An ecological survey was carried out to divulge the spatial distribution and macrofaunal composition of two mangrove ecosystems of Tamilnadu. We scrutinize their relationship with environmental factors and faunal distribution which were monitored by means of 12 surveys over a period of one year. With the intention of studying the macrofaunal composition and seasonal changes along the three stations, these areas were chosen closed to the mangrove environment towards sea. Total number of species varied between 2 to 15 in each group and the total abundance were ranged from 78 to 119 in Pitchavaram mangroves. The macrobenthos density was found to be greatest at S2 followed by S3 and S1. S2 had the maximum diversity index (1.38 in bivalves) and minimum at S1 (1.32 in polychaetes). While in Muthupettai, mangroves varied 114 to 158, the diversity index varied maximum 1.37 at S2 (Cerethidia cingulata) minimum 1.27 at S1 (Amphipods). In both stations, the dominated fauna were polychaetes, bivalves, gastropods amphipods and tanaids, reliably being the most copious group at all stations. The domineering polychaetes encountered during this study included Chaetopterus sp. Pista sp., Nephtys sp. in Gastropods Cerithedia cingulata, Meretrix meretrix and Peneaid shrimp larvae. The statistical findings revealed a significant distinction that existed between the benthic assemblages of the three stations in both ecosystems. The differences in environmental parameters might be accountable for the assemblages of benthic community between stations as well as temporal seasons.
