Benthic Invertebrate Assemblages Research Articles

Density data for Lake Erie benthic invertebrate assemblages from 1930 to 2019.

Benthic invertebrates are important trophic links in food webs and useful bioindicators of environmental conditions, but long-term benthic organism abundance data across broad geographic areas are rare and historic datasets are often not readily accessible. This dataset provides densities of benthic macroinvertebrates collected from 1930 to 2019 during surveys in Lake Erie, a Laurentian Great Lake. The surveys were funded by the governments of the United States and Canada to investigate the status and changes in the benthic community. From the total of 21 lake-wide and basin-wide benthic surveys conducted in Lake Erie from 1929 to 2019, we were able to acquire data for 17 surveys, including species-level data for 10 surveys and data by higher taxonomic groups for seven surveys. Our amassed Lake Erie dataset includes data from 11 surveys (including five with species-level data) conducted in the western basin in 1930-2019, seven surveys (six with species-level data) in the central basin, and eight surveys (seven with species-level data) in the eastern basin (1973-2019). This Lake Erie dataset represents the most extensive temporal dataset of benthic invertebrates available for any of the Laurentian Great Lakes. Benthic samples were collected using Ponar or Shipek bottom dredges and taxa densities were calculated as individuals per square meter using the area of the dredge. Density data are provided for taxa in the Annelida, Arthropoda, Mollusca, Cnidaria, Nemertea, and Platyhelminthes phyla. Current taxonomy was used for most groups but, in a few cases, older taxonomic names were used for consistency with historical data. Analysis of this dataset indicates that eutrophication, water quality improvement, and dreissenid introduction were the major drivers of changes in the benthic community in the western basin, while hypoxia was a major factor in the central basin, and dreissenid introduction was the most important driver in the eastern basin. Considering the rarity of high taxonomic resolution long-term benthic data for lake ecosystems, this dataset could be useful to explore broader aspects of ecological theory, including effects of eutrophication, hypoxia, invasive species, and other factors on community organization, phylogenetic and functional diversity, and spatial and temporal scales of variation in community structure. In addition, the dataset could be useful for studies on individual species, including abundance and distribution, species co-occurrence, and how the patterns of dominance and rarity change over space and time. Use of this dataset for academic or educational purposes is encouraged as long as this data paper is properly cited.

Effect of coral‐giant clam artificial reef on coral recruitment: insights for restoration and conservation efforts

Coral recruitment is a vital process for the maintenance and recovery of coral reefs, particularly due to their decline from global change. While it is well established that larval settlement cues significantly influence coral recruitment, the investigation of recruitment success associated with the surrounding community mainly focuses on algae. To investigate other factors controlling this process, we examined the impact of benthic invertebrate assemblages on coral recruitment using artificial reefs. Three types of artificial reefs (mono‐, bi‐, and tri‐species) with different assemblages of three common species, Pocillopora acuta, Acropora cytherea, and Tridacna maxima, were studied over 8 months. This study revealed that benthic assemblages play a significant role in coral recruitment and survival. High biodiversity was found to enhance coral recruitment and inhibit potential negative cues from A. cytherea. Our findings underscore the importance of preserving high biodiversity using not only hard coral but a wide range of phyla, including bivalves, in coral restoration efforts. Maintaining sustainable populations is an important goal to reach in the face of the multiple threats that impact coral reefs.

Potential impacts of changing vegetation on benthic invertebrate assemblages in Odaigahara, Japan

Potential impacts of changing vegetation on benthic invertebrate assemblages in Odaigahara, Japan

Subfossil Chironomid Assemblages as Indicators of Remedial Efficacy in the Historically Contaminated St. Lawrence River at Cornwall, Ontario.

Long-term data are required to quantify the impacts of historic industrial pollution and subsequent remedial action on the nearshore benthic community in the St. Lawrence River Area of Concern at Cornwall, Ontario. Specifically, high-quality temporal records are needed to understand changes in benthic invertebrate assemblages in response to multiple possible drivers including industrial pollution, environmental heterogeneity, and climate warming. We compare long-term records of subfossil chironomid assemblages and geochemical variables among sediment cores from two Cornwall sites with differing pollution histories and a minimally disturbed downstream reference site. Chironomids were functionally absent from the Cornwall sediment cores when mercury and zinc concentrations were elevated. As metal concentrations decreased in more recent sediment intervals, chironomid abundance and the relative abundance of pollution-sensitive taxa increased. Recently deposited sediment in all three sediment cores display increased relative abundance of warm-water, macrophyte-associated taxa. We conclude that these temporal changes in chironomid assemblages provide evidence for ecological recovery for both of the impacted sites, consistent with the objectives of the current management strategy. These findings advance our understanding of industrial impacts on fluvial chironomid ecology, directly inform local management strategies, and further develop the application of chironomids as bioindicators for contaminated sediments.

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.

Land use in acid sulphate soils degrades river water quality – Do the biological quality metrics respond?

Land use in the Acid Sulphate (AS) soils induces metal and acidity pollution of aquatic ecosystems in coastal areas worldwide. Increasing utilization of AS soils poses increasing risks for deterioration of water bodies. We studied the effects of the coverage of AS soils, together with other catchment land cover attributes, on aquatic assemblages of fish, diatoms and benthic invertebrates in 42 sites along 15 lowland rivers in Finland during three subsequent years. Low pH and increasing content of several metals in the river water were related to high amount of AS soils in the catchment. Especially increasing iron content and water color were correlated to amount of forested areas in the catchment, whereas lower water color values and higher arsenic, chromium and iron concentrations were associated with wetlands. The assemblage structure of all three biological groups was strongly spatially structured among rivers and varied less temporally. The spatial structure of fish and diatoms were strongly affected by the acidic water, whereas invertebrates were more affected by low alkalinity and increasing concentrations of organic matter and iron. Especially fish and benthic invertebrate bioassessment metrics demonstrated for AS soil induced degradation in acidity by responding to low pH and high acidity, while the response from the diatoms index was weaker. The high metal concentrations alone did not seem to add to the degradation in biometrics without further increase in acidification. Our results highlight the importance of recognizing AS soil areas in the catchment to target the mitigation effects. A holistic approach in the mitigation of the adverse effects from AS soils is needed, using several mitigation methods in the catchment, and directing main efforts and protection from human disturbance to catchment areas with the highest proportion of AS soils. Our results suggest that status assessment of AS rivers should be based on multiple biological quality elements and that their metrics could be improved for better detection of impacts from acidity and metal pressures. The effects of metals and their concentrations on aquatic assemblages should be further examined.

Modeling demersal fish and benthic invertebrate assemblages in support of marine conservation planning.

Marine classification schemes based on abiotic surrogates often inform regional marine conservation planning in lieu of detailed biological data. However, these schemes may poorly represent ecologically relevant biological patterns required for effective design and management strategies. We used a community‐level modeling approach to characterize and delineate representative mesoscale (tens to thousands of kilometers) assemblages of demersal fish and benthic invertebrates in the Northwest Atlantic. Hierarchical clustering of species occurrence data from four regional annual multispecies trawl surveys revealed three to six groupings (predominant assemblage types) in each survey region, broadly associated with geomorphic and oceanographic features. Indicator analyses identified 3–34 emblematic taxa of each assemblage type. Random forest classifications accurately predicted assemblage distributions from environmental covariates (AUC > 0.95) and identified thermal limits (annual minimum and maximum bottom temperatures) as important predictors of distribution in each region. Using forecasted oceanographic conditions for the year 2075 and a regional classification model, we projected assemblage distributions in the southernmost bioregion (Scotian Shelf‐Bay of Fundy) under a high emissions climate scenario (RCP 8.5). Range expansions to the northeast are projected for assemblages associated with warmer and shallower waters of the Western Scotian Shelf over the 21st century as thermal habitat on the relatively cooler Eastern Scotian Shelf becomes more favorable. Community‐level modeling provides a biotic‐informed approach for identifying broadscale ecological structure required for the design and management of ecologically coherent, representative, well‐connected networks of Marine Protected Areas. When combined with oceanographic forecasts, this modeling approach provides a spatial tool for assessing sensitivity and resilience to climate change, which can improve conservation planning, monitoring, and adaptive management.

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.

Secondary production increases with species richness but decreases with species evenness of benthic invertebrates

Biodiversity is known to regulate ecosystem functioning under controlled experimental conditions. However, the ‘real‐world' consequences of biodiversity change remain uncertain, as biodiversity–ecosystem function (BEF) relationships observed in nature may be influenced by other drivers. Attempts to disentangle BEF relationships from the effects of confounding factors have so far focused mainly on primary producers, leaving comparatively little known about the impact of changes in consumer diversity despite ecosystems experiencing species extirpations and introductions across trophic levels. Using data from 176 benthic invertebrate assemblages distributed throughout the North Sea, we studied how a fundamental ecological function – secondary production – varies in relation to two components of biodiversity – consumer species richness and evenness – while statistically controlling the effects of abiotic and biotic covariates. Production was enhanced as richness increased or evenness decreased. The relationship with evenness was attributable to its negative covariance with the abundance of small organisms; however, the relationship with richness could not be fully explained by other drivers. Our study reaffirms experimental findings about the functional importance of biodiversity and suggests that losing or gaining consumer species will affect secondary production over a broad range of species richness (20–118 species) in natural ecosystems.

Benthic Data Collection in Lake Ontario: Continuation of a Long‐term Data Series

Photo 1. Marine technician Kathryn Johncock is collecting a benthic sample from Lake Ontario using Ponar bottom grab aboard of U.S. EPA Research Vessel Lake Guardian during 2018 benthic survey. Photo credit: A. Karatayev. Photo 2. Benthic samples are elutriated aboard and washed through a 500-μm net by Chris Korleski (U.S. EPA Great Lakes National Program Office, on left) and Alexander Karatayev (SUNY Buffalo State, on right). Photo credit: L. Burlakova. Photo 3. Exotic byssate bivalves quagga mussels were found in almost every benthic sample collected from Lake Ontario in 2018. Photo credit: A. Karatayev. Photo 4. Lake Ontario shoreline scattered with wind turbines. Photo credit: L. Burlakova. Photo 5. Lake Guardian is moving to the next station. Photo credit: L. Burlakova. These photographs illustrate the article “Density data for Lake Ontario benthic invertebrate assemblages from 1964 to 2018” by Burlakova, L. E., A. Y. Karatayev, A. R. Hrycik, S. E. Daniel, K. Mehler, L. G. Rudstam, J. M. Watkins, R. Dermott, J. Scharold, A. K. Elgin, T. F. Nalepa, E. K. Hinchey, and S. J. Lozano published in Ecology. https://doi.org/10.1002/ecy.3528.

Back to Ecology: Reference Conditions as a Basis for Assessment, Restoration and Sustainable Management of Large Rivers

Under the EU Water Framework Directive, ecological assessment and management are based on type-specific reference conditions. In the EU it may be difficult to find sites in large rivers with at least near-natural conditions, though this is not the case in southeast Europe, where stretches of large rivers still exist with at least near-natural conditions, meaning that there is little or no disturbance from hydromorphological alteration, water quality, land use in the catchment and alien species. We examined benthic invertebrate assemblages in 45 samples collected from near-natural sites of several large rivers: Sava, Drava, Mura, Kupa and Una. The near-natural benthic invertebrate assemblages of large rivers contained several rare or remarkable species, especially among stoneflies, e.g., Marthamea vitripennis, Xanthoperla apicalis. We compared benthic invertebrate communities in river sections with fine and coarse substrates and in three eco-hydromorphological (ECO-HM) types of large rivers, reflecting habitat heterogeneity: lowland-deep, lowland-braided and intermountain. Multivariate analysis of variance (PERMANOVA) was used to statistically evaluate similarities among assemblages. It was found that the composition of benthic invertebrate assemblages varied by both ECO-HM types and substrate category. Similarity percentage (SIMPER) analysis showed that the average dissimilarity of benthic invertebrate assemblages was high between all ECO-HM type pairs and between fine and coarse substrate. We found that habitat heterogeneity and substrate independently influenced benthic invertebrate assemblages. To achieve ecological goals in the management of large rivers, in addition to functionality, a holistic view with at least near-natural assemblages, including the names of the taxa present, should also be considered.

Density data for Lake Ontario benthic invertebrate assemblages from 1964 to 2018.

Benthic invertebrates are important trophic links in aquatic food webs and serve as useful bioindicators of environmental conditions because their responses integrate the effects of both water and sediment qualities. However, long-term data sets for benthic invertebrate assemblages across broad geographic areas are rare and, even if collected, historic data sets are often not readily accessible. This data set provides densities of benthic macroinvertebrates for all taxa collected during lake-wide surveys in Lake Ontario, a Laurentian Great Lake, from 1964 to 2018. This information resulted from surveys funded by the governments of the United States and Canada to investigate the status and changes of Lake Ontario benthic community. Of the 13 lake-wide benthic surveys conducted in Lake Ontario over the course of 54 yr, we were able to acquire taxonomic data to the species level for 11 of the surveys and data to the group level for the other two surveys. Density data are provided for taxa representing the Annelida, Arthropoda, Mollusca, Cnidaria, Nemertea, and Platyhelminthes phyla. Univariate and multivariate analyses revealed that the compositional structure of Lake Ontario invertebrate assemblages differed markedly by depth and were also significantly altered by the Dreissena spp. invasion in early 1990s. The introduction of invasive dreissenids has changed the community historically dominated by Diporeia, Oligochaeta, and Sphaeriidae, to a community dominated by quagga mussels and Oligochaeta. Considering the rarity of long-term benthic data of high taxonomic resolution in lake ecosystems, this data set could be useful to explore broader aspects of ecological theory, including effects of different environmental factors and invasive species on community organization, functional and phylogenetic diversity, and spatial scale of variation in community structure. The data set could also be useful for studies on individual species including abundance and distribution, species co-occurrence, and how the patterns of dominance and rarity change over space and time. Use of this data set for academic or educational purposes is encouraged as long as the data source is properly cited using the title of this Data Paper, the names of the authors, the year of publication, the journal name, and the article number.

The influence of a lost society, the Sadlermiut, on the environment in the Canadian Arctic

High latitude freshwater ecosystems are sentinels of human activity and environmental change. The lakes and ponds that characterize Arctic landscapes have a low resilience to buffer variability in climate, especially with increasing global anthropogenic stressors in recent decades. Here, we show that a small freshwater pond in proximity of the archaeological site “Native Point” on Southampton Island (Nunavut, Arctic Canada) is a highly sensitive environmental recorder. The sediment analyses allowed for pinpointing the first arrival of Sadlermiut culture at Native Point to ~ 1250 CE, followed by a dietary shift likely in response to the onset of cooling in the region ~ 1400 CE. The influence of the Sadlermiut on the environment persisted long after the last of their population perished in 1903. Presently, the pond remains a distorted ecosystem that has experienced fundamental shifts in the benthic invertebrate assemblages and accumulated anthropogenic metals in the sediment. Our multi-proxy paleolimnological investigation using geochemical and biological indicators emphasizes that direct and indirect anthropogenic impacts have long-term environmental implications on high latitude ecosystems.

Stream drying bioindication in Central Europe: A Biodrought Index accuracy assessment

With ongoing climate change and increasing water resource pressures, the knowledge and predictability of stream drying is essential for water management. However, the hydrological data for assessing the flow regime of temporary streams are often non-existent or scarce. The flow regime strongly affects stream ecological functioning and ecosystem processes. A few biological indices have been developed in the past decade to assess community responses to flow intermittency. One of them – the Biodrought Index, used to recognise antecedent stream drying based on benthic invertebrate assemblage composition – was initially intended for deployment in the Czech Republic. Here we report on a test of how reliably this index can be used in Central Europe. We used five independent data sets of macroinvertebrate samples collected during the flowing phase in five countries: Austria, Czech Republic, Germany, Hungary and Slovakia. Altogether 89, 26 and 220 samples were assessed from intermittent, near-perennial and perennial sites, respectively. Each sample was assigned to one of three flow intermittence categories according to the Biodrought Index and then compared with the flow regime recognised by hydrological observations and gauging station data. In most cases, the Biodrought Index clearly reflected the previous flow state and identified streamflow cessation. The misidentification rate between intermittent and perennial samples was very low, ranging from 0% to 6%. Classification rate of correctly recognised samples ranged from 54% to 93% and misclassification rate between near-perennial and perennial/intermittent category was 6% to 46%. Overall, this study confirmed the robustness and the reliability of the Biodrought Index, which proved to be an effective tool in assessing the recent hydrological history of small and medium-sized streams. The index can improve the interpretation of the macroinvertebrate assemblage data collected for ecological status assessment, can help to evaluate the effectiveness of river restoration projects or identify water resource pressures. Hence, we consider the Biodrought Index a useful method for indicating antecedent stream drying in the extensive area of Central Europe and thus helpful in monitoring and managing river ecosystems.

The physical–chemical environment and benthic invertebrate assemblages of two thermal springs located on carbonate and ophiolite rocks in northern Oman

ABSTRACT The paper compares the physical and chemical environments and associated benthic invertebrate assemblages of two thermal streams with different geology in Oman. Nakhal Thawarah is a thermal spring originating in carbonate rocks. Mur-Fayha has its origin in igneous ophiolite rocks. The main physical and chemical parameters that contribute to the differences are water temperature, pH, electrical conductivity, total dissolved solids, chloride, sulphate, calcium and magnesium. Two zones in each spring-stream system, the source and stretch analysed, reveal intra- and interstream differences in the physical and chemical environments controlling the occurrence and abundance of benthic invertebrates. Despite higher water temperatures, the diversity of benthic invertebrates in Nakhal Thawarah is relatively high. Mur-Fayha with high alkalinity is a harsh environment that has low diversity dominated by tolerant Chironomidae. This study indicates the need to conserve thermal springs in Oman from adverse effects of tourism.

Response of benthic invertebrate assemblages to seasonal and habitat condition in the Wewe River, Ashanti region (Ghana).

Aquatic macro-invertebrates play a vital role in the food chain of river ecosystem at several trophic guilds and consumer levels, and are used as biomonitoring tools for aquatic ecosystem health. However, hydrologic conditions of these ecosystems have been severely altered because of the increase in urban development and agricultural expansion. This study examined benthic invertebrate response to processes that structure their community in the Wewe River, segmented into intact, medium, and severe condition zones. We sampled in 100 stations in a period of 4 months in the wet (June–September, 2019) and 3 months in the dry (January–March, 2020) seasons. Geometric series, rarefaction, and Hill numbers models were used to quantify invertebrate assemblages, while ordination technique, canonical correspondence analysis, was used to evaluate the influence of predictive factors on their assemblages. A total of 2,075 individuals belonging to 20 family taxa were registered. There was no significant difference in benthic assemblages between the dry and wet seasons. Predictive factors accounted for 47.04 and 50.84% variances, respectively. Taxa distribution patterns differed significantly only in the severely disturbed zone during the wet season. Neptidae, Libellulidae, and Chironomidae were the most abundant taxa, indicating their broad range habitat preference and their ability to adapt to seasonal changes. Asellidae and Perlidae were the least detected, suggesting their sensitivity to elevated levels of some water quality parameters. The findings highlight the threats to the benthic community and overall functional state of the Wewe River, with the need to consider the proposed conservation interventions indicated in this study.

Benthic invertebrate assemblages and leaf‐litter breakdown along the eucrenal–hypocrenal ecotone of a rheocrene spring in Central Italy: Are there spatial and seasonal differences?

AbstractTo better understand the pattern of variation in biocomplexity of springs and first‐order streams, it is essential to explore how the characteristics of spring communities may vary from the spring source (eucrenal) to the first reach of the originating springbrook (hypocrenal). For these reasons, we assessed spatial and temporal variation of crenic assemblages and leaf‐litter breakdown along a 45‐m reach of a spring–springbrook system in Central Italy. We found that physicochemical and hydrological parameters of Vera Spring did not vary significantly along the 45‐m reach investigated. In contrast, total richness of assemblages was significantly higher at 20 and 45 m from the spring source, while abundances were more variable and did not show significant differences between seasons and among sites. The composition of assemblages did not show significant temporal trends in all sites investigated, while spatial differences along the eucrenal–hypocrenal ecotone were more prominent. The functional organization of assemblages was relatively stable in both space and time, and no spatial differences were observed in the rate of leaf‐litter breakdown, though the dry mass loss of poplar leaves was slightly higher at the most downstream site. We conclude that immediately after groundwater emergence, spring communities are less stable and more variable while they tend to be better organized at short distance downstream. Small and gradual spatial changes in the strength of competitive interactions and predation pressures may have a fundamental role in structuring spring communities more than variation in abiotic parameters and/or differences in quantity and quality of food resources.

Determination of total petroleum hydrocarbons and selected heavy metal (Pb, CO, V, Ni) concentration levels in surficial sediments of the Arvand River Estuary and their impact on benthic macroinvertebrates assemblages

ABSTRACT In the current study, the determination of total petroleum hydrocarbons (TPHs) and selected heavy metal (Pb, Co, V, Ni) concentration levels in surficial sediments of the Arvand River and their impacts on benthic invertebrate assemblages are investigated. For this purpose, a total of 100 surface sediment samples from 10 stations were collected for TPHs, heavy metals, macroinvertebrates, TOM, and grain size measurements using a Van-Veen grab sampler during winter 2018. A Horiba U10 multiparameter probe was used at each station for the in-situ measurement of environmental variables of water samples close to river bottom using a Nansen bottle sampler. Sediment quality guidelines along with Pearson’s correlation analysis and calculated diversity indices revealed that Arvand River Estuary (ARE) is threatened by contamination, especially with respect to Ni, Pb, and TPHs. The relatively high concentrations of Ni in most stations and Pb in some stations comparing to guidelines and other regions can be related to industrial activities as well as passing several ships and boats in the region. Shannon–Wiener diversity values recorded in the present study ranged between 0 and 2.01 indicating heavy to moderate pollution status in ARE. Altogether, the present study findings could be useful as the baseline for future research and better management for reducing contaminant levels.

Assessing the Ecological Status of European Rivers and Lakes Using Benthic Invertebrate Communities: A Practical Catalogue of Metrics and Methods

The Water Framework Directive requires that the ecological status of surface waters be monitored and managed if necessary. A central function in ecological status assessment has the Biological Quality Elements—organisms inhabiting surface waters—by indicating human impact on their habitat. For benthic invertebrates, a wide array of national methods are used, but to date no comprehensive summary of metrics and methods is available. In this study, we summarize the benthic invertebrate community metrics used in national systems to assess the ecological status of rivers, (very) large rivers, and lakes. Currently, benthic invertebrate assemblages are used in 26 national assessment systems for rivers, 13 assessment systems for very large rivers, and 21 assessment systems for lakes in the EU. In the majority of systems, the same metrics and modules are used. In the Red Queen’s race of ecosystem management this may be a disadvantage as these same metrics and module likely depict the same stressors but there is growing evidence that aquatic ecosystems are subject to highly differentiated, complex multiple stressor impacts. Method development should be fostered to identify and rank impacts in multi-stressor environments. DNA-based biomonitoring 2.0 offers to detect stressors with greater accuracy—if new tools are calibrated.

Benthic invertebrate assemblage changes in an urban bay of Lake Ontario: 1990 to 2012

Invasions by dreissenid mussels and the round goby have altered the makeup of benthos in many areas of the Great Lakes complicating the use of benthic invertebrate composition as an indicator of environmental conditions. The Ontario Ministry of the Environment, Conservation and Parks (MECP) has been monitoring the composition of benthos at nearshore stations since the 1990s. The interactive influences of environmental change and invasive species have been evident in areas of the Toronto Waterfront such as Humber Bay (HB), an area of intensifying urbanization. Dreissenid mussels were first detected in HB in 1994, became abundant in 2000, and were followed by the round goby in 2005. Both invasions overlapped with increasing population density in the watershed and efforts to reduce pollutant and nutrient inputs. Benthic invertebrate diversity increased post-dreissenids, with densities of gastropods and amphipods increasing during peak mussel abundance (2000–2003). Dreissenid abundance declined after 2005, and snails (Valvatidae) disappeared, corresponding with increasing goby abundance. Abundance of sphaeriid clams declined over the monitoring period. Water clarity increased and the chlorophyll a level declined in the mid-1990s, before dreissenids were abundant at the site. Trophic conditions inferred from invertebrate composition shifted from oligotrophic in 1990 to mesotrophic and back to oligotrophic in 2012. There was little change in sediment quality other than a subtle increase in clay and fine silt at the primarily silty site. The trajectory of changes in the benthos was more strongly correlated with the dreissenid and goby invasions than changes in environmental quality.