Research concerning deposited sediments has uncovered adverse effects on benthic invertebrates in their ability to settle and eventually metamorphosis on available substrata. Research has focused on the recruitment and settlement of scleractinian corals, however less is known what effects sedimentation has on motile invertebrates like abalone Haliotidae, with species spanning a large geographic range where brown algae, Laminariaceae, exists. Recruitment and subsequent settlement on available hard substrate also depend on the presence of crustose coralline algae (CCA), an integral component of post-larval abalone survival that is adversely affected by increases in sedimentation. A laboratory experiment was conducted with naturally derived sediments of varying quantities and grain-size to determine metamorphosis rates among competent larvae, or those who exhibit behavior just prior to settlement. Competent larvae are classified by the duration of the veliger phase which last between 8-9 days. Field data documenting sedimentation in habitats utilized by white abalone and sympatric species found in the Southern California Bight (SCB) were measured using sediment collectors attached to benthic devices known as Baby Abalone Recruitment Traps (BART’s). To supplement current sedimentation data within the home range of H. sorenseni, a set of sediment collectors were deployed by attaching them to existing BARTs around the La Jolla stocking site. Over the course of 6 days, measurements of passive sedimentation (mm) were recorded every other day and across all stocking sites with sediment collectors installed on existing BARTs.
Results/Conclusions
The laboratory experiment revealed upright coralline algae (UPC) to have significantly higher metamorphosis rates than crustose coralline algae (CCA) (P>0.001). This result further illuminates the relationship between the successful settlement of white abalone larvae and different growth forms of coralline algae, a known settlement inducer consisting of gamma-aminobutyric acid (GABA). Larvae subjected to increasing densities of sediment had a significant negative effect on metamorphosis rates across both treatment types (P>0.03). Deploying sediment collectors in proximity to BARTs may offer a better understanding of how sedimentation can affect high rugosity structures mimicking natural habitat, however more replicates over a larger range of sites must be conducted.