Doldan M.S., Rubilar T., Oehrens Kissner E.M., Kroeck M.A., Morsan E.M

Oyster species play an important role in marine ecosystems, hosting a wide diversity of organisms. It has been stated that epibiosis entails both benefits and disadvantages for the oysters. However, studies of multiple biological interactions of organisms associated with oyster reefs are scarse. In the Northern Patagonian gulfs, Argentina, Ostrea puelchana presents low-density beds; it is not a reef-forming species but it generates a three-dimensional structure as a result of successive settle of oyster larvae on the shells of a “founder” oyster. The aim of this study was to investigate the biodiversity of associated organisms to O. puelchana at multiple spatial scales. We described the community associated to the oyster beds of Northern Patagonian gulfs, and performed non-parametric multidimensional analyses to test whether oyster beds were similar in terms of community components. We also tested the effect of biological interactions such as the inquinilism of Tumidotheres maculatus -living inside the pallial cavity of the oyster-, the parasitism of Lithophaga patagonica –a shell burrower-, and the effect of the grazer chiton Chaetopleura sp. We recorded a total of 85 taxa in the community associated to oyster beds, mainly molluscs (30%), crustaceans (20%) and echinoderms (10%). The similitude among beds was moderate (non-transformed < 40%; square root transformation: 40-65%) and was influence by the dominance of the echinoderm Ophioplocus januarii and the slipper limpet of the genus Crepidula. A total of 31 taxa were recorded as epibionts, mainly polychaetes and molluscs Crepidula sp. and Tegula sp. Condition index of oysters was significative lower for oysters hosting T. maculatus or L. patagonica. Chaetopleura density correlated negatively with oyster recruits. Our findings contribute to the knowledge on the functional role that oysters of O. puelchana play in benthic ecosystems at San Matías Gulf (Northern Patagonia, Argentina), hosting a diverse assemblage of organisms such as invertebrates and algae via parasitism, symbiosis, inquinilism or commensalism.

Acknowledgments: Projects M025 and M026 from Universidad Nacional del Comahue.