Search Results (3)

Riverine floodplains are ecologically remarkable systems that have historically faced strong anthropogenic pressures. The aim of this study was to examine whether the phytoplankton functional approach by Reynolds is a useful tool for disentangling anthropogenic pressure from the impact of natural flooding on a riverine floodplain lake. Lake Sakadaš, part of the large conserved river–floodplain system along the Danube River (Kopački Rit, Croatia), was used as a case study. Historical data on phytoplankton dynamics from the 1970s, when the lake was exposed to direct inflows of agricultural wastewater, were compared with current data from a time when the lake was a strongly protected area. Analysis of the phytoplankton community, based on functional groups and their beta diversities, revealed clear variation between the observed periods. The heavy bloom of species from only one functional group with extremely high biomass indicated a highly impacted environment in the past. Recent data suggest that, with the cessation of direct pollution, near-natural hydrological conditions with flooding as a fundamental environmental driving factor, support algal assemblages characteristic of a naturally eutrophic lake. Assessing multiple pressures on floodplain lakes and disentangling their specific impacts on ecological statuses are crucial for defining the protection and sustainable management of these particularly sensitive and endangered freshwater systems. Full article

In this overview (introductory article to a special issue including 14 papers), we consider all main types of natural and artificial inland freshwater habitas (fwh). For each type, we identify the main biodiversity patterns and ecological features, human impacts on the system and environmental issues, and discuss ways to use this information to improve stewardship. Examples of selected key biodiversity/ecological features (habitat type): narrow endemics, sensitive (groundwater and GDEs); crenobionts, LIHRes (springs); unidirectional flow, nutrient spiraling (streams); naturally turbid, floodplains, large-bodied species (large rivers); depth-variation in benthic communities (lakes); endemism and diversity (ancient lakes); threatened, sensitive species (oxbow lakes, SWE); diverse, reduced littoral (reservoirs); cold-adapted species (Boreal and Arctic fwh); endemism, depauperate (Antarctic fwh); flood pulse, intermittent wetlands, biggest river basins (tropical fwh); variable hydrologic regime—periods of drying, flash floods (arid-climate fwh). Selected impacts: eutrophication and other pollution, hydrologic modifications, overexploitation, habitat destruction, invasive species, salinization. Climate change is a threat multiplier, and it is important to quantify resistance, resilience, and recovery to assess the strategic role of the different types of freshwater ecosystems and their value for biodiversity conservation. Effective conservation solutions are dependent on an understanding of connectivity between different freshwater ecosystems (including related terrestrial, coastal and marine systems). Full article

Although sources of seston are much more complicated in lakes compared to oceans, the influences of different sources on the spatiotemporal variations in seston stoichiometry are still underexplored, especially in large eutrophic floodplain lakes. Here, we investigated seston stoichiometric ratios across a typical large eutrophic floodplain lake (Lake Taihu, East China) over one year. In addition, we used the n-alkane proxies to examine the influence of the seston source on seston stoichiometry variation. Throughout the study, the average value of the C:N:P ratio of 143:19:1 across Lake Taihu was close to the canonical lake’s ratios (166:20:1). Similar to other eutrophic lakes, seston C:N ratios varied the least across all environments, but C:P and N:P ratios varied widely and showed a strong decreasing trend in ratios of N:P and C:P from growing season to senescence season. This seasonal change was mainly associated with the decreasing contribution from algal-derived materials in seston pools because the non-algal dominated seston exhibited significantly lower ratios than algal-dominated seston. Furthermore, the spatial heterogeneity of stoichiometric ratios was also related to the seston source. During the senescence season, the terrestrial-dominated seston from agricultural watershed exhibited the lowest ratios in estuary sites compared with other areas. Statistically, the predictive power of environmental variables on stoichiometric ratios was strongly improved by adding n-alkanes proxies. Apart from source indicators, particulate phosphorus (PP) contents also partly explained the spatiotemporal variations in stoichiometric ratios. This study, thus, highlights the utility of multiple-combined n-alkane proxies in addition to simple C:N ratios to get more robust source information, which is essential for interpreting the spatiotemporal variations in seston stoichiometric ratios among eutrophic floodplain lakes and other freshwater ecosystems. Full article