Environmental assessment of Sungai Perai, Penang, by using zooplankton as a bio-indicator

Zooplankton are crucial as bioindicators and aid in determining the level of water contamination. The effects of environmental disturbances can be detected through changes in species composition, abundance, and body size distribution of zooplankton. Using a plankton net, samples were collected from eight sampling sites during the neap and spring tides of January, February, April and May 2024. A total of 67 zooplankton taxa were recorded, including 44 Rotifera, 12 Cladocera, and 11 Copepoda. The predominant species viz: Brachionus calyciflorus, Anuraeopsis fissa, Filnia longiseta, Filinia terminalis, Moina sp, Calanus sp, Cyclops sp, Brachionus angularis, Brachionus urceolaris, Argonotholca foliaceae, Asplachna sp, Testudinella sp, and Adineta vaga were recorded in all the sampling sites in the river. The abundance of these species in any water body indicates a high degree of eutrophication in the river. Moina, Daphnia, and Cyclops also indicate the intrusion of organic matter and nutrients from runoffs and drains into the river. The Shannon H’ are 1.37, 1.34, 1.27, 1.33, 1.28, 1.36, 1.42, and 1.31 for sites A, B, C, D, E, F, G, and H respectively indicating the presence of contaminants in the river. The community structure of the zooplankton of Sungai Perai is influenced by factors such as tidal events and water quality parameters such as nutrients, dissolved oxygen, and temperature. This study demonstrated that zooplankton could indicate the condition of the Sungai Perai through changes in its community structure, distribution pattern, and abundance of vulnerable genera and species.