Interacting effects of copper, nitrogen and ultraviolet radiation on the physiology of three south Pacific kelps

Coastal ecosystems currently face multiple environmental impacts, such as nutrient loading, chemical contamination and enhanced ultraviolet (UV) radiation. Large kelps dominate many rocky shores worldwide and their capacity to handle environmental stress could have major consequences for these systems. The impacts of the interaction of copper (150 µg L–1), nitrate (350 µM) and short-term UV radiation on the physiological responses (photosynthetic activity, contents and anti-oxidant activity of phlorotannins) of three large kelps, Macrocystis pyrifera, Lessonia nigrescens and Durvillaea antarctica, from the coast of Chile were studied during a 2-week laboratory exposure. Macrocystis accumulated the most copper in its tissues, which decreased under nitrate-enriched conditions. Inhibition of photosynthetic activity by copper was observed in all three species (11–30%) after 12 days of incubation, with the strongest response in Lessonia. Nitrate enrichment mitigated the inhibitory effect of copper on photosynthesis in all three species. Soluble phlorotannin content decreased under copper and/or nitrate-enriched conditions with additional short-term UV exposure, particularly in Durvillaea, in which the strongest increase in the anti-oxidant activity of soluble phlorotannins was observed. Overall, the observed physiological responses reflect differences in morpho-functional processes and habitat characteristics of the three kelps and the importance of the interactions of multiple environmental factors.