Longitudinal impacts of anthropogenic pressures on benthic macroinvertebrate assemblages in a large transboundary Mediterranean river during the low flow period

Comparison of quantitative and semi-quantitative sampling methodologies for biomonitoring of Mediterranean streams using benthic macroinvertebrates: a case study from Greece

In Greece, the implementation of the Water Framework Directive for rivers is based mainly on benthic macroinvertebrates and uses a semi-quantitative method with a D-frame net, which is certified by the International Organization for Standardization. Before the official adoption of this method, a quantitative shovel sampler ("Cretan shovel") was used in southern Greece (Crete), which has been implemented for almost three decades due to the specific river habitats found in Crete (e.g., seasonal flow, narrow riverbeds, and coarse substrates). In this study, we compared community metrics, diversity indices, feeding groups, locomotion types, and ecological quality derived from data collected using timed semi-quantitative kick samples and quantitative shovel samples collected from the same sites simultaneously. In total, 20 samples from the north and south of Greece were collected. The majority of community metrics, diversity indices, and traits were comparable between samplers. However, there were statistically significant differences in the relative abundance of Ephemeroptera, Plecoptera, and Trichoptera, passive filterers' and the (semi) sessil groups, and Pielou's index. Most differences in the ecological quality between the kick and shovel samples were observed in 50% of the sites in northern Greece because the shovel is less effective at capturing motile zoobenthos. The ecological quality assessment in Crete by the Cretan shovel is comparable with the D-frame net in 75% of the samples. Thus, the Cretan shovel could efficiently sample the Cretan streams, which are characterized by coarse, narrow, turbulent, and hydrologically fluctuating river habitats. Such comparisons could improve sampling effectiveness and make additional data available to assess ecological quality.

Ecological Impacts of Altered Stream Hydrogeomorphic Characteristics Extend Beyond the Channel Boundary: Evidence From Urban Streams of Columbus, OH, United States

Urbanization in stream catchments can have strong effects on stream channel hydrogeomorphic features including channel dimensions, channel-floodplain connectivity, and flood regime. However, the consequences of hydrogeomorphic alterations on aquatic-terrestrial subsidy dynamics are largely unexplored. We examined the associations among hydrogeomorphic characteristics, emergent aquatic insect assemblages, and the density and trophic dynamics of riparian spiders of the family Tetragnathidae at 23 small urban stream reaches in the Columbus, OH (United States) Metropolitan Area. Naturally abundant stable isotopes of 13C and 15N were used to quantify the relative contribution of aquatically derived energy (i.e., nutritional pathways deriving from algae) to tetragnathid spiders and their trophic position. Bankfull discharge was negatively related to both emergence rate and family richness. On average, tetragnathid spiders relied on aquatically derived energy for 36% of their nutrition, with the greatest reliance found for spiders next to channels with wider flood-prone widths and proportionally fewer emergent insects of the family Chironomidae. Mean emergent aquatic insect reliance on aquatically derived energy was 32% and explained 44% of the variation in tetragnathid aquatically derived energy. A positive relationship between δ13C of tetragnathid spiders and emergent insects provides additional evidence of tetragnathid reliance on emergent insects. Mean tetragnathid trophic position was 2.85 and was positively associated with channel sinuosity and negatively associated with aquatic insect emergence rate. Sinuosity was also positively related to aquatically derived energy of emergent aquatic insects; as well as emergent insect family richness; % Ephemeroptera, Plecoptera, and Trichoptera (EPT); and aquatic insect emergence rate; implicating instream habitat-mediated shifts in emergent aquatic insect communities as an indirect mechanistic link between hydrogeomorphic processes and spiders. Our findings underscore that the impacts of stream hydrogeomorphic alterations can cascade into terrestrial food webs. These results suggest that monitoring and restoration of fluvial geomorphic form and function (e.g., sinuosity, slope, and hydrology) confer benefits to both aquatic and terrestrial riparian ecosystems in urban catchments.

Characterisation of Benthic Macroinvertebrate Communities in Small Watercourses of the European Central Plains Ecoregion and the Effect of Different Environmental Factors

Simple Summary

Macroinvertebrates are very important to aquatic ecosystems. They are food for vertebrates and their biodiversity serves as a testament of the quality of their habitats. The majority of research on macroinvertebrates simply describes the composition and population density of species living in large rivers and lakes. The aim of our study was to compare the biodiversity of macrozoobenthos assemblages and to determine the effect of physicochemical and hydrological conditions on their abundance and density in 10 small rivers in agricultural areas. Overall, 105 taxa were identified as species living in changing conditions. Oxygenation of water and nitrogen content were important factors determining the existence of macroinvertebrates in these rivers. Some groups of organisms showed sensitivity to changes in water temperature as well as to the flow and depth in rivers.

Abstract

Most publications on the influence of environmental factors on macroinvertebrate communities focus on large rivers, whereas relatively few examine small watercourses in agricultural areas, which, due to their size and pressure from intensive agricultural production, are much more susceptible to the effects of unfavourable environmental conditions or anthropopressure. The aim of our study was to compare the biodiversity of macrozoobenthos assemblages and to determine the effects of physicochemical and hydrological conditions on their abundance and density in 10 small rivers in agricultural areas located in northwest (53°23′ N 15°14′ E) and central (52°11′ N 20°48′ E) Poland. In total, 105 taxa were recorded, with the majority being euryoecious. Among the assessed physicochemical parameters, oxygenation was found to affect the density and number of taxa; another important factor was the content of nitrate nitrogen. Sensitivity to changes in water temperature was observed in some macrozoobenthos taxa (especially Decapoda). Of the examined hydrological parameters, the greatest effects were exerted by speed, flow, and depth.

Macroinvertebrate and fish communities in the watershed of a re-constructed Mediterranean water body: link to the ecological potential

The role of benthic macroinvertebrate and fish communities for assessing the ecological quality of an artificial re-constructed, after 50 years of dryness, Mediterranean water body (Karla Reservoir, Greece) is presented. Moreover, we provide knowledge on the structure of the biological communities and their functioning role, for inspiring feature actions that will contribute to biodiversity protection and ecosystem services. Water (physicochemical parameters), benthic macroinvertebrates, and fish were monitored during a 2-year survey (2013-2015) in Karla and Kalamaki reservoirs and the inflowing ditches. A clear temporal pattern was evident for all sampling stations studied, differentiating the low- and high-flow period samples as to their physicochemical parameters. Redundancy analysis (RDA) revealed NO₃-N, total nitrogen and total dissolved phosphorous as the most significant environmental parameters in explaining benthic invertebrate variance in ditches. Generally, tolerant to organic pollution macroinvertebrate taxa were abundant in ditches and reservoirs, while the fish fauna in Karla was composed almost exclusively of planktivorous and invertivorous species. Macroinvertebrate (GLBiI) and fish (GLFI) indices classified the ecological quality of Karla Reservoir as "poor" while ditches were classified as "bad" according to HESY-2. The anthropogenic pressures applied in the catchment and the benefits of improving water quality are discussed in the context of the implementation of Water Framework Directive 2000/60/EC for introducing sustainable management plans, taking into account some ecological restoration principles.

Potential impacts of climate change on flow regime and fish habitat in mountain rivers of the south-western Balkans

The climate change in the Mediterranean area is expected to have significant impacts on the aquatic ecosystems and particular in the mountain rivers and streams that often host important species such as the Salmo farioides, Karaman 1938. These impacts will most possibly affect the habitat availability for various aquatic species resulting to an essential alteration of the water requirements, either for dams or other water abstractions, in order to maintain the essential levels of ecological flow for the rivers. The main scope of this study was to assess potential climate change impacts on the hydrological patterns and typical biota for a south-western Balkan mountain river, the Acheloos. The altered flow regimes under different emission scenarios of the Intergovernmental Panel on Climate Change (IPCC) were estimated using a hydrological model and based on regional climate simulations over the study area. The Indicators of Hydrologic Alteration (IHA) methodology was then used to assess the potential streamflow alterations in the studied river due to predicted climate change conditions. A fish habitat simulation method integrating univariate habitat suitability curves and hydraulic modeling techniques were used to assess the impacts on the relationships between the aquatic biota and hydrological status utilizing a sentinel species, the West Balkan trout. The most prominent effects of the climate change scenarios depict severe flow reductions that are likely to occur especially during the summer flows, changing the duration and depressing the magnitude of the natural low flow conditions. Weighted Usable Area-flow curves indicated the limitation of suitable habitat for the native trout. Finally, this preliminary application highlighted the potential of science-based hydrological and habitat simulation approaches that are relevant to both biological quality elements (fish) and current EU Water policy to serve as efficient tools for the estimation of possible climate change impacts on the south-western Balkan river ecosystems.

Catchment land use as a predictor of the macroinvertebrate community changes between inlet and outlet of small water dams

Changes in land use practices have affected the integrity and the quality of stream water worldwide. Effective catchment management, in terms of land use alteration, depends on our ability to quantify ecologically significant changes and to discriminate among varying levels of impact. In this study, we assessed the structural and functional changes upstream and downstream of eight small water reservoirs in western Slovakia and the relationship between these changes and shifts in physicochemical parameters as a consequence of stream damming and catchment land use. Dams were categorized into two groups, the first with both inlet and outlet situated in deforested and agricultural landscape and the second with inlet flowing through natural and forested landscape, while outlet is situated in deforested and urban region. Using a "between-groups" principal components analysis and a "between-groups" fuzzy principal components analysis, we found significant differences in structural and functional composition of macroinvertebrate communities between inlets with forested catchment and outlets flowing through agricultural, urban landscape. The structural dissimilarity is best explained by the physicochemical and biological characteristics of the aquatic environment, while functional variation of communities is best explained by land use of an area surrounding the stream. The distance in structural and functional community composition between inlet and outlet was linked with difference in environmental conditions between these habitats. The change of structural community composition significantly reflected shift in the water temperature and phosphorus concentration, while the change of functional community composition was determined by change of nutrient concentrations (e.g., PO4, NO3, NH4) and pH.

Assessing ecological water quality with macroinvertebrates and fish: a case study from a small Mediterranean river

Biological elements, such as benthic macroinvertebrates and fish, have been used in assessing the ecological quality of rivers according to the requirements of the Water Framework Directive. However, the concurrent use of multiple organism groups provides a broader perspective for such evaluations, since each biological element may respond differently to certain environmental variables. In the present study, we assessed the ecological quality of a Greek river (RM4 type), during autumn 2003 and spring 2004 at 10 sites, with benthic macroinvertebrates and fish. Hydromorphological and physicochemical parameters, habitat structure, and riparian vegetation were also considered. Pollution sensitive macroinvertebrate taxa were more abundant at headwaters, which had good/excellent water quality according to the Hellenic Evaluation System (HES). The main river reaches possessed moderate water quality, while downstream sites were mainly characterised as having bad or poor water quality, dominated by pollution-tolerant macroinvertebrate taxa. Macroinvertebrates related strongly to local stressors as chemical degradation (ordination analysis CCA) and riparian quality impairment (bivariate analysis) while fish did not. Fish were absent from the severely impacted lower river reaches. Furthermore, external pathological signs were observed in fish caught at certain sites. A combined use of both macroinvertebrates and fish in biomonitoring programs is proposed for providing a safer assessment of local and regional habitat impairment.