Sargassum Muticum effects on Costaria Costata and Benthic Assemblages of Marine Primary Producers

Abstract

The introduced species Sargassum muticum has been part of Salish Sea ecosystems since the 1940s. It has become extremely common in both Europe and North America, growing in the shallow subtidal. I combined a series of in-lab growth and fluorometry measurements with subtidal surveys to discern the possible direct effects of S. muticum on the native kelp, Costaria costata, and the broader macro-benthic primary producer assemblage. In the laboratory, S. muticum did not show a decrease growth or photosynthetic rate. Similarly, subtidal surveys showed no significant difference in primary producer assemblage composition within and outside beds of Sargassum. My results disagree with previous literature and suggest that likely both abiotic and biotic factors may play a complicated role in Sargassum’s influence as an invasive species.