Diversity of benthic macroinvertebrates and water quality of Karasu Stream (Black Sea)

The study was conducted in Karasu Stream (Sinop Province, Black Sea Region of Turkey). The purpose of this study is, to determine the benthic macroinvertebrate composition of the stream, together with some of its environmental characteristics (water temperature, pH and dissolved oxygen) to evaluate the trophic level of the stream. Samplings of benthic macroinvertebrates and environmental variables were performed monthly at ten stations between February 2013 and January 2014. As a result, 18260 specimens were investigated and 175 taxa were determined. Chironomidae and Oligochaeta were the higher groups in terms of species richness with 48 and 38 taxa, respectively. The BMWP and ASPT indices indicate that all the stations belong to “slightly polluted (Class II)” or “unpolluted (Class I)” water quality levels.

Choice of benthic macroinvertebrate-based metrics for assessing water quality in the littoral zone under anthropogenic disturbance in southern Lake Kivu (Central Africa)

Benthic macroinvertebrates are widely used to assess the ecological quality of fresh waters. This is because they are in direct contact with the aquatic environment and respond differently to pollutants and changes in the watershed, which are difficult to assess by toxicological or chemical monitoring alone. this study used benthic macroinvertebrate parameters to assess the quality of the nearshore waters of lake Kivu. Twenty-six metrics covering various aspects of the community were tested using whisker plots to compare their sensitivity in discriminating between reference and disturbed stations. Nine parameters (% EPT taxa, % Diptera taxa, % Chironomid taxa, % Insect taxa; % no Insects taxa, ratio EPT/Chironomid taxa, % moderate tolerant taxa, % very moderate tolerant taxa, Family Biotic Index) were found to be sensitive and were able to discriminate between reference and disturbed stations. All sensitive metrics, with the exception of the percentage of EPT taxa, were positively and/or negatively correlated with the physico-chemical parameters affected by the changes in the littoral zone. The combined values of the three calculated biotic indices (ASPT, BMWP and FBI) showed that the biological water quality varies from moderate to good in the reference stations and from average to poor in the disturbed stations. It is concluded that metrics based on benthic macroinvertebrates are effective for assessing water quality in the littoral zone of Lake Kivu in the context of the lack of historical water quality databases and specific tools for toxicological assessment. It is suggested to compare the performance of this approach with others currently used in bio-indication.

Littoral macroinvertebrate communities of alpine lakes along an elevational gradient (Hohe Tauern National Park, Austria)

Alpine lakes support unique communities which may respond with great sensitivity to climate change. Thus, an understanding of the drivers of the structure of communities inhabiting alpine lakes is important to predict potential changes in the future. To this end, we sampled benthic macroinvertebrate communities and measured environmental variables (water temperature, dissolved oxygen, conductivity, pH, nitrate, turbidity, blue-green algal phycocyanin, chlorophyll-a) as well as structural parameters (habitat type, lake size, maximum depth) in 28 lakes within Hohe Tauern National Park, Austria, between altitudes of 2,000 and 2,700 m a.s.l. The most abundant macroinvertebrate taxa that we found were Chironomidae and Oligochaeta. Individuals of Coleoptera, Diptera, Hemiptera, Plecoptera, Trichoptera, Tricladida, Trombidiformes, Veneroida were found across the lakes and determined to family level. Oligochaeta were not determined further. Generalized linear modeling and permanova were used to identify the impact of measured parameters on macroinvertebrate communities. We found that where rocky habitats dominated the lake littoral, total macroinvertebrate abundance and family richness were lower while the ratio of Ephemeroptera, Plecoptera and Trichoptera (EPT) was higher. Zoo- and phytoplankton densities were measured in a subset of lakes but were not closely associated with macroinvertebrate abundance or family richness. With increasing elevation, macroinvertebrate abundances in small and medium-sized lakes increased while they decreased in large lakes, with a clear shift in community composition (based on families). Our results show that habitat parameters (lake size, habitat type) have a major influence on benthic macroinvertebrate community structure whereas elevation itself did not show any significant effects on communities. However, even habitat parameters are likely to change under climate change scenarios (e.g. via increased erosion) and this may affect alpine lake macroinvertebrates.

Habitat formed by the invasive macroalga Caulerpa filiformis (Suhr) Hering (Caulerpales, Chlorophyta) alters benthic macroinvertebrate assemblages in Peru

The green macroalga Caulerpa filiformis has been spreading on shallow soft sediment habitats along the Peruvian coast, colonizing previously unvegetated sediments to create monospecific meadows. We examined the nature of the impact of C. filiformis meadows on the density, taxonomic richness and assemblage structure of epifaunal and infaunal benthic macroinvertebrates. Specifically, we tested whether the spread of C. filiformis has resulted in different macroinvertebrate assemblages than those formed by the dominant native macroalgae (i.e., Rhodymenia spp.) and unvegetated sediments. Surveys were undertaken in two bays in each of two locations, in central and southern Peru, during winter 2017 and summer 2018. In general, our results show that macroinvertebrate assemblages were similar across all three habitats, although there were some differences, related to location and season, but with no clear patterns observed. Taxonomic richness and density was generally higher in the vegetated habitats than the unvegetated habitat, and where there were differences between the two vegetated habitats there was no consistent pattern of which habitat supported the highest richness or density. Given invading C. filiformis is primarily colonizing unvegetated habitats it would appear that this species is creating a new niche which supports similar assemblages, but higher taxonomic richness and density than unvegetated habitats. While our study suggests that C. filiformis is having a limited ecological impact we recommend that actions be put in place to limit the spread of this invasive species at the same time as increasing monitoring of the ecological impacts of this species as lags in the ecological impacts of invasive species are common.

Recovery of Subtidal Benthic Macroinvertebrate Communities Following Natural and Experimental Disturbances

<p>The recovery processes of subtidal benthic macroinvertebrate communities following large-scale natural and meso-scale experimental disturbances were studied in Wellington Harbour, New Zealand, a temperate semi-enclosed embayment. This is the first time that long-term effects (>1 year post-disturbance) of a naturally occurring toxic plankton bloom have been investigated in the Southern hemisphere. For 2 years macroinvertebrate communities were studied at three sites of differing hydrodynamic regime. Samples were taken with a Van Veen grab and washed through a 500 [mu]m mesh. Community recovery following the bloom was site-specific. Multivariate analyses revealed that at two sites community recovery was not completed >3 years post-bloom, whereas at the third site the community composition oscillated from year to year, but did not show any signs of a sequential recovery process. The hydrodynamic regime was identified as a major factor influencing the observed recovery processes. Communities exposed to an active hydrodynamic regime were less affected by the bloom and recovered faster, as they were naturally in a perpetual state of recovery as indicated by a dominance of r-selected species. The community at the hydrodynamically less active site was more affected by the bloom. Complete recovery to the pre-disturbance climax community dominated by K-selected species was estimated to take 4-5 years, if not interrupted by other disturbances. For the first time a defaunation experiment was conducted in a hydrodynamically active site to mimic the effects of a plankton bloom on the benthic macroinvertebrate community. Three sediment plots of 25 m2 were covered by plastic tarpaulins, thereby creating a benthic die-off caused by oxygen depletion. This method of defaunation had not been used in the subtidal before. Community recovery was studied for 1 year and compared with community composition in undisturbed control plots. Macroinvertebrate samples were taken by diver-operated cores and washed through a 500 [mu]m mesh. Recovery was slow until after 70 days when abundance and number of species increased synchronously in disturbed and control plots. Multivariate analyses showed that community composition fluctuated strongly in the first 100 days. After 1 year, although disturbed and control communities were converging, differences in community composition were still significant. Time for complete recovery was estimated to be approximately 2 years. Predictions of current succession models were generally fulfilled in both studies. Recovered communities were similar in their composition to either pre-disturbance or surrounding communities. The major deviation from model predictions was that no abundance peak of opportunistic species occurred in either study. Timing of the disturbance, in both studies past the major macroinvertebrate recruitment peak, and the hydrodynamic regime were identified as major factors influencing recovery processes of the communities studied. Such deviation from model predictions indicates that the general models cannot take into account the multiplicity and complexity of factors influencing recovery processes. Thus, their applicability in predicting recovery times and endpoints for specific disturbances at specific locations is limited. Location-specific models might be a useful alternative. Recommendations are made to combine uni- and multivariate techniques to assess recovery processes due to their different sensibilities to changes in community composition.</p>

Recovery of Subtidal Benthic Macroinvertebrate Communities Following Natural and Experimental Disturbances

<p>The recovery processes of subtidal benthic macroinvertebrate communities following large-scale natural and meso-scale experimental disturbances were studied in Wellington Harbour, New Zealand, a temperate semi-enclosed embayment. This is the first time that long-term effects (>1 year post-disturbance) of a naturally occurring toxic plankton bloom have been investigated in the Southern hemisphere. For 2 years macroinvertebrate communities were studied at three sites of differing hydrodynamic regime. Samples were taken with a Van Veen grab and washed through a 500 [mu]m mesh. Community recovery following the bloom was site-specific. Multivariate analyses revealed that at two sites community recovery was not completed >3 years post-bloom, whereas at the third site the community composition oscillated from year to year, but did not show any signs of a sequential recovery process. The hydrodynamic regime was identified as a major factor influencing the observed recovery processes. Communities exposed to an active hydrodynamic regime were less affected by the bloom and recovered faster, as they were naturally in a perpetual state of recovery as indicated by a dominance of r-selected species. The community at the hydrodynamically less active site was more affected by the bloom. Complete recovery to the pre-disturbance climax community dominated by K-selected species was estimated to take 4-5 years, if not interrupted by other disturbances. For the first time a defaunation experiment was conducted in a hydrodynamically active site to mimic the effects of a plankton bloom on the benthic macroinvertebrate community. Three sediment plots of 25 m2 were covered by plastic tarpaulins, thereby creating a benthic die-off caused by oxygen depletion. This method of defaunation had not been used in the subtidal before. Community recovery was studied for 1 year and compared with community composition in undisturbed control plots. Macroinvertebrate samples were taken by diver-operated cores and washed through a 500 [mu]m mesh. Recovery was slow until after 70 days when abundance and number of species increased synchronously in disturbed and control plots. Multivariate analyses showed that community composition fluctuated strongly in the first 100 days. After 1 year, although disturbed and control communities were converging, differences in community composition were still significant. Time for complete recovery was estimated to be approximately 2 years. Predictions of current succession models were generally fulfilled in both studies. Recovered communities were similar in their composition to either pre-disturbance or surrounding communities. The major deviation from model predictions was that no abundance peak of opportunistic species occurred in either study. Timing of the disturbance, in both studies past the major macroinvertebrate recruitment peak, and the hydrodynamic regime were identified as major factors influencing recovery processes of the communities studied. Such deviation from model predictions indicates that the general models cannot take into account the multiplicity and complexity of factors influencing recovery processes. Thus, their applicability in predicting recovery times and endpoints for specific disturbances at specific locations is limited. Location-specific models might be a useful alternative. Recommendations are made to combine uni- and multivariate techniques to assess recovery processes due to their different sensibilities to changes in community composition.</p>