Meeting Abstract
P3.110 Sunday, Jan. 6 Effects of flow on growth of juvenile colonial ascidians, Botrylloides violceus and Botryllus schlosseri LEE, H.R.*; SPAULDING, J.D.; COHEN, C.S.; Swarthmore College, Romberg Tiburon Center, San Francisco State University; Romberg Tiburon Center, San Francisco State University ; Romberg Tiburon Center, San Francisco State University hlee3@swarthmore.edu
The flow environment is critical to the growth and survival of sessile marine filter feeders. Juvenile colonial ascidians may face particular challenges in filter feeding due to their narrow siphons. Growth rates and zooid increase of newly settled Botryllus schlosseri and Botrylloides violaceus were measured under different flow rates in both the field and the lab. In the lab, juvenile ascidians were raised from oozooids in a flume, while in the field new recruits were collected on settling plates. Contrary to expectation, there was no correlation between flow rates and growth rates of B. violaceus in the field, possibly due to the small range of variation among flow rates tested in this study. In the lab, B. schlosseri juveniles had higher relative growth rates than B. violaceus. Under low flow, B. violaceus grew faster in terms of overall size while B. schlosseri grew faster in terms of number of buds. B. violaceus had low growth rates and high mortality rates under high flow rates. It is possible B. schlosseri has a unique niche in high flow environments where B. violaceus does not succeed. A census of colonial ascidians in marinas with varying flow environments may provide more insight into the interspecies dynamics between B. schlosseri and B. violaceus. Measuring growth rates in the lab under flow rates between 3 cm/sec and 9 cm/sec would help with understanding flow rates that promote maximal growth, although this may also vary with food concentration. These findings may be applied to tunicate lab rearing experiments as well as towards a more basic understanding of the conditions favoring the survival and growth of juvenile sessile invertebrates with internal filter-feeding mechanisms.
