Macroalgal distribution patterns and ecological performances in a tidal coastal lagoon, with emphasis on the non-indigenous Codium fragile ssp. tomentosoides

ii Codium fragile ssp. tomentosoides is a North-West Pacific macroalgae that has invaded numerous lagoons. The success of C. fragile has been explained by its dispersal capacity, growth rate, nutrient uptake, salinity and temperature tolerances, and grazer resistance. I compared distribution, recruitment and growth of Codium to native algae in Hog Island Bay, a shallow water lagoon in Virginia. To determine the extent of invaded habitats algae were mapped from 1998-02. Codium was fourth most abundant, and hence considered successful compared to most species in terms of its biomass. Codium was found both unattached or attached to bivalve shells, while the majority of the dominant Gracilaria verrucosa and Ulva curvata were incorporated into tube caps of the polychaete Diopatra cuprea. Preference experiments showed that Diopatra incorporated Ulva and Gracilaria most, Agardhiella subulata intermediate, and Codium and Fucus vesiculosus least, and that the first 3 species were fragmented in the process. Thus, Diopatra facilitated Ulva and Gracilaria, by providing an abundant substrate, reducin