KURZE, E/M*; KERSHNER, J; ADAMS, N/L; California Polytechnic State University, San Luis Obispo: In situ solar ultraviolet radiation delays development of sea urchin embryos Strongylocentrotus purpuratus

Ultraviolet radiation (UVR) causes delays in cell division and abnormal development of sea urchin embryos. We examined effects of solar UVR on development of embryos of the purple sea urchin Strongylocentrotus purpuratus.We exposed embryos to natural sunlight at two ocean depths (surface and 0.5 m) to test effects of UVR in-situ at Cal Poly’s Center for Coastal Marine Sciences pier in San Luis Obispo Bay, California. Freshly fertilized embryos were placed in Whirl-pak bags and exposed to or protected from natural sunlight in seawater at both depths for 30 mins. After exposure, embryos were sampled and fixed every 10 mins until all had reached the first cell division. The percentage of embryos that had divided was determined for each sample and the percentage of delay experienced was calculated for each sample ((time (t) for 50% of UV-irradiated embryos to divide-t for 50% of control embryos to divide)/ t for 50% of control embryos to divide). In surface waters, UVR levels were highest and caused a substantial delay in cleavage (21.43% � 5.40). UVR levels were much lower at a depth of 0.5 m, and delays in division were significantly lower (P=0.035) than those from embryos irradiated in surface waters, but still detectable (9.74% � 5.01). This indicates that even at 0.5 meters, where UVR levels are much lower than at the surface, embryonic development is still negatively affected by natural UVR. In addition, there was a significant relationship between amount of damage, as measured by percentage cleavage delay, and UVB dose (P=0.026), but not between the amount of damage and UVA dose (P=0.052). Further exploration of the relationship between penetration of UVR into the ocean and damage to embryos are needed to more fully understand the effects of natural UVR on marine organisms.