Benthic Invertebrate Communities Research Articles

Structure and function of benthic invertebrate assemblages of the Djerekarska River (southwestern Serbia, Pester plateau)

This study is focused on benthic invertebrate communities in the Djerekarska River in Serbia, sampled from June to December 2016. We examined how different microhabitats with various substrates influenced the structure and function of the community. Taxonomic analysis revealed 55 species from 43 genera and 35 families, with the most diverse groups being Trichoptera, Ephemeroptera, and Plecoptera. ANOVA showed that different substrate types impacted the functional feeding groups within the assemblages. Cluster formation was primarily influenced by the substrate structure; this was followed by shredders, gatherers and collectors, passive filters, active filter feeders, the river depth, biochemical oxygen demand, chemical oxygen demand, and the flow velocity; for grazers and scrapers, discharge and saturation did not significantly affect cluster formation. Using two-step cluster analysis, we identified three clusters based on the substrate structure. The first group consisted of organisms that prefer a stone substrate; the second group consisted of organisms that prefer a mixed stone/gravel/sand substrate; the third group consisted of organisms that prefer gravel and sand substrates. Each cluster had a dominant functional feeding group, such as shredders and predators in the first cluster, gatherers and collectors in the second cluster, and predators, grazers, and scrapers in the third cluster.

Фауна и сообщества донных беспозвоночных ручьёв и родников Айтуарской степи (Оренбургский государственный степной заповедник)

The benthic (invertebrate) community of streams and springs in the Aytuar steppe includes 49 taxon. Chironomids are the most diverse (11). Mayflies (10), caddisflies (7) and stoneflies (5) are rich in species. Among other invertebrates, non-chironomid dipterans (8), mollusks (3), oligochaetes (1), amphipods (1), alder flies (1), bugs (1) and beetles (1) were recorded. The specificity of the fauna is determined by the presence of the genetically Siberian species M. borealis. Its negative feature is the absence of such wide-spread European taxa as the caddisflies of the genera Beraea, Crunoecia, and Parachiona, as well as genetically Siberian elements, the mollusks Parasphaerium rectidens (Starobogatov et Streletzkaja, 1967), stoneflies Arcynopteryx compacta (McLachlan, 1872), and Nemoura arctica Esben-Petersen, 1910, may-flies Cinygma lyriformis (McDunnough, 1924) and Ephemerella aurivillii Bengtsson, 1908, caddisflies Asynarchus lapponicus Zetterstedt, 1840 and Apatania stigmatella (Zetterstedt, 1840), common in the northern regions of the Urals and Cis-Urals. Were identified groups of invertebrates that are characteristic of both spring-fed water bodies and elements of the benthic fauna of warm-water streams. Five types of zoobenthocenoses were identified in streams. The zoobenthocenosis of cobbled (boulder-pebble) substra-tum is the most typical. Its abundance is 7.19 thousand ind./m2 with a biomass of 17.75 g/m2. The second type is the sand-gravel and pebble zoobenthocenoses (20.28 thousand ind./m2 with a biomass of 27.48 g/m2). Zoobentocenoses of boulder substratum with moss fouling, sandy substratum and silts are less widespread. Two types of zoobenthocenoses are found in springs. A community with the abundance and biomass of 6.8 thousand ind./m2 and 10.88 g/m2 respectively develops on boulder-pebble substratum, and on sandy substratum with coarse CPOM a community with a moderate level of development (number 3.80 thousand ind./m2 with a biomass of 6.44 g/m2) is observed.

Habitat preferences and trophic interactions of the benthic invertebrate communities inhabiting depositional and erosional banks of a meander from Danube Delta (Romania)

River restoration and biodiversity conservation programs require an in-depth knowledge of the influence that sediment composition and hydraulic stress have on invertebrate fauna composition and spatial distribution, as well as on nutrients cycling and food webs’ structure and functionality. Compared to low-order streams, the traditional focus of river ecology, the knowledge of these ecosystem properties of the meanders developed along large, lowland watercourses, is currently insufficient. The present study assessed the ecological preferences and the trophic interactions of the benthic invertebrate communities inhabiting erosional and depositional banks developed within a meander of the River Danube flowing through its delta (Danube Delta, Romania). The invertebrates from two mesohabitats, the concave (i.e. erosional) and convex (i.e. depositional) banks developed in the apex region of the meander were sampled quantitatively and qualitatively, along with sediment samples for assessing the grain-size characteristics and hydrodynamic parameters (i.e., critical shear stress, the Reynolds number, the critical velocity and Shields parameter). For assessing their mesohabitat preferences, quantitative samples were taken from both banks, whereas for inferring the trophic interactions, stable isotopes of δ15N and δ13C were measured from qualitative samples, comprising both invertebrates and basal resources. The results showed that increased siltation with fine sediments in the depositional bank led to a community dominated by chironomids, oligochaetes and bivalves, whereas the opposite bank comprised crayfish, caddis fly larvae and amphipods with a preference for coarser sediments. The δ13C of most consumers revealed that the dominant forms of carbon entries in the analysed food webs were photosynthetic based, whereas certain snails, chironomids and basal resources from the depositional bank were 13C depleted (δ13C: −35 to −39 ‰). Such low ratios for δ13C (mean < −35 ‰) reflected the potential of carbon entry through the base of depositional food web as a result of methane oxidation at sediment-water interface (i.e. chemosynthesis), induced by the fine sediments deposition that could have favoured the methane production. Grazing methane-oxidising bacteria in the depositional meander bank could have provided the primary consumers with up to 50 % and the omnivores and predatory invertebrates with up to 30 % of their carbon, which could represent an important subsidy from an additional, chemosynthetic source. The impact of a supplementary carbon input was further reflected in increasing depositional food web basal niche diversity, which led to distinct trophic niches and lower interspecific competition of consumers compared to the erosional bank of the meander.

An Ecological Comparison of Benthic Invertebrate Communities Between Sewage and Tigris River Water – Baghdad

In the current study, two sites were selected from the city of Adhamiya, central Baghdad. The first site is the Adhamiya Corniche, which includes a sample of river water and the second includes domestic sewage in the same area. The total density of benthic invertebrates was 775 ind/m2, which is divided into 15 taxa. Biological indices were found, such as the stability index, the abundance index, the biodiversity index (Shannon’s index), the homogeneity index, and the invader’s guide. The result showed an increase in the density of benthic invertebrates, as well as an increase in the diversity of these organisms.

Effects of Round Goby on the Benthic Invertebrate Community and on Diets and Growth of Yellow Perch and White Perch in Oneida Lake, New York

AbstractFood web changes from the introduction of nonnative species can be complex, with sometimes unexpected effects or little effect due to food web interactions. Invasive Round Goby Neogobius melanostomus became common in samples in Oneida Lake, New York, by 2014. Data from a long‐term monitoring program allowed us to document the Round Goby expansion through time. Using shoreline seine, fyke net, bottom trawl, and video surveys, we estimated that Round Goby density reached over 25,000 fish/ha 6 years after detection and subsequently varied between 4,110 and 26,565 fish/ha. Concurrent benthic invertebrate sampling and long‐term fish diet sampling allowed us to assess the impacts of Round Goby on densities of several benthic invertebrate taxa and on invertebrate consumption by fish. Significant decreases in density after Round Goby arrival were found for amphipods (Amphipoda), caddisflies (Trichoptera), snails (Gastropoda), and dreissenid mussels Dreissena spp. Invertebrate densities after Round Goby arrival ranged from 19% to 48% of densities in the pre‐Round Goby period. For amphipods, snails, and, in some cases, caddisflies and chironomids (Chironomidae), frequency of occurrence in the diets of Yellow Perch Perca flavescens and White Perch Morone americana was lower after Round Goby became established. The decreased consumption of these invertebrates did not lead to decreases in fish growth; growth increased for some age‐classes of Yellow Perch and all age‐classes of White Perch. Despite potential Round Goby predation, densities of burrowing mayflies Hexagenia spp. expanded during this time and likely helped to offset reductions in consumption of other invertebrates by Yellow Perch and White Perch, as did consumption of Round Goby. Long‐term monitoring shows that Round Goby decreased the density of several benthic invertebrate species and decreased the consumption of these invertebrates by fish, but the effect on growth of Yellow Perch and White Perch was offset by consumption of Round Goby and burrowing mayflies.

Assessment of Anthropogenic Influences on the Benthic Invertebrate Community of Oghan River in Edo State, Nigeria

The influence of anthropogenic activities on a freshwater ecosystem was investigated by sampling for physicochemical parameters, heavy metals and benthic invertebrates of Oghan River in Ora Community, Ovia South-West Local Government Area of Edo State, Nigeria. Samples were collected monthly for a ten months period across three stations between 09:00 and 12:00 hrs on each sampling day for laboratory analysis following standard procedure. No significant variation (P &gt; 0.05) was observed between the parameters, although heavy metals in sediments were above the WHO recommended limit for freshwater ecosystems. For benthic organisms, about 386 individuals belonging to 23 taxa, 11 families and 6 orders were recorded. Among the orders, the most dominant were Diptera (44.94%), Odonata (28.31%), Ephemeroptera (13.77%) while the least was Diplogasterida (0.26%). The families were dominated by Chironomidae (32.47%), Baetidae (13.77%) and Libellulidae (12.73%). Species diversity (2.677) and richness (4.002) were highest in station 1 and lowest in stations 2 (2.357) and 3 (2.745) while species evenness was highest in station 3 (0.791) and lowest in station 1 (0.6924). The elevated levels of heavy metals and the decrease in sensitive benthic taxa observed in the river is an indication that anthropogenic activities could be impacting the water quality and benthic invertebrate community of the river.

Structure and functional composition of macroinvertebrate communities in coastal plain streams across a precipitation gradient

Abstract Climate change is expected to alter rainfall and temperature regimes across the world. The hydrology and riparian zone vegetation of lotic ecosystems are tightly linked to rainfall and a mechanistic understanding of the effects of rainfall on lotic ecosystems is needed to forecast the ecological impacts of climate change. However, it is difficult to isolate rainfall effects from other environmental variables that covary across climates. To address this, we leveraged a unique steep rainfall gradient with few covarying changes in elevation, temperature, and geology to evaluate the effects of rainfall on stream invertebrate communities. We surveyed nine streams in the Texas Gulf Coast Prairie distributed along a 550–1,350 mm/year rainfall gradient. Four sites were classified as drier semi‐arid streams (&lt;750 mm annual rainfall) and five sites were classified as wetter sub‐humid streams (&gt;750 mm annual rainfall). A suite of characteristics including benthic invertebrate community metrics, flow conditions, and water quality variables were assessed monthly for 14 months at each site to relate precipitation regime to stream structure and function. Precipitation regime was observed to be a master explanatory variable. As annual rainfall increased, the flow environment became more stable within seasons and predictable across seasons, influencing spatial structure and temporal variability of invertebrate community composition. Wetter streams were dominated by slower growing taxa without adaptions for desiccation resistance and strong dispersal. Wetter sites displayed seasonal variation in community composition and species richness, whereas temporal variation in communities in drier streams was controlled by stochastic variation in flow conditions. These observations show that differences in local annual rainfall correlated with major changes to community structure and functional composition. We hypothesise that this association is related to the connection of rainfall to hydrological stability, particularly the frequency of low flow disturbances, and the subsequent effects on riparian vegetation and temporally available niches to stream invertebrates. Our work adds to evidence that alterations in precipitation patterns associated with climate change have sweeping impacts on lotic fauna.

Structural diagnosis of benthic invertebrate communities in relation to salinity gradient in Baltic coastal lake ecosystems using biological trait analysis

This study is based on biological trait analysis (BTA), which provides a link between the distribution and biological characteristics of species. The paper investigates differences in the structure and functional diversity of benthic fauna in terms of seven biological traits (mobility, habitat, feeding type, habitat modification, body form, body size and feeding apparatus) in nine Baltic coastal lakes whose salinity ranged from 0.1 to 7.3 PSU. Mobile organisms were more common in lakes with higher salinity, while sessile and semi-mobile species preferred low-salinity or freshwater environments. There were also noticeable differences connected with feeding type: collectors and scrapers were more common in brackish lakes, and collectors were significantly dominant in freshwater and transitional ones. This indicates that Baltic coastal lakes are inhabited by similar species of benthic fauna, but that certain biological traits occur with different frequencies. We therefore identified features that may affect the functioning of coastal lakes with a relatively narrow salinity gradient (0.1–7.3 PSU). It seems to confirm the possibility of using BTA methods to determine key characteristics that are helpful for understanding the differences between aquatic ecosystems. The results may provide a basis for further research on changes in the functional diversity of lakes along the southern coast of the Baltic Sea, particularly in view of climate change, given their being small, shallow and less resilient lakes.

Combining Multispectral and Radar Imagery with Machine Learning Techniques to Map Intertidal Habitats for Migratory Shorebirds

Migratory shorebirds are notable consumers of benthic invertebrates on intertidal sediments. The distribution and abundance of shorebirds will strongly depend on their prey and on landscape and sediment features such as mud and surface water content, topography, and the presence of ecosystem engineers. An understanding of shorebird distribution and ecology thus requires knowledge of the various habitat types which may be distinguished in intertidal areas. Here, we combine Sentinel-1 and Sentinel-2 imagery and a digital elevation model (DEM), using machine learning techniques to map intertidal habitat types of importance to migratory shorebirds and their benthic prey. We do this on the third most important non-breeding area for migratory shorebirds in the East Atlantic Flyway, in the Bijagós Archipelago in West Africa. Using pixel-level random forests, we successfully mapped rocks, shell beds, and macroalgae and distinguished between areas of bare sediment and areas occupied by fiddler crabs, an ecosystem engineer that promotes significant bioturbation on intertidal flats. We also classified two sediment types (sandy and mixed) within the bare sediment and fiddler crab areas, according to their mud content. The overall classification accuracy was 82%, and the Kappa Coefficient was 73%. The most important predictors were elevation, the Sentinel-2-derived water and moisture indexes, and Sentinel-1 VH band. The association of Sentinel-2 with Sentinel-1 and a DEM produced the best results compared to the models without these variables. This map provides an overall picture of the composition of the intertidal habitats in a site of international importance for migratory shorebirds. Most of the intertidal flats of the Bijagós Archipelago are covered by bare sandy sediments (59%), and ca. 22% is occupied by fiddler crabs. This likely has significant implications for the spatial arrangement of the shorebird and benthic invertebrate communities due to the ecosystem engineering by the fiddler crabs, which promotes two vastly different intertidal species assemblages. This large-scale mapping provides an important product for the future monitoring of this high biodiversity area, particularly for ecological research related to the distribution and feeding ecology of the shorebirds and their prey. Such information is key from a conservation and management perspective. By delivering a successful and comprehensive mapping workflow, we contribute to the filling of the current knowledge gap on the application of remote sensing and machine learning techniques within intertidal areas, which are among the most challenging environments to map using remote sensing techniques.

Quantifying the ecological effects of water abstraction in Alpine streams through flume simulations

AbstractWater abstraction by small hydropower plants is a growing human pressure on Alpine stream ecosystems. Using a set of seminatural streamside flumes, we investigated the response of benthic invertebrate communities to a 50% experimental reduction of the natural discharge. We collected EPT taxa from upstream (control) and downstream (flow reduction) sections of the flumes before starting the simulations, and after 1 and 3 weeks of simulated flow reduction, while also collecting invertebrates drifting from each section every 24–48 h. Despite an initial (i.e., before simulation) difference in benthic densities and diversity between controls and treatments, these metrics changed and differed over time, with the reduced flow section becoming more diverse and with less individuals. Taxonomic composition differed between flow types, with a short‐term (1 week after the beginning of flow reduction) increase of taxonomic heterogeneity. There was no evidence that flow reduction affected functional diversity and homogenized functional composition of the communities. Drift composition differed between flow types with drift rates and richness lower under reduced flow. Functional dispersion was always significantly lower in the drift collected in low‐flow conditions where drift propensity was significantly higher for animals preferring medium to fast currents, living temporarily attached to the substrate and feeding as passive filterers; drift propensity was slightly lower for organisms moving as crawlers. Hence, short‐term taxonomic and functional changes in benthic invertebrate communities with reduction in flow are likely related to behavioural responses such as drift, thus providing insight on the potential mechanisms underlying community‐level effects of water abstraction.

Diversity and distribution of benthic invertebrates dwelling rivers of the Kruger National Park, South Africa

Meiobenthos (or meiofauna) are microscopic invertebrates that inhabit biofilms and interstitial spaces in rivers. They are diverse and extremely abundant, and they perform essential ecological functions by linking microbial production to higher trophic levels (e.g. macrobenthic invertebrates and fishes). However, meiobenthic communities remain poorly studied in Africa. Here, we sampled meio- and macrobenthic invertebrate communities associated with biofilms and sediments across an upstream–downstream gradient along the Olifants, Sabie and Crocodile rivers flowing through the Kruger National Park (KNP). We expected to link differences in community structure to environmental gradients as those rivers show different degrees of anthropogenic stress as they enter the park. Both meio- and macrobenthic communities differed across rivers and also structured along an upstream–downstream gradient. The upstream sites, which were the closest to the park borders, consistently showed a lower diversity in all three rivers. There, the invasive snail Tarebia granifera strongly dominated (making up 73% – 87% of the macrobenthos), crowding hard substrates, while concomitantly the abundances of biofilm-dwelling meiobenthos like nematodes and rotifers were substantially reduced. Nevertheless, the diversity and evenness of communities then tended to increase as water flowed downstream through the park, suggesting a beneficial effect of protected river reaches on benthic invertebrate diversity. However, for the Crocodile River, which makes up the southern border of the park, this trend was less conspicuous, suggesting that this river may experience the greatest threats. More generally, benthic invertebrate communities were driven by the concentrations of phosphates, sulphates, ammonium and organic matter and by substrate characteristics.Conservation implications: Meiobenthic organisms are very abundant in KNP rivers and react to environmental gradients; thus, they should be more considered for bio-monitoring or conservation of comprehensive assemblages of animals. Interestingly, protected reaches tended to show a reduced dominance of the invasive T. granifera and a higher diversity of benthic invertebrates.

Species Sensitivity Distributions of Benthic Macroinvertebrates in Fludioxonil-Spiked Sediment Toxicity Tests.

The fungicide fludioxonil, given its physicochemical properties, potentially accumulates and persists in sediments. Fludioxonil has a widespread agricultural use to control various fungal diseases. Its residues may cause toxic effects to benthic aquatic fauna, thereby impacting ecosystem service functions of aquatic ecosystems. To assess the potential environmental effects of fludioxonil in the sediment compartment of edge-of-field surface waters, sediment-spiked single-species toxicity tests with benthic macroinvertebrates were performed. In all experiments artificial sediment was used with an organic carbon content of 2.43% on dry weight basis. The single-species tests were conducted with 8 benthic macroinvertebrates covering different taxonomic groups typical for the Yangtze River Delta, China. The 28d-EC10 and 28-LC10 values thus obtained were used to construct species sensitivity distributions (SSDs). In addition, our dataset was supplemented with 28d-EC10 and 28-LC10 values for 8 different benthic invertebrates from a study in the Netherlands that used field-collected sediment. Based on SSDs constructed with 28d-EC10 or 28d-LC10 values hazardous concentrations to 5% of the species tested (HC5's) were obtained. The HC5 values based on the toxicity tests from China were lower than those from the Netherlands, although 95% confidence bands overlapped. The HC5 values derived from the separate datasets from China and the Netherlands, as well as from the combined dataset, were compared to the Tier-3 Regulatory Acceptable Concentrations (RAC) for fludioxonil and the benthic invertebrate community derived from a sediment-spiked outdoor microcosm experiment conducted in the Netherlands. The HC5 values obtained appeared to be lower than this Tier-3 RAC when expressed in terms of total sediment concentration, but not always when expressed in terms of pore water concentrations.

Impacts of piscicide-induced fish removal on resource use and trophic diversity of lake invertebrates

Chemical eradication of non-native species has become a widely used method to mitigate the potential negative impacts of altered competitive or predatory dynamics on biodiversity and natural ecosystem processes. However, the responses of non-target species can vary from rapid full recovery to delayed or absent recolonization, and little is known about the potential shifts in resource use and trophic diversity of native species following chemical treatments. We used a before-after-control-impact approach to study the effects of rotenone piscicide treatment on abundance and trophic niche of benthic invertebrates in three untreated and three treated lakes in central Norway, the latter group hosting non-native roach (Rutilus rutilus) and pike (Esox lucius) prior to rotenone treatment. Based on community composition data, the relative abundance of invertebrate grazers and collectors decreased while that of predators increased following fish removal in the treated lakes. The stable isotope data indicated minor shifts in resource use of, and trophic diversity among, benthic invertebrate communities. While the predatory dragonfly larvae (Odonata) and grazer snails (Lymnaeidae) showed increased δ13C values indicating increased reliance on littoral benthic algae, the collector mayfly larvae (Leptophlebia) showed decreased δ13C values following fish removal in treated lakes. Grazer snails also showed a shift to a lower trophic position, while the predatory dragonflies and collector mayflies showed no changes in δ15N values following fish removal. The community-level isotopic niches of benthic invertebrates showed no consistent changes, although the sample-size corrected and Bayesian estimates of standard ellipse areas (SEAC and SEAB) slightly increased in two of the three treated lakes due to an increased range in δ15N. In conclusion, our study findings indicate some changes in species assemblages but minor shifts in the resource use and trophic diversity of benthic invertebrate communities following fish removal in rotenone treated lakes.

Long-Term Monitoring of an In Situ Activated Carbon Treatment to Reduce Polychlorinated Biphenyl Availability in an Active Harbor.

Activated carbon-based amendments have been demonstrated as a means of sequestering sediment-associated organic compounds such as polychlorinated biphenyls (PCBs). In a 2012 effort, an activated carbon amendment was placed at a 0.5-acre amendment area adjacent to and underneath Pier 7 at the Puget Sound Naval Shipyard and Intermediate Maintenance Facility, Bremerton, Washington, USA to reduce PCB availability. Multiple postplacement monitoring events over a 3-year period showed an 80%-90% reduction in PCBs, stability of activated carbon, and no significant negative impacts to the benthic community. To further evaluate the long-term performance, a follow-on to the approximately 7-year (82-month) postplacement monitoring event was conducted in 2019. The results of in situ porewater and bioaccumulation evaluations were consistent with previous observations, indicating overall PCB availability reductions of approximately 80%-90% from preamendment conditions. Multiple measurement approaches for quantifying activated carbon and amendment presence indicated that the amendment was present and stable in the amendment area and that the activated carbon content was similar to levels observed previously. As in the previous investigation, benthic invertebrate community metrics indicated that the amendment did not significantly impair benthic health. An application of carbon petrography to quantify activated carbon content in surface sediments was also explored. The results were found to correspond within a factor of 1.3 (on average) with those of data for the black carbon content via a black carbon chemical oxidation method, an approach that quantifies all forms of black carbon (including activated carbon). The results suggest that at sites with low soot-derived black carbon content in sediment (relative to the targeted activated carbon dose), the black carbon chemical oxidation method would be a reasonable method for measurement of activated carbon dosage in sediment at sites amended with activated carbon. Environ Toxicol Chem 2022;41:1568-1574. © 2022 SETAC.

Structural factors driving benthic invertebrate community structure on historical shipwrecks in a large North Atlantic marine sanctuary

Shipwrecks are irreplaceable historical resources and valuable biological habitats. Understanding the environmental and anthropogenic factors affecting shipwrecks is critical for preservation in situ. We used remotely operated vehicles to study the benthic invertebrate communities on four shipwrecks in Stellwagen Bank National Marine Sanctuary (SBNMS, North Atlantic, USA). Shipwrecks included coal schooners and a passenger steamer, all >100 years old. These large, complex structures hosted dense populations of invertebrates (34 species), especially on high-relief and overhanging substrata. Some species that are otherwise rare in the community may proliferate through asexual reproduction and form dense populations on shipwrecks. We also investigated impacts of entangled fishing gear on the invertebrate communities on each shipwreck and found that areas with the most ghost gear have lower species richness and different community structure. Fishing, particularly bottom trawling, damages shipwrecks and poses a threat to these valuable cultural resources and biological habitats in SBNMS.

Signs of the times: Isotopic signature changes in several fish species following invasion of Lake Constance by quagga mussels

Since the arrival of the invasive quagga mussels Dreissena rostriformis bugensis in Lake Constance, significant changes in the zooplankton and benthic invertebrate community were observed. Five years later the quagga mussel has become the dominating species of the benthic community. Its effects on other components of the food web, especially those at higher trophic levels such as fish, remain unclear around the world. To evaluate the actual impact of quaggas on the local food web of Lake Constance, the stable isotope compositions of pelagic whitefish and different benthic fish species from before and after the quagga invasion were compared. A significant increase in δ13C was detected in pelagic whitefish one year after the establishment of the quagga mussel in the lake. This change was most likely the consequence of an increase in benthic-derived nearshore primary production and a shift towards more littoral feeding, than a change in dietary composition. Stomach content analysis of contemporary samples revealed that pelagic whitefish (Coregonus wartmanni) still feed exclusively on pelagic zooplankton. In contrast, benthic whitefish (Coregonus macrophthalmus), roach (Rutilus rutilus) and tench (Tinca tinca) show today high levels of quagga consumption. However, this behaviour alone could not explain the observed differences in δ15N from periods before and after the quagga invasion. The results suggest that energy sources and pathways have changed considerably for both pelagic and benthic dwelling fish species in Lake Constance following the establishment of quaggas.

Bioregionalization of the South Sandwich Islands through community analysis of bathyal fish and invertebrate assemblages using fishery-derived data

The South Sandwich Islands (SSI) are a volcanic archipelago in the Atlantic sector of the Southern Ocean; they are a biologically rich area, home to a range of benthic habitats such as hydrothermal vents and seamounts. A commercial longline fishery for two congeneric species of deep-sea fish, the Patagonian (Dissostichus eleginoides) and Antarctic (D. mawsoni) toothfish has been in operation annually at the SSI since 2005 and throughout its history has employed scientific observers to collect detailed information on the species caught during fishing operations. Previous studies have investigated the distributions and communities of benthic invertebrates, sampled via scientific cruises. Here we highlight the utility of demersal longlines as spatially extensive sampling tools to investigate both invertebrate and fish communities at the SSI. A clear gradient in the distribution of many fish and invertebrate species is evident across the latitudinal range of the archipelago, these distributions result in clear differences in fish communities between the north, mid, and south of the islands, whilst the invertebrate communities are less clearly delineated. Environmental variables were investigated as drivers in these communities, and seawater temperature appears to be a key abiotic factor in mediating the distributions of species and communities. As many of these communities are structured based on temperature dependent species distributions, it is likely climate change will alter these communities with poleward shifts in the ranges of many species.

Effects of Spartina alterniflora invasion on the benthic invertebrate community in intertidal wetlands

AbstractExotic species invasions have profound effects on native ecosystems, with the ecological effects of non‐native plants being especially pervasive. We investigated the impacts of a plant invasion on benthic invertebrate assemblages in intertidal wetlands of the Yellow River Delta, comparing benthic communities associated with exotic Spartina alterniflora against those associated with native plants (Tamarix chinensis, Suaeda salsa, and mudflat). Our study surprisingly found that the density, diversity, and richness of benthic invertebrates associated with S. alterniflora were higher than with native habitats. Multivariate analysis also revealed that the structure of benthic invertebrates in S. alterniflora habitats was different than in T. chinensis and mudflat habitats. The structure of invertebrates associated with the invasive S. alterniflora and native S. salsa was more similar, although the dominant species differed. Indicator species analyses indicated that each habitat was characterized by unique taxa. S. alterniflora invasion increased the beta diversity of the community, with the species turnover component being of most importance. Mollusks were most likely to be influenced by Spartina invasions. Given the extent of the S. alterniflora invasion in the Yellow River Delta, altered benthic invertebrate communities will likely have important implications for the ecology of the intertidal wetland ecosystems and deserve increased attention.

Aquatic community structure and stream habitat in a karst agricultural landscape

BackgroundWatersheds dominated by agriculture often have significant, negative impacts on local stream habitats and fauna. Our study examined stream biota and habitats within an entire stream in a karst agricultural landscape to determine if several decades of watershed conservation and management had reversed the severe degradation caused by poor land use and catastrophic soil erosion during the 1920s and 1930s.ResultsFish communities and stream habitats were degraded at over half of the 22 stream sites examined, and benthic macroinvertebrate communities were mostly poor throughout the entire stream. Poor fish communities were associated with missing or narrow riparian buffers, high percent fine sediments, high embeddedness of coarse substrates, and homogeneous run habitat. Invertebrate communities were dominated by filter-feeding taxa and those adapted to life on or within fine sediments. Stream sites with wide buffers and influenced by groundwater springs had higher fish community integrity and good to excellent instream habitat.ConclusionsOur results suggest that wide riparian buffers and karstic springs may have allowed recovery of some stream reaches, but more extensive buffers and additional soil conservation practices in upland areas likely are necessary to protect most stream segments and their biota from on-going agricultural activities. New state stream buffer laws instituted after this study resulted in establishment of vegetated buffers at all study sites, which may lead to improved stream habitat and biotic communities in future years. Benthic invertebrate community improvement also may require translocation of sensitive taxa from nearby watersheds due to limited dispersal abilities of many species currently absent from the study stream. Increased frequency and intensity of storm events and flooding may hinder future recovery of stream habitats and biota.

Comparison of Recruitment Patterns of Sessile Marine Invertebrates According to Substrate Characteristics.

A community of benthic invertebrates, including sessile adult-stage invertebrates, can negatively effect corrosion, deformation, and increased fuel consumption by attaching to artificial structures, a phenomenon known as marine biofouling. Investigating the relationship between benthic communities and artificial structures or substrates (to which the organisms attach) can help clarify the factors influencing marine biofouling. Therefore, in our study, natural (stone) and artificial (rubber, tarpaulin, and iron) substrates were installed in three harbors (Mokpo, Tongyeong, and Busan), and the structures of the communities attached to each substrate were compared. The total study period was 15 months (September 2016 to December 2017), and field surveys were performed at 3-month intervals. The three survey sites had significant differences in the structure of the sessile community present. In particular, Tongyeong was significantly different from Mokpo and Busan due to the continuous dominance of Cirripedia. When comparing natural and artificial substrate by sites, significant differences were observed in the community structure in all three surveyed sites. In Mokpo and Busan, colonial ascidians were dominant on natural substrate rather than artificial substrates; post-summer, Cirripedia coverage was higher on artificial substrates than natural substrate due to corrosion. Tongyeong showed a different pattern from that of Mokpo and Busan. After the summer, Bivalvia dominated on natural substrate over artificial substrates, affecting the differences between natural and artificial substrates. Our results demonstrate the recruitment patterns of sessile marine invertebrates according to substrate characteristics and can be used as basic information for biofouling management in marine environment.