24 Original ResearchArticle Zooplankton Diversity and Limnological Parameters in River Sal, Goa Fernandes Alisha and I. K. Pai* Department of Zoology, Goa University, Goa-403206, India *Corresponding Author : ikpai@unigoa.ac.in Received: June 21, 2018; revised: September 21, 2018; accepted: September 28, 2018 Abstract: Water is the key substance for the survival of all living organisms. The quality of water in terms of physicochemical parameters affect the conditions for the existence of zooplankton. India is blessed with thousands of water bodies, both large and small, ranging from pond to large lakes, rivers and streams of lentic or lotic nature. Despite several studies, still a large number of them are virgin and yet to be studied. Hence studies on the diversity and seasonal abundance of zooplankton in river Sal, one of the lesser known rivers of Goa was carried out. Analyses of physicochemical parameters showed the following range: Temperature (24.5-30 o C), pH (6.60-8.0), EC (17782-52845), total alkalinity (36.03-1188.33mg/l), DO (3.96-7.10mg/l), turbidity (10.35-34.12NTU), nitrates, (0.07-1.94 mg/l), phosphates (0.01-0.19 mg/l), calcium (15.76-1438 mg/l) and magnesium (1.93-240 mg/l). A total of 30 species belonging to Cladocera (10 sps.), Copepoda (9 sps.), Rotifera (9 sps.) and Ostracoda (2 sps.) were identified. Rotifers showed dominance in number followed by Copepoda, Cladocera and Ostracoda. The percentage of zooplankton population was highest (45%) during the pre-monsoon and lowest (22%) during the monsoon period. The observations further reveal the presence of Alona quadrangularis only during the monsoon season whereas Mesocyclops hyalinus and Testudinella patina only during the post-monsoon season. Shannon-Wiener Index, Simpsons diversity index, Margalef’s richness index and equitability were calculated for zooplankton diversity in this river. No vast variation was observed in the Shannon diversity index (H). Taxa richness was the least in the monsoon season while pre-monsoon season accounted for the highest diversity. Key words: Physicochemical, river Sal, seasonal variation, zooplankton Journal of Bioresources 5(2): 24-32 (2018) ISSN 2394-4315 Introduction The river Sal is a valuable resource for irrigation and aquaculture practices. In the last few decades, several coastal areas have changed from a virtual wilderness to haphazardly developed stretches full of concrete buildings and related structures leading to altered ecosystems. Further zooplankton plays an important role in indicating the water quality, eutrophication status and productivity of freshwater body (Mikschi, 1989). Also, the secondary production of an aquatic ecosystem directly or indirectly relies on them (Sharma et al., 2013). Zooplankton species are cosmopolitan in nature. The freshwater zooplankton comprises mainly of Protozoans, Rotifers, Cladocerans, Copepods and Ostracods. Rotifers, the tiny wheel animalcules are the most prominent group among the zooplankton of a water body irrespective of its trophic status. This may be due to the less specialized feeding, parthenogenetic reproduction, and high fecundity. These generally respond quickly to the environmental changes (Gannon and Stemberger, 1978). Cladocerans, also known as water fleas, are tiny aquatic crustaceans. They are highly