Meeting Abstract

P1.52  Monday, Jan. 4  Vulnerability of embryos in benthic intertidal egg masses in New Zealand to summertime ultraviolet radiation and conditions at low tide SMITH, J.; PHILLIPS, N.E.*; Victoria Univ. Wellington, New Zealand; Victoria Univ. Wellington, New Zealand nicole.phillips@vuw.ac.nz

The Southern Hemisphere is exposed to high intensities of ultraviolet radiation (UVR) in summer due in large part to human-induced ozone loss. Few studies, however, have focused on risks to New Zealand’s intertidal marine fauna, or how UVR may interact with other stressors in this physically challenging environment. A variety of marine species deposit benthic egg masses throughout the intertidal zone, exposing developing embryos to a host of physical stresses, including UVR. Using field surveys and outdoor experiments conducted over summer, we examined the potential interactions between UVR, desiccation and tidal pool conditions on the embryonic mortality of three common molluscan species: two rocky shore pulmonate limpets (Benhamina obliquata and Siphonaria australis) and the mudflat-dwelling bubble-shell Haminoea zelandiae. For egg masses from the field, embryonic mortality was significantly higher in egg masses that had been in full sun compared to shade for all three species. For S. australis, there was also greater mortality in egg masses in tidal pools or desiccated at low tide compared to those that remained submerged in flowing seawater. For H. zelandiae desiccation increased embryonic mortality compared to those in shallow tidal pools. These results were supported by outdoor experiments, where we manipulated exposure to UVR and low tide conditions in a factorial design. Results from this study suggest that the egg masses of these three species are vulnerable to UVR, but with species-specific vulnerability to other intertidal stressors and possible interactions with UVR. Embryos of these species may be at risk of high mortality particularly during mid-summer when extreme conditions of UV intensity and high temperature coincide with low tide cycles.