Water Resources Research Act Program

Details for Project ID 2015MA438B

Influence of nutrients on Microcystis blooms in the Charles River watershed

Institute: Massachuseits
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-29
Total Federal Funds: $5,000 Total Non-Federal Funds: $10,000

Principal Investigators: Pia Moisander

Abstract: This study addresses the issue of harmful algal blooms in Massachusetts freshwaters, with the focus on the Charles River watershed. Cyanobacteria are microscopic organisms that at times form massive accumulations in freshwater lakes, reservoirs, and rivers. Mass accumulations of cyanobacteria (CyanoHABs) occurring in many Massachusetts freshwaters are common across the country and the world. CyanoHABs often produce toxins (secondary metabolites) that can be harmful for the ecosystem and human health. Such toxins have been found in drinking water sources, thus managing the blooms and understanding the causative factors in each system is essential. CyanoHABs may also contribute to oxygen depletion in the ecosystem, and due to the additional negative consequences such as the bloom appearance, odor problems and slime formation, they overall reduce the recreational value of water bodies. Toxic cyanobacteria are considered emerging contaminants and a high priority issue by Massachusetts Department of Environmental Protection. This study directly addresses remaining key questions on understanding and managing CyanoHABs in Massachusetts. The study investigates the relative importance of major nutrients, nitrogen and phosphorus, on CyanoHAB formation during the main bloom season in the Charles River, where the cyanobacterium Microcystis aeruginosa has formed blooms over the past years. In temperate waters such as waters in Massachusetts, the blooms typically form during the warmest summer months, when the waters are warm and less mixed, yet sufficient nutrients are available. The relationship of nutrients and cyanobacteria is not straightforward, however, as numerous other factors influence the relative fitness of different phytoplankton species, and ultimately, whether one or more species becomes dominant, forming a ‘bloom’. For cyanobacteria, taxon-specific differences exist in nutrient and other growth preferences that determine which species has the best competitive strength in each system. In this study, the relative importance of nitrogen and phosphorus on growth of Microcystis in the Charles River watershed will be investigated. Water will be sampled monthly from two sites along the river for bioassay experiments during the main summer growth season from May to September. Samples will be collected from sites based on monitoring samples obtained from collaborative monitoring programs, and experiments conducted under conditions where nitrogen or phosphorus, or both nutrients are added to the incubations. Growth responses in Microcystis and overall phytoplankton are recorded, and influence of nutrients on presence of Microcystin, the main toxin produced by Microcystis, will be measured. With the direct incubation experiments conducted during the summer season at different sites, we will be able to address potential spatio-temporal variability in CyanoHAB nutrient limitation. This study will take advantage of existing monitoring programs in the Charles River, including the Charles River Watershed Association volunteer network. The results will communicated to MassDEP and CRWA, to be incorporated in larger scale planning of nutrient management in the system. This study will be conducted with the participation of several undergraduate students at the UMass Dartmouth.