Community structure and productivity of subtidal turf and foliose algal assemblages

Abstract

Foliose and turf-forming macroalgae form morphologically distinct assemblages on shallow reefs worldwide and frequently coexist in a patch mosaic. The relative contributions of these algal assemblages to reef productivity and the processes that maintain them, however, have rarely been studied. We found high (80%) species overlap between turfs and foliose macroalgae at Naples Reef off southern California, with differences between the 2 assemblages lying in species dominance and morphology rather than composition. Turfs were dominated by a small finely-branched red alga, Pterosiphonia dendroidea, while larger blade-forming red algae, particularly Chondracanthus corymbiferus and Rhodymenia californica, dominated foliose assemblages. Foliose dominants were common in turfs, but were small. Areaspecific rates of net primary production of foliose assemblages were ̃3× higher than those of turfs, while rates of carbon-specific production and turnover times of turfs were ̃3× higher than those of foliose assemblages. These findings suggest that factors other than the growth potential of each assemblage determined their relative biomass. Turfs were net heterotrophic, with net community production. © Inter-Research 2009.