Polychaetes (Annelida, Polychaeta) associated with lithic and biogenic substrata in Mesophotic Coral Ecosystems in Puerto Rico and the US Virgin Islands

Abstract

There are no studies on the taxonomy and ecology of the polychaetes from the Caribbean Mesophotic Coral Ecosystems (MCE) and this work represents the first effort to identify and catalog the polychaetes of these ecosystems in the Caribbean. To fill this information gap, several substrata samples were collected using technical diving from several mesophotic localities (between 46-91 m) in Puerto Rico and the U.S. Virgin Islands, between 2007 and 2012. The samples were processed on board, washed on sieves with mesh eye of 1.0 mm and 0.125 mm; sediment and organisms retained were fixed in 95% ethanol, for future studies. In the laboratory, samples were analyzed under the stereo-microscope and specimens belonging to 76 genera (distributed among 34 families) were identified. All of them have been previously reported from marine substrata around the Caribbean, but from other ecosystems. Syllidae was the family best represented across all sampled localities, with the largest number of genera (15) and the highest number of individuals (5,755 or 80.85% of the total recorded fauna). Haplosyllis was the most abundant and most frequently sampled genus in the sampled sites. Bajo de Sico, an MCE on the west coast of Puerto Rico, was the locality with the highest abundance (1,183 individuals), while the extended MCE off La Parguera Natural Reserve, on the southwest coast of Puerto Rico, was the locality with the highest number of genera (59), which seems related to the greater spatial heterogeneity of substrata and the high variety of microhabitats that it offers. The greatest generic diversity and the highest abundances were found in the upper zone (UM) of the mesophotic range (30-60 m) compared to the lower zone (LM) (60-91 m).