A COMMUNITY ANALYSIS OF THE SOFT BOTTOM MEGAFAUNA (CRUSTACEA, MOLLUSCA) FROM THE SOUTHWESTERN REGION OF SANTA MARTA, COLOMBIAN CARIBBEAN

Abstract

Soft bottom megabenthic communities have been poorly studied in the Caribbean Sea. In this study we describe the structure and species composition of a Crustacea-Mollusca megafaunal community based on beam trawl samples taken between 13 and 60 m depth at the southwestern region of Santa Marta, Colombian Caribbean. Classification and ordination analyses using abundance data of crustaceans and molluscs produced two main groups (A and C), which seem to be controlled by depth and sediment characteristics. Group A consisted of species collected at the deeper stations and high content of silts (between 30 and 60 m depth) and exhibited the highest density and biomass mean values. The decapod Chasmocarcinus cilindricus was found as the characteristic species for the group A. The bivalve Laevicardium pictum occurred as characteristic in the shallower cluster C (14 to 17 m) where the sediment was coarser. Trachypenaeus similis, Portunus spinicarpus, Lupella forceps and Penaeus duorarum were generalist species for both groups and were found as the most abundant species overall. There was not a clear evidence of temporal variation of the groups, however an increase in the abundance of dominant species at the shallower area during March may be related to the upwelling phenomenon known for the Santa Marta area.