<![CDATA[Prolonged anthropogenic disturbance contributes to the degradation of Merdada Lake. Tourism development, intensive water extraction, fertilizer and pesticide application, and the conversion of land into agricultural areas have accelerated soil erosion, sediment accumulation, nutrient loading, and siltation, which ultimately reduce water quality and influence zooplankton communities. This study assessed the suitability of zooplankton as a bioindicator by examining community composition, abundance, daily variation, ecological indices, and key environmental constraints as indicators of trophic conditions. Sampling was carried out randomly in May 2021 at five observation sites with three replicates, conducted during nighttime (7:00 PM), early morning (5:00 AM), and morning (9:00 AM). The zooplankton community consisted of several functional groups, including Cladocerans, Copepods, Nauplius, Protozoa, and Rotifers. Abundance ranged from 5.51 to 22.47 individuals per liter, with Rotifers, particularly Philodina sp., being the most dominant group. Peak abundance was recorded at night, reflecting diel movement patterns associated with vertical migration and food availability. Ecological index analysis revealed poor-moderate diversity (H’ = 1.76–1.90), moderate -high evenness (E = 0.72–0.80), and high dominance (C = 0.79–0.82), which indicates an unstable community structure and ecological. Variations in zooplankton structure and daily dynamics were strongly associated with light intensity, nitrate concentration, dissolved oxygen, and alkalinity. Overall, the findings demonstrate that zooplankton communities are sensitive to environmental changes and can serve as effective bioindicators of water quality in Merdada Lake. Overall, zooplankton communities are responsive to water quality conditions in Merdada Lake.]]>
