Comparative Study on Macrobenthic Community Structure with Special Reference to oligochaetes during Drought and Flooded Phases in a Tropical Kole Wetland, India.  

Vineetha S. , Bijoy Nandan S. , Rakhi Gopalan K.P.
Department of Marine Biology, Microbiology & Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, Fine Arts Avenue, Kochi-682016, Kerala, India
Author    Correspondence author
International Journal of Marine Science, 2015, Vol. 5, No. 41   doi: 10.5376/ijms.2015.05.0041
Received: 22 Apr., 2015    Accepted: 26 May, 2015    Published: 23 Jun., 2015
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Vineetha S., Bijoy Nandan S., and Rakhi Gopalan K.P., 2015, Comparative Study on Macrobenthic Community Structure with Special Reference to Oligochaetes During Drought and Flooded Phases in a Tropical Kole Wetland, India, International Journal of Marine Science, 5(41): 1-10 (doi: 10.5376/ijms/2015.05.0041)

Abstract

Wetlands experience dynamic hydrofluxes which is a major determinant of biotic community structure. Benthic organisms form an integral part of aquatic environment and constitute an important link in the food web. The habitat loss and fragmentation caused by hydrological alterations in wetlands can affect the benthic fauna. This study analyzed the benthic community especially oligochaete species in a wetland during two different phases. Maranchery Kole wetland, a part of Vembanad Kole wetlands (Ramsar site) behaved as two systems within a short span of one year; as flooded phase when the system was a pure aquatic body and drought phase where the system was dry resembling a grass land with isolated water patches. Macrobenthic abundance in flooded and drought phases were (355±122 ind./m2) and (166±60 ind./m2) respectively. The decrease in habitable area along with its consequential effects resulted in a reduced numerical abundance of macrobenthos in the drought phase. Oligochaete abundance was significantly higher in flooded phase (ANOVA F1, 53=5.11, p<0.05). On the contrary insect abundance was higher in drought phase (124±168 ind./m2) than flooded phase (91±156 ind./m2). As insects are characterized by flight dispersal mode they were less affected by habitat isolation caused by the fragmented water patches. Eighteen oligochaete species were identified consisting of 14 species of the family Naididae, 3 of Tubificidae and 1 of Lumbriculidae. Allonais gwaliiorensis, Dero dorsalis, Branchiodrilus hortensis, Pristinella acuminata, Nais andhrensis, Dero nivea were exclusive to drought phase and Pristina breviseta, Pristinella minuta, Pristinella menoni, Aulophorus hymnae, Lumbriculus variegates exclusive to flooded phase. The ANOSIM results revealed that the oligochaete species composition was similar in both the phases (Global R=0.05, p>0.05). Species richness (Margalef’s index) and species diversity (Shannon Wiener index) was higher in drought phase or disturbed phase than flooded phase or undisturbed phase reflecting a glimpse of intermediate disturbance theory. No significant correlation emerged between the environmental variables and benthic abundance implying that the relationship with the measured environmental variables might be weaker or overridden by other unmeasured variables. Further the generalized environmental requirements in aquatic oligochaetes and chironomid larvae, the most abundant taxa in the wetland could be the reason for the lack of correlation.

Keywords
Oligochaetes; Kole wetlands; Benthos; Diversity; Flooded phase; Drought phase
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