Meeting Abstract

96.1  Sunday, Jan. 6  Shake, Settle and Hold: Turbulent shear stimulates settlement in sea urchin larvae HODIN, J.*; FERNER, M.C.*; GAYLORD, B.; Hopkins Marine Station, Stanford Univ., Pacific Grove, CA USA; Romberg Tiburon Center, San Francisco State Univ., CA USA; Bodega Marine Laboratory, Univ. of California at Davis USA seastar@stanford.edu, mferner@sfsu.edu

For nearshore invertebrates with dispersing larvae, the greatest set of challenges facing such larvae is to return to and recognize suitable nearshore habitat, to successfully settle there, and to do so at a developmental stage that maximizes the likelihood of survival to reproduction. Much progress has been made identifying environmental cues that larvae use to identify settlement sites; such cues typically operate at or around the scale of a larva. Is it possible that larvae are also sensitive to habitat-scale cues –on the order of meters to kilometers– that would indicate approach to potentially rare settlement sites? Here we show for the first time that marine invertebrate larvae increase their settlement rate following exposure to intense turbulent shear characteristic of high-energy nearshore habitats. We exposed purple urchin larvae (Strongylocentrotus purpuratus) to turbulent shear spanning the range found in open ocean conditions to levels they would experience when approaching wave-swept rocky shores. We then immediately subjected the larvae to a settlement test using elevated KCl in seawater. We found that exposure to strong turbulence causes previously refractory, pre-competent larvae to respond to KCl and settle. In other words, turbulent shear appears to trigger these larvae to enter the competent state, thereby allowing them to respond to chemical or other surface cues if they arrive in a suitable area, and then complete settlement and metamorphosis. We discuss a planned comparative approach to further explore turbulence as a habitat indicator, as well as functional tests of settlement timing on juvenile performance.