Abstract

Marine phytoplankton in the world's oceans plays a major role in the global carbon cycle.These microorganisms fix atmospheric CO2 which is partly exported to the deep sea. In the future, marine phytoplankton may play an important role in determining the magnitude of the oceanic sink of anthropogenic CO2. However,the depletion of stratospheric ozone and subsequent increase in ultraviolet (UV) irradiance at the sea surface has been shown to affect the performance of phytoplankton negatively.In this report, model calculations are presented of the potential UV effect on global primary production for recent ozone layer conditions compared to those of 18 years ago. During the appearance of the ozone hole above the Antarctic (September-December), the calculated decrease in dept-integrated primary production over the past 18 years amounts to 2.2 percent.In the Arctic, a decrease of up to 0.6 percent is estimated during the period March-May. The ozone related change in total global export production over the past decades was no more then marginal. Locally, however, Negative effects can be significant. The maximum change in export production appeared in November in the Southern Ocean it was lowered with 1.2% for this month. Due to many uncertainties, large errors may occur in these kind of assessments. For instance, more information is needed about the adaptation of algal species to UV radiation, their differential sensitivity to UV radiation, and consequent changes in the entire ecosystem. Further, more insight has to be gained in the role and functioning of the biological pump, both on a spatial and temporal scale. Only then, future developments can be predicted with some certainty.