Introducing a zooplanktonic index for assessing water quality of natural lakes in the Mediterranean region

Planktonic communities as indicators of water quality in a tropical reservoir

Surface water bodies have been significantly altered by various human activities in the watersheds. Assessing these ecosystems is crucial for maintaining an ecological balance and protecting public health. This study aimed to analyse the water quality of a tropical public supply reservoir by evaluating the dynamics of planktonic communities. A total of 69 water quality parameters, in addition to phytoplankton and zooplankton biomonitoring data, were analyzed between 1989 and 2020. Preliminary and descriptive statistical analysis, trophic state index, Shannon-Wiener diversity index, statistical tests, and multivariate statistics analysis were applied. The results showed a change in the composition of the planktonic communities over time, with a greater abundance of cyanobacteria and an increase in the density of the Crustacea class in the final years of monitoring, indicating a more degraded environment. There was a reduction in the diversity of phytoplankton species. However, the concentrations of physical and chemical parameters remained low over the years, and oligotrophic conditions were prevalent in the reservoir. Therefore, the analysis of bioindicators provided information that was not observed when the physical and chemical parameters of water quality were analyzed. Possibly due to environmental variables not considered in this study, or due to the cumulative or synergistic effects caused by changes in the environment. It is evident that integrating bioassessment into the monitoring of water bodies is essential for a comprehensive ecological classification and for maintaining the integrity of the ecosystem.

Zooplankton distribution and its associated hydrology across Indian Sundarbans over the last decade: Insights from current trends and future directions

Zooplankton play a crucial role in estuarine ecosystems by aiding nutrient cycling through trophic chains and contributing to large-scale water filtration. The present review highlights the zooplankton research conducted over the last decade (2014-2024) in the Indian Sundarbans, with a focus on research trends, species distribution, hydrological associations, and long-term monitoring and conservation strategies. The study reveals a surge in zooplankton research after 2019, with an emphasis on both small- and large-scale studies. However, tidal creek/canals remain less explored compared to rivers. A lack of methodological standardization in zooplankton research is evident across the Indian Sundarbans. The Saptamukhi-Thakuran-Matla river stretch exhibited the highest species diversity, with 70 species recorded. Similarly, the tidal creeks and canals of Sagar Island were identified as species-rich habitats, with 63 species reported. Oithona brevicornis was found in seven riverine stretches, while Paracalanus parvus and Labidocera euchaeta were each recorded from six rivers, but Bestiolina similis was mostly reported as the numerically predominant zooplankton species. Salinity emerged as the most influential hydrological factor for zooplankton distribution, followed by dissolved oxygen and water temperature. However, increasing pollution, climate change-induced cyclones, salinization, and human activities are threatening zooplankton communities of the Indian Sundarbans. Furthermore, the review underscores the need for long-term monitoring strategies in the Sundarbans, by addressing the integration of remote sensing method, automated devices, data repositories, and ecological modeling approaches. Additionally, the present review recommends future policies for zooplankton conservation, emphasizing habitat protection, water quality assessment, stakeholder engagement, and securing funding to implement long-term monitoring initiatives.

Improved export coefficient model for identification of watershed environmental risk areas

As a complex system under the joint action of man and nature, land use/cover directly or indirectly affects the environmental quality of the freshwater ecosystem. Studying the response of water environment quality to land use/cover change was significant to accurately simulate lake water quality and effectively enhance the management level. As an empirical model, the classical export coefficient model has been widely used and developed in agricultural non-point source pollution research because of its simple structure and convenient application. However, it assumes that the export coefficient of a particular type of land use/cover was constant, ignoring the influence of surface runoff and interception on the output intensity of pollutants in pollutant migration. This study improved the classical export coefficient model by adding factors such as precipitation, surface cover, and topography, evaluated the contribution of land use/cover to total nitrogen load into the lake in Dianchi Lake Basin, and applied the pollution assessment results to the identification of watershed environmental risk areas. The results showed that the improved export coefficient model could better simulate the relationship between land use/cover and total nitrogen load into Dianchi Lake from the basin. At the same time, spatial characteristics of the total nitrogen load contribution of the terrestrial could be represented. The high-risk areas in the basin were mainly cultivated land and construction areas with low vegetation coverage around lakes or downstream. The contribution per unit area to the TN load into the lake from areas with a high risk was 14.28 t/km², which was 3.47 times that of medium-high-risk areas and 52.28 times that of the medium-risk area. Land use control measures in high-risk areas in the basin should be further strengthened, especially in the lakeside zone.

Optimal Method for Biomass Estimation in a Cladoceran Species, Daphnia Magna (Straus, 1820): Evaluating Length–Weight Regression Equations and Deriving Estimation Equations Using Body Length, Width and Lateral Area

Assessing the biomass of zooplankton compensates for the difference between number of individuals and the accumulated body weight of the community, which helps assess aquatic ecosystem food web functions. Daphnia are crustaceans that play an intermediate role in biological interactions within food webs. The morphology and body specification of Daphnia differ during growth; hence, it is essential to apply species-specific equations to estimate biomass. We evaluated the length–weight regression equations used previously to estimate Daphnia magna biomass and conducted regression analyses using various body specifications and biomass measurements taken directly using devices such as a microbalance and microscopic camera. Biomass estimated using an equation from the Environmental Protection Agency was significantly different from the direct measurement: average biomass was lower, indicating that the equation possibly underestimated actual biomass. The biomass of D. magna had a higher multiple R2 value when length was compared with width and area, and a linear regression equation was the most suitable equation for biomass estimation. Because body specifications and biomass are affected by various environmental factors, the development of accurate species-specific biomass estimation equations will contribute to obtaining fundamental data with which the biological responses of zooplankton to aquatic ecosystem changes can be assessed.