August 1, 2011.
Settlement among native and invasive tunicates in fouling communities were observed at weekly intervals at the Pillar Point Harbor at Half Moon Bay, California. Our hypothesis is that because tunicates are filter feeding organisms, their settling reates will be dependant on flow rates. Settlement plates and plaster dissolution module plates (Clods) were used to quantify flow and settlement variations weekly for one summer month using high resolution field microscopy. Three genera of colonial tunicates (Botrylloides sp., Didemnum vexillum and Distaplia sp.) along with two solitary tunicates Ascidia sp., Cionia sp. and a bryozoan Watersipora sp. were quantified in the field to minimize disturbance to comulative settlement plates. Flow data was collected every 7 days from clod plates that were associated with each settlement array. Results showed no significant evidence that local measures of flow using 7 day clods were predictive of settlement rattes. However, anecdotal observations showed that the presence or absence of predators had a great impact on settlement rates. A significant decrease in settlement rate activity was observed in association with a temperature warming event and increased algal growth on plates. In summary, although variability in settlement rate was observed, it appears more related to their environmental pressures rather than flow.
Romberg Tiburon Center for Environmental Studies (RTC)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation.