Lentic and lotic assemblages of zooplankton in a tropical reservoir, and their association with water quality conditions

Zooplankton assemblages in relation to water quality parameters at lentic and lotic habitats of Air Itam Reservoir, Penang, Malaysia, were analysed. Five sampling stations were designated, including three stations located in the reservoir (Stations A, B, and C) and two stations in the upstream inflow and downstream outflow (Stations D and E, respectively). The most common and dominant zooplankton found in the lake were Polyarthra vulgaris, Ceriodaphnia cornuta, Mesocyclops leuckarti, and Thermocyclops crassus. Water Quality Index, calculated as recommended by the Malaysian Department of Environment, ranged between 88.46 and 93.6, showed that the reservoir was clean. Low numbers of species and value of the Shannon-Wiener Diversity Index were recorded at stations located upstream and downstream of the reservoir. Cluster analysis based on the abundance of zooplankton species distinguished the sampling stations into two groups (lentic and lotic groups, comprised of Stations A, B, and C; and Stations D and E, respectively). This study showed that zooplankton occurrence and abundance were associated with the quality of their environment, and zooplankton community provides information about the reservoir ecosystem, thus reflecting the importance of biomonitoring in lake assessment and management.