Meeting Abstract

S7-2.2  Saturday, Jan. 5  Living where the flow is right: How flow affects feeding in bryozoans. PRATT, M. C.; Mt. Holyoke College marneypratt@gmail.edu

Bryozoans are suspension feeding colonial animals that remain attached to the substratum or other surfaces. Therefore, bryozoans rely on water flow to supply nutrients, eliminate wastes, and disperse gametes and larvae. The effect of water flow on food capture is especially important because energy acquisition is essential to perform most other life processes, and therefore feeding performance may be a good proxy for fitness. How well a bryozoan can feed in a particular flow regime could help determine the distribution and abundance of that bryozoan. I tested how flow velocity affects feeding rate in four species of bryozoans in the laboratory and how these species perform in different flow regimes in the field. I found that one species, Membranipora membranacea, had a higher ingestion rate than the other three species at all flow velocities tested. Membranipora also had a higher ingestion rate at intermediate velocities, while velocity did not have as strong an effect on ingestion rate in the other three species. As predicted from the feeding experiments, all four species had greater abundance, attained a larger size, grew faster, and survived longer in flow regimes where feeding is higher. Also as predicted, Membranipora had greater abundance, attained a larger size, grew faster, and survived longer than the other three species in slower and faster flow regimes in the field. Understanding how flow affects feeding can help us predict the distribution and abundance of bryozoans in the field. Because especially efficient filterers like Membranipora can grow faster and have higher survival in a wide range of flow habitats, this species may be able to outcompete many other species and make it a potentially effective invasive species as has been seen in the Gulf of Maine.