The ecological role of brachiopods in the Namuncurá MPA/Burdwood Bank, off southern South America

Abstract

Extant brachiopods have been very little studied, despite being abundant along the Argentine marine platform and southern areas of the Subantarctic region. In this survey, we examined brachiopod assemblages from the Namuncurá MPA/Burdwood Bank area, off southern South America. The material (n = 1203) was recovered from 43 stations ranging in depth from 50 to 785 m during two oceanographic expeditions. Two species (Liothyrella uva and Terebratella dorsata) together represent 95% of the total abundance, with no significant decrease in body size over depths of 800 and 400 m respectively. A third species (Magellania venosa) was found in very small quantities shallower than 200 m, and with a large variation in size. There is a greater proportion (63.37%) of brachiopods with epibionts/encrusters, mainly bryozoans and tubiferous polychaetes, which are more common on the ventral valves of larger specimens, and mainly at depths shallower than 400 m. It was also observed that empty shells serve as a microhabitat for micromolluscs, mainly bivalves. The brachiopods showed signs of drilling predation (8.74%), but they were also prey for other unidentified predators. These predators left a different kind of damage concentrated around the shell margins (19.20%), which should be the subject of further investigation. Based on these results, it is interpreted that brachiopods from the Namuncurá MPA/Burdwood Bank appear to play an important role in the biotic and trophic interactions of benthic Subantarctic marine fauna, whether acting as substrates, refuges, or food.