September 1, 1999-August 31, 2003
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Physical factors such as light, temperature and nutrient availability are known to limit marine productivity and play an important role in determining species distribution and community structure. Most understanding of the role of physical factors is based on studies with a single variable with other conditions being optimized for growth. Consequently, little information is available on physiological responses to the natural environment where several physical factors may be suboptimal. The ability to understand the constraints on marine productivity requires not only an understanding of potential synergistic or antagonistic interactions but also an analysis of their effects on algae with different ecological strategies. This investigation will examine the response of marine red macroalgae to simultaneous nitrogen limitation and ultraviolet radiation stress. Both factors are known to be important determinants of marine primary productivity and they frequently co-occur. This is true not only of the tropics, but also in cold- temperate oceans such as the Gulf of Maine. Red macroalgae were selected for this research because they provide the opportunity to study interactions between UV and nitrogen limitation in a group of algae with similar physiological and morphological characteristics but with well-defined differences in UV-tolerance and well-characterized contents of mycosporine-like amino acids. Furthermore, in contrast to phytoplankton, benthic macroalgae experience a more predictable light climate and are relatively long-lived, exposing individuals to a wider range of environmental conditions. The red algae studied from the Gulf of Maine will include Porphyra umbilicalis, Chondrus crispus, Membranoptera alata and Phycodry rubens. These species range from UV-tolerant intertidal and shallow sublittoral species to UV-susceptible species from the deeper sublittoral. The investigators anticipate that the costs and benefits of UV-tolerance and the impact of nitrogen limitation will vary between UV-tolerant and UV-susceptible species. The research will focus on the effect of nitrogen metabolism (limited or replete) on (a) short and long-term effects of UV-stress (e.g., short-tem inhibition of photosynthesis, lipid peroxidation, and growth), (b) UV-photoprotection including contents of sunscreens such as mycosporine-like amino acids (MAAs), antioxidants such as ascorbate, gluathione and tocopherols, and enzymes of reactive oxygen metabolism such as catalase, superoxide dismutase and ascorbate peroxidase, and (c) ability to recover from UV-stress (e.g., the role of protein synthesis in recovery). The research will also examine the effect of UV-stress on nitrogen metabolism (e.g., nitrogen content and rates of uptake and assimilation). The research will involve measurements on field-collected material, laboratory experiments under controlled conditions and outdoor experiments in flowing seawater and natural radiation manipulated by a variety of UV and photosynthetically active radiation (PAR)-filters. The research will substantially contribute to an understanding of the effect of UV and inorganic nitrogen availability on marine productivity and, in particular, elucidate the importance of interactions between these factors. The research involves collaboration between faculty at an undergraduate teaching institution (Westfield State College, MA) and a Land and Sea Grant research University (University of Maine). In addition to graduate education, the project has a substantial research experience for undergraduate component, providing undergraduates from Westfield State College with the opportunity to become involved in research.
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Shick, J. Malcolm and Grobe, Carl, "Collaborative Reseach: Nitrogen Limitation and Ultraviolet Stress in Marine Macroalgae" (2005). University of Maine Office of Research and Sponsored Programs: Grant Reports. 105.