The Association of Bay Scallops (Argopecten irradians concentricus) with Seagrass and Macroalgae along the Florida Gulf Coast

ABSTRACT Bay scallops (Argopecten irradians concentricus Say, 1822) exhibit a strong association with seagrass habitat from the time of larval settlement, but alternative habitats, such as macroalgae species, may also serve as important habitats for this species. The association of Florida bay scallops with the percent cover of observed seagrass, macroalgal species, and several substrate types (e.g., mud, shell, and rocks) was examined to determine whether a variety of seagrass and macroalgal species significantly influences the abundance of bay scallops in Florida. Sampling occurred at eight study sites along the Gulf coast of Florida, from Tampa Bay in the south to St. Andrew Bay in the north. SCUBA divers used a point-intercept approach along a transect to assess habitat type and percent cover, in addition to recording bay scallop abundance. Generalized additive models for location, scale, and shape were used to model bay scallop abundance as a function of habitat type. Across all sites, bay scallop abundance was positively correlated with percent cover of seagrass and negatively correlated with bare substrate, such as mud and sand. Five out of the 13 habitat types observed in association with bay scallops in this study were significant factors in models of bay scallop abundance including Acetabularia spp. (J.V. Lamouroux, 1812), Caulerpa spp. (J.V. Lamouroux, 1809), Gracilaria spp. (Greville, 1830), Syringodium filiforme (Kütz, 1860), and Thalassia testudinum (Koenig, 1805). The two most important habitat variables were T. testudinum and Gracilaria spp., and there was an observed threshold response of bay scallop abundance to these habitat variables at low to medium percent cover. This is the first study to identify the importance of both seagrass and several macroalgal species for Florida bay scallops and suggests that bay scallop restoration efforts may benefit from restoring seagrass and macroalgae.