Benthic biocoenosis: influence of edaphic factors in the tropical mangroves of Cochin, Southern India

Abstract

Biocoenosis of macrobenthic communities in relation to environmental and mangrove flora was studied in mangrove ecosystem of Cochin backwaters during 2010–2012 period. A total of 48 species in 45 genera belonging to 38 families of macrobenthos were collected with a mean numerical density of 1628 ± 2283 ind m−2. Malacostraca was the dominant taxa in terms of benthic density (55%) and diversity with 17 spp., then polychaeta (11 spp.), mollusca (9 spp.) and others (9 spp.). The dominant species were amphipods Idunella sp. (40,170 ind m−2), Cheiriphotis geniculata (34,169 ind m−2), polychaete Dendronereis aestuarina (38,808 ind m−2), tanaid Ctenapseudes chilkensis (29,419 ind m−2), bivalve Indosphenia kayalum (23,835 ind m−2) and oligochaete Tubificoides psuedogaster (16,946 ind m−2). The PCA and redundancy analysis revealed that the nature of the substratum determined by sediment texture, organic matter, total organic carbon, sediment nutrients were found to be an influencing factor in the differential distribution and community structure of macrobenthic organisms in mangroves of Cochin. Mangrove plant density also exhibited significant correlation with the density of macrofauna. This study has noted a decline in species composition as well as diversity and richness of macrobenthic fauna compared to the previous study notably polychaetes reported in 1993 in Cochin mangroves. Moreover, community structure exhibited significant change with newer associations of species especially opportunistic oligochaetes, corophiids and tanaids that are tolerant of various anthropogenic stressors. This change in community assemblage and biodiversity, thus demanding efficient management strategies for mangrove ecosystem through integrated planning, rehabilitation and periodic benthic faunal surveillance coupled with mangrove floral assessment.