Biological diversity of the green mussel Perna viridis (L.), Mytilidae, community from Bahadurgad Island off Malpe south west coast of India

The biological diversity of the green mussel Perna viridis (L.), Mytilidae, community was studied at Bahadurgad Island off Malpe, near Udupi, south-west coast of India. A total of 4,262 individuals belonging to 94 species were recorded. The green mussel Perna viridis was rich in both number and biomass. The intertidal biodiversity of Bahadurgad Island was composed of algae (11 spp.), porifera (1 sp.), coelenterata (4 spp.), platyhelminthes (2 spp.), aschelminthes (1 sp.), ectoprocta (4 spp.), annelida (24 spp.), mollusca (22 spp.), arthropoda (23 spp.), echinodermata (1 sp.) and fish (1 sp.). Among polychaetes, the genera Phyllodoce with four species, Eulalia and Perineries with three species each and Neries with two species were encountered. Rest of the genera was represented by a single species each. Among crustaceans, the maximum species richness was contributed by decapoda comprising ten species of crabs, one species of shrimp (Alpheus malabaricus) and amphipoda (6 spp.), cirripedia (5 spp.) and isopoda (1 sp.). The genera Modiolus (M. modiolus, Modiolus sp.) and Thias (T. rustica, T. tissoti) were represented by two species each. Chitons were represented by Acanthopluera granulata and Ischiochiton ruber. Hydroid was represented by three species (Clava leptosyla, Lovenella gracilis, Tubularia sp.). Sea anemones with two species (Haliplanella sp., Clava leptosyla) were recorded. During the study period, Chthamalus sp. (1,566 ind.) was dominant, followed by Perna viridis (944 ind) and Trochus radiatus (42 ind.). The species diversity (log , H’) ranged from 1.4009 to 2.5296. The minimum (0.4119) and maximum (0.6466) values of evenness were recorded during monsoon (September 2006) and post-monsoon (December 2005) seasons, respectively. The species diversity was affected more by the distribution of individuals among species. Analysis of hierarchical cluster with complete linkage revealed the presence of two large groups. Group A was composed of coelenterates, gastropods, cirripedes, decapods, bivalves, amphipods, bryozoans, whereas group B consisted of algae, polyplacophora, polychaeta and others(porifera, platyhelminthes, aschelminthes, isopoda, echinodermata, fish). The Principle Component Analysis yield three components with Eigen value more than one. The component one (bryozoa, amphipoda, air temperature, water temperature, mussel bed temperature, pH, salinity and dissolved oxygen) accounted for 40.78% of variation, followed by component two (coelenterata, gastropoda, cirripedia, decapoda, porifera, aschelminthes, echindodermata, chordata) that accounted for 39.66% of variance and component three (algae, polychaetes, polyplacophora, bivalves, rainfall) accounted for 19.56% of variance.