Compound Ascidian Filtration Rates, Growth Rates, Recruitment, Damage to Seagrass and Distributions in St. Joseph Bay

Compound ascidians are common aggressive organisms that can encrust the blades of seagrass and cause damage to seagrass ecosystems. This interaction was studied in St. Joseph Bay, home to four compound ascidians; Botrylloides sp. A (yellow), Botrylloides sp. B (red), Distaplia sp. and Didemnum sp. This investigation sought to quantify the effect compound ascidians pose to seagrass meadows. During May - October 2020 field and lab studies were conducted measuring ascidian filtration rate, growth rate, recruitment, damage to seagrass, and distribution over time in the Bay. The ascidians studied have a rapid growth rate, a high filtration rate, and cause damage to the seagrass. Botrylloides sp. A (yellow) had a high recruitment rate, and Didemnum sp. increased in abundance at the end of the summer. Further research with increased sample sizes and monitoring throughout the year will help to determine what circumstances favor these ascidians.