Distribution of Invertebrate Larvae in Relation to Physical Structure and UVB-light Intensity in the Water Column off Anvers Island, Antarctic Peninsula

The antarctic coastal zone is inhabited by a diverse and abundant fauna of benthic (bottom-dwelling) invertebrates. Benthic adults are largely shielded from UV-B damage by the overlying water column. Many also possess morphological, biochemical, and behavioral defenses, including shells and UV-absorbing compounds. Many antarctic invertebrates reproduce by releasing gametes freely into the water (Pearse, McClintock and Bosch 1991). Their embryonic and larval life stages are spent adrift in the water column. Embryos and larvae that are dispersed into surface waters may be exposed to potentially damaging levels of UV-B light, particularly during periods of ozone depletion. During the spring and summer in 1996-1997 and 1997-1998 at Palmer Station (64° 46’ S, 64° 04’ W), our group studied the effects of UV-B on the eggs, embryos, and larvae of benthic marine invertebrates. One primary objective of this work was to determine the vertical and seasonal distribution of larvae, relative to the penetration of UV-B and to the physical structure (density, salinity, temperature) of the water column. Initial results from this component of our study are presented here.