The detrimental effects of elevated intensities of mid-UV radiation (UVB), a result of stratospheric ozone depletion during the austral spring, on the primary producers of the Antarctic marine ecosystem have been well documented. Here we report that natural populations of Antarctic zooplankton also sustain significant DNA damage [measured as cyclobutane pyrimidine dimers (CPDs)] during periods of increased UVB f lux. This is the first direct evidence that increased solar UVB may result in damage to marine organisms other than primary producers in Antarctica. The extent of DNA damage in pelagic icefish eggs correlated with daily incident UVB irradiance, ref lecting the difference between acquisition and repair of CPDs. Patterns of DNA damage in fish larvae did not correlate with daily UVB f lux, possibly due to different depth distributions and͞or different capacities for DNA repair. Clearance of CPDs by Antarctic fish and krill was mediated primarily by the photoenzymatic repair system. Although repair rates were large for all species evaluated, they were apparently inadequate to prevent the transient accumulation of substantial CPD burdens. The capacity for DNA repair in Antarctic organisms was highest in those species whose early life history stages occupy the water column during periods of ozone depletion (austral spring) and lowest in fish species whose eggs and larvae are abundant during winter. Although the potential reduction in fitness of Antarctic zooplankton resulting from DNA damage is unknown, we suggest that increased solar UV may reduce recruitment and adversely affect trophic transfer of productivity by affecting heterotrophic species as well as primary producers.

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Laboratory experiments were conducted on juvenile summer flounder Paralichthys dentatus (25–80 mm total length) from Delaware and North Carolina nurseries to compare their responses to temperature and to ration limitation. Ad libitum feeding rates, maximum growth rates, and growth efficiency were measured at temperatures from 2 to 20°C. Although ad libitum feeding rates did not differ between fish from the two locations, North Carolina juveniles had higher maximum growth rates and growth efficiencies than Delaware juveniles between 6 and 18°C. Growth rates and changes in biochemical condition were also measured for different rations at temperatures that persist during the months following settlement (10–16°C). Survival was high (>98%) after 10–14 d of starvation and suboptimal rations at 10–16°C, but growth rates were highly dependent on feeding rates. Maintenance rations remained constant between 10 and 16°C, but scope for growth increased with temperature, Scope for growth of North Carolina juveniles was higher than that of Delaware juveniles between 10 and 16°C, and growth rates of North Carolina juveniles were more sensitive to changes in ration. Changes in RNA:DNA ratios over the course of each 10–14‐d experiment depended primarily on ration; ratios increased as temperature and feeding rate increased. Low‐temperature tolerance (at 1–4°C) of juveniles was highly dependent on the rate of temperature decline, not on feeding rate, Time until 50% mortality (LT50) varied from 14 d (–1.3°C/d, fast rate) to 31 d (–0.3°C/d, slow rate); North Carolina juveniles were significantly less tolerant of decreasing temperatures than were Delaware juveniles.