STOWING AWAY ON SHIPS THAT PASS IN THE NIGHT: SCLEROBIONT ASSEMBLAGES ON INDIVIDUALLY DATED BIVALVE AND BRACHIOPOD SHELLS FROM A SUBTROPICAL SHELF

Abstract

ABSTRACT This study evaluates encrustation and bioerosion of brachiopods (Bouchardia rosea) and bivalves (Semele casali) occurring on the inner shelf of the Southeast Brazilian Bight, accounting for differences in water depth, sediment type, host size, and time averaging. Frequencies of colonization covary across sites, but brachiopods are more frequently encrusted than bivalves at all sites, although this difference may disappear after standardization for shell size, depending on the chosen metric. Size selectivity during sclerobiont colonization appears to change as a function of their population density, rather than substrate differences between hosts. Sediment grain size and composition do not appear to exert environmental controls on encrustation or bioerosion, nor does either vary as a function of water depth alone. Radiocarbon-calibrated aspartic acid racemization dating of individual host valves shows similar age ranges and age structures for both hosts. Both epifaunal brachiopods and infaunal biv...