Sahyadri Conservation Series: 22 ENVIS Technical Report: 52,  November 2012
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ECOLOGICAL PROFILE OF SHARAVATHI RIVER BASIN
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Ramachandra T.V. Subash Chandran M.D. Joshi N.V. Sreekantha
Raushan Kumar Rajinikanth R Desai, S.R. Subhash Babu
Energy and Wetlands Research Group, Centre for Ecological Sciences, Indian Institute of Science, Bangalore – 560012, India.
*Corresponding author: cestvr@ces.iisc.ernet.in
ZOOPLANKTON OF THE SHARAVATHI RIVER BASIN

Zooplankton are tiny organisms in the aquatic ecosystem responsible for energy transfer from producers to higher trophic level. They occur in both lentic and lotic aquatic ecosytems. In the Sharavathi River Basin, a study was carried out to know the zooplankton diversity of the region. The study carried out in 13 localities recorded 37 species belonging to Rotifera, Copepoda and Cladocera groups.

Introduction

Zooplankton - so called “secondary producers” are the major components in the aquatic ecosystem, both in lotic and lentic. They are responsible for energy transfer from primary producers to other higher trophic levels and their importance in aquatic ecosystem has already been investigated (Edmondson, 1974; Hutchinson, 1957; Wetzel, 1975). Rotifera, Cladocera and Copepoda are the major groups among freshwater zooplankton. A detailed knowledge about zooplankton composition and their seasonal fluctuations is essential for proper management of water bodies.

In India, systematic studies on freshwater zooplankton were initiated by Baird (1860). Since then, numerous limnological investigations have been conducted, but the majority of them were in regional levels viz., Rajasthan (Biswas, 1971; Nayar, 1971); Karnataka (Patil and Gauder, 1980), Kerala (Nair and Nayar, 1971), Punjab (Vashist and Batish, 1971); Kashmir (Quadri and Yousuf, 1978). Members of rotifera in India were relatively well studied (Segars et al, 1994) and enlisted 300 taxa. Recently Michael and Sharma (1988) reported 93 cladoceran taxa belonging to 8 families from inland waters of India. Copepoda are the least studied group among the three groups. The present systematic study on freshwater zooplankton deals with rotifers, cladocerans and copepods from 13 localities of Sharavathi River basin. Segers et al., (1994) reported about 300 species of rotifers from Indian inland waters but the information about Rotifers from lotic water system is still far from complete. Cladocerans are the favorite prey of most of the fishes. The gut content analysis of some carp fishes revealed the fact that nearly 70% of food consumed by fish was Cladocera (Edmondson, 1974).

Materials and Methods

The samples were collected using plankton nets with a mesh size of 50 µm and 75 µm, and samples were fixed in 4% formaldehyde solution. Later zooplankton was sorted out using binocular microscope. Rotifera was mounted on glycerin medium and identified under a compound microscope based on its lorica morphology and trophi structure. Taxonomically important parts of Cladocera and Copepoda were dissected under the binocular microscope by means of two tungsten needles and mounted on slides for further identification. Measurements were carried out using calibrated ocular micrometers. Species identification was done using available literature of Dussart and Fernanto (1988), Flossner (1972), Golden (1968), Lindberg (1957), Michael and Sharma (1982), Reddy (1994) and de Vande (1984).

Study Area

The study was carried out in 13 selected localities (Table 59) of Sharavathi River basin. The details of the sampling localities are given below.

Table 59. Localities in the study area at Sharavathi River Basin.

Location
Nagara
Sharavathi
Mavinaholé
Haridravathi
Muppane
Talakalale dam
Dam out let
Holebagilae
Huliholé
Yenneholé
Valagere
Nagodiholé
Rocky pool in Jog falls

Results

 

Rotifera

Rotifera (Rotatoria) are pseudocoelomate, bilaterally symmetrical animals. They are mostly considered as a separate phylum (Hymann, 1951). Rotifers occur in nearly every water body i.e., from trickles on rocks to rivers, from bogs to lakes. Majority of rotifers inhabit freshwater but some genera also occur in brackish water and marine environment. Most species are free-living while some are epizoic or parasitic. Generally the size of the rotifera range from 400 µm to 0.2 mm. Twelve species belonging to four families are recorded in the present study (Table 60). Lecane bulla is recorded from 10 sites.

Table 60. Rotifers recorded in the study.

Species Sites
1 2 3 4 5 6 7 8 9 10 11 12 13
Family- Brachionidae
Brachionus quadridentatus Hemann, 1783               +          
B. calciflorus Pallas, 1776 +   +           +        
B. falcatus (Zacharias, 1898) +   + + +                
Keratella tropica (Apsein, 1907) +                 +      
Plationus platulus ( Muller, 1786)                           +
Family: Trichotridae
Macrochetus collinsi ( Gosse, 1867) +                        
Family: Colurellidae
Lepadella patella (O.F.Muller)                         +
Family: Lecanidae
Lecane bulla (gosse, 1888). + + + + + + + + + +     +
L. inopinata HarringandMayers, 1926. +                        
L. lateralis sharma, 1978. +                 +      
L. quadridentata ( Ehrenberg, 1886)   +             +        
Lecane sp.       +   +     + +      

Cladocera

Cladocera belongs to Class Crustacea and Sub-class Branchiopoda. They are commonly known as 'water fleas' and are mostly found in freshwater habitat. They are ubiquitous in distribution, i.e., they are found in the Arctic to Antarctic, in temperate and tropical latitudes. Recently they were also reported from ground water (Dumont, 1987; Negrea 1983). The size is ranging from 0.2 mm to 18 mm. Like other Zooplankton cladocerans are excellent food for Zooplanktivorous fish. Cladocerans are the major representatives in the present study with 18 species recorded from the 13 localities (Table 61).

Table 61. Cladocerans recorded in the study.

Species Sites
1 2 3 4 5 6 7 8 9 10 11 12 13
Family: Sididae
Latonopsis australis (Sars, 1888)    +                        
Diaphanosoma sarsi Richard, 1895   +     +                
Family : Daphniidae
Ceriodaphnia cornuta Sars, 1885         + +              
Simocephalus serrulatus (Koch, 1841) +                        
Scapholebris kingii sars, 1903           +                  
Family: Moinidae
Moina micrura Kurz, 1874       + + +     +          
Moinodaphnia macleayi (King, 1853)       +                  
Family: Macrothricidae
Macrothrix spinosa King, 1953.   +             +        
M. triserialis (Brady, 1886 )   +                      
M. odiosa (Gurney, 1907)                   +      
Family: Ilyocryptidae
Ilyocryptus spinifer Herrick, 1882.                 +        
Family: ChydoridaeSub-family: Chydorinae
Alonella excisa (Fischer, 1884)       +                  
Chydorus sphaericus (Muller, 1776) +   +                   +
C. parvus ( Daday, 1898) +                        
Ephimeroporus barrosi (Richard, 1894)       + +                
Sub-family: Aloninae
Alona verrucosa (Sars, 1901) +                 +      
A. affinis (Leydig, 1860)                           +
Leydigia acanthocercoids ( fischer, 1884)                 +        

Copepoda

Copepods are the very ancient arthropods. Zoogeographical data suggest that the copepoda of continental waters were rich and diversified. Their habitat ranges from small ditches to large rivers and lakes. Majority of them are freshwater and some are marine. In freshwaters, they occur as free living, parasitic or semi-parasitic. Most of them are very small with size ranging from 0.3 mm to 5 mm. In inland waters copepods are well known up to family level, but numerous species are yet to be discovered. Of the three groups of zooplankton, Copepoda was least represented in terms of diversity with only seven species (Table 62).

Table 62. Copepodans recorded in the study.

Species Sites
1 2 3 4 5 6 7 8 9 10 11 12 13
Family: CyclopidaeSub-family: Cyclopinae
Mesocyclops ogunnus Onabamiro, 1943 +                        
M. splendidus Lindberg, 1943.     + +         +        
Microcyclops varicans Sars, 1863   +                 +      
Thermocyclops decipiens (Kiefer, 1926b)                         +
Family: Diaptomidae
Heliodiptomus cinctus (Gurney, 1907)   +           +          
Allodiaptomus mirabilipes (Kiefer, 1936) +       + + +            
Tropodiaptomus informis Kiefer, 1930                           +

Discussion

In the present study, 39 species of zooplankton were recorded from different localities along the River Sharavathi. Compared to lentic ecosystem, the species richness was low in lotic ecosystem. This is mainly due to the extreme complex nature of the zooplankton (Throp and Covich, 1991). Being a secondary producer, these organisms are very much related to their specific algal food. Most of them feed on unicellular algae, while some feed on filamentous algae. The sporadic increase in density of zooplankton associated with algal bloom was observed by Lefevre (1950); Ruttner (1970) and Edmondson (1974). Phytoplankton like Microcystis sp. are toxic to some zooplankton.    

In the present investigation, the Rotifers exhibited maximum diversity. Species richness was more in the genus Lecane and Branchionous. Lecane bulla was distributed evenly in all sampling sites. No large sized rotifers were recorded during the present study; this may be due to presence of predatory fishes in the reservoir. Further more, the lack of riparian vegetation along the margin of river may directly be able to influence the prey-predatory relationship in running water system.

Cladocerans and copepods were the second largest group in this study. During the study period 20 species of Cladocera belonging to 7 families were recorded. Most of them were smaller in size, ranged from 0.2 mm to 0.4 mm. The high-pressure perdition and turbulent flow of river water can shape the community structure of zooplankton. One of the important observations in the present study was the absence of any zooplankton in sites 11 and 12, which may be due to the complete absence of primary producers in that water. As far as Karnataka state is concerned, the freshwater copepods are the least studied group with only a few reported studies (Reddy, 1994). In the present study 7 species of copepods were recorded. Tropodiaptomus informis and Thermocyclops decipiens were reported from locality 13, i.e., found only in rocky pools. Further more, a cyclopidae species Mesocyclops ogunus was restricted to locality 1, while other species were distributed to more than one locality (see species-locality list).

Conclusion

The freshwater zooplankton fauna of Sharavathi River is rich and highly diversified. They were showing a typical tropical assemblage. Large zooplankton species were absent in this river system, probably due to high predatory pressure. The alteration of the natural lotic system like construction of dam and bunds will lead to eutrophication and finally it eliminates some endemic species from the same ecosystem. So, the knowledge about the physico-chemical and biological factors of a lotic ecosystem becomes a prerequisite for better management of the ecosystem. 

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