You are here:
Vulnerability of Rhode Island Salt Marshes to Sea Level Rise and Poor Water Quality
Citation:
Watson, Elizabeth B. Vulnerability of Rhode Island Salt Marshes to Sea Level Rise and Poor Water Quality. Narragansett Bay Journal. Narragansett Bay Estuary Program, PROVIDENCE, RI, (28):4-5, (2014).
Impact/Purpose:
The purpose of this article is to communicate with the public about how sea level rise is affecting coastal marshes.
Description:
Across the northeastern Unites States, salt marshes are losing ground. Edges are eroding, tidal channel networks are expanding, and new ponds are forming and expanding within salt marshes. This leaves shorelines - and in some cases houses - more vulnerable to nor'easters and tropical storms. This salt marsh dieback is primarily a consequence of accelerating rates of sea level rise, which is occurring broadly across the Northeast. However, several lines of evidence suggest poor water quality, changes in ecosystem structure, altered hydrology and sediment transport, fungal pathogens, and introduction of non-native species may also be contributing to die-back. In Rhode Island, researchers from the Environmental Protection Agency’s Atlantic Ecology Division are collaborating with University of Rhode Island scientists and students, the Narragansett Bay National Estuarine Research Reserve, and Save the Bay in order to better understand the consequences of sea level rise combined with poor water quality to coastal marsh health and long-term marsh survival. Narragansett Bay lends itself to such an effort, as its north to south nutrient input gradient comprises a natural experiment to examine the role of eutrophication on marsh health. Eutrophication refers to the response of aquatic ecosystems to nitrogen and phosphorus, through fertilizers and sewage inputs. Narragansett Bay provides a window into how salt marshes function and survive across a range of coastal development impacts. Over the summers of 2011 and 2012, EPA researchers conducted a series of experiments, where the principal salt marsh plant (Spartina alterniflora) was grown under various flooding and nutrient availability scenarios in both laboratory and field experiments. Marsh loss rates for many Rhode Island marshes were calculated using historic and current air photos. Studies have also included several novel tools such as imaging salt marsh peat using computed tomography (CT) scans and measuring soil gas flux rates using field analyzers. Data from these experiments show that substantial losses of marsh vegetation in Rhode Island have occurred between the 1970s and today, through shoreline and channel erosion, and the formation of dieback areas. Higher loss rates have been found for marshes that are lower in elevation, implicating increased inundation related to accelerated sea level rise as a driver of marsh loss. Additionally, inundation experiments suggest that plant belowground growth is tied closely to flooding, with higher flooding rates associated with poor growth. Our results suggest that increased inundation acts as a destabilizing force in Northeastern marshes, causing declines in plant productivity, lower organic matter accumulation rates, and additional stress. The results of these experiments will be published in a forthcoming issue of the journal Climatic Change.
