Intellectual Merit: "Green tides " or blooms of green macroalgae occur worldwide, but are most common in temperate latitudes. These blooms are extremely productive,albeit ephemeral, communities. They are often associated with eutrophication; however, a variety of abiotic and biotic factors, including competitors, light, temperature, and nutrient levels, may limit their abundance and productivity. In temperate regions, green algal blooms have been blamed for eradicating seagrass meadows and altering faunal community structure. These effects are usually associated with shading and anoxia, but increasing evidence suggests that toxins produced by some bloom-forming macroalgae directly affect co-occurring algae and invertebrates. The causes, extents, and histories of blooms of ulvoid green algae that occur in the Pacific Northwest are not as well known as in other regions. Preliminary studies suggest that blooms have the ability to alter marine community structure and diversity. Fragmentation of eelgrass meadows by ulvoid blooms has frequently been observed, and blooms can reduce shoot density. In these waters, seagrasses are critically important as habitat and as a food source for numerous ecologically important species, including fish, shellfish,c rabs, birds and mammals. Initial evidence suggests that the mechanisms by which green algal blooms in the Pacific Northwest affect co-occurring species are varied and may include both direct and indirect effects of toxins produced by the algae. The goal of this project is to study the causes and consequences of ulvoid algal blooms in the Pacific Northwest. Environmental factors associated with bloom formation will be measured by monitoring sites where blooms typically have and have not occurred in the past. Manipulative field experiments will be used to determine the effects of light and nutrients on the growth and physiology of bloom forming algae. Field measurements will be used to measure grazing rates on algae and bioassay guided fractionation methods will be used to isolate algal toxins. Toxicological assays will be used to assess the effects of toxins on macroalgae, seagrasses, invertebrates, and fish. Broader Impacts: This research will provide a better understanding of the mechanisms that initiate the formation of blooms and contribute to their persistence. This project will examine the production of toxins, a novel mechanism for the harmful effects of ulvoid blooms. Ulvoid blooms and their deleterious effects have been described previously; however, the mechanisms for the effects of these blooms have usually been attributed to their ability to smother other plants and animals or to the harmful effects of decreased oxygen concentrations that occur as the algae decompose. Preliminary experiments suggest that direct toxicity may be important and that this effect differs between ulvoid algal species. Knowledge of the species in the blooms that are most likely to cause toxic impacts and the nature of the toxins present will aid in the development of management plans by both agencies and aquaculturists. This project will provide training for graduate students at the Shannon Point Marine Center (SPMC) and undergraduates at both Seattle Pacific University (SPU)and SPMC, as well as graduate student research assistants at SPMC and undergraduate research assistants at SPU. In addition, students participating in SPMC 's Research Experiences for Undergraduates (REU) program and Minorities in Marine Science Undergraduate Program will work on the project. Two of the study sites are of particular interest to local citizens' groups. Members of these groups will be invited to assist in the research and data from the project will be shared with these groups. To further enhance understanding of macroalgal blooms, a web site will be created with general information about algal blooms, information about this project, results, and water quality data.
