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EVALUATION OF THE HEALTH OF EELGRASS
(Zostera marina L.) BEDS
WITHIN THE MARYLAND COASTAL BAYS
Technical Report NPS/NER/NRTR—2007/014
Lora Harris, Stephen Granger, and Scot t Nixon
University of Rhode Island
Graduate School of Oceanography
South Ferry Road
Narragansett, RI, 02882
March 2007
U.S. Department of the Interior
National Park Service
Northeast Region
Philadelphia, Pennsylvania
_______________________________
Introduction
Unlike many
shallow areas along the U.S. East coast that have experienced a decline
of seagrass habitat in recent decades, yearly overflights of Chicoteague
Bay (MD/VA) conducted by the Virginia Institute of Marine Science have
documented an impressive colonization and expansion of Zostera marina
habitat since the late 1980’s. The area covered by submerged aquatic
vegetation (SAV) in this system more than tripled between 1987 and 2001
(Fig 1). However, despite the overall positive trend observed in seagrass
coverage within Chincoteague Bay, anecdotal reports from commercial
fishermen and field observations taken during routine water quality
monitoring by National Park Service scientists indicate that some beds
in the central region of Chincoteague Bay have experienced losses. Field
observations indicated that impacted beds display large patches with
a complete loss of plants, and large numbers of dead rhizomes in the
sediment.
In addition, there are growing concerns that water quality in the northern
Maryland/Virginia Coastal Bays complex has been declining in recent
years and that nuisance macroalgae are growing more widespread and persistent.
An increase in nutrient inputs as a result of development pressure in
and around Ocean City, Maryland has been identified as a possible contributing
factor. As a consequence of these conflicting reports concerning seagrass
health (overall health vs local die-back) and water quality in Chincoteague
Bay, we field-tested a number of seagrass growth parameters that might
be interpreted as metrics of eelgrass health and of anthropogenic nitrogen
enrichment at several locations in the Maryland Coastal Bays during
the summer of 2001.
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