Publication Date
4-8-2008
Abstract
Eelgrass (Zostera marina L.) meadows play an important role in coastal environments by stabilizing sediments, sheltering and nourishing fish, shellfish and wildlife, and preserving water quality while filtering sediments and recycling nutrients. Because they grow in nearshore environments, eelgrass beds are vulnerable to coastal development and since they are responsive to perturbations they can be used as an indicator of ecosystem health. In order to study the correlation between wastewater discharges of nitrogen, degrading water quality and eelgrass declines in southeastern MA, MADEP undertook a long-term statewide mapping program (commencing in 1994) to evaluate the status and trend of eelgrass abundance. Within MADEP the eelgrass mapping project is being closely coordinated with the Massachusetts Estuaries Project (MEP), a multi-year $12 million collaboration among coastal communities designed to address the impact of excess nutrient loading in Massachusetts coastal watersheds. MADEP is using remote sensing techniques and ground truthing to develop a database of seagrass distribution and abundance and has 12 years of mapping data showing that eelgrass has declined in a majority of 30 estuaries inventoried over a period of 10-12 years. Rates of decline average 3%/y with some declines as fast as 5-8%/y. During the 12 year period eelgrass has completely disappeared from some embayments. These declines are accompanied by a loss of important positive naturally occurring feedback loops for maintaining good water quality which led to changes in the bio-physical state of these embayments. MADEP has also been in the forefront of water quality investigations by evaluating the utility of incorporating an optical water quality model into future eelgrass conservation and restoration programs. The optical water quality model is being developed to link eelgrass declines with factors such as chlorophyll, suspended material and dissolved organic matter that influence water transparency and may be responsive to management actions.