PREP Publications

Abstract

Eelgrass (Zostera marina) is essential to estuarine ecology because it filters nutrients and suspended particles from water, stabilizes sediments, provides food for wintering waterfowl, and provides habitat for juvenile fish and shellfish, as well as being the basis of an important estuarine food web. Healthy eelgrass both depends on and contributes to good water quality. The UNH Seagrass Ecology Lab, has mapped the distribution of eelgrass every year from 1986 through 2009 in the Great Bay. The entire Great Bay Estuary (Great Bay, Little Bay, tidal tributaries, Piscataqua River, Little Harbor, and Portsmouth Harbor) was mapped by these researchers in 1996 and from 1999 through 2009. In 1989, there was a dramatic crash of the eelgrass beds in the Great Bay itself down to 300 acres (15% of normal levels). The cause of this crash was an infestation of a slime mold, Labryrinthula zosterae, commonly called “wasting disease” (Muehlstein et al., 1991). The eelgrass beds recovered following the infestation but have experienced a slow, steady decline since their initial recovery. Between 1990 and 2008, the eelgrass acreage in Great Bay and Little Bay has declined by 37 and 87 percent, respectively. In 2007 and 2008, no eelgrass was found in Little Bay and the Piscataqua River; in Portsmouth Harbor, eelgrass cover has also been declining. All of the eelgrass in the Winnicut River was lost between 1990 and 2008. Eelgrass seedlings and young plants have been occasionally detected at low levels in the other tributaries to Great Bay and Little Bay. However, historical maps indicate that eelgrass formerly existed in these rivers (DES, 2008). The Piscataqua Region Estuaries Partnership (PREP) coordinates environmental monitoring in the Great Bay Estuary and Hampton-Seabrook Harbor. Maps of eelgrass distribution in the Great Bay Estuary provide useful information on water quality and critical habitats within the estuary and the environmental quality of the system. The PREP has developed a series of environmental indicators to track trends and to evaluate progress toward management goals. Eelgrass distribution is part of the PREP Monitoring Plan to gather data on these indicators (PREP, 2008). PREP intends to contract with UNH-JEL to continue this monitoring program in 2010 through 2014 to ensure that the record of annual eelgrass assessments will be unbroken. The methods used in this study do not include georectified imagery due to cost constraints. PREP intends to collect georectified imagery approximately every 10 years. Eelgrass was mapped using georectified imagery in 1996 and 2007. After this QAPP expires, PREP intends to establish a new contract with UNH-JEL to collect georectified imagery in 2015 using the protocols from NOAA C-CAP (NOAA, 1995) or its successor guidance. Maps of eelgrass in the estuary will be used by PREP, the NH Department of Environmental Services, UNH, and other coastal resource managers to evaluate trends in eelgrass populations over time.

Publication Date

7-13-2010

Publisher

Piscataqua Region Estuaries Partnership

Document Type

Report

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