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Possible Impacts of Ozone Depletion on Trophic Interactions and Biogenic Vertical Carbon Flux in the Southern Ocean,

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Among the most productive region of the Southern Ocean is the marginal ice edge zone that trails the retreating ice edge in spring and early summer. The timing of this near-surface phytoplankton bloom coincides with seasonal stratospheric ozone depletion when UV irradiance is reportedly as high as in mid-summer. Recent investigations indicate that antarctic marine phytoplankton are presently UV stressed. The extent to which increasing UV radiation diminishes the ability of phytoplankton to fix C02 andor leads to changes in their species composition is equivocal. The colonial stage in the life cycle of the alga Phaeocystis pouchetii is one of the major components of the bloom. We have found that this alga produces extracellular products which are strongly UV-B absorbing. When exposed to increasing levels of UV-B radiation, survival of antarctic colonial Phaeocystis was significantly greater than colonies of this species from temperate waters and of the single-celled stage of its life cycle which produces no UV-B-absorbing compounds. Phaeocystis is apparently a minor dietary component of Antarctic krill, Euphausia superba, and its nutritional value to crustacea is reportedly low. Phytoplankton, principally diatoms, together with fecal pellets and molted exoskeletons of grazers contribute most of the particulate carbon flux from the euphotic zone to deep water.

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This article is from 'Proceedings of the International Conference on the Role of the Polar Regions in Global Change Held in Fairbanks, Alaska on 11-15 June 990. Volume 2', AD-A253 028, p397-400. See also Volume 1, AD-A253 027.



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