Date of Award

Winter 2020

Project Type


Program or Major

Biological Sciences

Degree Name

Doctor of Philosophy

First Advisor

Larry G Harris

Second Advisor

Jessica A Bolker

Third Advisor

James F Haney


This dissertation examines several aspects of the biology and ecology of Codium fragile and Placida dendritica in the Gulf of Maine. Scientific interest in nonindigenous species was examined to determine if any patterns were evident that might indicate a change in the status of an invasive species. Interest in C. fragile had waned in recent years, the timing of which coincides with the decreased ecological dominance and apparent naturalization of the alga. Laboratory and field studies were combined to quantify the dynamics in the population of C. fragile and in the recruitment dynamics of P. dendritica. Results of laboratory research indicate a strong influence of temperature on the biology and physiology of P. dendritica; however, field research indicates that abundance of C. fragile may be a more significant driver of the recruitment of the sea slug than temperature. A mathematical model was reconciled the effects of temperature and algal abundance on larval recruitment to determine if recruitment P. dendritica can be accurately predicted from the two measurements. Calibration and testing of the model indicated that temperature was largely responsible for the individual reproductive output and duration of larval development, while the abundance of C. fragile likely has a greater influence on the timing of maximum recruitment each year.