Effects of Increased UV and Sea Ice Retreat on Antarctic Marine Larvae

Increased UV radiation caused by a decrease in the levels of stratospheric ozone has the potential to harm marine organisms. The sharpest decrease in ozone can be found over the Antarctic continent during the austral spring. Invertebrates may be particularly susceptible to the effects of increased UV-R because most have a planktonic stage in which their embryos and larvae live in surface waters. Marine invertebrates in the Antarctic are likely to be affected to a greater extent than those in tropical and temperate biomes as there is not only a greater amount of UV-R coming through the atmosphere in these latitudes, but the larval stages are in the water column for a greater period, have slower metabolism, and a stenothermal physiology. These factors have the potential to affect recruitment of new individuals into marine populations. One of the major forms of damage is the creation of cyclobutane pyrimidine dimers (CPD) in DNA. Previous work has shown that photolyase, a protein that repairs UV-R induced CPDs on DNA, is present in echinoderm larvae, and increases the repair rates of UV-R damaged DNA. During the austral spring of 2007 laboratory and field experiments were carried out on Sterechinus. neumayeri at Cape Evans on Ross Island, Antarctica, and at the ice edge north of Cape Royds. The effects of depth, and consequently dose of UV-R on expression of photolyase was determined. We established that photolyase can be induced by increased UV-R in S. neumayeri, and consequently is dependent on depth of the water column. There also appears to be an upper limit, where increases in UV-R do not induce further photolyase expression. With predictions that the annual ozone hole will be present for at least another 50 years and the possible retreat of sea ice, ambient levels of UV-R in the marine environment of Antarctica will increase. The results of this research suggest that S. neumayeri can compensate for increased DNA damage to UV-R at relatively low levels. But if the levels increase to those found under thin sea ice or open water, the rate of damage might be greater than the rate of repair.