Cascading effects of climate change and UV envirotoxins on the nutritional quality of the food base in marine ecosystems

With the current focus on ecosystem-based approaches to the management of marine resources establishing the effects of various environmental variables on the flow of energy through marine ecosystems is essential, and strongly prioritized. The research pro posed here uses two variables (temperature and UV radiation) ? both of which are strongly influenced by human activity ? in order to evaluate the flow of essential nutrients through the marine food web and to assess possible impac on higher trophic levels . The polunsaturated fatty acids (PUFAs) contained in marine microalgae are passed on to fishes through herbivorous zooplankton. These PUFAs are essential for the survival and growth of young fishes. Exposure to UV radiation decreases the PUFA content of microalgae, thereby reducing the levels of these dietary components that are available to be taken up by fishes. Such a reduction in the nutritional quality of the food base may have significant implications for the overall productivity and health of mari ne ecosystems. Among the different UV-sunscreens, the mycosporine-like amino acids (MAAs) are the most important ecologically. The biogenesis of MAAs is present in bacteria, fungi and algae, but is absent in metazoans. Marine metazoans, however, can obtai n MAAs from their food. Very little information is available on the transfer of MAAs from primary producers-to-herbivores-to primary consumers (e.g. ichthyoplankton), as well as on how MAA concentrations relate to the survivorship of these organisms when exposed to UV radiation. We propose to test the hypothesis that a UV-induced alteration in the FA and/or MAA content of the food base is transmitted up through the food web to fish larvae, negatively affecting their growth and survival. We will also evalu ate whether increases in temperature exacerbate this effect.