strong spatial structuring (COI ΦST = 0.230, 28S ΦST = 0.255) across this transect. Based on the congruence of mitochondrial and nuclear differentiation, as well as differences in shell shape, we identified a primary dispersal barrier in the southern Atlantic subtropical gyre (15–18°S). This barrier is maintained despite the presence of expatriates, a gyral current system, and in the absence of any distinct oceanographic gradients in this region, suggesting that reproductive isolation between these populations must be strong. A secondary dispersal barrier supported only by 28S pairwise ΦST comparisons was identified in the equatorial upwelling region (between 15°N and 4°S), which is concordant with barriers observed in other zooplankton species. Both oceanic dispersal barriers were congruent with regions of low abundance reported for a similar basin‐scale transect that was sampled 2 years later. Our finding supports the hypothesis that low abundance indicates areas of suboptimal habitat that result in barriers to gene flow in widely distributed zooplankton species. Such species may in fact consist of several populations or (sub)species that are adapted to local environmental conditions, limiting their potential for adaptive responses to ocean changes. Future analyses of genome‐wide diversity in pteropods could provide further insight into the strength, formation and maintenance of oceanic dispersal barriers.
... In other words, they are nowadays inhabiting warmer surface temperatures than they were 80 years ago. This is an important result as it is the exception to the general expectations of range shifts (generally polewards to cooler waters) under warming scenarios (Beaugrand et al., 2009). Indeed, Antarctic range shifts have been found in the Atlantic sector, both for E. superba and salps (Pakhomov et al., 2002;Atkinson et al., 2004Atkinson et al., , 2019, in keeping with those found for aquatic and terrestrial ectotherms more generally (Parmesan and Yohe, 2003). ...
... Three "universal" responses to rapid warming have been described for ecototherms. Copepods may shift (1) in geographical range (i.e., polewards range shifts Beaugrand et al., 2009), (2) in phenology (i.e., earlier when warmer , and (3) in body size (i.e., smaller species' , life stages or adult sizes in warmer environments Daufresne et al., 2009;Horne et al., 2016). The relative degree of expression of these responses is poorly known for zooplankton generally; it is certainly not known for Antarctic copepods. ...
Article
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In the Southern Ocean, several zooplankton taxonomic groups, euphausiids, copepods, salps and pteropods, are notable because of their biomass and abundance and their roles in maintaining food webs and ecosystem structure and function, including the provision of globally important ecosystem services. These groups are consumers of microbes, primary and secondary producers, and are prey for fishes, cephalopods, seabirds, and marine mammals. In providing the link between microbes, primary production, and higher trophic levels these taxa influence energy flows, biological production and biomass, biogeochemical cycles, carbon flux and food web interactions thereby modulating the structure and functioning of ecosystems. Additionally, Antarctic krill (Euphausia superba) and various fish species are harvested by international fisheries. Global and local drivers of change are expected to affect the dynamics of key zooplankton species, which may have potentially profound and wide-ranging implications for Southern Ocean ecosystems and the services they provide. Here we assess the current understanding of the dominant metazoan zooplankton within the Southern Ocean, including Antarctic krill and other key euphausiid, copepod, salp and pteropod species. We provide a systematic overview of observed and potential future responses of these taxa to a changing Southern Ocean and the functional relationships by which drivers may impact them. To support future ecosystem assessments and conservation and management strategies, we also identify priorities for Southern Ocean zooplankton research.
... Alterations in the physical environment together with the spatial and temporal shifts in phytoplankton blooms propagate changes in zooplankton phenology, distribution, community composition and thus in the overall energy content (Fig. 3). Studies have shown that the greatest changes were observed at the boundary of the Arctic shelf seas at transition zones between the Atlantic and Arctic (Gregory et al., 2009). The reduction of sea ice surface and thickness as well as of the associated algal flora in the Arctic marginal ice zone have been recorded as a potential problem for the maturation and reproduction of Calanus glacialis, an endemic arctic herbivorous zooplankton species (Søreide et al., 2010). ...
... Consequently grazer zooplankton taxa have been shifting their distribution in the Atlantic-Arctic, following warm water masses and phytoplankton shifts. A comprehensive study focused on the changes of nine planktonic calanoid species assemblages (a total of 108 calanoid species/taxa) in the north-eastern part of the North-Atlantic Ocean between 1958 and 2005 (Gregory et al., 2009). The authors reported an overall northward shift of several species assemblages and changes in species composition in different parts of the studied range, e.g. a decrease in the abundance of subarctic species and an increase in cold-temperate mixed water species south from Iceland since 2003. ...
Article
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The Atlantification of the European Arctic has been an increasingly discussed topic in polar science over the past two decades. The alteration of local marine ecosystems towards a more temperate state and the appearance/range expansion of subarctic-boreal species at higher latitudes is a complex phenomenon induced mainly by the changing properties of Atlantic water (AW) transported from the south. Areas under the direct influence of AW experience biological Atlantification of their communities on all trophic levels, resulting in the growing complexity of arctic food webs. Here, besides summarising the main documented messages of biological Atlantification, we take a critical view on the threat posed on Arctic marine communities. We take into account the formation of the Arctic marine fauna, as well as the nature of (re)colonisation of Arctic sites by boreal organisms when evaluating the extent of the issue. We take a look at the history of Arctic colonisations by boreal organisms in an attempt to identify ‘neonative taxa returning home’. We also highlight the role of floating plastic debris as an ‘instrument from the toolbox of the Anthropocene’ aiding the distribution of marine taxa.
... Such temperature-related factors (particularly the occurrence of extreme events, e.g., marine heatwaves, Laufk€ otter et al., 2020) are therefore expected to have adverse impacts at warmer (lower-latitude) distributional limits, while providing potential benefits at cooler (higher-latitude) range limits. The overall outcome is therefore poleward population movement, as already observed for many marine macrophytes, zooplankton, and fish (e.g., Gregory et al., 2009;Perry et al., 2005). The rate of that movement will depend on species' mobility and reproductive strategies, and may also be constrained by temperature extremes, hydrodynamic conditions, and trophic interactions . ...
Chapter
The impacts of anthropogenic climate change are already discernible throughout the ocean, from the equator to the poles, and from the surface to abyssal depths. Further climate change impacts are inevitable; however, their damage to marine organisms and ecosystems, and the services they provide, can be greatly reduced if greenhouse gas emissions are rapidly reduced. This review covers six main climate-related drivers (warming, acidification, deoxygenation, sea level rise and storm events, sea ice loss, stratification, and nutrient supply) and their impacts on 13 marine ecosystems, broadly defined. Seven of these are near-shore (coral reefs, kelp ecosystems, seagrass meadows, rocky and sandy intertidal, saltmarshes, estuaries, and mangroves) and six are in shelf seas and the open ocean (shelf sea benthos, upper ocean plankton, fish and fisheries, cold water corals, ice-influenced ecosystems, and the deep seafloor). Three cross-cutting issues are emphasized: that climate change impacts are not single factors, but interact together and with other human pressures in a multistressor context; that there are fast and slow climate processes in the ocean, with overall temporal uncertainties relating to future societal behavior; and that there can be high spatial heterogeneity in marine ecosystem impacts and vulnerabilities.
... These changes may alter the energy transfer through the pelagic food web and potentially also impact benthic invertebrates through their pelagic early life stages. Furthermore, biogeographical distributional shifts may change community composition with repercussions on energy transfer and ecosystem structure (Beaugrand et al., 2009;Chust et al., 2013). In order to document changes and to be able to distinguish between natural seasonal variability and climate change impacts on ecosystems structure and functioning, we need to establish baselines, such as detailed species inventories and how community composition varies seasonally. ...
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Phyto- and zooplankton in Arctic and sub-Arctic seas show very strong seasonal changes in diversity and biomass. Here we document the seasonal variability in the mesozooplankton community structure in a sub-Arctic fjord in Northern Norway based on monthly sampling between November 2018 and February 2020. We combined traditional morphological zooplankton identification with DNA metabarcoding of a 313 base pair fragment of the COI gene. This approach allowed us to provide the most detailed mesozooplankton species list known for this region across an entire year, including both holo-and meroplankton. The zooplankton community was dominated by small copepods throughout the sampling period both in terms of abundance and relative sequence counts. However, meroplankton was the most diverse group, especially within the phylum polychaeta. We identified four distinct periods based on the seasonal analysis of the zooplankton community composition. The pre-spring bloom period (February-March) was characterized by low abundance and biomass of zooplankton. The spring bloom (April) was characterized by the presence of Calanus young stages, cirripedia and krill eggs. The spring-summer period (May-August) was characterized by a succession of meroplankton and a relatively high abundance of copepods of the genus Calanus spp. Finally, the autumn-winter period (September-December) was characterized by a high copepod diversity and a peak in abundance of small copepods (e.g., Oithona similis, Acartia longiremis, Pseudocalanus acuspes, Pseudocalanus elongatus, Pseudocalanus moultoni, Pseudocalanus minutus). During this period, we also observed an influx of boreal warm-water species which were notably absent during the rest of the year. Both the traditional community analysis and metabarcoding were highly complementary and with a few exceptions showed similar trends in the seasonal changes of the zooplankton community structure.
... While C. glacialis can produce eggs on internal energy stores even if neither ice algae nor phytoplankton are available at the time of reproduction, egg production will be reduced and recruitment will be low if little food is available for growth and development from boreal habitats. Zooplankton community shifts have been registered in subarctic seas, i.e. a polewards displacement of temperate species coinciding with a decrease of subarctic and arctic species has been documented for the North Atlantic (Beaugrand et al. 2009) and the subarctic Pacific (Mueter et al. 2009). In the Barents Sea, the polar cod stock has decreased since 2006 (Hop and Gjøsaeter 2013;Bakketeig et al. 2017). ...
Chapter
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The marine pelagic primary production is an important energy source for most Arctic ecosystems, both marine and terrestrial. Single‐celled algae in the water column and in sea ice are at the base of the food web. There are two main drift patterns for sea ice and the upper polar mixed layer in the Arctic Ocean: the Beaufort Gyre (BG) and the Transpolar Drift (TPD). The TPD and the interconnected current systems in the Nordic seas and the Arctic Ocean form the trans‐Arctic highways, transporting zooplankton and ice fauna species over long distances. Regardless of how a continued warming of the Arctic may affect the productivity of the system, there are two key areas where climate change is likely to have an effect on the Arctic pelagic ecosystem: the timing of key life history events; and extension of boreal species northwards.
... Changes in the Slope Current may consequently impact downstream ecosystems through a number of mechanisms. There is growing evidence that recent warming trends have 345 impacted shelf sea species distributions, leading to "subtropicalization" of the North Sea: warmer-water species of zooplankton and fish species have been observed (and in some cases, now breeding) in UK coastal waters (Montero-Serra et al., 2015;Beaugrand et al., 2009;Beare et al., 2004). Not only is the species distribution being altered, the warmer water is https://doi.org/10.5194/os-2021-60 ...
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Oceanic influences on shelf seas are mediated by flow along and across continental slopes, with consequences for regional hydrography and ecosystems. Here we present evidence for the variable North Atlantic influence on European shelf seas over the last four decades, using ocean analysis and reanalysis products, and an eddy-resolving ocean model hindcast. To first order, flows oriented along isobaths at the continental slope are related to the poleward increase of density in the adjacent deep ocean that supports a geostrophic inflow towards the slope. In the North Atlantic, this density gradient and associated inflow has undergone substantial, sometimes abrupt, changes in recent decades. Inflow in the range 10–15 Sv is identified with eastward transport in temperature classes at 30° W, in the latitude range 45–60° N. Associated with major subpolar warming around 1997, a cool and fresh branch of the Atlantic inflow was substantially reduced, while a warm and more saline inflow branch strengthened, with respective changes of the order 5 Sv. Total inflow fell from ~ 15 Sv pre-1997 to ~ 10 Sv post-1997. In the model hindcast, particle tracking is used to trace the origins of poleward flows along the continental slope to the west of Ireland and Scotland, before and after 1997. Backtracking particles up to 4 years, a range of subtropical and subpolar pathways is identified from a statistical perspective. In broad terms, cold, fresh waters of subpolar provenance were replaced by warm, saline waters, of subtropical provenance. These changes have major implications for the downstream shelf regions that are strongly influenced by Atlantic inflow, the northern North Sea in particular, where “subtropicalization” of ecosystems has already been observed since the late 1990s.
... The elevated abundance of CV and females of C. finmarchicus, an expatriate species from the boreal-Atlantic, in the northward flowing eastern jet could particularly be of importance for the Arctic marine ecosystem. Due to ongoing climate change and associated rising temperatures in the Arctic, shifts in the biogeographical distribution of pelagic species can be observed, with Atlantic species extending their ranges northward (Beaugrand et al., 2009). Further, due to rising temperatures, the width of the MIZ is constantly increasing during summer (Strong and Rigor, 2013), possibly providing an extending area for submesoscale dynamics and associated fast-flowing jets, which may accelerate ' Atlantification' processes in the Arctic, although further supportive evidence is needed. ...
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Submesoscale structures, characterized by intense vertical and horizontal velocities, potentially play a crucial role in oceanographic dynamics and pelagic fluxes. Due to their small spatial scale and short temporal persistence, conditions for in situ measurements are challenging and thus the role of such structures for zooplankton distribution is still unclear. During RV Polarstern expedition PS107 to Arctic Fram Strait in July/August 2017, a submesoscale filament was detected, which initiated an ad hoc oceanographic and biological sampling campaign. To determine zooplankton taxonomic composition, horizontal and vertical distribution, abundance and biomass, vertical MultiNet hauls (depth intervals: 300–200–100–50–10–0 m) were taken at four stations across the filament. Zooplankton data were evaluated in context with the physical-oceanographic observations of the filament to assess submesoscale physical-biological interactions. Our data show that submesoscale features considerably impact zooplankton dynamics. While structuring the pelagial with distinct zooplankton communities in a vertical as well as horizontal dimension, they accumulate abundance and biomass of epipelagic species at the site of convergence. Further, high-velocity jets associated with such dynamics are possibly of major importance for species allocation and biological connectivity, accelerating for instance processes such as the ‘Atlantification’ of the Arctic. Thus, submesoscale features affect the surrounding ecosystem in multiple ways with consequences for higher trophic levels and biogeochemical cycles.
... It is unclear why the euphausiids alone among the most dominant zooplankton taxa in this region have shown a particular decline since the 1990s. In contrast, in the North Sea, it has been widely documented that most boreal and cold-temperate species have declined over the last 60 years, particularly since the late 1980s, and have been replaced by more warm-water and temperate species 14,15,18 . For example, the boreal copepod C. finmarchicus has decreased by 50% in the North Sea since the late 1980s regime shift. ...
Article
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In the North Atlantic, euphausiids (krill) form a major link between primary production and predators including commercially exploited fish. This basin is warming very rapidly, with species expected to shift northwards following their thermal tolerances. Here we show, however, that there has been a 50% decline in surface krill abundance over the last 60 years that occurred in situ, with no associated range shift. While we relate these changes to the warming climate, our study is the first to document an in situ squeeze on living space within this system. The warmer isotherms are shifting measurably northwards but cooler isotherms have remained relatively static, stalled by the subpolar fronts in the NW Atlantic. Consequently the two temperatures defining the core of krill distribution (7–13 °C) were 8° of latitude apart 60 years ago but are presently only 4° apart. Over the 60 year period the core latitudinal distribution of euphausiids has remained relatively stable so a ‘habitat squeeze’, with loss of 4° of latitude in living space, could explain the decline in krill. This highlights that, as the temperature warms, not all species can track isotherms and shift northward at the same rate with both losers and winners emerging under the ‘Atlantification’ of the sub-Arctic.
... In both areas, there are more than 62 monitoring sites, providing high spatial and temporal resolution zooplankton data based on 40 Continuous Plankton Recorder (CPR) standard areas (O'Brien et al. 2013). These long-term data give detailed information on the zooplankton species and the zooplankton community change over time in the eastern North Atlantic (Greve et al. 2004;Beaugrand 2005;Beaugrand et al. 2009Beaugrand et al. , 2014Pitois et al. 2009;Eloire et al. 2010) and western North Atlantic (Pershing et al. 2005;Kane 2007;Johnson et al. 2011). ...
Article
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Characterization of species diversity of zooplankton is key to understanding, assessing, and predicting the function and future of pelagic ecosystems throughout the global ocean. The marine zooplankton assemblage, including only metazoans, is highly diverse and taxonomically complex, with an estimated ~28,000 species of 41 major taxonomic groups. This review provides a comprehensive summary of DNA sequences for the barcode region of mitochondrial cytochrome oxidase I (COI) for identified specimens. The foundation of this summary is the MetaZooGene Barcode Atlas and Database (MZGdb), a new open-access data and metadata portal that is linked to NCBI GenBank and BOLD data repositories. The MZGdb provides enhanced quality control and tools for assembling COI reference sequence databases that are specific to selected taxonomic groups and/or ocean regions, with associated metadata (e.g., collection georeferencing, verification of species identification, molecular protocols), and tools for statistical analysis, mapping, and visualization. To date, over 150,000 COI sequences for ~ 5600 described species of marine metazoan plankton (including holo- and meroplankton) are available via the MZGdb portal. This review uses the MZGdb as a resource for summaries of COI barcode data and metadata for important taxonomic groups of marine zooplankton and selected regions, including the North Atlantic, Arctic, North Pacific, and Southern Oceans. The MZGdb is designed to provide a foundation for analysis of species diversity of marine zooplankton based on DNA barcoding and metabarcoding for assessment of marine ecosystems and rapid detection of the impacts of climate change.
... The zooplankton species were grouped by their biogeographical association (cf. 28,29,45 ; see Table 4) to enable us to determine the effect (if any) of the North Atlantic regime shift on the networks. ...
Article
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Robust time-series of direct observations of jellyfish abundance are not available for many ecosystems, leaving it difficult to determine changes in jellyfish abundance, the possible causes (e.g. climate change) or the consequences (e.g. trophic cascades). We sought an indirect ecological route to reconstruct jellyfish abundance in the Irish Sea: since zooplankton are jellyfish prey, historic variability in zooplankton communities may provide proxies for jellyfish abundance. We determined the Bayesian ecological network of jellyfish–zooplankton dependencies using jellyfish- and zooplankton-abundance data obtained using nets during a 2-week cruise to the Irish Sea in 2008. This network revealed that Aurelia aurita abundance was dependent on zooplankton groups Warm Temperate and Temperate Oceanic as defined by previous zooplankton ecology work. We then determined historic zooplankton networks across the Irish Sea from abundance data from Continuous Plankton Recorder surveys conducted between 1970 and 2000. Transposing the 2008 spatial dependencies onto the historic networks revealed that Aurelia abundance was more strongly dependent over time on sea surface temperature than on the zooplankton community. The generalist predatory abilities of Aurelia may have insulated this jellyfish over the 1985 regime shift when zooplankton composition in the Irish Sea changed abruptly, and also help explain its globally widespread distribution.
... At present, one of the major environmental drivers stressing organisms and ecosystems is climate change (e.g., Doney et al., 2002;Bijma et al., 2013;Bindoff et al., 2019). Ocean warming is inducing rapid changes in ecosystems (Burrows et al., 2011), and marine organisms are responding by varying their distributions, biomass, and phenology (Edwards and Richardson, 2004;Gregory et al., 2009;Boyce et al., 2010;Hoegh-Guldberg and Bruno, 2010). Phytoplankton is responding to climate change faster than other primary producers, with shifts described in both their distribution and phenology (Poloczanska et al., 2013). ...
Article
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Pico-sized Synechococcus , Prochlorococcus , and eukaryotes are the dominant photosynthetic organisms in the vast warm and oligotrophic regions of the ocean. In this paper, we aim to characterize the realized niches of the picophytoplanktonic community inhabiting the Red Sea, the warmest oligotrophic sea, which is considered to be a model for the future ocean. We quantify population abundances and environmental variables over several oceanographic surveys, and use stepwise regression, principal-component analysis (PCA), and compositional-data analysis to identify the realized niches of the three picophytoplanktonic groups. Water temperature varied from 21.4 to 32.4°C within the upper 200-m water column, with the warmest waters being found in the South, where nutrients increased. Synechococcus dominated the biomass, contributing 47.6% to the total picophytoplankton biomass, followed by picoeukaryotes (26.4%) and Prochlorococcus (25.9%), whose proportions contrast significantly with those reported in the subtropical ocean, where Prochlorococcus prevails. There were positive and significant relationships between temperature and the three populations, although these were weak for Prochlorococcus ( R ² = 0.08) and stronger and steeper for Synechococcus ( R ² = 0.57). The three populations centered their maximum abundances (Lorentzian fits) at similar low nutrient values. Synechococcus were centered close to the surface at ≈77% of surface photosynthetically active radiation (PAR) and ≈30.6°C. The picoeukaryotes were centered at lower light (≈6.4% surface PAR) and warm waters (≈30°C). Prochlorococcus was segregated from the surface waters and centered deep at low light (≈3.2% surface PAR). Light and temperature were the most influential factors determining the community composition, with Synechococcus dominating ∼74% of the picophytoplankton biovolume in the warmest (>30°C) waters. In the warm and mesotrophic southern Red Sea, the moderate abundances of picoeukaryotes and Synechococcus suggest increasing competition with nano and microphytoplankton. Our observations agree with predictions of increasing vertical segregation of picophytoplankton communities with future warming and reveal Synechococcus ’s significant capacity to adapt to warming.
... Barnard et al., 2004;Beaugrand et al., 2002); (iii) document distributional, phenological and physiological responses of marine species to climate change (e.g. Beaugrand et al., 2009;Helaouët and Beaugrand, 2009;Thackeray et al., 2016; and (iv) anticipate the consequences of global warming in the pelagic realm (e.g. Reid et al., 1998;Beaugrand et al., 2015). ...
Article
Annual plankton succession has been investigated for many decades with hypotheses ranging from abiotic to biotic mechanisms being proposed to explain these recurrent patterns. Here, using data collected by the Continuous Plankton Recorder (CPR) survey and models originating from the MacroEcological Theory on the Arrangement of Life, we investigate Annual Phytoplankton Succession (APS) in the North Sea at a species level. Our results show that this phenomenon can be predicted well by models combining photosynthetically active radiation, temperature and macro-nutrients. Our findings suggest that APS originates from the interaction between species’ ecological niches and the annual environmental fluctuations at a community level. We discuss our results in the context of traditional hypotheses formulated to explain this recurrent pattern in the marine field.
... Changes in the Slope Current may consequently impact downstream ecosystems through a number of mechanisms. There is growing evidence that recent warming trends have 345 impacted shelf sea species distributions, leading to "subtropicalization" of the North Sea: warmer-water species of zooplankton and fish species have been observed (and in some cases, now breeding) in UK coastal waters (Montero-Serra et al., 2015;Beaugrand et al., 2009;Beare et al., 2004). Not only is the species distribution being altered, the warmer water is https://doi.org/10.5194/os-2021-60 ...
Article
Full-text available
Oceanic influences on shelf seas are mediated by flow along and across continental slopes, with consequences for regional hydrography and ecosystems. Here we present evidence for the variable North Atlantic influence on European shelf seas over the last 4 decades using ocean analysis and reanalysis products, as well as an eddy-resolving ocean model hindcast. To first order, flows oriented along isobaths at the continental slope are related to the poleward increase in density in the adjacent deep ocean that supports a geostrophic inflow towards the slope. In the North Atlantic, this density gradient and associated inflow have undergone substantial, sometimes abrupt, changes in recent decades. Inflow in the range 10–15 Sv is identified with eastward transport in temperature classes at 30∘ W in the latitude range 45–60∘ N. Associated with major subpolar warming around 1997, a cool and fresh branch of the Atlantic inflow was substantially reduced, while a warm and more saline inflow branch strengthened, with respective changes of the order of 5 Sv. Total inflow fell from ∼ 15 Sv pre-1997 to ∼ 10 Sv post-1997. In the model hindcast, particle tracking is used to trace the origins of poleward flows along the continental slope to the west of Ireland and Scotland before and after 1997. Backtracking particles up to 4 years, a range of subtropical and subpolar pathways is identified from a statistical perspective. In broad terms, cold, fresh waters of subpolar provenance were replaced by warm, saline waters of subtropical provenance. These changes have major implications for the downstream shelf regions that are strongly influenced by Atlantic inflow, in particular the northern North Sea, where “subtropicalization” of ecosystems has already been observed since the late 1990s.
... It is expected that climate change will impact directly on the populations of cetaceans and seabirds by modifying the physical and chemical characteristics of their environment and indirectly by affecting the distribution, availability and accessibility to their prey (Hemery et al., 2007;Simmonds, 2016). Among the different processes characterising climate change, ocean warming is believed to be forcing range shifts due to the changes in the location of thermal niches (Edwards and Richardson, 2004;Gregory et al., 2009), altering food web dynamics (Hays et al., 2005) and producing a northerly shift of marine megafauna species (Hemery et al., 2007;). While ocean acidification could produce trophic cascades Sydeman et al., 2012) due to changes in primary production (Duarte et al., 2013), the sea level rise could reduce breeding grounds (Croxall et al., 2012). ...
... Shelf seas contain diverse and productive ecosystems (Lauria et al., 2012) that have undergone profound changes in recent times as a result of both natural and anthropogenic modes of climate variability (Southward et al., 1995;Beaugrand and Reid, 2003;Schmidt et al., 2020). Marine zooplankton are one of the most sensitive taxa to changes in environmental conditions and monitoring their long-term abundance and diversity has facilitated the detection of ecosystem-wide changes in several shelf basins (Southward et al., 1995;Beaugrand et al., 2009;Conversi This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. et al., 2010). ...
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Although gelatinous zooplankton are an important component of marine ecosystems, gelatinous mesozooplankton that are <2 cm are underrepresented in monitoring programmes. Here, the interannual variability of gelatinous mesozooplankton abundance and diversity was estimated from 167 zooplankton net samples that were collected in the Celtic Sea during seven fisheries surveys between 2007 and 2019 and analysed alongside environmental parameters. Compositional changes occurred interannually, including an overturn in the abundance ratio of two siphonophores (Muggiaea atlantica and Agalma elegans). Analysis of annual mean gelatinous abundance revealed no linear trend over time (Spearman, r = −0.09, p = 0.287); however, the interannual abundance varied by a factor of 33 (minimum mean abundance in 2013 = 7.36 ± 4.86 individuals m−3; maximum in 2017 = 244.82 ± 84.59 individuals m−3). Holoplanktonic taxa dominated the abundance of the gelatinous community (93.27%) and their abundance was negatively associated with summer sea surface temperature (represented by the 16°C isotherm in July), and the Eastern Atlantic Pattern index 3 months prior (April). Our data suggest that gelatinous mesozooplankton in the Celtic Sea may become less abundant with further ocean warming, and further highlight the need to monitor gelatinous mesozooplankton with a high taxonomic resolution moving forward.
... Shelf seas contain diverse and productive ecosystems (Lauria et al., 2012) that have undergone profound changes in recent times as a result of both natural and anthropogenic modes of climate variability (Southward et al., 1995;Beaugrand and Reid, 2003;Schmidt et al., 2020). Marine zooplankton are one of the most sensitive taxa to changes in environmental conditions and monitoring their long-term abundance and diversity has facilitated the detection of ecosystem-wide changes in several shelf basins (Southward et al., 1995;Beaugrand et al., 2009; Conversi V C International Council for the Exploration of the Sea 2021. All rights reserved. ...
Article
Although gelatinous zooplankton are an important component of marine ecosystems, gelatinous mesozooplankton that are <2 cm are underrepresented in monitoring programmes. Here, the interannual variability of gelatinous mesozooplankton abundance and diversity was estimated from 167 zooplankton net samples that were collected in the Celtic Sea during seven fisheries surveys between 2007 and 2019 and analysed alongside environmental parameters. Compositional changes occurred interannually, including an overturn in the abundance ratio of two siphonophores (Muggiaea atlantica and Agalma elegans). Analysis of annual mean gelatinous abundance revealed no linear trend over time (Spearman, r = −0.09, p = 0.287); however, the interannual abundance varied by a factor of 33 (minimum mean abundance in 2013 = 7.36 ± 4.86 individuals m−3; maximum in 2017 = 244.82 ± 84.59 individuals m−3). Holoplanktonic taxa dominated the abundance of the gelatinous community (93.27%) and their abundance was negatively associated with summer sea surface temperature (represented by the 16°C isotherm in July), and the Eastern Atlantic Pattern index 3 months prior (April). Our data suggest that gelatinous mesozooplankton in the Celtic Sea may become less abundant with further ocean warming, and further highlight the need to monitor gelatinous mesozooplankton with a high taxonomic resolution moving forward.
... Empirical studies showed that elevated temperature benefits foraging rate but also burdens metabolic costs, thus altering population fitness (Fry, 1971;Sandersfeld et al., 2015). Thus, global warming could be an important environmental forcing driving spatial heterogeneity of marine organism's abundance distribution (Beaugrand et al., 2009;McGinty et al., 2011) possibly through the spatial movement of fitness-taxis. ...
Article
Size-spectrum models are a recent class of models describing the dynamics of a whole community based on a description of individual organisms. The models are motivated by marine ecosystems where they cover the size range from multicellular plankton to the largest fish. We propose to extend the size-spectrum model with spatial components. The spatial dynamics is governed by a random motion and a directed movement in the direction of increased fitness, which we call ‘fitness-taxis’. We use the model to explore whether spatial irregularities of marine communities can occur due to the internal dynamics of predator-prey interactions and spatial movements. This corresponds to a pattern-formation analysis generalized to an entire ecosystem but is not limited to one prey and one predator population. The analyses take the form of Fourier analysis and numerical experiments. Results show that diffusion always stabilizes the equilibrium but fitness-taxis destabilizes it, leading to non-stationary spatially inhomogeneous population densities, which are travelling in size. However, there is a strong asymmetry between fitness-induced destabilizing effects and diffusion-induced stabilizing effects with the latter dominating over the former. These findings reveal that fitness taxis acts as a possible mechanism behind pattern formations in ecosystems with high diversity of organism sizes, which can drive the emergence of spatial heterogeneity even in a spatially homogeneous environment.
... Ocean warming is influencing and modifying species diversity [3], abundance patterns and community composition [83,84], driving extinctions [93], and triggering poleward and regional-scale shifts [88] in species distribution causing biogeographical changes [12,47,91,48,50,150,85]. The magnitude of changes in species distribution and of response rate to climate change-induced stressors [132] vary by a series of factors, including: a species' thermal threshold [50]; sessility [65]; population size; habitat alteration and degradation [91,57]; resource availability; competition with invasive species [102,123]; predator-prey dynamics [125]; migration strategy, and light regimes and reproductive fitness [20,71,87,109,50,145,164]. Shifts are likely to become more rapid and erratic instead of gradual and monotonic [50] with resulting non-linear community responses [133]. ...
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Land is a vital natural resource for human socio‐ecological well‐being. Around the world, land is being degraded due to various natural and anthropogenic factors such as flooding, wind erosion, agriculture and human settlement, and anthropogenic climate change. While significant research has been conducted on the separate dyads of (i) anthropogenic climate change and land degradation and (ii) land degradation and health, limited consideration has been given to the cause‐and‐effect relationships between anthropogenic climate change‐triggered land degradation and planetary health consequences. Using a systematic literature review and the Driving Force, Pressure, State, Exposure, Effect (DPSEE) Framework, this study synthesizes the complex causal relationships of anthropogenic climate change‐triggered land degradation and its planetary health consequences. Our findings demonstrate that anthropogenic climate change has induced and accelerated natural and anthropogenic land degradation through an array of pathways, resulting planetary health consequences that can be grouped in six categories: (i) food and nutritional insecurity, (ii) communicable and non communicable diseases, (iii) livelihood insecurity, (iv) physical and mental health, (vi) health hazards related to extreme weather events, and (vi) migration and conflict. Interlinkages exist between these six planetary health impact categories, adding to the complexity of the causal pathways. These collective impacts are hampering realization of the UN Sustainable Development Goals around the world. The findings of this study and our DPSEE Framework can help policymakers identify and integrate actions to better manage the planetary health impacts of climate change‐induced land degradation. This article is protected by copyright. All rights reserved.
... Their abundance is higher in the NPTZ and decreases abruptly when the temperature falls below 15 • C. Therefore, the occurrence/disappearance of this group can be used as an indicator of the northern boundary of the NPTZ. Moreover, warm water type I species could also be used to denote the northward expansion of plankton due to global warming (Beaugrand et al., 2009). ...
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Located from 35° to 45° latitude in both hemispheres, the transition zone is an important region with respect to the planktonic biogeography of the sea. However, to the best of our knowledge, there have been no reports on the existence of a tintinnid community in the transition zone. In this research, tintinnids along two transects across the North Pacific Transition Zone (NPTZ) were investigated in summer 2016 and 2019. Eighty-three oceanic tintinnid species were identified, 41 of which were defined as common oceanic species. The common oceanic species were further divided into five groups: boreal, warm water type I, warm water type II, transition zone, and cosmopolitan species. Undella californiensis and Undella clevei were transition zone species. Other species, such as Amphorides minor, Dadayiella ganymedes, Dictyocysta mitra, Eutintinnus pacificus, Eutintinnus tubulosus, Protorhabdonella simplex, and Steenstrupiella steenstrupii, were the most abundant in the NPTZ but spread over a much larger distribution region. Species richness showed no obvious increase in the NPTZ. Boreal, transition zone, and warm water communities were divided along the two transects. Tintinnid transition zone community mainly distributed in regions with water temperatures between 15 and 20°C. The tintinnid lorica oral diameter size classes were dominated by the 24–28 μm size class in three communities, but the dominance decreased from 66.26% in the boreal community to 48.85% in the transition zone community and then to 22.72% in the warm water community. Our research confirmed the existence of tintinnid transition zone species and community. The abrupt disappearance of warm water type I species below 15°C suggested that this group could be used as an indicator of the northern boundary of the NPTZ.
... This may partially explain the selective foraging of herring on copepods in late 2018 and 2019, when we observed increased densities of small-bodied copepods in Trinity Bay. Distribution shifts and decline of large-bodied copepods in high latitude systems have been reported throughout the North Atlantic and Pacific (Beaugrand et al., 2009) and are attributed to higher temperatures and reduced sea ice ( (Pitois and Fox, 2006;Coyle and Gibson, 2017). Given the importance of large copepods to forage fish diets, including herring, throughout the North Atlantic (Darbyson et al., 2003;Dommasnes et al., 2004;Prokopchuk and Sentyabov, 2006;Raab et al., 2012; this study), a shift in dominance from Calanus spp. to smaller, less-nutritious copepods could trigger bottom-up effects and alter forage fish energy budgets. ...
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Atlantic herring (Clupea harengus; hereafter herring) is a forage fish that transfers energy from lower to higher trophic levels and sustains high-volume fisheries in the North Atlantic. This study aims to improve our understanding of the ecology of Newfoundland herring and its vulnerability to climate change by identifying key prey items and describing adult herring feeding strategies. We compared plankton assemblages to stomach content and stable isotope analyses from herring collected in Trinity Bay, Newfoundland, in late summer and autumn 2017-2019. Six distinct zooplankton communities were identified across all years, with a shift in community structure in September 2018. This shift coincided with a change from fresher, warmer waters (12-17 • C) to more saline, cooler waters (10.5 • C). The most frequently consumed prey items were amphipods (Themisto spp.) and calanoid copepods (primarily Calanus and Temora spp.). Fish eggs, larvae, and juveniles, primarily identified as capelin, were observed in stomach contents in all years. Fish contributed most to diets in 2017, which corresponded with the peak year for larval densities in Trinity Bay, suggesting that piscivory may increase at higher larval densities. Herring were opportunistic feeders, although some individuals exhibited selective feeding on copepods, amphipods, euphausiids, and the early life stages of fishes. Stable isotope analyses supported the finding that herring piscivory is prevalent in eastern Newfoundland. Given its adaptive feeding strategy and wide range of consumed prey, we conclude that adult Newfoundland herring is resilient to bottom-up changes observed in the environment.
... Chapitre 5. Structure globale de l'écosystème planctonique Among others, important results include evidence that Calanoid copepods are migrating northward in response to temperature variations (Beaugrand et al., 2009). The impacts of copepod community structure on carbon fluxes have also been investigated, and indicate that climate change, by modifying large-bodied copepod distribution, has modified activity of the biological carbon pump in the North Atlantic Ocean (Brun et al., 2019). ...
Thesis
Les organismes planctoniques, acteurs clés des écosystèmes, soutiennent les réseaux trophiques et ont un rôle majeur dans les cycles biogéochimiques et la régulation du climat. Tandis que la répartition spatio-temporelle de la diversité planctonique peut être étudiée à plusieurs niveaux, du gène jusqu’à l’écosystème, comprendre les mécanismes qui sous-tendent cette organisation est un défi. En effet, la structure de la diversité résulte de différents processus évolutifs et écologiques qui peuvent agir simultanément sur le vivant. Depuis le début du XXIème siècle, le milieu océanique fait l'objet d’une surveillance croissante. De nombreuses plateformes d’observation ont été déployées permettant l’acquisition de très nombreuses données couvrant de multiples caractéristiques environnementales. En parallèle, les technologies d’étude du vivant se sont développées, conduisant à un échantillonnage sans précédent des organismes planctoniques. En particulier, les données à haut débit de séquençage et d’imagerie permettent de fournir des informations moléculaires, taxonomiques et fonctionnelles à l’échelle des communautés. L’objectif de cette thèse était d’explorer la structure des écosystèmes planctoniques à l’aide des données à haut débit de séquençage et d’imagerie. Le couplage avec les données environnementales pourrait contribuer à une meilleure compréhension de la répartition spatiale de la diversité planctonique, des espèces jusqu’au communautés. Dans une première partie, la diversité génétique de protistes a été étudiée à l’échelle de l’espèce. L’hypothèse était que les données métagénomiques pourraient permettre d’accéder à l’organisation de cette diversité mal caractérisée pour les protistes, ainsi qu’aux mécanismes qui la sous-tendent. Dans une deuxième partie, le lien entre diversité génétique et diversité fonctionnelle a été exploré. La transparence a été ciblée. Ce trait fonctionnel est peu exploré à l’échelle des communautés et les bases moléculaires sont mal identifiées. Une approche permettant de faire émerger ce trait des données d’imagerie a été utilisée, ayant conduit à l’exploration de sa biogéographie et ses bases moléculaires. Dans la dernière partie, le haut potentiel de complémentarité entre jeux de données de séquençage, d’imagerie et environnementaux a été exploré, afin de mettre en lumière la structure multi-échelle de l’écosystème planctonique et d’identifier sa structure globale. Enfin, l’ensemble des résultats a été discuté pour mettre en évidence les apports que peuvent fournir ces données à la compréhension des écosystèmes planctoniques, ainsi que les limites auxquelles elles peuvent faire face.
... Changes in species composition have been reported in various marine ecosystems, and these changes are driven mainly by climate change and fishing (Holbrook et al., 1997;Gregory et al., 2009;Möllmann and Diekmann, 2012;Wernberg et al., 2016;Kleisner et al., 2017). Climate change has been proposed to strongly affect the distribution and abundance of populations (Rose, 2005;Perry et al., 2005;Rijnsdorp et al., 2009), and fishing directly changes not only species abundance but also predator-prey interactions and community structure (Pauly et al., 1998;Bianchi et al., 2000;Frank et al., 2005). ...
Article
Climate change and intensive fishing have affected not only population abundance, but also species composition. Cephalopods have been increasing in abundance in the world ocean under climate change due to their flexible life-history traits, including the over-exploited China Seas. Despite the increasing importance of coastal cephalopods in the China Seas, there have been no reports of changes in either species composition, nor the ecological roles of species with different life-history traits. Thus, this study first presents the changes in species composition of coastal cephalopods throughout the China Seas as summarized from fishery-independent survey reports over the last six decades. This is followed by an investigation of species composition of cephalopods in Haizhou Bay in the Yellow Sea. The ecological roles of two currently targeted cephalopods, Amphioctopus fangsiao and Loliolus spp. (Loliolus beka and Loliolus japonicus), are evaluated using an ecosystem model. The species composition of coastal cephalopods in the China Seas has changed since the 1960s, from species of large size and high value to small-size, low-value species. Cephalopod species composition in Haizhou Bay shows great seasonality, which is probably due largely to the characteristics of their life cycle. The population abundance of A. fangsiao and Loliolus spp. appear to be affected by ambient water temperature, and population distribution of Loliolus spp. seems to correlate with water depth. Occupying the highest trophic level in this ecosystem, A. fangsiao potentially displays strong top-down control over other organisms. Loliolus spp. are keystone species showing higher keystoneness in the autumn, owing to a low abundance of fish species which normally prey on them. The species-specific life-history traits and ecological roles of cephalopods are therefore important factors to consider in order to manage them effectively.
... The increasing northward inflow of warm and saline Atlantic waters is referred to as 'Atlantification' or 'Borealization' of the Arctic (Polyakov et al., 2017). Associated with Atlantic water masses are boreal-Atlantic species, which are rapidly expanding their ranges poleward (Beaugrand et al., 2009). For instance, copepods (Beaugrand et al., 2002;Weydmann et al., 2014), gelatinous zooplankton (Mańko et al., 2020) and fishes (Fossheim et al., 2015;Vihtakari et al., 2018) are shifting northward in their biogeographic distribution. ...
Article
Full-text available
The Arctic Ocean is rapidly changing. Air temperature is rising two to four times faster in the Arctic than the global average, with dramatic consequences for the ecosystems. Polar zooplankton species have to cope with those increasing temperatures, whilst simultaneously facing increasing competition by boreal-Atlantic sister species advected into the Arctic Ocean via a stronger Atlantic inflow. To assess the sensitivity of Arctic and Atlantic zooplankton to rising temperatures, respiration rates of dominant Arctic species ( Calanus hyperboreus , Calanus glacialis , Paraeuchaeta glacialis , Themisto libellula ) and their co-occurring Atlantic congeners ( Calanus finmarchicus , Paraeuchaeta norvegica , Themisto abyssorum ) were measured at ambient temperatures and simulated conditions of ocean warming from 0 to 10°C during three expeditions with RV Polarstern to the Arctic Fram Strait. Arctic zooplankton showed only slowly increasing respiration rates with increasing temperatures, also indicated by low Q 10 ratios. In contrast, boreal-Atlantic representatives responded to higher temperatures by a rapid and steeper increase in their respiration rates (higher Q 10 ), suggesting higher metabolic activity. These results imply that Arctic species are physiologically more tolerant to ocean warming than expected but might be outcompeted by their Atlantic congeners beyond a certain temperature threshold in areas of strong distribution overlap. Thus, the ‘Atlantification’ of the Arctic zooplankton community seems to be driven rather by ecological interactions than by physiological limitations. Changes in zooplankton community composition and biodiversity will have major consequences for trophodynamics and energy flux in Arctic ecosystems, since polar species tend to be larger than their southern counterparts and have a higher lipid content, providing more energy-rich food for higher trophic levels.
... However, while for some marine species that can move (e.g., pelagic species or phytoplankton), shifting their distribution far and fast enough to avoid the rapid temperature changes may be possible (Poloczanska et al., 2013), for others that cannot move (e.g., sessile invertebrates, marine plants or seaweeds), the redistribution process (via successful reproduction, dispersal and recruitment events over generations), may be too slow to outcompete the fast rate of change (Hoegh-Guldberg, 2012;Burrows et al., 2014;García-Molino et al., 2015). Whatever the case, changes of distribution to track optimal thermal conditions within or between generations are one of the most observed responses for marine species in recent decades (Gregory et al., 2009;Poloczanska et al., 2016;Lenoir et al., 2020). Some species are even benefiting from the new abiotic conditions and are further expanding their distributional range to new places (Yamano et al., 2011;Smale et al., 2015;Lonhart et al., 2019), while many others are disappearing from large areas Atkinson et al., 2019). ...
Thesis
Climate change has emerged as one of the greatest and most pervasive threats that our natural heritage will have to face in the coming decades. Together with other anthropogenic pressures such as pollution, overfishing or habitat degradation, climate change is causing enormous impacts on oceans, affecting all kind of marine communities and driving major losses to biodiversity. In this framework of global change, the Mediterranean Sea, which has been identified as one of the major hotspots of marine biodiversity, has also become a hotspot of climate change. Consequently, some of its most emblematic and ecologically important communities are now under threat. This is the case of the coralligenous assemblages, which are temperate benthic communities which stand out for their great structural complexity and exceptional biodiversity (they harbour approximately 10% of Mediterranean species). Most of the constituent species of these communities exhibit high longevity and slow population dynamics. Consequently, they are especially vulnerable to disturbances that increase adults mortality. In fact, thermal anomalies linked to ocean warming have impacted the coralligenous assemblages in several ways during last decades, triggering changes that go from the observed mass mortalities of benthic organisms to potential changes at the community and ecosystem levels. However, despite the increasing interest of the scientific community to conserve the coralligenous, how these benthic communities are responding to climate change at the community level is poorly understood. In this thesis, we have taken this leap by integrating responses from species to the ecosystem level, through populations and communities. In particular, we have combined field observations of ecological and environmental changes, aquaria experiments, ecological theory, and cutting-edge quantitative research to improve our understanding of the bio-ecological consequences of ocean warming for Mediterranean coralligenous assemblages. In the first three chapters, we gathered field and experimental data on sensitivity of several coralligenous species and populations to marine heatwaves (MHWs) by conducting a literature review on previous mass mortality events occurred in the Mediterranean and by carrying out scaled-up thermotolerance experiments. The results of Chapter 1 revealed contrasting patterns of sensitivity to MHWs among different coralligenous species and populations. The posterior multi-specific thermotolerance experiment (including corals, sponges and tunicates) conducted in Chapter 2 confirmed the high response diversity to warming among co-occurring species observed in the field. These results demonstrate that co-occurring species that are taxonomically and morpho-functionally similar can have contrasting thermotolerances. Moreover, the observed patterns suggest that coralligenous assemblages could have certain degree of insurance against MHWs, since the decline of sensitive species could potentially be compensated by other functionally similar species that are more resistant. The results of the multi-population thermal experiment conducted in Chapter 3 with 12 populations of the red gorgonian Paramuricea clavata (Risso, 1826) revealed that this species, which has a key habitat-forming role in coralligenous assemblages, is highly sensitive to thermal stress across its distributional range. Moreover, we found little local adaptation to average thermal regime and little acclimatization to local above-average warm temperatures prior to the experiment. These findings, which were obtained at a spatial scale never addressed before (> 2000 km) for P. clavata, question the adaptive potential of this species to climate change. In Chapter 4, we further explored the vulnerability of Mediterranean habitat-forming octocorals to climate change by exploring the long-term recovery capacity of Corallium rubrum (Linnaeus, 1758) and P. clavata from recurrent MHWs. We explored the long-term trajectories (15 years) of different populations that were firstly impacted by the 2003-MHW in terms of changes in biomass, density and size structure. We found that all impacted populations have followed collapse trajectories. These results further highlight the high vulnerability of these species to the ongoing climate change. Finally, we took the leap from species and populations to the community and ecosystem levels in Chapter 5, to explore if MHWs have driven changes in the functional community structure of coralligenous assemblages, which could imply changes for ecosystem functioning. Specifically, we conducted a multi-taxa, trait-based analysis and found that MHW are shifting the functional identity of coralligenous assemblages (i.e., dominant functional traits). Interestingly, the observed changes were driven primarily by the decline of a single functional group (habitat-forming octocorals), whose species are functionally unique. Consequently, by severely affecting habitat-forming octocorals, MHWs are leading to assemblages that are deficient in key functional traits, likely causing changes in ecosystem functioning. Overall, this thesis provides an integrated, long-term view of the interconnected responses to ocean warming found in coralligenous assemblages. The combined results of this thesis suggest that despite structural changes induced by climate change, most ecosystem functions count on certain degree of insurance against MHWs. However, some essential functions (e.g., 3D-habitat provision) could be highly compromised or even totally disappear, threatening the overall assemblage stability. Given the current climate change trends, identifying and preserving the mechanisms that maintain essential ecosystem functions and the overall ecosystem stability is critical. In this thesis, we have identified the general loss of arborescent octocorals as the greatest disruptive process for coralligenous assemblages. Therefore, the future trajectories of these emblematic Mediterranean communities will greatly depend on the design and implementation of measures that favour the conservation and adaptive management of these key habitat-forming species in the face of climate change.
... Shelf seas contain diverse and productive ecosystems (Lauria et al. 2012) that have undergone profound changes in recent times as a result of both natural and anthropogenic modes of climate variability (Southward et al. 1995;Beaugrand and Reid 2003;Schmidt et al. 2020). Marine zooplankton are possibly the most sensitive animals to changes in environmental conditions and monitoring their long term abundance and diversity has facilitated the detection of ecosystem-wide changes in several shelf basins (Southward et al. 1995;Beaugrand et al. 2009;Conversi et al. 2010). In fact, the fourth descriptor of the European Union's Marine Strategy Framework Directive includes zooplankton as an important factor influencing the state of a food web due to pelagic-benthic coupling (EU, 2017). ...
Thesis
Full-text available
Gelatinous zooplankton are a natural and globally important group of marine organisms, as they provide regulating, provisioning and supporting services to ecosystems. However, gelatinous zooplankton are still a major issue for human activities in several parts of the world, and there is concern that in these regions, the abundance of gelatinous zooplankton may be increasing over time. Added uncertainty comes from the lack of information for the abundance of gelatinous zooplankton at a regional level, particularly in offshore waters, and for gelatinous mesozooplankton that are < 2 cm in size. This thesis sought to improve these knowledge gaps by generating two decade-long datasets for the abundance and diversity of two poorly represented groups of gelatinous zooplankton in the Celtic Seas region of the North East Atlantic (NEA), using fisheries surveys as a research platform. To generate baseline information for gelatinous mesozooplankton species in the Celtic Seas, we identified two fisheries research surveys that were actively collecting zooplankton samples in the region, that could be re-analysed for gelatinous mesozooplankton. However, the net methods used to sample zooplankton on the two types of fisheries survey were different. To evaluate whether each net type (i.e. a Gulf VII sampler and a ring net) estimated the abundance and diversity of gelatinous mesozooplankton similarly, simultaneous deployments of the Gulf VII and ring net were made at 15 sites in July 2017 in Irish and UK shelf waters, and their gelatinous catches were compared. The difference in the estimates of gelatinous mesozooplankton abundance and taxon richness of the Gulf VII and the ring net samples were not significant. This confirmed that zooplankton samples from these two fisheries surveys could be re-analysed to generate a novel long-term data set for gelatinous mesozooplankton in the Celtic Seas. Using zooplankton samples from the two aforementioned fisheries surveys, species abundance data was generated for gelatinous mesozooplankton in the Celtic Sea for seven summers over a 13-year period (2007 – 2019). Total abundance was highly variable each summer, but did not increase or decrease linearly over time. However, subtle compositional changes occurred interannually, including a gradual shift in the abundance ratio of two siphonophore species Muggiaea atlantica and Agalma elegans. Holoplanktonic species dominated the abundance of the gelatinous mesozooplankton community (93.27%) and their abundance was negatively associated with sea surface temperature in July (represented by the position of the 16°C isotherm), and this was underpinned by natural climate variability (represented by the Eastern Atlantic Pattern index). Importantly, these findings suggest that gelatinous mesozooplankton abundance in the Celtic Sea may be lower as a consequence of future ocean warming. The aggregations of one oceanic jellyfish, Pelagia noctiluca, have negatively affected the aquaculture industry in the NEA, especially in Ireland and Scotland. Despite this, there is very little long-term information for their abundance and distribution in the NEA. To investigate the frequency and scale of P. noctiluca aggregations in this region, we collected semi-quantitative data for this species from an autumn-winter fisheries survey, which deployed 1,948 trawls over 11 years (2008 – 2018) covering most of the Celtic Seas. P. noctiluca was present on the Irish shelf in every year of the study (which is much higher than the historical record), and large aggregations of this warm-temperate species occurred in 5 of 11 years, as isolated events. When aggregations occurred, the highest by-catch density was recorded in the northern Irish shelf (maximum catch of P. noctiluca was 195 kg in 2009). P. noctiluca occurrence and abundance was related to wind patterns and two modes of hydroclimatic variability (the North Atlantic Oscillation index and the Eastern Atlantic Pattern index), which could reflect changes in advective processes that transport offshore populations onto the Irish shelf. A recent increase in the occurrence of P. noctiluca detected in the present work may pose a rising threat to coastal enterprise in the North East Atlantic, namely the aquaculture industry. Together, the present work revealed that different groups of gelatinous zooplankton species displayed different trends in abundance over time in the NEA, and this was likely a result of differences in specific biological traits such as life history type, geographical distribution and temperature preference. The diversity of trends (and associated mechanisms) described here further emphasises the complexity and diversity of gelatinous zooplankton, and the need to study this group of organisms at a high taxonomic resolution and over regional or sub-regional scales.
... Dovekies are diving seabirds that feed on a variety of zooplankton, including fish larvae, euphausids and their primary prey, copepods (Fort et al., 2010). Given that the ranges of their preferred prey, Calanus glacialis, Calanus finmarchicus and Calanus hyperboreus, are shifting northward as a result of climate change (Beaugrand et al., 2009), dovekies will likely have to switch to a less nutritious species or increase foraging effort, both of which may increase daily energy expenditure (DEE) (Amélineau et al., 2016;Grémillet et al., 2012). So far, dovekies have shown a remarkable resilience to the shift, but their ability to buffer its effects may be reaching its limit (Amélineau et al., 2019;Grémillet et al., 2012;Harding et al., 2009b). ...
Preprint
Animal-borne telemetry devices provide essential insights into the life-history strategies of far-ranging species and allow us to understand how they interact with their environment. Many species in the seabird family Alcidae undergo a synchronous moult of all primary flight feathers during the non-breeding season, making them flightless and more susceptible to environmental stressors, including severe storms and prey shortages. However, the timing and location of moult remains largely unknown, with most information coming from studies on birds killed by storms or shot at sea. Using light-level geolocators with saltwater immersion loggers, we develop a method for determining flightless periods in the context of the annual cycle. Four Atlantic puffins (Fratercula arctica) were equipped with geolocator/immersion loggers on each leg to attempt to overcome issues of leg-tucking in plumage while sitting on the water, which confounds the interpretation of logger data. Light level and saltwater immersion time-series data were combined to correct for this issue. This approach was adapted and applied to 40 puffins equipped with the standard practice deployments of geolocators on one leg only. Flightless periods consistent with moult were identified in the dual-equipped birds, whereas moult identification in single-equipped birds was less definitive and should be treated with caution. Within the dual-equipped sample, we present evidence for two flightless moult periods per non-breeding season in two puffins that undertook more extensive migrations (> 2000km), and were flightless for up to 76 days in a single non-breeding season. A biannual flight feather moult is highly unusual among non-passerine birds, and may be unique to birds that undergo catastrophic moult, i.e. become flightless when moulting. Though our conclusions are based on a small sample, we have established a freely available methodological framework for future investigation of the moult patterns of this and other seabird species.
... These important changes in the composition and biomass of species are likely to influence whole ecosystems(Scheffer et al. 2001, Hoegh-Guldberg and Bruno 2010, Doney et al. 2012). The alteration of ecosystem structure and functioning is indirectly influencing lower trophic levels, especially planktivorous organisms through top-down trophic propagation (e.g.Beaugrand et al. 2009, Chust et al. 2014). However, ecosystem consequences of climate change remains poorly understood(Payne et al. 2016a), with only few studies concerning marine systems (e.g.Albouy et al. 2013, Woodworth-Jefcoats et al. 2017, Lotze et al. 2019). ...
Thesis
Full-text available
Environmental conditions are shaping the spatial distribution of marine species worldwide. However, climate change may alter their future distribution, impacting marine resources exploitation and ecosystems balance. In this context, this PhD identifies climate induced impacts in species and geographical areas, by focusing on some species, indigenous or non-indigenous, of commercial interest in the Mediterranean.Based on the ecological niche concept, that defines the potential distribution of a species according to the environmental conditions in which it is observed, we developed a contemporary and future distribution modelling procedure for marine species. This procedure includes an ensemble of statistical algorithms, future climate models and scenarios while accounting for common ecological niche modelling limitations. Applied to small pelagic fish and cephalopods, we projected major climate induced impacts in the Mediterranean Sea by 2100, including local extinctions in its south-eastern basin. Conversely, we projected a distributional range expansion of most of the studied species towards the North, Norwegian and Baltic seas. In the Gulf of Lion, the small pelagic fish distributional range shifts may indirectly impact their harvesting capacity as well as the productivity of low trophic levels. The combined effects of climate warming and the opening of the Suez Canal induced biological invasions, especially in the South-East Mediterranean. These non-indigenous Mediterranean species may be of commercial interest subject to future harvesting. After quantifying the invasive potential of several non-native Mediterranean marine species, according to their functional and ecological traits, we applied our modelling procedure to estimate their future distributional range expansion. We projected a major distributional range expansion of non-native species in the whole Mediterranean Sea by 2100, especially for warming exceeding 2°C.This work highlights the sensitivity of the Mediterranean Sea to climate change while proposing adaptation and conservation perspective of species and ecosystems facing the upcoming climate trends of the 21st century.
... Ocean warming is influencing and modifying species diversity [3], abundance patterns and community composition [83,84], driving extinctions [93], and triggering poleward and regional-scale shifts [88] in species distribution causing biogeographical changes [12,47,91,48,50,150,85]. The magnitude of changes in species distribution and of response rate to climate change-induced stressors [132] vary by a series of factors, including: a species' thermal threshold [50]; sessility [65]; population size; habitat alteration and degradation [91,57]; resource availability; competition with invasive species [102,123]; predator-prey dynamics [125]; migration strategy, and light regimes and reproductive fitness [20,71,87,109,50,145,164]. Shifts are likely to become more rapid and erratic instead of gradual and monotonic [50] with resulting non-linear community responses [133]. ...
Article
Full-text available
A planetary health perspective views human health as a function of the interdependent relationship between human systems and the natural systems in which we live. The planetary health impacts of climate change induced ocean biodiversity loss are little understood. Based on a systematic literature review, we summarize how climate change-induced ocean warming, acidification, and deoxygenation affect ocean biodiversity and their resulting planetary health impacts. These impacts on the planets’ natural and human systems include biospheric and human consequences for ecosystem services, food and nutrition security, human livelihoods, biomedical and pharmaceutical research, disaster risk management, and for organisms pathogenic to humans. Understanding the causes and effects of climate change impacts on the ocean and its biodiversity and planetary health is crucial for taking preventive, restorative and sustainable actions to ensure ocean biodiversity and its services. Future courses of action to mitigate climate change-related ocean biodiversity loss to support sound planetary health are discussed.
... Over 1000 peer-reviewed publications have arisen from its data (reviewed by Batten et al., 2019). This ranges from climate change impacts on planktonic zooplankton distribution over multiple decades (Beaugrand et al., 2002(Beaugrand et al., , 2009, non-native diatom introduction as a result of Arctic ice melt (Reid et al., 2007), climate change environmental influences of harmful algae taxa (Hinder et al., 2012), and food web links of plankton to shellfish and seabirds (Wulf et al., 2018;MacDonald et al., 2019). The CPR survey also records phytoplankton color index (PCI), a visual estimation of green color against a standard color chart from 0 (no color) to 3 (green). ...
Chapter
In the last 10 years there has been an explosion of new taxa (from species to phyla) observed using DNA-based identification tools. These tools are useful for identifying morphologically challenging and “hidden” taxa to complement light microscopy observations. Frequently, DNA tools, such as metabarcoding are used to identify whole communities of thousands of taxa from a single water sample, at exceptional speed. Here, we show how DNA tools can be used to identify plankton taxa that are challenging to identify microscopically or are impossible to identify from partially degraded, archival continuous plankton recorder (CPR) samples, numbering 500,000, dating back up to 1958. Such methods now allow us to enhance microscopy-based taxonomy by identifying these hidden taxa, and observing how plankton communities have changed over decades. We detail several case studies that have used DNA tools on CPR samples. We discuss future challenges and opportunities for this unique sample archive.
... Hooded seals from both stocks travel broadly outside the breeding season, covering much of the North Atlantic Arctic (Andersen et al. 2013, Vacquiè-Garcia et al. 2017b. Prey abundance and distribution in both the Greenland Sea and Northwest Atlantic are undergoing significant change that is very likely to impact hooded seals (e.g., Beaugrand et al. 2009, Christiansen 2017, Koen-Alonso and Cuff 2018, Buren et al. 2019, ICES 2019b, Pedersen et al. 2020. A recent dietary study on Greenland Sea hooded seals found that their diet is dominated by polar cod (Boreogadus saida), which is undergoing serious declines throughout the Barents region (Enoksen et al. 2017). ...
Technical Report
Full-text available
This document provides an update on the status of marine mammals in the circumpolar Arctic from 2015– 2020
... Planktic foraminifera and shelled pteropods are groups of calcifying organisms that are ubiquitous in pelagic marine ecosystems (e.g., Beaugrand et al., 2009;Schiebel and Hemleben, 2017). These organisms are major pelagic producers of calcite and aragonite (most common forms of marine CaCO 3 ), respectively, and alongside coccolithophores play an important role in the ocean biogeochemical cycles and the organic and inorganic carbonate flux to the ocean floor (Milliman, 1993;Buitenhuis et al., 1996Buitenhuis et al., , 2019Schiebel, 2002;Berelson et al., 2007). ...
Article
Full-text available
Planktic foraminfera and shelled pteropods are important calcifying groups of pelagic fauna in all oceans. Their calcium carbonate shells are sensitive to changes in ocean carbonate chemistry predisposing them as an important indicator of ocean acidification. Moreover, planktic foraminfera and shelled pteropods contribute significantly to food webs and vertical flux of calcium carbonate in polar pelagic ecosystems. Here we provide, for the first time, information on the under-ice planktic foraminifera and shelled pteropod abundance, species composition and vertical distribution along a transect (82°–76°N) covering the Nansen Basin and the northern Barents Sea during the polar night in December 2019. The two groups of calcifiers were examined in different environments in the context of water masses, sea ice cover, and ocean chemistry (nutrients and carbonate system). The average abundance of planktic foraminifera under the sea-ice was low with the highest average abundance (2 ind. m–3) close to the sea-ice margin. The maximum abundances of planktic foraminifera were concentrated at 20–50 m depth (4 ind. m–3 and 7 ind. m–3) in the Nansen Basin and at 80–100 m depth (13 ind. m–3) close to the sea-ice margin. The highest average abundance (13 ind. m–3) and the maximum abundance of pteropods (40 ind. m–3) were found in the surface Polar Water at 0–20 m depth with very low temperatures (–1.9 to –1 °C), low salinity (<34.4) and relatively low aragonite saturation of 1.43–1.68. The lowest aragonite saturation (<1.3) was observed in the bottom water in the northern Barents Sea. The species distribution of these calcifiers reflected the water mass distribution with subpolar species at locations and depths influenced by warm and saline Atlantic Water, and polar species in very cold and less saline Polar Water. The population of planktic foraminifera was represented by adults and juveniles of the polar species Neogloboquadrina pachyderma and the subpolar species Turborotalita quinqueloba. The dominating polar pteropod species Limacina helicina was represented by the juvenile and veliger stages. This winter study offers a unique contribution to our understanding of the inter-seasonal variability of planktic foraminfera and shelled pteropods abundance, distribution and population size structure in the Arctic Ocean.
... Monitoring zooplankton communities provides us with critical insight on the state of the pelagic ecosystem, as well as the implications for consumers, including harvestable species. Compared to organisms in other marine and terrestrial habitats, most planktonic species are characterized by relatively short generation times and react very rapidly to shifts in the physical environment, acting as first sentinels of climate change (Richardson, 2008;Beaugrand et al., 2009). ...
Article
Full-text available
Although metabarcoding is a well-established tool for describing diversity of pelagic communities, its quantitative value is still controversial, with poor correlations previously reported between organism abundance/biomass and sequence reads. In this study, we explored an enhanced quantitative approach by metabarcoding whole zooplankton communities using a highly degenerate primer set for the mitochondrial marker cytochrome oxidase I and compared the results to biomass estimates obtained using the traditional morphological approach of processing zooplankton samples. As expected, detected species richness using the metabarcoding approach was 3–4 times higher compared to morphological processing, with the highest differences found in the meroplankton fraction. About 75% of the species identified using microscopy were also recovered in the metabarcoding run. Within the taxa detected using both approaches, the relative numbers of sequence counts showed a strong quantitative relationship to their relative biomass, estimated from length-weight regressions, for a wide range of metazoan taxa. The highest correlations were found for crustaceans and the lowest for meroplanktonic larvae. Our results show that the reported approach of using a metabarcoding marker with improved taxonomic resolution, universal coverage for metazoans, reduced primer bias, and availability of a comprehensive reference database, allow for rapid and relatively inexpensive processing of hundreds of samples at a higher taxonomic resolution than traditional zooplankton sorting. The described approach can therefore be widely applied for monitoring or ecological studies.
... Dovekies are diving seabirds that feed on a variety of zooplankton, including fish larvae, euphausids and their primary prey, copepods (Fort et al., 2010). Given that the ranges of their preferred prey, Calanus glacialis, Calanus finmarchicus and Calanus hyperboreus, are shifting northward as a result of climate change (Beaugrand et al., 2009), dovekies will likely have to switch to a less nutritious species or increase foraging effort, both of which may increase daily energy expenditure (DEE) (Amélineau et al., 2016;Grémillet et al., 2012). So far, dovekies have shown a remarkable resilience to the shift, but their ability to buffer its effects may be reaching its limit (Amélineau et al., 2019;Grémillet et al., 2012;Harding et al., 2009b). ...
Article
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Seabirds are particularly vulnerable to the direct and indirect effects of climate change, however little is known about those impacts outside of the breeding season. This lack of knowledge is problematic because the conditions encountered during migration and wintering strongly shape seabird population dynamics. It is therefore essential to understand the effects of climate on their winter distribution and migration routes. Linking the distribution of organisms to environmental factors is therefore a primary task benefiting from the concept of energyscapes (defined as the variation of an organism's energy requirements across space according to environmental conditions) which has recently provided a mechanistic explanation for the distribution of many animals. In this context, we have predicted the current and future winter habitats of five species representing 75% of the seabird community in the North Atlantic (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla). To this aim, we monitored the movements of more than 1500 individuals to identify the birds' preferred habitats through resource selection functions based on the modeling of their energy expenditure and prey availability. Electronic tracking data were also overlaid with cyclone locations to map areas of high exposure for the seabird community across the North Atlantic. In addition, we explored the energetic consequences of seabird exposure to storms using a mechanistic bioenergetic model (Niche MapperTM). Finally, we examined the impact of total summer sea ice melt from 2050 on Arctic bird migration. Our analyses predict a northward shift in the preferred wintering areas of the North Atlantic seabird community, especially if global warming exceeds 2°C. Our results suggest that cyclonic conditions do not increase the energy requirements of seabirds, implying that they die from the unavailability of prey and/or inability to feed during cyclones. Finally, the melting sea ice at the North Pole may soon allow 29 species of Arctic birds to make new trans-Arctic migrations between the Atlantic and the Pacific. We also estimate that an additional 26 currently migratory species could remain in the Arctic year-round. This work illustrates how climate change could radically alter the biogeography of migratory species and we provide a methodological toolbox to assess and predict these changes by combining movement ecology and energetic physiology.
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We show that the distributions of both exploited and nonexploited North Sea fishes have responded markedly to recent increases in sea temperature, with nearly two-thirds of species shifting in mean latitude or depth or both over 25 years. For species with northerly or southerly range margins in the North Sea, half have shown boundary shifts with warming, and all but one shifted northward. Species with shifting distributions have faster life cycles and smaller body sizes than nonshifting species. Further temperature rises are likely to have profound impacts on commercial fisheries through continued shifts in distribution and alterations in community interactions.
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Hutchinson's (1957; Cold Spring Harbour Symp Quant Biol 22:415-427) niche concept is being used increasingly in the context of global change, and is currently applied to many ecological issues including climate change, exotic species invasion and management of endangered species. For both the marine and terrestrial realms, there is a growing need to assess the breadth of the niches of individual species and to make comparisons among them to forecast the species' capabilities to adapt to global change. In this paper, we describe simple non-parametric multivariate procedures derived from a method originally used in climatology to (1) evaluate the breadth of the ecological niche of a species and (2) examine whether the niches are significantly separated. We first applied the statistical procedures to a simple fictive example of 3 species separated by 2 environmental factors in order to describe the technique. We then used it to quantify and compare the ecological niche of 2 key-structural marine zooplankton copepod species, Calanus finmarchicus and C. helgolandicus, in the northern part of the North Atlantic Ocean using 3 environmental factors. The test demonstrates that the niches of both species are significantly separated and that the coldwater species has a niche larger than that of its warmer-water congeneric species.
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Global climate change is expected to modify the spatial distribution of marine organisms. However, projections of future changes should be based on robust information on the ecological niche of species. This paper presents a macroecological study of the environmental tolerance and ecological niche (sensu Hutchinson 1957, i.e. the field of tolerance of a species to the principal factors of its environment) of Calanus finmarchicus and C. helgolandicus in the North Atlantic Ocean and adjacent seas. Biological data were collected by the Continuous Plankton Recorder (CPR) Survey, which samples plankton in the North Atlantic and adjacent seas at a standard depth of 7 m. Eleven parameters were chosen including bathymetry, temperature, salinity, nutrients, mixed-layer depth and an index of turbulence compiled from wind data and chlorophyll a concentrations (used herein as an index of available food). The environmental window and the optimum level were determined for both species and for each abiotic factor and chlorophyll concentration. The most important parameters that influenced abundance and spatial distribution were temperature and its correlates such as oxygen and nutrients. Bathymetry and other water-column-related parameters also played an important role. The ecological niche of C. finmarchicus was larger than that of C. helgolandicus and both niches were significantly separated. Our results have important implications in the context of global climate change. As temperature (and to some extent stratification) is predicted to continue to rise in the North Atlantic sector, changes in the spatial distribution of these 2 Calanus species can be expected. Application of this approach to the 1980s North Sea regime shift provides evidence that changes in sea temperature alone could have triggered the substantial and rapid changes identified in the dynamic regimes of these ecosystems. C. finmarchicus appears to be a good indicator of the Atlantic Polar Biome (mainly the Atlantic Subarctic and Arctic provinces) while C. helgolandicus is an indicator of more temperate waters (Atlantic Westerly Winds Biome) in regions characterised by more pronounced spatial changes in bathymetry.
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It has been assumed that the volume of seawater filtered by each sample remained constant and close to 3 m,. In this study, the volume filtered for each CPR sample was measured on two routes (SA and IN), monitored by the CPR survey, between 1995 and 2000.Although the filtered volume was near the theoretical value of 3 m, on the SA route (3.2 m,), it was significantly higher on the IN route (3.8 m,). A significant negative relationship was found between the volume filtered and the speed of the ships. This relationship indicates that the faster the speed of the ship, the lower the volume filtered. This could have implications for the CPR survey as the speed of the ships has increased continuously since the end of the 1950s. However, no significant correlation was found between the long-term changes in the speed of the ships and two commonly used indicators of plankton variability: the Phytoplankton Colour and the Total Copepods indices. This absence of relationship may indicate that the effect found is small in comparison with the influence of hydroclimatic forcing, although a more extensive study is needed to confirm these findings.
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This paper examines spatial distribution in the pelagic diversity of calanoid copepods in the North Atlantic and the North Sea, taking into account changes at seasonal and diel scales. Based on 40 yr of sampling by the Continuous Plankton Recorder (CPR) survey, the diversity (as number of taxa) was estimated on a regular grid for each month and time of day. Principal components analysis (PCA) allowed spatial decomposition of diversity, detection of major seasonal and diel patterns, the location of regions where these occur, and finally the modelling of temporal changes at seasonal land diel scales. The results underline the importance of hydrography and topography in the regulation of pelagic diversity, By considering these abiotic factors and the characteristics of seasonal and diel changes in diversity, a partition of the North Atlantic and the North Sea is proposed. This demonstrates the importance of the warm North Atlantic Current and the continental slope currents and undercurrents along the European Continental Shelf. It is suggested that modification in the path or intensity of these currents could imply marked changes in the structure and functioning of ecosystems west and north of the British Isles.
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Many seabirds in the North Sea feed on lesser sandeels Ammodytes marinus during the breed- ing season. Unprecedented breeding failures were recorded at many seabird colonies on the east coast of Britain in 2004. We used demographic, dietary and behavioural data from a long-term study of a colony of common guillemots Uria aalge, the most abundant seabird species in the North Sea, to set the 2004 season in context. Birds at this colony showed greatly reduced breeding success and those chicks that did survive left the colony in very poor condition. The main prey item fed to chicks in 2004 was sprat Sprattus sprattus rather than sandeels, and parents increased the amount of time spent foraging, frequently leaving chicks unat- tended in order to maintain a normal feeding rate. The calculated daily food intake of chicks derived from these values did not differ markedly from previous years and therefore the magnitude of the impact on chick growth and breeding success appeared dispro- portionately large. However, nutrient analyses of fish collected from birds in 2004 revealed them to be of sig- nificantly lower energy value than expected. Poor food quality therefore appeared to be the proximate cause of seabird breeding failure in 2004 giving support to the 'junk-food' hypothesis. Single-prey loaders such as guillemots will be particularly sensitive to reductions in the energy value of food items. The reasons for the poor fish condition in this part of the North Sea are currently unknown, but the results provide further evidence of major changes in the North Sea food web.
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Analyses of long-term time series of North Sea plankton and sea surface temperature (SST) data reveal that the annual planktonic larval abundance of three benthic phyla, Echinodermata, Arthropoda, and Mollusca, responds positively and immediately to SST. Long-term outcomes for the planktonic abundance of these three phyla are different, however. The planktonic larvae of echinoderms and decapod crustaceans have increased in abundance from 1958 to 2005, and especially since the mid-1980s, as North Sea SST has increased. In contrast, the abundance of bivalve mollusc larvae has declined, despite the positive year-to-year relationship between temperature and bivalve larval abundance continuing to hold. We argue that the changes in meroplankton abundance, coincident with increased phytoplankton and declining holoplankton, reflect the synchronous effect of rising SST and related changes in the pelagic community on the reproduction and recruitment of many benthic marine invertebrates. Under this scenario, the long-term decline in bivalve mollusc larvae will reflect increased predation on the settled larvae and adults by benthic decapods. These alterations in the zooplankton may therefore describe an ecosystem-wide restructuring of North Sea trophic interactions.
Chapter
Principal component analysis has often been dealt with in textbooks as a special case of factor analysis, and this tendency has been continued by many computer packages which treat PCA as one option in a program for factor analysis—see Appendix A2. This view is misguided since PCA and factor analysis, as usually defined, are really quite distinct techniques. The confusion may have arisen, in part, because of Hotelling’s (1933) original paper, in which principal components were introduced in the context of providing a small number of ‘more fundamental’ variables which determine the values of the p original variables. This is very much in the spirit of the factor model introduced in Section 7.1, although Girschick (1936) indicates that there were soon criticisms of Hotelling’s method of PCs, as being inappropriate for factor analysis. Further confusion results from the fact that practitioners of ‘factor analysis’ do not always have the same definition of the technique (see Jackson, 1981). The definition adopted in this chapter is, however, fairly standard.
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Autocorrelation in fish recruitment and environmental data can complicate statistical inference in correlation analyses. To address this problem, researchers often either adjust hypothesis testing procedures (e.g., adjust degrees of freedom) to account for autocorrelation or remove the autocorrelation using prewhitening or first-differencing before analysis. However, the effectiveness of methods that adjust hypothesis testing procedures has not yet been fully explored quantitatively. We therefore compared several adjustment methods via Monte Carlo simulation and found that a modified version of these methods kept Type I error rates near a. In contrast, methods that remove autocorrelation control Type I error rates well but may in some circumstances increase Type II error rates (probability of failing to detect some environmental effect) and hence reduce statistical power, in comparison with adjusting the test procedure. Specifically our Monte Carlo simulations show that prewhitening and especially first-differencing decrease power in the common situations where low-frequency (slowly changing) processes are important sources of covariation in fish recruitment or in environmental variables. Conversely, removing autocorrelation can increase power when low-frequency processes account for only some of the covariation. We therefore recommend that researchers carefully consider the importance of different time scales of variability when analyzing autocorrelated data.