Maryland Bay Grasses Decline in
Weather-related declines in
Upper Bay overshadow Mid-Bay bay grass increases
April, 2012 - Marylandís bay grasses declined for the
second year in a row, a result of extreme weather conditions in both 2010 and
2011. Bay grass coverage fell 14% from 40,053 acres in 2010 to approximately
34,461 acres in 2011. However, muddy waters from Hurricane Irene and Tropical
Storm Lee delayed, and in some cases prevented, complete mapping in several
sections of the Bay.
After several years of increase, bay grasses in the upper Bay (above Chesapeake
Bay bridge) dropped by 34% in 2011. About 13,287 acres were mapped in Marylandís
portion of the upper Bay compared to the 21,353 acres in 2010. Most of the
losses occurred on the Susquehanna Flats and the Elk and Sassafras Rivers on the
Eastern Shore. Bay grasses in this area were affected by heavy early spring
rains which created poor early season growing conditions. In late summer, both
Hurricane Irene and Tropical Storm Lee again muddied the water again for over
two months. While total acreage was lower in 2011 than 2010, the mapping in that
portion of the Bay was conducted later in the season than usual (early November)
when the plants naturally die-back. Some of the bay grass declines may have
resulted from poor growing conditions resulting from very muddy water, but later
than usual mapping also played a major factor.
Bay grasses in Maryland portion of the Middle Bay Zone, from the Chesapeake Bay
Bridge south to the state line, increased by about 12%, from 18,700 to 21,174
acres offsetting the declines in the upper Bay. These numbers are estimates,
however. Due to extremely poor water clarity in 2011, portions of the Patuxent
and Potomac Rivers, were either not mapped during the aerial survey, or only
partially mapped. In such cases, 2010 acreage values were used to estimate total
bay grass acreages for the mid Bay.
Grass beds in Eastern Bay, Choptank, Little Choptank and Honga Rivers, increased
by over 4,400 acres (139 %) in 2011. These areas are home to widgeon grass, a
type of bay grass known for large annual fluctuations. The expansion of widgeon
grass in the mid-Bay most likely resulted from lower than normal salinities,
which allowed many more seeds to germinate, and also good mid-summer growing
conditions as confirmed by State of Maryland monitoring.
Despite the widgeon grass increases, there was some bay grass loss in the
mid-Bay (Tangier and Pocomoke Sounds and in the Manokin and Big Annemessex
Rivers). These areas are dominated by eelgrass, a type of bay grass still
recovering from a heat-related die-off in 2005. These declines resulted from
higher than normal water temperatures in summer of 2010 and 2011, along with
long-term declining water clarity.
The full impact of Hurricane Irene and Tropical Storm Lee on Marylandís bay
grasses will not be seen until the 2012 mapping is completed. As always,
Maryland DNR biologists will continue to monitor the health of Marylandís waters
and underwater grasses since they are an important habitat in the Chesapeake Bay
and provide food and shelter for many animals, including blue crabs, largemouth
bass and canvasback ducks. Healthy bay grass beds also protect shorelines from
erosion, produce oxygen and filter polluted water.
Restoring bay grasses and the Chesapeake Bay
Because bay grasses are sensitive to even small changes in water pollution, they
serve as a key indicator of Chesapeake Bay health. Polluted runoff entering the
Bay contains nutrients that can fuel algal blooms and sediments that block
sunlight needed for bay grass growth. Further reductions in the amount of
polluted runoff and sediment entering Marylandís waterways are necessary for
providing a clean and healthy Chesapeake Bay for all Marylanders, young and old.
Programs to plant cover crops, upgrade sewage treatment plants and septic
systems, restore natural filters, conserve high priority lands, restore habitats
and foster smarter, greener growth and living in Maryland will benefit bay
grasses and the Bayís other natural resources. Beneficial individual actions we
can take include maintaining your septic system, sensible lawn care and planting
trees and shrubs.
For more information, visit:
Bay Grasses: identification, importance and status
Restoring the Chesapeake Bay: Marylandís Actions and Progress:
What can you do to help the Bay:
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