Different responses of taxonomic and functional trait structure of benthic macroinvertebrate assemblages to eutrophication in a large Chinese freshwater lake

Functional trait measures have the potential to represent local habitat conditions and are considered promising tools for biomonitoring and bioassessment programs. Macroinvertebrates are an ecologically significant group in freshwater ecosystems and possess a range of functional traits which are employed to assess ecological quality. Nevertheless, the relationships between macroinvertebrate functional structure and anthropogenic disturbances remain poorly understood. In this study, we conducted a comparison of how functional trait-based and taxonomy-based composition of macroinvertebrate assemblages responded to eutrophication in Lake Taihu, a typical large eutrophic freshwater lake in China. Specifically, we examined both the taxonomy-based and trait-based compositions of benthic macroinvertebrates varied along the eutrophication gradient. Eutrophication was associated with remarkable decreases in the abundance of gastropod taxa and increases in Oligochaeta and Chironomidae. Ten categories belonging to six traits were significantly different among three site groups. The eutrophic and transition sites showed higher abundance of Size2, burrowers, and integument-respiration organisms than macrophytic sites, whereas abundance of Size1, conical-shaped, sprawlers, scrapers, and lung-respiration were higher in macrophytic sites. Both taxonomic (36.8%) and functional compositions (39.8%) of macroinvertebrate assemblages were influenced by the same variables: CODMn and transparency. Our study showed that macroinvertebrate trait-based approaches can be considered a useful supplement to traditional taxonomic approach for biomonitoring programs in freshwater lakes.

Effects of conventionally treated and ozonated wastewater on the damselfly larva oxylipidome in response to on-site exposure

Pharmaceutical residues discharged through insufficiently treated or untreated wastewater enter aquatic environments, where they may adversely impact organisms such as aquatic invertebrates. Ozonation, an advanced wastewater treatment technique, has been successfully implemented to enhance the removal of a broad range of pharmaceuticals, however diverse byproducts and transformation products that are formed during the ozonation process make it difficult to predict how ozonated wastewater may affect aquatic biota. The aim of this study was to investigate effects on fatty acid metabolites, oxylipins, in a common invertebrate species, damselfly larvae, after on-site exposure to conventional wastewater treatment plant (WWTP) effluent and additionally ozonated effluent at a full-scale WWTP. Subsequent ozonation of the conventionally treated wastewater was assessed in terms of i) removal of pharmaceuticals and ii) potential sub-lethal effects on the oxylipidome. Northern damselfly (Coenagrion hastulatum) larvae were exposed for six days in the treatment plant facility to either conventional WWTP effluent or ozonated effluent and the effects on pharmaceutical levels and oxylipin levels were compared with those from tap water control exposure. Ozonation removed pharmaceuticals at an average removal efficiency of 67% (ozone dose of 0.49 g O₃/g DOC). Of 38 pharmaceuticals detected in the effluent, 16 were removed to levels below the limit of quantification by ozonation. Levels of two oxylipins, 12(13)-EpODE and 15(16)-EpODE, were reduced in larvae exposed to the conventionally treated wastewater in comparison to the tap water control. 15(16)-EpODE was reduced in the larvae exposed to ozonated effluent in comparison to the tap water control. One oxylipin, 8-HETE, was significantly lower in larvae exposed to conventional WWTP effluent compared to ozonated effluent. In conclusion, the study provides proof-of-principle that damselfly larvae can be used on-site to test the impact of differentially treated wastewater.

Compensatory indirect effects of an herbicide on wetland communities

The direct effects of large-scale disturbances are readily studied because their effects are often apparent and result in large changes to ecosystems. Direct effects can cascade through the ecosystem, leading to indirect effects that are often subtle and difficult to detect. Managing anthropogenic disturbances, such as chemical contamination, requires an understanding of both direct and indirect effects to predict, measure, and characterize the impact. Using a replicated whole-ecosystem experiment and path analyses (assesses the effects of a set of variables on a specified outcome, similar to multiple regression), we examined the direct and indirect effects of a glyphosate-based herbicide and nutrient enrichment on wetland communities. The latter did not impact any measured endpoints. The strongest drivers of macrophyte, benthic invertebrate, and amphibian assemblages were the ephemerality and the size of wetlands, factors which were not altered by herbicide applications. The herbicide had a direct negative effect on macrophyte cover, amphibian larval abundance, and the proportion of predatory benthic invertebrates. However, both amphibians and invertebrates were positively affected by the reduction in the macrophyte cover caused by the herbicide applications. The opposing directions of the direct and indirect effects lead to no net change in either group. The compensatory dynamics observed herein highlight the need for a better understanding of indirect effects pathways to determine whether common anthropogenic disturbances alter the ecological communities in small wetland ecosystems.

Shorebird predation on benthic invertebrates after shrimp-pond harvesting: Implications for semi-intensive aquaculture management

How to improve habitat quality for wildlife is of particular importance in areas dedicated to food production, due to increasing pressures of global demands associated to human population growth. Semi-intensive aquaculture ponds can provide a potentially important foraging habitat for migratory shorebirds throughout the non-breeding season. Therefore, understanding the availability of benthic invertebrates in aquaculture ponds will help to identify proper management decisions for shorebird conservation. We used an exclosure experiment during the first three days after shrimp harvesting at semi-intensive aquaculture ponds in north-west Mexico to assess shorebird predation on benthic invertebrates. We found that shorebird predation did not deplete total benthic invertebrate density (particularly polychaete worms), but significantly affected the prey size distributions and biomass in the ponds during a short-time window of just three days. Shorebirds removed 0.6 g ash-free dry weight m^-2, equivalent to 43% of the initial biomass and showed high selectivity for polychaetes larger than >40 mm as prey, potentially explaining the absence of large polychaetes at the end of the experiment. This depletion was the likely cause of the daily decrease observed in overall density of foraging shorebirds at recently harvested ponds. These results can serve to identify management actions that allow an extended use of semi-intensive aquaculture ponds as foraging sites for migratory shorebirds during the non-breeding season, with potential applications to develop standards for a friendlier aquaculture management.

Non-targeted investigation of benthic invertebrates (Chironomus riparius) exposed to wastewater treatment plant effluents using nanoliquid chromatography coupled to high-resolution mass spectrometry

Nanoliquid chromatography (nanoLC) was coupled to high-resolution mass spectrometry (HRMS) to perform a non-targeted investigation on benthic invertebrates, Chironomus riparius exposed to wastewater treatment plant (WWTP) effluents. Insect larvae represent a complex and low-weight matrix that required the use of a miniaturized Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method of extraction followed by nanoLC-HRMS to perform the analysis. The optimization of this coupling in terms of separation conditions including trapping step, detection conditions and data treatment provided reproducible fingerprints on insect larvae exposed to WWTP effluents with both in situ and ex-situ approaches. Statistical treatments such as principal component analysis highlighted the impact of WWTP effluents on the metabolome of insect larvae and showed the influence of exposure conditions. The identification of discriminating signals (m/z, t_R) matched with several potential endogenous biomarkers. These are mainly fatty acids, indicating a change in lipid metabolism that can be correlated with exposure to WWTP effluents. Several xenobiotics have also been detected, including ibuprofen and propranolol, whose identities have been confirmed by analytical standards. This work demonstrates the effectiveness and sensitivity of nanoLC-HRMS based environmental non-targeted approaches in ecotoxicological studies and provides the first profiling data for a very small aquatic invertebrate.

Trophic transfer of toxic elements in the estuarine invertebrate and fish food web of Daliao River, Liaodong Bay, China

In order to study element accumulation and trophic transfer in the food web, sixteen benthic invertebrate species and nine fish species were collected from the Daliao River estuary for analysis of toxic elements and nitrogen stable isotope in the muscle tissue. The concentrations ranged between 1.44-17.98, 0.01-9.30, 0.17-36.15, 0.7-145.4, 0.01-0.33, 0.14-14.88, 0.10-2.51, 0.02-0.14, and 19.3-221.1mgkg^-1 for As, Cd, Cu, Hg, Ni, Pb, Sb, and Zn, respectively. As, Cd, Cu, and Zn were significantly higher in the benthic invertebrates than in fish, whereas Hg and Sb were significantly lower. In addition, the benthic invertebrates were characterized by the highest bioaccumulation factor (BAF) for Cd, whereas the fish were characterized by the highest BAF for Hg. A significant decrease in Cd, Cr, Cu, and Ni levels, and a significant increase in Hg and Sb levels were observed with increasing trophic levels.

Ecological risk assessment for residual coal fly ash at Watts Bar Reservoir, Tennessee: Limited alteration of riverine-reservoir benthic invertebrate community following dredging of ash-contaminated sediment

Benthic invertebrate communities were assessed after the December 2008 release of approximately 4.1 million m(3) coal fly ash from a disposal dredge cell at the Tennessee Valley Authority (TVA) Kingston Fossil Plant on Watts Bar Reservoir in Roane County, Tennessee, USA. Released ash filled the adjacent embayments and the main channel of the Emory River, migrating into reaches of the Emory, Clinch, and Tennessee Rivers. Dredging was completed in summer 2010, and the benthic community sampling was conducted in December 2010. This study is part of a series that supported an Ecological Risk Assessment for the Kingston site. Benthic invertebrate communities were sampled at transects spread across approximately 20 miles of river that includes both riverine and reservoirlike conditions. Community composition was assessed on a grab sample and transect basis across multiple cross-channel transects to gain an understanding of the response of the benthic community to a fly ash release of this magnitude. This assessment used invertebrate community metrics, similarity analysis, geospatial statistics, and correlations with sediment chemistry and habitat. The community composition was reflective of a reservoir system, with dominant taxa being insect larva, bivalves, and aquatic worms. Most community metric results were similar for ash-impacted areas and upstream reference areas. Variation in the benthic community was correlated more with habitat than with sediment chemistry or residual ash. Other studies have reported that a benthic community can take several years to a decade to recover from ash or ash-related constituents. Although released ash undoubtedly had some initial impacts on the benthic community in this study, the severity of these effects appears to be limited to the initial smothering of the organisms followed by a rapid response and the initial start of recovery postdredging.