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Temporal and spatial variation in the food web structure in artificial reef areas and adjacent habitats in Haizhou Bay
Abstract
Artificial reef is regarded as an effective tool for restoring habitats and supporting the marine ecosystem. While the energy flow and material exchange in the food web of artificial reef ecosystem still remain vacant and should be further understood. In this study, stable isotopic characteristics (δ13C and δ15N) were used to identify the trophic niches and potential carbon sources of consumers (fish and invertebrates) in artificial reef areas and adjacent habitats in Haizhou Bay (the estuary area (EA), the aquaculture area (AA), the artificial reef area (AR), the natural area (NA) and the comprehensive effect area (CEA)) in spring and autumn. The results showed that the average δ13C for all consumers decreased from -16.99 ± 2.07‰ to -21.81 ± 1.66‰, and the average δ15N ranged from 11.37 ± 0.35‰ to 14.69 ± 0.64‰ in all seasons. A SIBER model revealed highly similar trophic niche among habitats in autumn, and lower overlap in spring. The SIMMR model showed that phytoplankton and sedimentary organic matter (SOM) were the major contributors to consumers, and particulate organic matter (POM) accounted for less contribution. In AA and NA phytoplankton and SOM generally contributed fairly equally to most fish, while single SOM sources were major contributors to nearly all the species in AR and CEA. Our findings reveal that ARs can serve as seascape mosaics to increase fish community diversity because of their high variation in the δ13C value and the trophic niches from EA to the NA. Preliminary multidisciplinary studies are needed for the mitigation of effects before any implementations deployed to the offshore waters that influence habitat connectivity, especially some habitat–specific migratory species.
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Artificial reef is a man-made object that is deployed purposefully on the seafloor to restore the offshore fishery resources and the ecological environment. To secure its ecological effects, it is important to study the possible instability of artificial reefs, like drifting and reversing caused by burial and scour in different seafloor conditions. In the present study, experiments of local scour around an artificial reef are carried out in steady currents. The effect of the open-area ratios and the open-hole heights of the cubic reefs, and the bottom angles of the triangular reefs on the time-scale of the scour process and the equilibrium scour depth are investigated. The results indicate that for the cubic artificial reef, the scour depth decreases with the increasing open-area ratios, and increases with the increasing open-hole heights. In the present study, the optimal prototype of the cubic reef with an open-area ratio of 0.49 and open-height of 0.7m produces the minimum scour depth. For the triangular reef, the scour depth increases when the bottom angle increases. Moreover, based on the experimental results, empirical equations of the effects of the cut-opening and the bottom angle on the maximum equilibrium scour depth are proposed. The formulas will provide theoretical support and practical guidance for the optimized design and construction of artificial reefs.
Quantification of the physical and biological factors that influence the spatial structuring of food webs is central to inform effective resource management. We used baseline‐corrected stable isotope ratios (δ13C and δ15N) of 63 invertebrate and fish to investigate food web structure across a continental shelf gradient—the Celtic Sea Shelf in the Northeast Atlantic Ocean. Hierarchical clustering on δ13C and δ15N showed that the shelf food web is characterized by four trophic levels with trophic groups spread across pelagic and benthic trophic pathways. Four biomass‐weighted isotopic diversity metrics provided indicators on the status of the system, showing a relatively complex food web with high trophic redundancy at intermediate trophic levels suggesting resilience to disturbances. Two sets of statistical models, at the community scale and for each trophic group, identified five distinct trophic assemblages associated with different chlorophyll a concentrations, water depth, and bottom temperature. A cold, vertically mixed‐water assemblage over the outer shelf comprised the largest habitat and most diverse assemblage, highlighting the importance of cold productive conditions in the Celtic Sea. Trophic group model results were used to generate spatial area predictions to compare functioning of groups using isotopic overlap (similarity and nestedness) metrics. Isotopic niche area was larger (spanning two trophic levels) in shallow habitats, but not in habitats underlying high primary production or nutrient‐rich water masses, suggesting stronger benthic‐pelagic trophic coupling in inner shelf habitats. Results suggest that depth and intensity of pelagic production are major drivers of trophic structure and functioning of Celtic Sea communities.
As marine ecosystems are harvested or modified by anthropogenic or natural factors, there is an increasing demand for indicators of trophic web health or status. The Magellanic Penguin (Spheniscus magellanicus) is a widely distributed species that forages in the Patagonian Shelf. During breeding, this species is a central-place forager that feeds mainly on schooling fish, with Argentine anchovy (Engraulis anchoita) being the dominant prey in the north and Fuegian sprat (Sprattus fuegensis) in the south of the Argentine Patagonian distribution (40–55°S). Like most forage fish, both prey species display large natural interannual recruitment fluctuations. We used stable isotope analysis of adult Magellanic penguin blood obtained at twelve colonies along its Patagonian latitudinal range to assess changes in isotopic niche and in trophic level as a response to interannual changes in abundance and spatial segregation of forage fish size classes, respectively. Magellanic penguins showed large isotopic niche fluctuations among breeding seasons, explained by the contribution of forage fish in their diet. Furthermore, the size of the isotopic niche negatively correlated with forage fish biomass estimated from acoustic surveys and with their contribution in penguin diet. We defined an isotopic niche size threshold that indicates low abundance of forage fish in nearby feeding grounds. In addition, the trophic level of Magellanic penguins increased with latitude, which corresponds to the size-distribution of both main forage fish species, showing that penguins from different colonies target different size classes of their main prey. We present here a simple and easy to implement indicator to monitor the status of the base of the food web in one of the most productive marine areas in the world, which constitutes the feeding ground of a diverse group of high trophic level predators and sustains large-scale fisheries.
The physical properties of habitats are crucial determinants of community structure with significant effects on food web dynamics. We examined the effects of rock pool physical properties (e.g. pool size, water depth) and short-term temporal (seasonal) change (e.g. temperature, nutrients) on food web structure at small spatial scales (c. 500 m) on the warm temperate coast of South Africa. Using stable carbon and nitrogen isotope signatures, we characterised food web structure with Layman metrics and quantified food web size, defined as the total area in isotopic space occupied by consumer species. The effects of rock pool physical properties and seasonal changes on species counts and food web structure were evaluated using a Bayesian generalised linear mixed model approach. Substratum type, water depth, pool size, phosphate concentrations, salinity and temperature all influenced overall food web dynamics. A winter reduction of sand cover led to a more heterogeneous substratum and a significant increase in species counts, while consumer niche similarity decreased with increasing pool size in summer. The range of δ15N values, or trophic height, was negatively and positively affected by salinity and phosphate levels, respectively. Overall, the effects of pool physical properties on food web structure were moderated by seasonality.
Human activities have reduced the carrying capacity of many estuarine systems by degrading and removing habitat. Artificial reefs may increase estuarine rocky‐reef habitat, but our understanding of their ecological impact is limited. In particular, the question of whether fish on artificial structures are produced by the habitat or attracted from nearby natural rocky‐reefs is of concern.
We used baited remote underwater video at artificial reef sites and nearby natural reef sites to investigate the influence of artificial reefs on fish abundance in estuaries with low amounts of natural rocky‐reef. We measured total fish abundance and the abundance of three species of fisheries importance (all in the family Sparidae) before artificial reef deployment (Reefballs®), 1 year after and 2 years after. This design was replicated in three widely separate estuaries over 4 years.
During the 2 years post‐deployment, abundance of Sparidae fish increased on both artificial and natural rocky‐reefs, even when artificial reefs were deployed in different years and seasons. Total fish abundance increased at artificial reef sites with no evidence of change at natural rocky‐reef sites.
Our findings provide evidence that the fish seen on artificial reefs were not attracted from the nearby rocky‐reefs and were likely ‘produced’ by the addition of artificial reefs in these estuaries. Artificial reefs can increase the carrying capacity in these estuaries by providing refuge that would otherwise be unavailable.
Synthesis and applications. The increased fish abundance in three estuaries at both artificial reef and natural reef locations shows that purpose‐built artificial reefs can be used in conjunction with restoration/protection of existing natural habitat, to increase estuarine carrying capacity and fish abundance. This may be for fisheries enhancement or estuarine restoration.
Life history strategies and potential marine niche use of Arctic charr Salvelinus alpinus (n = 237, 84–652 mm, total body length, LT) were determined during the ice‐free season (2012) at three different watercourses in south‐western Greenland. All Arctic charr were collected from freshwater habitats. Based on stable isotopes of δ³⁴S, the Arctic charr were categorized as either marine‐ or freshwater‐dependent feeders. The use of time‐integrated trophic tracers (stable isotopes of δ¹³C, δ¹⁵N, δ³⁴S) suggested that several trophic groups of Arctic charr operate alongside within each fjord system. The groups suggested were one group that specialized in the marine habitat, in addition to two freshwater resident morphs (small‐sized resident and/or large‐growing cannibalistic individuals). Stomach contents consisted entirely of freshwater and terrestrial prey (i.e., insects), indicating that marine‐dependent feeders also fed in freshwater habitats after return from their marine migration. Growth and maturity patterns further supported variable life history strategies within each watercourse. The life history strategy patterns and marine trophic niche use were consistent across the watercourses along several hundred kilometres of coastline. This study represents the first ecological baseline for partially anadromous populations of Greenland Arctic charr.
A study on the trophic ecology of fishes is one of the approaches to acquire a better understanding of fish feeding strategies, prey inclinations, niche competition and increase knowledge on the working of marine biological system. The present work aims to determine diet composition and trophic niche overlap among species of engraulid fishes in the coastal area of Pabean. Sampling was performed monthly from April 2016 to March 2017 and fishes were captured using gill nets and guiding barriers. During research period, seven species of engraulid were collected, namely Thryssa hamiltonii (with total length ranged from 47-186 mm), Thryssa mystax (53-151 mm), Thryssa kammalensis (66-112 mm), Thryssa setirostris (106-132 mm), Stolephorus indicus (54-133 mm), Stolephorus dubiosus (56-75 mm) and Stolephorus tri (66-91 mm). Prey of fishes were classified into four taxonomic groups i.e., Bacillariophyceae, Polychaeta, Crustacea and Pisces. Crustacea was the most consumed category (IRI>90%), recorded for all species of engraulid fishes, followed by Bacillariophyceae (<10%), polychaeta and fish juveniles (<5%). This finding indicates that all engraulid fishes in Pabean waters are crustasivore. Inter-specific feeding overlap was high, indicates that feeding competition among engraulid fishes tends to be high when food resources is decreased.
The need for theories that address food web assembly and complexity over multiple spatial scales are critical to understanding their stability and persistence. In a meta-food web – an integrated network of local food webs – spatial heterogeneity in physical processes may have profound effects on food web function and energy flow. In the Arctic, surface water connectivity plays a vital role in determining fish assemblage composition, and potentially, food web structure. We examined lentic food web complexity associated with heterogeneity in surface water connectivity among Arctic lakes at the local scale, by contrasting lakes over a stream-lake connectivity gradient, and at the regional scale, by contrasting two locations with different surface water conditions (i.e., wet and dry) on the Arctic Coastal Plain of Alaska. Among lakes and across locations, increased hydrologic connectivity between streams and lakes increased the number of fish species and increased the complexity of the food web. The interaction of the region's hydrologic connectivity, local stream-lake connections, and the trophic niches of relevant fish species produced integrated, complex meta-food webs. Fully understanding mechanisms that support meta-food web stability are crucial when assessing future changes to Arctic stream-lake networks and the function and persistence of aquatic food webs.
Marine ecosystem models that incorporate fisheries and climate change are essential for forecasting and guiding sustainable ecosystem management decisions. A key challenge in developing and applying ecosystem models that are able to provide robust predictions for management is to accurately represent the structure and dynamics of food webs. Ecosystem models vary in complexity and formulation and there is no set method routinely used to evaluate the skill of a model to correctly represent food web characteristics. One approach for evaluation is the comparison of modelled food web attributes with measures of stable isotope composition of taxa. While this approach has been used in some studies, its full potential has not been realised. Critically, directly modelling the assumed underlying processes that give rise to stable isotope signatures in ecosystem models has only just begun to be explored. Here, we examine the process of building ecosystem models and assess the potential for incorporating stable isotope results into this process, including the evaluation of model skill. We consider both size- and species- based ecosystem modelling approaches for their potential in this regard. We discuss that whilst conceptually achievable, in practice this is highly challenging through highlighting the advances and challenges in using stable isotope data, including the implications of precision associated with isotope-based measurements. We conclude with a proposed framework for explicitly integrating stable isotope data into both size- and species- based ecosystem models as an example of how signatures may be more powerfully used in the modelling process, and highlight key needs for future work.
Investigating the niche overlap of ecologically similar species can reveal the mechanisms that drive spatial partitioning in high-diversity systems. Understanding how food resources are used and whether the diets of neighboring species are different are particularly important when considering the coexistence and functional role of species. Territorial damselfish on coral reefs are considered to be herbivores that defend algal mats from other food competitors. However, this guild contains numerous small species whose functional role and dietary diversification is poorly understood. Here, the relationships between diet and spatial distribution of seven intermediate-sized territorial damselfishes at Kimbe Bay, Papua New Guinea (5°30′S, 150°05′E) were investigated. These species partition habitat across three reef zones with distinct patterns of fine-scale distribution. It was predicted that neighboring species partition food resources with minimal dietary overlap. Examination of isotope ratios of carbon and nitrogen delineated three distinct feeding strategies: pelagic, reef-based, and an intermediate group feeding on both prey types. None of the species appear to be strict herbivores. Adjacent species exhibited high–intermediate trophic niche partitioning when examining pelagic versus reef-based production sources, with two species previously described as benthic herbivores exhibiting pelagic feeding. The study demonstrates that diet reinforces the patterns of spatial partitioning and coexistence among ecologically similar damselfishes. These findings add to a growing view that interspecific differences among similar species are lost when categorizing species into broad functional classifications, and that previous studies suggesting that territorial damselfish are strictly reef-based feeders may not be applicable in all systems or for all species.
Stable isotope technique was applied to investigate the small and medium-size consumers including not only fish, shrimps, crabs, cephalopods, snails and bivalves, but also the specimens of their potential carbon sources, which were collected in the marine ranching area of Haizhou Bay during the spring of 2015. IsoSource model was adopted to calculate the contribution of potential carbon sources to the consumers. Biospeciemens collected in the summer of 2014 were compared with those in the spring of 2015, aiming to analyze the seasonal variation in the trophic structure of food web. Six quantitative community indices were calculated based on the isotope values of the organisms in Haizhou Bay. The results showed that the δ¹³C values of consumers ranged from -18.9‰ to -17.1‰, and the δ¹³C values of three potential food sources ranged from -18.1‰ to -23.4‰ in the spring of 2015. The calculation results of IsoSource model further demonstrated that the phytoplankton was the most important carbon source for consumers (80.8%), followed by sediment organic matter (10.8%) and particulate organic matter (8.4%). There was a significant difference in the δ¹³C values between the biospecimens in the summer of 2014 and those in the spring of 2015, while no significant difference was observed in δ¹⁵N values. Trophic structure of community-wide differed remarkably in different seasons indicated by the six quantitative community indices. The δ¹³C range, total area, mean nearest neighbor distance and standard deviation of nearest neighbor distance of the community were much higher in 2014 than those in 2015, but the δ¹⁵N range and mean distance to centroid showed no significant change. The trophic structure redundancy was lower in the summer of 2014 compared with that in the spring of 2015, however, the diversity of food resources was higher in the summer of 2014.
Stable isotope analyses and derived population-level metrics were used to quantitatively analyse spatial and seasonal heterogeneity in the fish trophic dynamics in relation to environmental variables in Mwanza Gulf, Lake Victoria (Tanzania). The fish community in Lake Victoria, including the top predator Nile perch, is generally omnivorous with a heavy reliance on invertebrates. This is in contrast to findings based on stomach content analyses of Nile perch, which showed a stronger reliance on fish. We tested two hypotheses: (1) during the rainy seasons multiple carbon sources influence the food-web structure inside the Gulf, leading to increased carbon ranges and trophic diversity. (2) During dry periods, the food-web structure mainly relies on pelagic primary production, reducing carbon ranges and trophic diversity. Carbon sources indeed varied seasonally and spatially, affecting the fish community at the highest trophic levels. With the onset of rains, carbon sources became spatially highly differentiated with enriched δ¹³C values of fish in shallow water inside the Gulf and depleted δ¹³C values in open waters. Metrics associated with niche size correlated significantly with seasonally varying environmental variables, while δ¹³C ranges correlated with spatially varying environmental variables.
Stable-isotope analysis supplemented with stomach contents data from published sources was used to quantify the trophic niches, trophic niche overlaps and potential trophic redundancy for the most commonly caught fish species from an East African nearshore seagrass community. This assessment is an important first step in quantifying food-web structure in a region subject to intense fishing activities. Nearshore food webs were driven by at least two isotopically distinct trophic pathways, algal and seagrass, with a greater proportion of the sampled species feeding within the seagrass food web (57%) compared with the algal food web (33%). There was considerable isotopic niche overlap among species (92% of species overlapped with at least one other species). Narrow isotopic niche widths of most (83%) species sampled, low isotopic similarity (only 23% of species exhibited no differences in δ(13) C and δ(15) N) and low predicted trophic redundancy among fishes most commonly caught by fishermen (15%), however, suggest that adjustments to resource management concerning harvesting and gear selectivity may be needed for the persistence of artisanal fishing in northern Tanzania. More detailed trophic studies paired with information on spatio-temporal variation in fish abundance, especially for heavily targeted species, will assist in the development and implementation of management strategies to maintain coastal food-web integrity.
A goal of designed artificial reefs (ARs) is to enhance fish abundance, species diversity and fishing opportunities by providing food and refuge for fish. Quantifying the contribution of ARs to coastal ecosystems and fisheries productivity requires an understanding of fish presence at the structure and connectivity with surrounding habitats. In the present study, the movements and presence of 10 eastern fiddler rays (Trygonorrhina fasciata), 17 Port Jackson sharks (Heterodontus portusjacksoni) and 18 bluespotted flathead (Platycephalus caeruleopunctatus) were monitored using acoustic telemetry around a designed AR in 38-m depth near Sydney, Australia. Fiddler rays exhibited an average short-term presence of 43% at the AR, and 26% over the ~20-month monitoring period, which was significantly higher than the other two species. Fish tagged at the AR showed high affinity to the site at which they were tagged compared with fish tagged on natural reef. All three species moved frequently between the AR and the other reefs in the area, indicating that the AR may increase the connectivity between adjacent habitats and aid the dispersion of benthic species. The moderate presence at the AR suggests that these species may contribute to some biomass production at this AR by incorporating this reef in their natural range.
Burial of organic carbon in marine sediments has a profound influence in
marine biogeochemical cycles and provides a sink for greenhouse gases such
as CO2 and CH4. However, tracing organic carbon from primary
production sources as well as its transformations in the sediment record
remains challenging. Here we examine a novel but growing tool for tracing
the biosynthetic origin of amino acid carbon skeletons, based on naturally
occurring stable carbon isotope patterns in individual amino acids (δ13CAA).
We focus on two important aspects for δ13CAA utility in sedimentary paleoarchives: first, the fidelity
of source diagnostic of algal δ13CAA patterns across
different oceanographic growth conditions, and second, the ability of
δ13CAA patterns to record the degree of subsequent
microbial amino acid synthesis after sedimentary burial. Using the marine
diatom Thalassiosira weissflogii, we tested under controlled conditions how δ13CAA
patterns respond to changing environmental conditions, including light,
salinity, temperature, and pH. Our findings show that while differing
oceanic growth conditions can change macromolecular cellular composition,
δ13CAA isotopic patterns remain largely invariant. These
results emphasize that δ13CAA patterns should accurately
record biosynthetic sources across widely disparate oceanographic
conditions. We also explored how δ13CAA patterns change as
a function of age, total nitrogen and organic carbon content after burial,
in a marine sediment core from a coastal upwelling area off Peru. Based on
the four most informative amino acids for distinguishing between diatom and
bacterial sources (i.e., isoleucine, lysine, leucine and tyrosine),
bacterially derived amino acids ranged from 10 to 15 % in the sediment layers from the
last 5000 years, and up to 35 % during the last glacial period. The
greater bacterial contributions in older sediments indicate that bacterial
activity and amino acid resynthesis progressed, approximately as a function
of sediment age, to a substantially larger degree than suggested by changes
in total organic nitrogen and carbon content. It is uncertain whether archaea may
have contributed to sedimentary δ13CAA patterns we
observe, and controlled culturing studies will be needed to investigate
whether δ13CAA patterns can differentiate bacterial from archeal
sources. Further research efforts are also needed to understand how closely
δ13CAA patterns derived from hydrolyzable amino acids
represent total sedimentary proteineincous material, and more broadly
sedimentary organic nitrogen. Overall, however, both our culturing and
sediment studies suggest that δ13CAA patterns in sediments
will represent a novel proxy for understanding both primary production
sources, and the direct bacterial role in the ultimate preservation
of sedimentary organic matter.
Coastal ecosystems such as estuaries, tidal wetlands and shallow coastal waters are often highly productive and provide important habitats to many recreationally and commercially important fish and invertebrates that use these areas as nursery, feeding and/or reproduction grounds. The diversity of coastlines found worldwide results in differences in types of provisioning and function, and in community structure and trophic organisation. Since almost all coastal fishery species require particular components of the seascapes during specific stages of their life-cycles, it is important to understand the way fish use different habitats throughout ontogeny. Access to rich feeding environments is a key contributor to habitat value, and so knowledge on food webs and feeding relationships, and how these vary over space and time, is central to understanding the importance of the different coastal environments. However, the functional roles of the different habitats in supporting fishery species are still not well understood for most regions. In this study, we review and discuss the available literature to identify key knowledge gaps in the understanding of habitat- and context-specific food webs and trophic interactions supporting fisheries species relying on coastal ecosystems. We use Australia and Australian fisheries species as a case-study, as Australia’s extensive coastline encompasses many of the coastal ecosystems and habitats found globally. Given the ever increasing transformation of coastal landscapes by either direct human action or by sea level rise and changing climate, these knowledge gaps need to be urgently addressed for appropriate management and mitigation of various impacts.
Stable isotopes (δ
13C and δ
15N) were used to analyse the food web downstream of the largest estuary on the French coast: the Gironde. The different sources of organic matter supporting the most abundant and commercially important fish species were determined, as well as habitat connectivity for fish. Stable isotope analysis was performed in different producers (marine, freshwater and local sources), primary consumers (zooplankton and macrozoobenthos) and nine fish species (Alosa alosa, Engraulis encrasicolus, Sprattus sprattus, Liza ramada, Pomatoschistus minutus, Platichthys flesus, Solea solea, Dicentrarchus punctatus and Argyrosomus regius) in three habitats of the downstream area of the estuary in June–July 2012. All sources and invertebrates had significantly different isotopic signatures in different habitats. Only sole, S. solea, presented distinct dual isotopic signatures, indicating a higher feeding location fidelity, no other fish species showed significant differences in isotopic signatures. This overlap was interpreted as evidence that fish had not been feeding exclusively in the habitat where they were collected, instead ingesting food with different isotopic signatures, reflecting high habitat connectivity for these fish. As the base of the fish food web significantly differed among habitats, the present study indicated the suitability of stable isotopes in tracing fish movements and their fidelity/connectivity for habitats separated by less than 10 km, particularly estuarine habitats without salinity differences but located on opposite banks. The SIAR mixing model estimations of organic matter contribution to fish diets in the Gironde estuary were quite similar for the fish species investigated. The major organic source was marine-derived POM, with contributions >75 % for each species. Freshwater and local POM (generally indicated as the sources structuring estuarine food webs) contributed little to the overall fish food webs in the Gironde estuary. Only flounder, P. flesus, and shad, A. alosa, migratory amphihaline species, utilised freshwater POM in greater proportion than marine. The observed low freshwater POM-high marine POM contribution to the fish food web seems to be explained by the reduced intertidal surface of the system. This characterization of the trophic base and habitat connectivity for the most important Gironde estuary fish provides a novel insight for future management of the estuary, especially in the current context of global change.
Submarine Groundwater Discharge (SGD) is an important, yet poorly recognized pathway of material transport to the marine environment. This work reports on the results of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) concentrations in the groundwater seeping to the Bay of Puck. The loads of carbon via SGD were quantified for the Baltic Sea sub-basins and the entire Baltic Sea.
The annual averages of DIC and DOC concentrations in the groundwater were equal to 64.5 ± 10.0 mg C L−1 and 5.8 ± 0.9 mg C L−1. The DIC and DOC fluxes via SGD to the Baltic Sea were estimated at 283.6 ± 66.7 kt yr−1 and 25.5 ± 4.2 kt yr−1. The SGD derived carbon load to the Baltic Sea is an important component of carbon budget, which turns the status of the sea into firmly heterotrophic.
The carbon load to the World Ocean, which was calculated basing on few reports on groundwater discharges and the measured carbon concentrations, amounts to- (142–155) × 103 kt yr−1 (DIC), and (13–14) × 103 kt yr−1 (DOC). The carbon flux via SGD amounts to some 25% of the riverine carbon load, and should be included into the World Ocean carbon budget.
The underwater topography in the offshore sea area of north Jiangsu is complicated, including the middle radial sand ridges and northern Haizhou bay underwater shoal. Therefore, it forms special marine dynamic conditions and typical shoal wetland ecosystem. Previous researches of these sea areas were mainly focused on the forms of morphogenesis and the characteristic of conformation of sand ridges. Few studies have done on three dimensional hydrodynamic and water quality simulation. This paper introduced EFDC (Environ-mental Fluid Dynamics Code) to study the tidal current fields, dilution and diffusion of the sewage outlet near Yangkou Port. Comparison between computation results and the observed data indicates that this model could reasonably simulate hydrodynamic fields. Based on the computed tidal current field, the distributions of COD concentration were simulated. The range of contamination diffusion derived from sewage outlet was very limited, and the influence range of sewage came to the maximum when ebb slacks in neap tide period.
The effects of solar radiation, both visible and ultraviolet (UV-R, 290 to 400 nm), on the kelp Laminaria saccharina (L.) Lamour were examined in relation to depth distribution and tidal height in the Gulf of Maine. Despite the high attenuation of visible and UV-R, shallow subtidal L. saccharina exhibited significant decreases in midday measurements of steady-state quantum yields of Photosystem 11 (PSII) fluorescence compared to deeper conspecifics. Decreases in PSII quantum yields under low-tide conditions at midday were more pronounced and associated with higher coefficients of non-photochemical quenching than yields of the same algae measured at midday under high-tide conditions. Steady-state quantum yields in shallow algal populations had not recovered by early morning of the following day. Laboratory experiments were conducted to partition out the effects of high visible radiation versus UV-R effects on steady-state quantum yields observed in the field. Algae exposed to solar visible PAR (photosynthetically active radiation; 400 to 700 nm), PAR + UV-A (ultraviolet-A radiation; 320 to 400 nm), and PAR+UV-A+UV-B (ultraviolet-B radiation; 290 to 320 nm) treatments exhibited daily midday depressions in steady-state quantum yields, similar to those observed in field samples at low tide. The PAR + UV-A + UV-B treatment showed a significantly greater depression in PSIl quantum yields than field samples at low tide, and took longer to recover at night. Algae exposed to the UV-R component of the spectrum also showed a significant decrease in gross primary production and contained less areal chlorophyll a than field samples, while nonphotochemical quenching (a measurement of the dissipation of excess excitation energy) was significantly higher during midday exposures to UV-B. Significantly greater concentrations of the UV-Babsorbing compound mycosporine-glycine, a mycosporine-like amino acid (MAA), were present in the shallow field and experimental PAR+UV-A+UV-B-treated algae. Our results suggest that exposure to midday visible irradiances resulted in dynamic photoinhibition, while exposure to visible and UV-R irradiance in the Gulf of Maine results in both dynamic and chronic photoinhibition that causes a decrease in gross primary production of L. saccharina in shallow waters or under low-tide conditions.
Fifty years ago, GE Hutchinson defined the ecological niche as a hypervolume in n-dimensional space with environmental variables as axes. Ecologists have recently developed renewed interest in the concept, and technological advances now allow us to use stable isotope analyses to quantify these niche dimensions. Analogously, we define the isotopic niche as an area (in δ-space) with isotopic values (δ-values) as coordinates. To make isotopic measurements comparable to other niche formulations, we propose transforming δ-space to p-space, where axes represent relative proportions of isotopically distinct resources incorporated into an animal's tissues. We illustrate the isotopic niche with two examples: the application of historic ecology to conservation biology and ontogenetic niche shifts. Sustaining renewed interest in the niche requires novel methods to measure the variables that define it. Stable isotope analyses are a natural, perhaps crucial, tool in contemporary studies of the ecological niche.
Coastal lagoons are characterized by high habitat heterogeneity where natural habitats coexist with artificial ones, historically set up to support human activities. Increasing anthropogenic pressure may lead to progressive degradation of the most vulnerable lagoonal habitats and the associated biological communities. One of the strictly estuarine-dependent fish species that may be affected by the degradation of lagoon habitats is the South European toothcarp Aphanius fasciatus, archetype of Mediterranean lagoon residents.
Carbon and nitrogen stable isotopes were used to disentangle the influence of habitat types (natural vs artificial) and fish community (multi-trophic context) on the trophic niche features of A. fasciatus. Fish communities and organic matter sources were sampled in two Mediterranean lagoons located at the northernmost (Lagoon of Venice) and at the mid-latitude (Stagnone di Marsala, Trapani) of A. fasciatus distribution.
Results showed evidence of high trophic adaptability of A. fasciatus, whose omnivorous feeding habit resulted in seasonal changes in isotopic niche width and niche partitioning with co-occurring species, constituting an advantage in habitats characterized by high seasonal variation of resources availability. Furthermore, while macrophytes drove the main trophic pathways leading to A. fasciatus in natural habitats, artificial habitats were mainly based on sedimentary organic matter routes. These outcomes broaden our knowledge on how natural and artificial habitats trophically support A. fasciatus populations and results are discussed in light of the ecological implications for environmental management of coastal lagoons.
The deployment of artificial reefs (ARs) has become a popular technique for creating new hard-bottom habitats, and for enhancing biodiversity and resource abundance for fisheries. We compared colonizing faunal assemblages and reef-associated food-web structures between ARs and nearby natural reefs (NRs) off the Korean coast using stable isotope techniques. Reef communities showed high compositional disparities in colonizing assemblages. Distinct δ¹³C and δ¹⁵N ranges of functional groups could be used to distinguish pelagic from benthic trophic pathways in the reef food web. The isotopic niches of entire faunal assemblages, as well as individual functional groups, overlapped between NRs and ARs, resulting in equivalency for the isotopic functional indices. Mixing model estimates for carnivorous invertebrates and fish suggested strong trophic links to reef-associated faunal prey at both reef types. Finally, these results highlight a convergence in trophic structure between ARs and NRs in accordance with functional diversity in the colonized faunal assemblages.
Systems of marine spatial planning (MSP) are now being introduced in many countries, with the intention of more rational arrangement of maritime uses and interests. It would be expected that marine conservation, especially the designation of marine protected areas (MPAs), would be incorporated into MSP. In practice, however, MSP and MPA designation are often taking place in parallel to each other, with relatively little integration between them, partly because of marine conservation's longer history and established institutional frameworks which cannot be simply subsumed into MSP processes. There are, nonetheless, a series of options available by which the two sets of process could be more closely linked. These options can be conceptualised temporally, by, for example, MSP improving the status of pre-existing MPAs, or spatially, by, for example, facilitating the creation of multiple-use MPAs. These difficulties and possibilities are illustrated through two national European experiences.
Coastal habitats are interlinked by ecological connectivity, defined as the exchange of organic matter or organisms between habitats. The degree of this connectivity will depend in particular on the geometric properties of the landscape. The increasing anthropogenic alterations in estuaries therefore raises the need to understand how their morphological characteristics influence fluxes between habitats. We used stable isotopes to investigate the variability of ecological connectivity between three estuaries and their adjacent coastal areas by tracking the origin of the organic matter (estuarine vs coastal) underlying the diet of the migrant species Eucinostomus argenteus. The chosen estuaries were geomorphologically distinct, exhibiting, in particular, differences in their degree of connection to the sea, corresponding to the morphological features (shape, mouth width) controlling key physico-chemical variables in this habitat (e.g. salinity). The sampling of the basal food sources contributing to the food web was performed in the three estuaries and in their adjacent coasts. The variability in stable isotope ratios between estuaries was examined for both fish and sources of organic matter. In the three estuaries, Bayesian models were applied for each season (dry and rainy) to quantify the relative contribution of sources from estuarine and coastal environments supporting the diet of the silver mojarra. The share of coastal organic matter increased with the degree of sea connection, indicating that the properties of the seascape can regulate the intensity of interactions between ecosystems. Variations in ecological connectivity are likely to affect the functioning of ecosystems as they influence trophic pathways and energy flows between adjacent habitats. Morphological modifications could thus significantly disturb ecosystems by altering the structure of food web, thereby affecting certain ecosystem services such as the availability of living marine resources.
The Bay of Biscay (North-East Atlantic) has long been subjected to intense direct and indirect human activities that lead to the excessive degradation and sometimes overexploitation of natural resources. Fisheries management is gradually moving away from single-species assessments to more holistic, multi-species approaches that better respond to the reality of ecosystem processes. Quantitative modelling methods such as Ecopath with Ecosim can be useful tools for planning, implementing and evaluating ecosystem-based fisheries management strategies. The aim of this study was therefore to model the energy fluxes within the food web of this highly pressured ecosystem and to extract practical information required in the diagnosis of ecosystem state/health. A well-described model comprising 30 living and two non-living compartments was successfully constructed with data of local origin, for the Bay of Biscay continental shelf. The same level of aggregation was applied to primary producers, mid-trophic-levels and top-predators boxes. The model was even more general as it encompassed the entire continuum of marine habitats, from benthic to pelagic domains. Output values for most ecosystem attributes indicated a relatively mature and stable ecosystem, with a large proportion of its energy flow originating from detritus. Ecological network analysis also provided evidence that bottom-up processes play a significant role in the population dynamics of upper-trophic-levels and in the global structuring of this marine ecosystem. Finally, a novel metric based on ecosystem production depicted an ecosystem not far from being overexploited. This finding being not entirely consistent over indicators, further analyses based on dynamic simulations are required.
Conservation of marine ecosystems is important for the sustainable utilization of marine resources under environmental changes and anthropogenic impacts. In Japan, fishery management has been based on single-species stock assessments and little attempts have been made to assess and manage the impacts of multi-species multi-gear fisheries except for a few local case studies. In this study, we analyzed two local Ecopath food-web models constructed for Japanese waters (Northeastern Japan and Seto Inland Sea). We adopted a comparative approach to assess the ecosystem characteristics and fishery impacts through a comparison of these models with other published Ecopath models for various periods and regions of the world ocean. Among the metrics derived from Ecopath outputs, total biomass and total productivity represented the gross metabolic activities of the systems, and trophic level fractionation of biomass and catch reflected the trophic structure of the food webs and fishery removals. Loss of food for top predators, primary production required, and mean and variance of trophic level of catch were good indicators of the impacts and patterns of fishery removals. Our results illustrate the characteristics of food webs and fisheries in Japanese local ecosystems: The Northeastern Japan model showed the moderate productivity of the ecosystem, and fishery removals from lower and wider trophic levels. The Seto Inland Sea model indicated large impacts of fisheries on the low productivity neritic system. Such profiling of ecosystems and fisheries provides good overviews that will help initiate stakeholder discussion toward the set-up phase of ecosystem-based fishery management in Japan.
The stable isotope ratios of carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) and total mercury concentrations (THg) of the three marine catfish species Aspistor luniscutis , Bagre bagre and Genidens genidens were evaluated to understand their trophic relationship in northern Rio de Janeiro state, south-eastern Brazil. The δ ¹³ C was similar among the three marine catfishes, whereas δ ¹⁵ N was similar in A. luniscutis and B. bagre and lower in G. genidens . THg was higher in G. genidens and lower in B. bagre . The greater assimilation of Sciaenidae fishes and squids by A. luniscutis and B. bagre resulted in smaller isotopic niche areas and trophic diversity but higher isotopic niche overlap, trophic redundancy and evenness. For G. genidens , the similar assimilation of all prey items resulted in the broadest isotopic niche among the marine catfishes. The higher mercury content in G. genidens is consistent with an increased important contribution of prey with a higher Hg burden. The bioaccumulation process was indicated by significant correlations of δ ¹⁵ N and THg with total length and total mass. Additionally, a significant correlation between THg and δ ¹⁵ N reflected the biomagnification process through the food web.
Scotland's marine food webs support a diversity of species and habitats. They contribute to maintaining the balance of the natural environment. Previous studies show that these ecosystems are contaminated by persistent organic pollutants and trace metals; with animals in higher trophic levels (e.g. cetaceans and pinnipeds) containing concentrations that are among the highest found in the ocean. Contaminants represent one of many pressures to which species and habitats are exposed. In assessing the contribution of contaminants to the overall pressure, measuring contaminants at a specific trophic level and then using trophic magnification factors (TMFs) to estimate concentrations at other trophic levels permits assessments across the food web, as well as allowing the adjustment of contaminant concentrations to a particular trophic level for comparison to assessment criteria. Fatty acid (FA) signatures and stable isotope (SI) ratios were used to develop a picture of Scottish marine food web ecology and reliably ascribe trophic levels to a wide range of species. Fatty acid trophic markers (FATMs) were used as trophic level indicators and with SI analysis, permitted identification of the mean trophic level of each species and determination of the feeding patterns and predator-prey relationships existing in the Scottish marine food web. Two hundred and eleven (211) samples comprising of seven fish species, one shark species, fourteen marine invertebrate species, three marine mammal species and two zooplankton species from different locations around Scotland were found to have mean trophic levels ranging from 1.47 ± 0.11 in zooplankton to 5.02 ± 0.35 in harbour seal. Fatty acid profile showed specific dietary information which differed between the eleven taxonomic classes and twenty-seven species. The organic and inorganic contaminant concentrations of the species for which trophic level has been determined, together with TMFs, will be reported in future papers.
Artificial reefs (ARs) have been advocated and implemented as management tools for recreational fisheries, species conservation and habitat replacement. For ARs to function as substitute habitat for degraded natural reefs, they should perform as close as possible to local natural reefs, however this is seldom investigated. Here we evaluated the performance of new custom-designed reef structures (CDARs) as fish habitat. As a benchmark for their success, we compared fish abundance, diversity and community composition on CDARs to another commonly used AR type (Reef Balls (RBs)) and nearby natural reefs. Fish were monitored on all reef types over two recruitment seasons at three locations in Port Phillip Bay, Australia. Overall, there were no consistent differences in fish density among reef types, although densities on both AR designs were markedly lower than natural reefs at some locations. However, fish species richness on the CDARs was, on average, 2× higher than natural or RB reefs. There were large dissimilarities in fish community composition among reef types across all locations and years. These dissimilarities declined over time with the CDARs becoming more similar to natural communities than to RB reefs. Our results suggest that CDARs can play a role in reef fish conservation where natural reefs are under threat, supporting natural community structure and enhancing local biodiversity. Overall, our findings suggest that location of deployment, rather than design, has a more significant influence on fish abundances on ARs, whereas reef design is an important determinant of species diversity and community structure irrespective of location. ARs represent an important management tool for enhancing fisheries productivity and conservation in areas where reef habitat has been degraded or lost. However, failure to incorporate consideration of reef location and design into future AR deployments may lead to poor performance and failure to achieve restoration or conservation goals.
Artificial reefs are deployed in coastal systems to meet a range of social objectives and infrastructure requirements, such as recreational diving and fisheries enhancement. Such reefs are typically deployed on soft sediments and yet we know little of their effect on the biophysical characteristics of the surrounding benthos. This study investigated the composition of benthic infauna, sediment characteristics, and demersal fish foraging activity surrounding a large, steel, designed offshore artificial reef (OAR), measuring 12 m × 16 m x 12 m (height x length x width) and weighing approximately 42 tonnes.
Using a gradient approach we established four transects with sediment sampling sites located 15, 30, 60, 120 and 240 m from the OAR. Taxon richness of infauna was lower close to the OAR (15, 30 m), and abundances of total infauna elevated at 15 m, driven largely by two families of polychaete (Onuphidae and Spionidae). Sediment characteristics (grain size, total organic carbon, metals) did not vary with distance from the OAR. Using unbaited videos we established that fish foraging activity on the soft sediments was enhanced close to the OAR (15 m), with a 5–10 fold increase in total foraging time that was largely accounted for by the activity of four benthivorous fish species (blue morwong Nemadactylus douglasii, the silver trevally Pseudocaranx georgianus, and goatfishes Upeneichthys vlamingii and U. lineatus). Fish foraging may cause changes in the composition of benthic infauna due to disturbance and selective predation. The effective benthic ‘ecological halo’ or ‘footprint’ of the OAR was 15 times the area of the actual reef. We demonstrate that a single large OAR can influence the surrounding benthic invertebrate and vertebrate communities, but that the effects are highly localised.
Laoshan Bay is one of numerous gulfs of the Yellow Sea and an important fish enhancement and release area. It is vital for the Yellow Sea fishery resources that carry out proliferation and implement effective fisheries conservation and management in Laoshan Bay ecosystem. Based on bottom trawl survey conducted in Laoshan Bay in June and August 2014, the dominant fish species of fish community during summer were analyzed and their feeding ecology was studied by stable carbon and nitrogen isotopes method. The stable carbon isotope ratio (δ¹³C) is often used to assess basal sources in food web with a slight enrichment, while the stable nitrogen isotope ratio (δ¹⁵N) is indicator of trophic level, as a major increase with each trophic level. In terms of the index of relative importance (IRI), there were 10 dominant species of fish community in Laoshan Bay during summer, including Amblychaeturichthys hexanema, Ctenotrypauchen chinensis, Odontamblyopus rubicundus, Johnius belengerii, Argyrosomus argentatus, Lanmichthys polyactis, Chelidonichthys kumu, Cynoglossus joyneri, Clupanodon punctatus and Thrissa kammalensis. There were significant differences in dominant fish species composition of fish community between two months in summer. The range of δ¹³C of dominant fish species ranged from -20.66‰ to -17.53‰ in June and from -21.06‰ to -17.33‰ in August. There were significant differences in δ¹³C between dominant fish species. According to δ¹³C of this research, combining with results of stomach contents analysis, the results show that the main food source of fish community was benthic prey in June, but the food source of fish community was more extensive in August. The range of δ¹⁵N of dominant fish species was 10.86‰~15.47‰ in June and 9.40‰-13.10‰ in August. There were significant differences in δ¹⁵N between dominant fish species and the biggest difference were 4.61‰ and 3.70‰, respectively. The dominant species of fish community in Laoshan Bay in June included fish with middle trophic level and high trophic level, the mean trophic level of fish community was 3.90, and was mainly benthivores. The dominant species of fish community in Laoshan Bay in August included fish with middle trophic level and low trophic level, the mean trophic level of fish community was 3.37, including zooplankivores and benthivores, mainly benthivores. Linear regression analysis showed that in addition to J. belengerii, C. punctatus, C. joyneri and C. kumu, whose trophic level showed not linear correlation with the length, and the trophic level of rest of the dominant species was significantly positive correlation with the body length. This was mainly because with the increase of body length, they increase feeding on prey with high trophic level, but reduce feeding on prey with low trophic level, and their trophic level also increases.
外海潮波传播到近海河口海湾过程中，由于地形作用而发生变形，表现为潮汐潮流涨落潮的不对称。本文利用海州湾附近18天连续高频观测资料，分析了潮汐和潮流的不对称性，潮波向海州湾传播过程中，潮波变形较小，潮流变形较大，4个站位均为涨潮占优，本研究可为海州湾的泥沙输运、污染物迁移等研究提供参考。 Tidal current and water level are distorted from their sinusoidal forms during propagation into coastal waters and entry into bays, which gives rise to tidal asymmetry. On the base of continuous observation data for 18 days, the characters of the tidal asymmetry are analyzed. The results show that the duration of falling tide is longer than the rising tide, which means that the flood flow is dominated. The study results can provide reference for the sediment transport and the pollutant transport in Haizhou bay.
Resource pulsing is a widespread phenomenon, but its effects on ecosystem dynamics are often difficult to predict. Hydrological pulsing, in particular, is known to influence the structure and dynamics of fluvial and coastal ecosystems, but little information is available for its effects on trophic connectivity between wetlands and estuaries. In this study, we investigated the hypothesis that hydrologic pulsing drives one-way trophic subsidies (e.g. suspended organic matter and freshwater fish) from wetland to estuary. Our study system is a coastal lagoon with an ephemeral mouth that, when closed, stores freshwater as a sustained flood pulse that is subsequently released when a connection with the sea is reestablished. We monitored isotopic composition of consumers and food sources over the course of an entire flood pulse to infer trophic linkages and spatial subsidies. Before the flood peak (April and May), freshwater and estuarine zones were largely dependent on local primary production sources (seston and C3 plants vs. C4 plants and microphytobenthos, respectively), essentially functioning as disconnected compartments. A sustained pulse of freshwater inflow (June to August) induced greater habitat connectivity and a net flow of biomass and energy from the freshwater zone into the estuarine zone. The opening of the lagoon outlet channel abruptly terminated the flood pulse and reduced freshwater subsidies to estuarine consumers, and both zones returned to dependence on autochthonous production. Our findings contribute to current concerns that artificial opening of sandbars in coastal lagoons alters natural ecological dynamics with significant effects on biodiversity and ecosystem processes.
The use of miniaturized digital temperature logging devices on coral reefs is increasing dramatically due to the threat of global warming. Shallow coral reef environments are characterized by extremely high solar radiation and highly transparent seawater, raising the possibility of solar heating of devices deployed in these settings. In this study, we compared temperature measurements under a variety of shading treatments to investigate the potential error associated with high irradiance levels in shallow, clear waters. Results of this experiment showed that mid-day water temperature readings by unshaded loggers were significantly higher by 2.2°C on average compared with shaded loggers. Loggers shielded with reflective tape showed less error but still reported significant heating, with water temperatures that were on average 0.15°C higher than shaded loggers. There were no significant differences among shade treatments during nighttime hours, indicating that irradiance is the source of the errors documented here. Care must be taken to shield temperature loggers from irradiance while providing good circulation of water around the sensors. One option is to place the loggers in a naturally occurring, cryptic or shaded habitat on the reef. When deployed in open reef areas, in mesocosms, or in experimental aquaria, loggers can be shielded in protective, opaque plastic tubes that are open at both ends.
Artificial habitats have been used for centuries to successfully modify environments for the benefit of Man. In the aquatic environment, the use of artificial habitat technologies is of growing interest worldwide. Opportunities exist in both developed and developing nations to apply these technologies in many areas, including classical scientific investigations of ecosystem structure and function, engineering advances in underwater technology, and fisheries and environmental management. The applications of artificial habitat technologies are taking on ever greater economic, social, and environmental importance globally, not only in developed countries such as Japan where highly sophisticated technologies are used, but also in developing nations, where lower cost practices are in use. There is growing pressure to increase production, while at the same time preserve or enhance the environments and ecosystems surrounding fisheries. This book provides a comprehensive review of the facts, issues, and global trends emerging regarding the use of artificial habitats in aquatic ecosystems. It presents the most recent scientific advances in ecology and engineering technologies related to the building of artificial habitats, and it also presents many of the fisheries management and socioeconomic and environmental issues. Artificial Habitats for Marine and Freshwater Fisheries will be of interest to a broad audience including natural resource scientists, planners, and managers, particularly those interested in aquatic and fisheries science and management; organizations and individuals interested in commercial and recreational fishing; ecologists; environmental economists, engineers, lawyers, and social scientists; and geographers. Key Features * Presents a global scope * Draws together, for the first time, disparate literature * Contains contributions by authors in the United States and Japan * Features engineering chapters that focus on Japanese advanced technology often not available to the English language audience.
The potential for enhancing fish abundance, species richness, and biomass on artificial reefs was examined by attaching floating attractants and manipulating structural complexity of small concrete reefs each approximately 1.3 m in diameter, 1 m high. Experimental design consisted of a comparison of fish assemblages among three treatments (10 replicate, hemisphere-shaped reefs each): 10-m floating line attached (Streamer); concrete block in the central void space (Block); and no floating line or concrete block (Control). Reefs were deployed on sandy substrate at 20-m depth off Fort Lauderdale, Florida, USA. Divers recorded fish census data on slates 18 times over 24 months. Species composition, numbers of individuals per species, and estimated total length (TL; by size class: 20 cm) for all fishes within 1 m of each reef were recorded. Size classes were used to calculate fish biomass. There was a significant difference among treatments. Block reefs had higher numbers of individuals, species, and biomass than Streamer or Control reefs (p 0.05). These results highlight the importance of structural complexity in artificial reefs designed to enhance fish recruitment, aggregation, and diversity. Copyright 2002 Published by Elsevier Science Ltd on behalf of the International Council for the Exploration of the Sea.
Off-shall seawater in China was often polluted and eutrophicated more or less because of human activities. The ecosystem services could be incorporated into the decision-making process by managers only if the ecosystem services were economically marked. Therefore, it was important to evaluate the value of ecosystem service (VES) and service value loss due to marine pollution and eutrophication. Taking Haizhou Bay as the study area, the potential and actual economic values of marine ecosystem were evaluated. The assessment results showed that the total potential value of ecosystem service of Haizhou Bay was 16.64×108 Yuan in 2005, with an average unit VES of 1.90×106 Yuan/km2. Within the total potential VES, the provision services, culture services, and regulation services accounted for 53.39%, 35.48%, and 10.84%, respectively. Considering the service loss due to red tide, greenhouse gas emission, and pollutant accumulation in fish, alga, and shellfish, the actual VES was 14.08×108 Yuan in Haizhou Bay, with the average of 1.61 ×106 Yuan/km2. The value of provision services, culture services, and regulation services accounted for 48.32%, 41.94%, and 9.74%, respectively, in total actual VES. The VES loss due to the eutrophication and seawater pollution was 2.56 × 108 Yuan, accounting for 15.41% of the potential VES. The deterioration of the marine environment greatly influenced the services of food provision and climate regulating at present. Moreover, the values provided by other services, such as tourism, would decrease if the marine environment is further deteriorated. Compared with the averaged service value of marine ecosystem in other areas of China, the VES in Haizhou Bay was relatively low. This indicated that there existed a big improvement space for development and utilization of ecosystem services in the study area. However, it could not be neglected that the development brought the ecosystem deterioration and decreased the marine ecosystem services in bay area, and it needs to trade off the benefit from development and the loss due to deterioration caused by human activities.
We reviewed the published literature to provide an inventory of Laurentian Great Lakes artificial reef projects and their purposes. We also sought to characterize physical and biological monitoring for artificial reef projects in the Great Lakes and determine the success of artificial reefs in meeting project objectives. We found records of 6 artificial reefs in Lake Erie, 8 in Lake Michigan, 3 in Lakes Huron and Ontario, and 2 in Lake Superior. We found 9 reefs in Great Lakes connecting channels and 6 reefs in Great Lakes tributaries. Objectives of artificial reef creation have included reducing impacts of currents and waves, providing safe harbors, improving sport-fishing opportunities, and enhancing/restoring fish spawning habitats. Most reefs in the lakes themselves were incidental (not created purposely for fish habitat) or built to improve local sport fishing, whereas reefs in tributaries and connecting channels were more frequently built to benefit fish spawning. Levels of assessment of reef performance varied; but long-term monitoring was uncommon as was assessment of physical attributes. Artificial reefs were often successful at attracting recreational species and spawning fish; however, population-level benefits of artificial reefs are unclear. Stressors such as sedimentation and bio-fouling can limit the effectiveness of artificial reefs as spawning enhancement tools. Our investigation underscores the need to develop standard protocols for monitoring the biological and physical attributes of artificial structures. Further, long-term monitoring is needed to assess the benefits of artificial reefs to fish populations and inform future artificial reef projects.
Ressourcenteilung (unterschiedliche Nischenweite) und Nahrungssegregation (Nahrungsbreite) sind Mechanismen, die Koexistenz bei konkurrierenden Arten ermöglichen.
Wir testeten an Hand der stabilen Isotope Kohlenstoff (δ13C) Stickstoff (δ15N) und Schwefel (δ34S) die Hypothese einer Nahrungssegregation bei syntop lebenden invasiven Mysiden (Schwebgarnelen) und Gammariden (Flohkrebsen) die sich in konsistenten Unterschieden in den Mustern der stabilen Isotope widerspiegeln sollte. Wir analysierten Proben von 5 Standorten entlang des Bodensees und Rheins in Österreich und Deutschland, um auf eine Konsistenz der zwischenartlichen Isotopen-Muster in unterschiedlichen Habitaten schliessen zu können. Hierbei schätzten wir den relativen Anteil verschiedener Periphyton- und Sestonnahrungsquellen der Mysiden mit Hilfe eines IsoError mixing models. Die sympatrischen, nicht einheimischen Mysiden Limnomysis benedeni und Katamysis warpachowskyi unterschieden sich in δ13C, δ15N and δ34S, wiesen jedoch ähnliche Muster auf. Dies deutet auf unterschiedliche Nahrungsnischen und eine habitatspezifische, aber ähnliche Ressourcenaufteilung hin, indem beide Arten verschiedene Komponenten der verfügbaren Futterquellen, hauptsächlich aus dem Seston, nutzen. Die Gammariden Dikerogammarus villosus (“killer shrimp”) und Gammarus roeselii zeigten keine signifikanten δ13C und δ15N Unterschiede, sodass eine beträchtliche Überlappung der Nahrungsnischen dieser sympatrischen Invasoren vorliegt. Unsere Daten zeigen zudem, dass beide Gammariden ihre Ernährungweise plastisch umstellen können und so auf veränderte Habitatbedingungen und/oder Rivalen- bzw. Räuberdruck reagieren können. Die gleichsinnigen Interaktionen der invasiven Gammariden-Arten, gepaart mit ihrer Gefrässigkeit, würden eine erfolgreiche Invasion erleichtern, die negative Auswirkungen auf die lokale Biodiversität bis hin zum Aussterben einheimischer Arten haben könnte.
Spatial distribution of metal concentrations in the surface sediment samples collected from 19 marine at Guanhe estuary in Haizhou Bay, Lianyungang was studied. Heavy metal (Cu, Zn, Pb, Cd, Cr, As, Ni, Mn) concentrations were determined and geo-accumulation index (Igeo) was calculated to understand the pollution status of the study area based on the background values. The ranges of the measured concentrations in the sediments are as follows: 8.65–27.8 mg/kg for Cu, 215–319 mg/kg for Zn, 37.0–72.4 mg/kg for Pb, 0.55–3.45 mg/kg for Cd, 34.3–92.1 mg/kg for Cr, 30.0–51.9 mg/kg for As, 21.3–49.6 mg/kg for Ni, 430–837 mg/kg for Mn. Geoaccumulation index (Igeo) shows that Cd contamination exists in the entire study area and contamination of other metals are also present in some locations depending on the sources, of which sewage outlets and commercial ports are the main sources of contaminants to the area.
Trophic studies are fundamental components of our understanding of biology and ecology, from observing individual organisms to modelling ecosystem function. When measuring fish gut contents, we rely on collecting samples that represent snapshots in time. Many limitations in extrapolating from these snapshots are well understood. However, there seems to be a widespread belief that when quantifying the composition of gut contents, more detail always provides more information. We highlight some fundamental problems with the apparently more quantitative approaches (i.e. ‘bulk’ methods measuring biomass or volume of each prey type) and suggest that frequency of occurrence (%F) provides the most robust and interpretable measure of diet composition. The additional information provided by bulk methods contains unquantifiable and potentially significant error from a variety of sources. In our experience, the contents of most guts cannot be unambiguously separated into prey categories for quantification because of the presence of unidentifiable and inseparable partially digested material. Even where separation is possible, the composition of a gut at one point in time is affected by many unquantifiable factors unrelated to the actual composition of the diet. Consequently, bulk methods provide ambiguous interpretations from superficially quantitative models. Where research questions require more detail, these problems mean there is little alternative to time-consuming approaches like prey reconstruction. However, for the descriptions of dietary composition presented in many studies, %F provides robust data that overcome many of the limitations of the more detailed approaches and provides considerable logistical and economic benefits.