Meromictic lakes serve as natural laboratories for investigating microbially mediated biogeochemical cycling because their stable redox stratification supports diverse metabolic processes. Lake Suigetsu is a typical meromictic lake in Japan characterized by a permanent oxycline separating the oxic brackish mixolimnion from the anoxic saline sulfidogenic monimolimnion. Recently, Lake Suigetsu's vertical bacterial composition, especially of autotrophs, sulfide oxidizers, and sulfate reducers, has gained significant attention. However, little is known about microbial communities particularly the abundant heterotrophs that contribute to the biogeochemical cycling by degrading organic matter. To characterize biogeochemical cycling in Lake Suigetsu, we investigated the microbial community structures under the amplicon sequencing variants that distinguish species and/or intraspecies populations in each layer of Lake Suigetsu by using 16S rRNA gene amplicon sequencing analysis. We revealed the layer-specific microbial communities and there were abundant heterotrophs in each layer, in addition to the previously reported autotrophs. In the upper of monimolimnion sample, approximately 20
A comprehensive methodology for quantifying swash and filtration flow rates and for sampling subsurface water in sandy-beach ecosystems was developed and validated under wind velocities ranging from 1 to 9 m s−1. Using simple field methods, swash and filtration flows were investigated on a sandy beach in a shallow brackish lake. The annual mean swash flow rate was estimated to be 271 m3 m−1 d−1, a value comparable to the lake discharge on a shoreline-length basis. The filtration-to-swash flow ratio was estimated to be 0.5
Fish communities integrate lentic ecosystem energy flows by adjusting diet, trophic position, and niche breadth in response to environmental variation. Yet empirical evidence on fish trophic structure and energy pathways in dystrophic systems remains scarce. Using a stable isotopic approach (δ13C and δ15N), we investigated the origin of assimilated biomass, diet composition, and isotopic niche dynamics focused on multiple fish trophic groups over an intra-annual cycle in a subtropical dystrophic lagoon. We found that macrophytes were the dominant basal source supporting fish biomass, particularly for detritivorous and omnivorous fishes, with median contributions ranging from 86 to 93
Coastal lagoons are systems threatened by anthropogenic pressures. In order to develop and apply adapted management strategies, it is essential to understand their ecological functioning. In particular, eukaryotic plankton communities play a fundamental role in sustaining the entire trophic network and functioning of the ecosystem. We used DNA-metabarcoding to study seasonal diversity and trophic interactions of plankton communities in three Corsican coastal lagoons with contrasting morphologies and functioning. The main results demonstrate the influence of seasonal and morphological factors on community structure and trophic relationships among these planktonic communities. Biguglia favors an herbivorous food web but is dominated by mixoplankton, Urbino is distinguished by a high diversity of heterotrophic protists, and Santa Giulia by the development of picophytoplankton and the emergence of a protozooplankton community. This study also shows the emergence of mixoplankton including potentially harmful dinoflagellates present in the three lagoons, and sometimes dominant, linked to anthropogenic pressure, and highlights their integration into the trophic networks in relation to the lagoon characteristics. This is a fundamental step towards understanding plankton succession and ecological network functioning in different coastal lagoon configurations, and thus towards the thoughtful management of these ecosystems under current and future pressures.
Body size is a key functional trait influencing trophic interactions; energy transfer; and community structure in freshwater ecosystems. We examined patterns of adult body size and size variability in cladocerans across a broad elevational gradient (0–3600 m) and multiple freshwater habitats in the Pearl River Basin; China. Using hierarchical mixed-effects models; we quantified the relative contributions of taxonomic structure; environmental gradients; and spatial factors to variation in body size. Mean body size was strongly structured across taxonomic levels; with family and genus accounting for most of the variance; whereas species-level and spatial components contributed comparatively little. After accounting for hierarchical structure; mean body size increased significantly with elevation (approximately 3
