Interactions between native barnacles, non-native barnacles, and the eastern oyster Crassostrea virginica
In Mosquito Lagoon, an estuary on the east coast of Florida, USA, large numbers of barnacles compete with the eastern oyster Crassostrea virginica (Gmelin, 1791) for space to recruit and grow. Compared to historic middens, there has been a five-fold increase in barnacle numbers on extant reefs. This change included not only increased numbers of the native barnacle species, Balanus eburneus Gould, 1841, but also the introduction of Balanus amphitrite Darwin, 1854. Our research focused on the influence of Balanus spp. on larval settlement, growth and survival of C. virginica. To determine if either barnacle species reduced oyster settlement, we conducted still water and flow settlement trials by providing larvae of C. virginica with oyster shells having varying densities of B. amphitrite and B. eburneus. Oyster settlement was significantly affected by the interaction of flow and barnacle density for both barnacle species. Next, the effects of both water motion and suspended sediments on settlement of C. virginica and B. amphitrite were compared on shells without barnacles. The interaction of flow and sediment impacted settlement of C. virginica, but not B. amphitrite. Finally, shells with a single 1-wk oyster spat per shell and varying barnacle densities were tracked in the field for 4 wks. Barnacles significantly reduced growth and survival of oysters. Again, there were no species-specific differences. Our results suggest that the increase in barnacle numbers, rather than the arrival of B. amphitrite, has had a negative impact on C. virginica populations in this estuary. © 2009 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.
Boudreaux, ML; Walters, LJ; Rittschof, D
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