The occurrence and ecology of Renilla spp. over the southwest Atlantic continental shelf (28–34ºS)

Abstract

Sea pansies are marine colonial cnidarians of the genus Renilla (Pennatulacea: Renillidae) and play a significant ecological role in the continental shelf food webs. Renilla species are endemic to the Americas and most have been reported in the southwest Atlantic. Austral winter expeditions were undertaken at random isobaths over the Pelotas Basin shelf, southernmost Brazil (28–34ºS), to report the current occurrence of Renilla spp. and the key factors controlling their distribution, as well as to infer the ecological interactions between sea pansies and other marine species. Renilla muelleri, R. musaica, and the endemic R. tentaculata were recorded over this shelf area. Their spatial distribution, as determined by a multivariate canonical correspondence analysis, was mainly associated with environmental parameters, such as bottom water temperature, salinity, and substrate composition. A high abundance of small individuals (both recruit and juvenile colonies) suggests the occurrence of recruitment events for some species. Renilla populations over this southwest Atlantic shelf can be negatively affected by ecological interactions occurring among sand dollars, and benthic and pelagic predators, in addition to human activities.