A trophic mass balance model of the eastern Chukchi Sea with comparisons to other high-latitude systems

The Chukchi Sea is a seasonally ice-covered, marginal Arctic-shelf sea that possesses both large petroleum reserves and abundant biological communities, including migratory mammals and seabirds. We developed a mass balance food web model for the eastern Chukchi Sea to evaluate the trophic structure of this ecosystem and to compare food web properties of the Chukchi Sea to those of other high-latitude marine ecosystems. We compiled data on biomass levels, diet composition, demographic rates (production, consumption), and fishery removals, and used these data to construct an Ecopath trophic mass balance model. The majority of biomass was concentrated in benthic invertebrates and most of the mass flow above trophic level 2.0 was through these groups. We found that density estimates of most fish groups derived from trawl survey data using area-swept methods were insufficient to match the consumptive demands of predators, and that densities needed to be several-fold greater to meet modeled demand. We also used a set of system metrics derived from a common modeling framework to highlight differences in ecosystem structure between the eastern Chukchi Sea and other high-latitude systems. The extent of benthic dominance observed in the eastern Chukchi Sea was unique among the systems examined, both in terms of food web structure and associated mass flows between benthic and pelagic components. In relation to total biomass density, the eastern Chukchi Sea had low production when compared with the other systems, and this lower turnover rate suggests that recovery from disturbance might be slow.     

Macrofauna communities of the Dogger Bank (central North Sea) in the late 1990s: spatial distribution,species composition and trophic structure

Macrofauna samples were taken in May 1996–1998 at 28 stations on the Dogger Bank (central North Sea) to describe species composition, spatial distribution and trophic structure of the macrofaunal communities. In general, five communities could be distinguished depending on the influence of different water masses, depth, type of sediment and food availability. Except for those species which feed in the sediment, macrofauna communities did not show any correlation to the measured sediment variables. In fact, macrofauna communities of the Dogger Bank were mainly structured by lateral food supply via frontal systems. This was indicated by the dominance of interface feeders foraging in the benthic boundary layer, which are able to switch from surface deposit to suspension feeding depending on flow conditions. The importance of sandlickers in the shallowest parts of the Dogger Bank hints at an important contribution of benthic primary production to the nutritional and energetic needs of the benthic community. Electronic Publication     

Benthic communities along a littoral of the Central Adriatic Sea (Italy)

Bacteria, meio- and macrofauna were investigated at different depths in a coastal area of the Central Adriatic Sea, yielding information about the composition and abundance of the benthic community. In particular, 14 nematode genera were recorded for the first time in the Upper Adriatic Sea. All communities resulted as being significantly different between inshore and offshore stations, especially when the season interaction was considered. Sediment grain size seemed to be the main natural variable, along with trophic resources, affecting the distribution and composition of these benthic components, whilst there was no clear evidence of competition for food sources and predatory pressure between the communities. Meiofauna appeared the most useful community for detecting disturbances and river influences. In particular, the lowest copepod abundance in the shallow waters seemed to be related to a greater anthropogenic disturbance inshore, whilst meiofaunal abundance and diversity together with the nematode maturity index suggest the influence of the Foglia and Metauro rivers and the small stream Arzilla.     

Establishment of trophic continuum in the food web of the Yellow Sea and East China Sea ecosystem: Insight from carbon and nitrogen stable isotopes

The determination of trophic level for the biology in a marine ecosystem is very important as alteration of its structure and function may be reflected in the tro-phic level of component species. A change in trophic level indicates variation in an organism’s feeding bi-ology or in the pathway of energy flow from primary producers to the consumer. The gut content analysis is a traditional method for studying trophodynamics of food web in marine ecosystems. Species composition and amounts in al…     

The barnacles (Cirripedia: Thoracica) collected by the Viking expedition in chemobiotic benthic communities of the Norwegian and Barents Seas

The barnacles (Cirripedia Thoracica) collected by the Viking expedition in chemobiotic benthic communities of Arctic Ocean-Nyegga area in Norwegian Sea and Håkon Mosby Mud Volcano area in the Barents Sea are investigated. The species (Weltnerium nymphocola in Håkon Mosby Mud Volcano area and Hamatoscalpellum hamatum in Nyegga area) that were found are common inhabitants of the Barents and Norwegian sea benthic communities. The absence of obligatory barnacle fauna that was revealed in investigated chemobiotic benthic communities of the Arctic Ocean shows they are similar to corresponding communities of the Atlantic Ocean, while the specific obligatory barnacle fauna is noted for chemobiotic benthic communities of the Pacific and Indian oceans.     

Establishment of trophic continuum in the food web of the Yellow Sea and East China Sea ecosystem: Insight from carbon and nitrogen stable isotopes

Stable carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) are used to study the trophic structure of food web in the Yellow Sea and East China Sea ecosystem. The trophic continuum of pelagic food web from phytoplankton to top preyer was elementarily established, and a trophic structure diagram in the Yellow Sea and East China Sea was outlined in combination with carbon isotopic data of benthic organisms, which is basically consistent with and makes some improvements on the simplified Yellow Sea food web and the trophic structure diagram drawn based on the biomass of main resource population during 1985–1986. This result indicates that the stable isotope method is a potential useful means for further studying the complete marine food web trophic continuum from viruses to top predators and food web stability.     

Indicators of the Ecological Impact of Bottom-Trawl Disturbance on Seabed Communities

The Ecosystem Approach to Fisheries requires that managers take account of the environmental impacts of fishing. We develop linked state and pressure indicators that show the impact of bottom-trawling on benthic communities. The state indicator measures the proportion of an area where benthic invertebrate biomass (B) or production (P) is more than 90% of pristine benthic biomass (B _0.9) or production (P_0.9). The pressure indicator measures the proportion of the area where trawling frequency is sufficiently high to prevent reaching predicted B_0.9 or P_0.9. Time to recovery to B_0.9 and P_0.9 after trawling, depending on the habitat, was estimated using a validated size-based model of the benthic community. Based on trawling intensity in 2003, 53.5% of the southern North Sea was trawled too frequently for biomass to reach B_0.9, and 27.1% was trawled too frequently for production to reach P_0.9. As a result of bottom-trawling in 2003, in 56% of the southern North Sea benthic biomass was below B_0.9, whereas in 27% of the southern North Sea benthic production was below P_0.9. Modeled recovery times were comparable to literature estimates (2.5 to more than 6 years). The advantages of using the area with an ecological impact of trawling as a pressure indicator are that it is conceptually easy to understand, it responds quickly to changes in management action, it can be implemented at a relevant scale for fisheries management, and the necessary effort distribution data are centrally collected. One of this approach’s greatest utilities, therefore, will be to communicate to policy makers and fishing enterprises the expected medium- to long-term ecological benefits that will accrue if the frequency of trawling in particular parts of fishing grounds is reduced.     

The barbs (Barbus spp.) of Lake Tana: a forgotten species flock?

Synopsis All living species occupy an ecological niche, and are positioned within a trophic hierarchy. Extinct organisms presumably held similar behavioral and coevolutionary characteristics in the past, and were susceptible to the same kinds of natural ecological pressures operating today. Paleoecological investigations are limited by the incompleteness of the fossil record, and particularly by a lack of behavioral data that are so fundamental to ecological studies of living communities and habitats. Opportunities to examine the coevolutionary structure of ancient communities from empirical data are extremely rare. One such opportunity is provided by the Lower Cretaceous Santana Formation of north-eastern Brazil, a series of richly fossiliferous strata approximately 110 million years old. Many fossil fishes from the Santana Formation contain identifiable prey, including decapod crustaceans and fishes. A trophic hierarchy of these organisms is reconstructed here, and their ecological relationships are discussed. Comparison is made with a similar fish fauna from the Upper Jurassic Solnhofen Limestone of Germany. Low-level, intermediate and high-level predators are identified in each fauna. Predator-prey relationships in the Santana fauna are strongly hierarchical, and are more focussed at the intermediate predator level than in Solnhofen. Comparison with a model of predator-prey relationships between fishes and benthic fauna of the Baltic Sea (which like the Araripe Basin represents a semi-enclosed environment) suggests that heavy predation on teleosts such asRhacolepis, occupying an intermediate trophic level, may have permitted benthic decapods to proliferate and exclude other benthic organisms. Less intense predation on fishes at the intermediate trophic level would allow their numbers to increase, thereby increasing the intensity of predation on the benthos at the base of the trophic hierarchy.     

Evaluating ecosystem structure and functioning of the East China Sea Shelf ecosystem,China

As China’s second-largest large marine ecosystem, the East China Sea Shelf has suffered from overfishing, eutrophication, and physical disturbance over the last several decades. A trophic mass-balance model of this ecosystem was developed in order to characterize the structure and functioning of its food web, to identify its keystone species, and to quantify the ecological impacts of fishing that it sustained during the early 2000s. Using a multivariate statistical analysis, we identified 38 functional groups for the trophic model, including fish and invertebrate groups targeted and not targeted by fisheries. Pelagic sharks and rays were identified as the keystone species in the ecosystem. Strong benthic–pelagic coupling was indicated in this ecosystem. In particular, this study highlighted the interdependent relationships that exist among plankton, benthic invertebrates, and detritus. Recent fishing activities were characterized by high exploitation rates for various commercially targeted and non-targeted species, leading to the removal of much of the ecosystem’s fishable production. Overall, our findings give a preliminary explanation of the current problems of eutrophication and fishery depletion and other changes in the East China Sea Shelf, and highlight the need for developing ecosystem-based fisheries management.     

基于营养通道模型的渤海生态系统结构十年变化比较

根据1982年和1992年渤海渔业资源和生态环境调查数据,应用EwE建模软件,构建了两个时期的营养通道模型,并比较分析了10a间渤海生态系统结构以及渔业资源的变化.模型包含鳀、黄鲫、蓝点马鲛、其它中上层鱼类、小黄鱼、花鲈、其它底层鱼类、底栖鱼类、浮游动物、浮游植物、碎屑等17个功能群, 基本覆盖了渤海生态系统能量流动的途径.分析结果表明,1992年渤海生态系统的总生物量比1982年有所下降;小型中上层鱼类成为渔业资源的主要成分,其生物量较1982年明显增加;由于低营养级层次渔获物数量的增加,渔获物平均营养级有所下降.从系统规模看1982年大于1992年.1982年到1992年的十年间, 引起渤海生态系统结构变化的主要原因是初级生产力的变化以及捕捞因素.1982年与1992年渤海生态系统均处于不成熟的发育期,仍有较高的剩余生产量有待利用,因此渔业资源恢复的物质基础是有保证的.     

Ecological Monitoring of the Water Area of Port Vostochnyi (Wrangel Bay) in the Sea of Japan (1995–2002)

Benthic surveys carried out in 1989 (literature data), 1995, and 2001 (original data) revealed changes in the structure of soft bottom communities of Wrangel Bay (Peter the Great Bay, Sea of Japan), where a deep-water port of Vostochnyi is situated. The functioning of the port has caused no significant environmental pollution by heavy metals, hydrocarbons, and other pollutants. Bottom dredging and the siltation induced by it have drastically lowered the benthos biomass, changed benthic communities, and altered their trophic structure. Sestonophages have disappeared nearly altogether being replaced by detrivores. The ecological state of the benthos is characterized as unstable.     

Contribution of sea ice microbial production to Antarctic benthic communities is driven by sea ice dynamics and composition of functional guilds

Organic matter produced by the sea ice microbial community (SIMCo) is an important link between sea ice dynamics and secondary production in near‐shore food webs of Antarctica. Sea ice conditions in McMurdo Sound were quantified from time series of MODIS satellite images for Sept. 1 through Feb. 28 of 2007–2015. A predictable sea ice persistence gradient along the length of the Sound and evidence for a distinct change in sea ice dynamics in 2011 were observed. We used stable isotope analysis (δ¹³C and δ¹⁵N) of SIMCo, suspended particulate organic matter (SPOM) and shallow water (10–20 m) macroinvertebrates to reveal patterns in trophic structure of, and incorporation of organic matter from SIMCo into, benthic communities at eight sites distributed along the sea ice persistence gradient. Mass‐balance analysis revealed distinct trophic architecture among communities and large fluxes of SIMCo into the near‐shore food web, with the estimates ranging from 2 to 84% of organic matter derived from SIMCo for individual species. Analysis of patterns in density, and biomass of macroinvertebrate communities among sites allowed us to model net incorporation of organic matter from SIMCo, in terms of biomass per unit area (g/m²), into benthic communities. Here, organic matter derived from SIMCo supported 39 to 71 per cent of total biomass. Furthermore, for six species, we observed declines in contribution of SIMCo between years with persistent sea ice (2008–2009) and years with extensive sea ice breakout (2012–2015). Our data demonstrate the vital role of SIMCo in ecosystem function in Antarctica and strong linkages between sea ice dynamics and near‐shore secondary productivity. These results have important implications for our understanding of how benthic communities will respond to changes in sea ice dynamics associated with climate change and highlight the important role of shallow water macroinvertebrate communities as sentinels of change for the Antarctic marine ecosystem.     

Development of an Index of Trophic Completeness for benthic macroinvertebrate communities in flowing waters

The analysis of the trophic structure of benthic macroinvertebrate communities can be used in biological assessments of the condition of river ecosystems. Using the trophic, or functional approach, the Index of Trophic Completeness (ITC) was developed. The goal was to overcome the problems and drawbacks of using conventional diversity or biotic indices in biological assessments of rivers, such as limitation to distinct geographical regions or focus on species richness without regard for ecosystem functioning. Following an extensive review of the literature on the trophic characteristics of benthic macroinvertebrates, a large number of species (±300) were characterized according to a number of trophic criteria: plant:animal ratio in the diet, feeding mechanism, food size, food acquisition behaviour, and energy and substance transfers. On the basis of their trophic characteristics, the species could be divided into 12 trophic groups. After examination of data from geographically diverse rivers, it was concluded that any undisturbed riverine benthic macroinvertebrate community should be represented by members of each of these 12 trophic groups, with each group fulfilling a function in the benthic community. Being a community which plays a central role in the functioning of the aquatic ecosystem, the benthic invertebrates are expected to respond to disturbances to the hydrobiocoenose. The outcome of an ITC assessment is clearly presentable in the form of a pie graph with 12 wedges, each representing one of the 12 defined trophic groups. Functionally complete communities are represented by 12 wedges; a blank wedge indicates that a trophic group is not represented. This paper describes the preliminary developments in the ITC method, its potential as a biological assessment method in rivers in different geographical zones, and presents examples of trial mappings of Russian and European rivers. The application of the ITC to these rivers demonstrated the absence of ITC trophic groups at sites under the influence of anthropogenic activity.     

Increased Benthic Algal Primary Production in Response to the Invasive Zebra Mussel (Dreissena polymorpha) in a Productive Ecosystem, Oneida Lake, New York

Increased water clarity associated with zebra mussel (Dreissena polymorpha) populations may favor benthic algal primary production in freshwater systems previously dominated by pelagic phytoplankton production. While zebra mussel-mediated water clarity effects on benthic primary production have been implicated in published reports, few production estimates are available. This study estimates benthic primary production in Oneida Lake, NY before and after zebra mussel invasion (1992), using measured photosynthetic parameters ( , α^B and β) from sampled benthic algal communities. In the summers of 2003 and 2004, primary production was measured as O₂ evolution from algal communities on hard (cobble) and soft (sediment) substrate from several depths. We also backcast estimates of benthic primary production from measurements of light penetration since 1975. Estimates of whole-lake epipelic and epilithic algal primary production showed a significant (4%) increase and exhibited significantly less interannual variability subsequent to the establishment of zebra mussels. We applied our model to two lakes of differing trophic status; the model significantly overestimated benthic primary production in a hypereutrophic lake, but there was no significant difference between the actual and predicted primary production values in the oligotrophic lake. The hypereutrophic lake had higher zebra mussel densities than Oneida (224 vs. 41 per sample respectively). Though total community respiration (measured in total darkness) was factored into our model predictions of production, our model may need modification when heterotrophic respiration is a large portion of total community metabolism.     

Effects of chronic bottom trawling disturbance on benthic biomass, production and size spectra in different habitats

Bottom trawling has widespread impacts on benthic communities and habitats. It is argued that the impact of chronic bottom trawling on benthic infauna depends on the natural disturbance levels to which benthic communities are adapted. We analysed biomass, production and size structure of two communities from a muddy and a sandy habitat, in relation to quantified gradients of trawling disturbance on real fishing grounds. We used an allometric relationship between body mass and individual production to biomass ratio to estimate community production. Chronic trawling had a negative impact on the biomass and production of benthic communities in the muddy habitat, while no impact was identified on benthic communities from the sandy habitat. These differences are the result of differences in size structure within the two communities that occur in response to increasing trawling disturbance.     

Diurnal bottom feeding of predator fish strengthens trophic cascades to benthic algae in experimental flow-through pools

Mechanisms that determine the strength of trophic cascades from fish to benthic algae via algivorous invertebrates in stream communities have not been clarified. Using seven fish species, we tested the hypothesis that the interspecific variation of predatory behavior of fishes affects the strength of trophic cascades in experimental streams. One or two species of fish were introduced into flow-through pools of 2.5 m² and the abundances of benthic invertebrates and algae were monitored. Pike gudgeon, a diurnal benthic feeder, triggered a strong trophic cascade but masu salmon, a diurnal drift feeder, did not have a cascading effect. Japanese dace, which is both a diurnal benthic and drift feeder, increased the algal biomass, but the nocturnal benthic feeder cut-tailed bullhead had little cascading effect. The diurnal benthic feeder silver crucian carp also had a cascading effect, but no trophic cascade was triggered either by Asian pond loach or by Japanese common catfish, both of which are nocturnal benthic feeders. Thus, diurnal benthic fish exerted a stronger cascading effect than diurnal drift feeders or nocturnal fish. The combination of two fish species enhanced the per-capita strength of trophic cascades, probably because one of the two species, the benthic feeder, preyed on more invertebrates than in the single-species pools.     

Benthic-pelagic trophic interactions within the fish assemblage in the western Bering Sea shelf area according to stomach content analysis and ratios of C and N stable isotopes

The composition, abundance, diet and trophic status of zooplankton, bottom invertebrates, fish and nekton were analyzed based on the data collected by the staff of the TINRO-Center during complex bottom trawl catches on the Bering Sea shelf in the fall of 2004. The stomach contents of mass fish species were analyzed and the nitrogen and carbon isotopic composition of 36 mass species of plankton, benthos, nekton and nektobenthos, which together make up the basis of pelagic and bottom communities, was determined. It was found that zooplankton noticeably differ from benthic invertebrates in carbon isotopic composition: δ¹³C values in zooplankton varied from −20.3‰ to −17.9‰; in benthos—from −17.5‰to −13.0‰; and in fish—from −19.2‰ (juvenile walleye pollock) to −15.3‰ (saffron cod). The levels of ¹³C isotope in the tissues of fish depended mostly on the share of pelagic or benthic animals in their diet. δ¹⁵N values in the studied species ranged from 8.6‰ (in sea urchins) to 17.2‰ (in large Pacific cods), which corresponds to a trophic level of 2.8. Obviously the δ¹⁵N values reflect the degree of predation and generally show the ratio of primary, secondary and tertiary consumers in a fish’s diet. Trophic interactions manifest a high degree of interdependence between benthic and pelagic communities (even without taking into account such lower components of the food web as phytoplankton, bacteria, and protozoa) occurring in most nektonic species that depend on both bottom and pelagic food.     

Are Antarctic suspension-feeding communities different from those elsewhere in the world?

This paper reviews the trophic ecology of benthic suspension feeders in Antarctic shelf communities, studied within SCAR's EASIZ Programme, in comparison with published information from other seas. Dense benthic suspension-feeder communities capture large quantities of particles and may directly regulate primary, and indirectly, secondary production in littoral food chains. Most work has been performed in temperate and tropical seas; however, little is known about suspension feeders in cold environments. Recent studies on Antarctic littoral benthic suspension feeders suggest the period of winter inactivity may last only a few weeks. This contrasts with the hypothesis that in Antarctic communities there is a prolonged period of minimal activity lasting at least 6 months during the austral winter. Results from other oceans may explain how dense benthic communities could develop under such conditions. Alternative food sources, i.e. the "fine fraction", sediment resuspension, lateral advection and efficient food assimilation may play a significant role in the development of suspension-feeder dominated, very diversified, high biomass and three-dimensionally structured communities on the Antarctic shelf.     

Predator diversity enhances secondary production and decreases the likelihood of trophic cascades

We manipulated the diversity of top predators in a three trophic level marine food web. The food web included four top benthic marine fish predators (black goby, rock goby, sea scorpion and shore rockling), an intermediate trophic level of small fish, and a lower trophic level of benthic invertebrates. We kept predator density constant and monitored the response of the lower trophic levels. As top predator diversity increased, secondary production increased. We also observed that in the presence of the manipulated fish predators, the density of small gobiid fish (intermediate consumers) was suppressed, releasing certain groups of benthic invertebrates (caprellid amphipods, copepods, nematodes and spirorbid worms) from heavy intermediate predation pressure. We attribute the mechanism responsible for this trophic cascade to a trait-mediated indirect interaction, with the small gobiid fish changing their use of space in response to altered predator diversity. In the absence of top fish predators, a full-blown trophic cascade occurs. Therefore the diversity of predators reduces the likelihood of trophic cascades occurring and hence provides insurance against the loss of an important ecosystem function (i.e. secondary production).     

Modelling the importance of sediment bacterial carbon for profundal macroinvertebrates along a lake nutrient gradient

In dimictic, temperate lakes little is known about the quantitative importance of trophic coupling between pelagic and profundal communities. Although it is a generally accepted paradigm that profundal secondary production is dependent on autochthonous pelagic production (primarily diatoms), the importance of interactions between phytodetrital inputs, sediment bacteria, and macroinvertebrates are still not well understood. In this study, we used theoretical models to estimate macroinvertebrate carbon requirement (production + respiration) and bacterial production for lakes of different trophic categories. Comparisons of estimates show that the importance of bacterial production as a carbon source for benthic macroinvertebrates is inversely related to lake trophic state. Assuming that infauna assimilates 50% of ingested bacterial carbon, this food source could account for between 47% (oligotrophic lakes) and 2% (hypertrophic lakes) of their carbon demand. These calculations indicate that bacterial carbon should not be an important C-resource for profundal macroinvertebrates of eutrophic and hypertrophic lakes.