Meeting Abstract
Sea urchin adults have relatively diverse diets of benthic macroalgae, whereas larvae are thought to feed primarily on unicellular phytoplankton. Although recent research demonstrates that kelp detritus can serve as a high-quality food source, it is not entirely understood what role various other macroalgae may play in the diets of larvae. Our goal in this study was to determine if other benthic seaweeds found in adult urchin habitats could provide for similar larval growth, as does kelp. In a pilot study, we determined that larvae of the sea urchin, Arbacia punctulata, would consume lab-made detritus of the common intertidal seaweeds Ulva intestinalis and U. lactuca, Laminaria agardhii (kelp), Fucus sp., and Chondrus crispus, but preferred kelp and Fucus. Next, we reared A. punctulata larvae under four replicated food treatments: high and low concentrations of the unicellular microalga Isochrysis galbana (a standard proxy for phytoplankton), and separate seaweed slurries made from kelp and Fucus. We found that A. punctulata larvae can grow while consuming kelp and Fucus detritus. However, the larvae reared under the Fucus and kelp diets did not grow as extensively within 10 days as larvae provided with a high, satiation diet of Isochrysis. Larvae consuming Isochrysis grew to the 8-arm stage within 10 days whereas the majority of the larvae fed Fucus and kelp were still at the 4-arm stage. We are continuing data analysis of this experiment as well as a second experiment that replicated the conditions of the first and will present comprehensive results from both at the SICB Annual Meeting. This project provides an avenue for further research into the diets of sea urchin larvae. Future related studies might examine the effects on larval growth of mixed macro- and microalgae food treatments.
