Hydrodynamic triggers to larval oyster dive responses

Published work on this topic:

Wheeler JD, Helfrich KR, Anderson EJ, Mullineaux LS (2015). Isolating the hydrodynamic triggers of the dive response in eastern oyster larvae. Limnology and Oceanography 60: 1332-1343.

Wheeler JD, Helfrich KR, Anderson EJ, McGann B, Staats P, Wargula AE, Wilt K, Mullineaux LS (2013). Upward swimming of competent oyster larvae (Crassostrea virginica) persists in highly turbulent flow as detected by PIV flow subtraction. Marine Ecology Progress Series 488: 171 −185.

Larval oysters are moderately strong swimmers, for invertebrates, and exhibit a range of interesting swimming behaviors which include maintenance of vertical position, upward helical swimming, and diving. I am interested primarily in downward swimming behaviors of competent-to-settle pediveliger larvae: downward swimming may indicate active attempts by larvae to approach benthic settlement habitats. Larvae descend in the water column via active downward swimming, sinking, or “diving”: a flick and retraction of the ciliated velum to propel a transient downward acceleration. Diving may play an important role in active settlement, since diving larvae move rapidly downward in the water column.

One objective of my research is to determine potential hydrodynamic triggers to this diving behaviour by observing larval oysters in a grid-stirred turbulence tank. Quantifying larval behaviour in a turbulent flow field involves the simultaneous tracking of larvae and the surrounding flow, to fully decouple swimming from advection. We visualize flow fields by seeding the turbulence tank with tiny passive particles and use particle image velocimetry (PIV) to correlate particle position from frame to frame, by which we estimate a fine resolution flow field in time and space which larvae experience. Using this local flow data, we can identify how larval responses, such as dives, are related to turbulent field properties which they experience.