Invasive tunicate (Ascidiacea) metabolic and filtration rates in comparison to native tunicate and bivalve species

Abstract

Several invasive species of tunicates (Ascidiacea) have become cosmopolitan and widely distributed in coastal areas worldwide over the past few decades. These nonindigenous tunicates have consequently caused fouling problems in aquaculture and marine harbors. The goal of our project was to enrich the understanding of how invasive tunicates interact with other organisms in the ecosystem. Two species of invasive tunicates (Didemnum vexillum and Botrylloides violaceus) and one species of native tunicate (Aplidium glabrum) were evaluated for their metabolic rates. The filtration rates for native blue mussels (Mytilus edulis) and invasive tunicates (Diplosoma listerianum) were determined. D. vexillum regenerated NH4+ at a faster rate than A. glabrum and B. violaceus. Both tunicates and blue mussels were feeding on phytoplankton as their major food source, although the size of particles utilized by different organisms was not examined in this study. Invasive tunicates were strongly competing with mussels to filter feed, but were not inhibiting mussel’s filtration rate.