Effects of water quality and seasonality on Zooplankton responses

Zooplankton, vital components of aquatic ecosystems, are highly sensitive to water quality variations and seasonal changes, making them effective bioindicators. This review examines the key water quality parameters like temperature, dissolved oxygen (DO), pH, salinity, nutrient levels, and pollution along with seasonal fluctuations, influence zooplankton abundance, diversity, and physiological responses. Water quality significantly shapes zooplankton communities. Temperature fluctuations alter metabolic rates and reproductive cycles, while declining DO, often linked to eutrophication, reduces diversity and biomass, favoring hypoxia-tolerant species. Extreme pH levels and rising salinity from agricultural runoff disrupt zooplankton osmoregulation, reducing species richness. Nutrient enrichment promotes algal blooms, initially benefiting zooplankton but later inducing population declines due to hypoxia and toxic algal byproducts. Heavy metals, pesticides, and microplastics impair zooplankton growth, reproduction, and enzyme activity, favoring pollution-resistant species. Seasonality further drives zooplankton dynamics. Spring and summer witness population peaks due to warmer temperatures and higher phytoplankton productivity, while autumn and winter bring declines due to lower temperatures and food scarcity. Seasonal succession patterns show cladocerans and copepods dominating in warmer months, while rotifers prevail in colder seasons. The interactive effects of water quality and seasonality produce complex zooplankton responses. During warmer months, eutrophication-induced hypoxia reduces zooplankton abundance, whereas in winter, pollution effects are less pronounced due to lower metabolic rates. Climate change-driven temperature shifts are altering seasonal patterns, disrupting trophic interactions. Understanding the combined influence of water quality and seasonality on zooplankton is crucial for ecological monitoring and water resource management. Long-term studies using zooplankton as bioindicators can enhance ecological risk assessments and support sustainable aquatic conservation strategies.