NETN Monitoring Salt Marsh Vegetation (2010-2013)

Northeast Temperate Network

Track the status and trends of the ecological health of salt marsh and estuarine areas in coastal NETN parks. NETN identified the biological integrity of intertidal marsh habitats as a high-priority vital sign for Acadia National Park, Boston Harbor Islands National Recreation Area, and Saugus Ironworks Iron Works National Historic Site. The protocols will be closely based on the Northeast Coastal and Barrier Network's monitoring programs and will provide details on the development and implementation of a robust and rigorous tidal marsh vegetation monitoring program for marshes of management interest in these parks. Salt marsh vegetation species diversity and percent cover will be measured using a fully randomized 1 meter-squared quadrat sampling approach on a three-year repeating sampling cycle. A non-parametric multivariate community analysis will be conducted to assess changes in salt marsh community structure within individual marshes over time. The mean elevation of salt marsh surfaces must increase to keep pace with the annual rise in sea level and subsidence of salt marsh organic substrates. If the sedimentation rates in a salt marsh do not equal or exceed the net loss in elevation due to the steady increase in sea level and salt marsh subsidence, it will “drown”. When a salt marsh “drowns”, the surface of the marsh becomes sub-tidal which can cause drastic habitat changes such as the conversion of vegetated salt marsh to unvegetated mud flat. Understanding changes in relative salt marsh elevation is important for interpreting changes in salt marsh vegetation communities. This project is also part of a worldwide effort to monitor sea level rise with sediment erosion tables (SETs) and cryogenic coring devices. For more information on salt marsh elevation monitoring, see https://irma.nps.gov/DataStore/Reference/Profile/2318476. Salt marshes, particularly in the U.S. northeast, serve as critical habitat for forage species as well, which in turn provide an important food resource for other adult fish species and coastal bird populations. Salt marsh ecosystems also perform a variety of ecologically important chemical functions including organic and inorganic waste retention, transformation and removal; a significant role in global carbon, nitrogen, and sulfur biogeochemical cycling (with important ramifications to climate change and coastal eutrophication); sediment entrapment; and buffering of uplands from storm and wave impacts, erosion, and coastal flooding. Nutrient enrichment of the coastal zone is a worldwide consequence of human population growth. The population density of Northeast coastal fringe is more than double that of any other region of the country, and it continues to grow. The consequent residential, agricultural, and urban expansion will result in a continued increase in anthropogenic nutrient loading to the region’s coastal zone. Estuaries can generally assimilate some degree of enrichment without major ecological ramifications, but excessive nutrient inputs typically lead to dense blooms of phytoplankton and fast-growing macroalgae, loss of seagrasses, and decreased oxygen availability in sediments and bottom waters. Cascading effects may include changes in the species composition and abundance of invertebrates, decline in fish and wildlife habitat value, and the collapse of commercially harvestable fin- and shellfish stocks.

NETN Monitoring Salt Marsh Vegetation (2010-2013)

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