Study of Zooplankton diversity in two selected lakes in Dhaka city, Bangladesh

Abstract

Urban aquatic ecosystems are essential components of the urban environment, playing crucial ecological roles such as water purification, habitat provision, and biodiversity support. Despite their immense significance, these ecosystems face numerous challenges due to climate change and anthropogenic pressures. Therefore, this study aimed to investigate the zooplankton diversity in Dhanmondi and Ramna Lakes, two major urban water bodies in Dhaka, Bangladesh, to understand the influence of different environmental parameters and seasonal changes on the abundance and composition of zooplankton between April 2022 and August 2023. Zooplankton were sampled from eight stations per lake during the dry and wet seasons using a 64-μm plankton net, and water quality parameters (temperature, pH, DO, conductivity, salinity, TDS) were measured in situ. Quantitative estimation and identification were conducted using Sedgewick–Rafter counting and standard taxonomic keys. Statistical analyses included ANOVA, correlation, and multivariate regression. A total of 53 taxa were recorded, with 34 taxa in Dhanmondi and 19 in Ramna. Branchiopoda were the dominant group in both lakes (53–55%), while Bdelloidea and Insecta were least abundant. Seasonal variation showed consistently higher dominance of Branchiopoda in both seasons, whereas Bdelloidea and Flagellata remained low. Water quality comparison revealed a significant difference only in TDS (p < 0.001). Correlation analysis showed strong negative relationships between temperature and DO, while regression indicated DO and pH as the main predictors of zooplankton abundance, explaining 36–37% of the variation.This findings are not only vital for preserving biodiversity but also for ensuring the proper management of these two vital urban ecosystems as it revealed the zooplankton community dynamics as well as their seasonal variability. Furthermore, the findings of this study will inform improved conservation and management practices so that the urban lakes continue to thrive and provide essential ecological services.