Spatial and seasonal variation in polychaete communities according to their trophic categories in Southwest Tobago, West Indies

ABSTRACT Bon Accord Lagoon (BAL), Tobago is home to a Thalassia testudinum (K.D. Koenig, 1805) dominated seagrass community and polychaetes usually show an affinity to seagrass beds compared to other environments. The objectives of this study were to investigate the polychaete community associated with the Thalassia beds in BAL, determine seasonal variation, and compare with the neighbouring hard bottom polychaete community in Mt. Irvine Bay (MIB). Benthic macroinvertebrates were sampled using a 15 cm diameter corer at a depth of 10 cm. Six stations were sampled during the wet and dry seasons of 2018. Samples were sieved in the field using a 0. 5 mm mesh screen. They were stained and preserved with a 10% formalin-seawater mixture, sorted and macrofaunal species identified to the lowest possible taxonomic level. Thirty – one polychaete families were ranked according to trophic categories as described by Fauchald and Jumars (1979) and updated where possible. Average family density for the dry season was recorded at 206.89 ± 307.53 ind/m2 and 129.55 ± 227.23 ind/m2 for the wet. Maldanidae and Syllidae recorded highest densities for dry and wet seasons respectively. Deposit feeders were the largest trophic group represented across both seasons in the BAL with Maldanidae being the most dominant. Carnivorous polychaetes dominated MIB with Syllidae being the most dominant. BAL showed higher diversity and richness compared to MIB. Based on functional traits of the community the environment at BAL can be regarded as healthy. This study establishes a much-needed baseline for future research and management of marine biodiversity in southwest Tobago.