Biodiversity knowledge is essential for understanding ecosystem stability and resilience. Traditionally, biodiversity research relies on morphological taxonomy; however, advances in environmental DNA (eDNA) metabarcoding offer faster and potentially more comprehensive approaches. This study compares morphological taxonomy and COI metabarcoding for assessing zooplankton (Rotifera, Diplostraca, and Copepoda) biodiversity across four seasons in Lake Volvi (Northern Greece). A total of 60 taxa were identified, with limited overlap between methods: 35
To quantify the current and future invasion dynamics of the globally invasive free-floating macrophyte Pistia stratiotes L. across China’s freshwater ecosystems, we tested whether adding hydrological variables improves habitat suitability predictions. We integrated water temperature and pH with bioclimatic and topographic predictors in a MaxEnt model. Using 468 filtered occurrence records and 24 environmental variables, we projected habitat suitability under four Shared Socioeconomic Pathways (SSP126, SSP245, SSP370, and SSP585) for the 2030s (2021–2040) and 2050s (2041–2060). The hydrology-integrated model performed better (area under the curve, AUC = 0.977; True Skill Statistic, TSS = 0.845) than the model without hydrological variables (AUC = 0.966; TSS = 0.832). Current high-suitability habitats were concentrated in subtropical and tropical southern China, whereas projections indicated northward expansion, especially under SSP245. The dominant drivers were mean temperature of the driest quarter, temperature annual range, water temperature and water pH, with warm, thermally stable, and near-neutral aquatic conditions favoring suitability. An environmental space niche analysis based on principal component analysis showed high current–future climatic niche overlap, suggesting a redistribution of suitable climatic space rather than a major niche displacement. These findings support early warning and targeted management of P. stratiotes in freshwater ecosystems.
Margaritifera margaritifera is a freshwater mussel species that is critically endangered in Europe. Conservation actions to restore functioning populations are being undertaken across Europe, but few publications are available on positive results that include improved natural juvenile mussel recruitment. In this paper, we outline the conservation measures taken and the positive effects they have had on the demographic profile of the River Ehen M. margaritifera population in the north of England. Increased near-bed velocity flows, reduced nutrient and sediment sources and a higher water table leading to wetness in the surrounding land, and an improved supply of gravels from a reconnected mountain stream are considered likely to have contributed to the observed increase in juvenile mussel numbers. The average percentage of juvenile mussels (< 30 mm) in demographic studies changed from a low of 0.103
Diatom cell size is widely recognized bioindicator in aquatic environmental monitoring, while decadal-scale morphological variations in response to eutrophication remain poorly understood. This study explored temporal variations in cell size of the dominant diatom Aulacoseira granulata (Ehrenberg) Simonsen based on sedimentary diatom records from mesotrophic Liangzi Lake and eutrophic Shahu Lake in the Yangtze River floodplain. In eutrophic Shahu Lake, mean valve diameter and volume of A. granulata decreased as sedimentary total phosphorus (TP) rose from 680 to 2400 mg kg−1 between 1963 and 2012 CE, concurrent with increases in its mean height, height-to-diameter ratio, and specific surface area. In contrast, morphological parameters exhibited non-significant trends in mesotrophic Liangzi Lake between 1982 and 2022 CE When data from both lakes were combined, mean valve diameter of A. granulata decreased by 1.9 μm and mean height increased by 1.2 μm along the TP gradient from 660 to 2400 mg kg−1. Both light limitation and silicon depletion associated with eutrophication favor smaller and slender cells with enhanced resource uptake efficiency. Taken together, morphological parameters of A. granulata can serve as a useful proxy of lake eutrophication, complementing traditional community-based approaches in environmental research.
This study evaluated the vertical distribution of As, Cr, and Zn and their interactions with sediment characteristics, microphytobenthic biomass and major biological functional groups. Sediment samples covered by biofilms or microbial mats were collected from eight sites with varying anthropogenic impacts in the Bahía Blanca Estuary, Argentina. Concentrations of As, Cr, and Zn were measured across three depth layers alongside particle size and X-ray diffraction analyses. Cyanobacteria and diatom abundance, as well as chlorophyll a and carbohydrate levels, were determined in the surface layer. Arsenic showed a variable distribution pattern across sites and strata, exceeding the Threshold Effect Level (TEL) at all sites, in at least one stratum. The highest concentrations of Cr and Zn were detected at urban and industrial effluent discharge sites, with Zn exceeding the TEL and Probable Effect Level (PEL) at both sites, and Cr exceeding the TEL in some samples. Additionally, sewage, industrial, and stormwater discharge sites showed the highest carbohydrate concentrations and cyanobacterial abundance. These results demonstrate the significant impact of discharged effluents on coastal systems. This organic overloading poses an ecological risk, as it consequently increases the bacterial load and metabolic activity in the affected areas.
