Chesapeake Bay News

The latest Virginia Institute of Marine Science Bay Grass Survey shows that the abundance of underwater grasses in Chesapeake Bay increased by 18 percent last year, from 64,917 acres in 2007 to 76,861 acres in 2008.

This is the fourth largest total acreage of bay grasses recorded since the bay-wide survey began in 1984. Bay grasses increased in abundance in several areas.

Maryland waters had a 12% increase, the second highest level seen in Maryland waters since the Virginia Institute of Marine Science began its annual bay grass survey in 1984. The 12 percent increase in Maryland’s portion of the Chesapeake Bay and its rivers brings the State to 41 percent of its bay grass restoration goal. Maryland’s bay grasses totaled 47,286 acres in 2009, up from 42,237 acres in 2008.

In addition to increased bay grasses, the Chesapeake Bay’s blue crab population has increased substantially for the second straight year. The latest winter dredge survey shows a 60% increase in Maryland’s crab population.

“Because bay grasses are sensitive to even small changes in water pollution, they serve as a key indicator of Chesapeake Bay health,” explained Maryland Department of Natural Resources Secretary John Griffin. “Healthy bay grass beds protect shorelines from erosion, produce oxygen and filter polluted water.”

Grasses on the Susquehanna Flats, near Havre de Grace, have quadrupled since the early 1990s, and a single bed now covers approximately 12.5 square miles, the largest in the Bay. Other improved areas include the upper Potomac River, from the Woodrow Wilson Bridge south to Mattawoman Creek.

Bay grasses in the middle section of the Chesapeake Bay, the area south of the Bay Bridge to the Virginia state line, also increased including areas located on the lower Eastern Shore and in Tangier Sound near Smith Island.

Growth of eelgrass, along with widgeon grass, accounted for about 60 percent of the baywide increase. These notable gains include 1,337-acres (11%) in the Tangier-Smith Island region, 1,092-acres (9%) in the eastern lower Chesapeake Bay and 1,794-acres (29%) in Mobjack Bay. Widgeon grass showed a very strong resurgence in the 2,985-acre increase (24%) in the Honga River.

While healthy bay grasses expanded in the upper Chesapeake Bay and on the Eastern Shore, several rivers on the middle Western Shore experienced bay grass declines.

The Magothy River, near Annapolis, and Piscataway Creek, in the upper Potomac River, both lost over half of their grasses in 2009. Bay scientists are working to understand the causes of these declines in order to better target restoration efforts in these rivers.

Bay grasses, a favorite home to the blue crab, increased 20 percent in 2008 in Maryland’s portion of the Chesapeake Bay and its tributaries. The majority of the 7,221-acre increase resulted from a continued expansion on the Susquehanna Flats, home of the largest bay grass beds in the Chesapeake Bay. While the new number — 42,237 acres (up from 35,016 acres in 2007) — marks a significant increase, Maryland bay grass acreage remains far short of the 2010 restoration goal of 110,000 acres.

“Whether they fish, boat, swim in its waters, or simply enjoy its world-class seafood, the waters of the Chesapeake Bay are a vital resource for Maryland families… and bay grasses are vital to a healthy Bay,” said Governor Martin O’Malley. “While this increase is encouraging, we must continue to take aggressive action, collectively and individually, to reduce nutrient and sediment pollution from the major Bay sources. By properly maintaining septic systems, practicing sensible lawn care or planting trees, every Marylander can make a difference.”

Bay grasses, or submerged aquatic vegetation (SAV) are critical to the Chesapeake by providing food and shelter for a wide range of fish, shellfish and waterfowl including largemouth bass, blue crabs and the canvasback duck. Healthy bay grass beds also protect shorelines from erosion, produce oxygen, remove excess nutrients from the water and trap sediment that would otherwise cloud the water.

“Because bay grasses are sensitive to even minor changes in water quality, they serve as a key indicator of the health of our waterways,” said Natural Resources Secretary John Griffin. “So, while these increases are good news for some portions of the Bay, there are still places where poor water quality continues to restrict recovery.

Maryland’s increase in bay grass acreage has been driven by the Susquehanna Flats beds, which now cover about 15,000 acres or about 23 square miles. The Flats, located at the top of the Chesapeake Bay, is actually a delta formed below the mouth of the Susquehanna River near Havre de Grace. These thriving beds are home to over 12 different types of bay grasses.

Increasing in size since 1991, these vast beds have also become more dense. Today they act like a giant water filter, often producing visibility up to eight feet, a level unrivaled in other areas of the Bay. These substantial increases have co-occurred with long-term reductions in nitrogen loads reaching the Bay at the Susquehanna River as confirmed by State monitoring.

In addition to the remarkable growth on the Susquehanna Flats, bay grasses in the Elk River increased nearly 20 percent to 2,347 acres meeting its acreage goal for the first time in 2008. Expansion of bay grass beds in the Northeast River continued a 3-year trend, increasing an additional 60 percent to 182 acres in 2008, far exceeding the 89-acre goal for the river.

Numerous other areas have also met bay grass restoration goals for several years now, including the Bohemia, Bush and upper Potomac Rivers, and Mattawoman Creek, though grass in the Bohemia and Bush have been declining in recent years. Also encouraging, bay grasses in the middle Patuxent and Middle Rivers, Piscataway Creek, and the upper Chesapeake Bay directly below the Susquehanna Flats are all approaching their restoration goals.

Grasses in the Potomac River — from near the Woodrow Wilson Bridge south to about Mattawoman Creek — have shown steady increases since 2000, and have exceeded the restoration goal by 47 percent. This is due in part to major upgrades in wastewater treatment at the Blue Plains Facility in Washington, DC. Long-term water quality monitoring has confirmed reduced levels of nitrogen in the Potomac River since the partial wastewater treatment plant upgrade in 1996 and the full upgrade was completed in 2000.

Increases in bay grass coverage on Maryland’s lower Eastern Shore were driven primarily by the recovery of eelgrass, a higher salinity-tolerant type of bay grass, after significant reductions in eelgrass populations resulting from a bay-wide dieback in 2005. Several regions, including Tangier and Pocomoke Sounds and the Manokin and Big Annemessex Rivers, have seen increases in eelgrass since 2006. In the Honga River, bay grass acreage nearly doubled in 2008 due to a resurgence of widgeon grass, another type of bay grass tolerant of saltier waters.

Despite this encouraging progress, other Bay areas are showing steady declines in bay grass acreage. Poor water quality continues to hamper bay grass recovery in the middle zone (Kent Island south to the Potomac and Pocomoke Rivers). Several regions, including the Choptank, Little Choptank and lower Potomac Rivers, continue to experience substantial declines in bay grass acreages.

Bay grasses acreage is estimated through an aerial survey, which is flown from late spring to early fall. Additional information about the aerial survey and survey results, is available at www.vims.edu/bio/sav/.

BayStat is a statewide tool designed to assess, coordinate and target Maryland’s Bay restoration programs, and to allow citizens to track its progress. To learn more about the health of Chesapeake Bay and its tributaries, the sources of the problems, and the effectiveness of the wide variety of programs designed to address these problems and restore the Bay, visit www.baystat.maryland.gov.

Underwater bay grasses covered nearly 65,000 acres of the Chesapeake Bay and its tidal rivers in 2007, about 35 percent of the 185,000-acre baywide restoration goal, according to data from scientists with the Chesapeake Bay Program. Though a 10 percent increase from 59,000 acres in 2006, bay grasses have not yet recovered to the recent high of 90,000 acres in 2002.

Bay grasses — also called submerged aquatic vegetation or SAV — are critical to the Bay ecosystem because they provide habitat and nursery grounds for fish and blue crabs, trap sediments, absorb excess nutrients and reduce shoreline erosion. Bay grasses are also an excellent measure of the Bay’s overall condition because they are not under harvest pressure and their health is closely linked to water quality.

“While we saw a slight increase in SAV baywide in 2007 — due in part to increases in the very large and dense beds in the upper Bay and upper Potomac River — overall there is concern about SAV in many areas because of declining water clarity,” said Bob Orth, scientist with the Virginia Institute of Marine Science and leader of the SAV baywide annual survey.

In the upper Bay zone (from the Chesapeake Bay Bridge north), bay grasses covered about 19,000 acres, 80 percent of the 23,630-acre goal and an increase from about 15,500 acres in 2006. The massive grass bed on the Susquehanna Flats, which is now visible on satellite images, dominated this zone. Bay grasses in the Flats increased from 8,743 acres in 2006 to 11,726 acres in 2007, 97 percent of the restoration goal for that segment. However, much of the rest of the upper Bay zone had little grasses, particularly on the Eastern Shore from the Sassafras River to the Chester River.

In the middle Bay zone (from the Chesapeake Bay Bridge to the Potomac River), bay grass acreage decreased slightly to about 30,000 acres, 26 percent of the 115,229-acre restoration goal. Grass beds remained reasonably robust in the Severn, upper Patuxent and upper Potomac rivers. Bay grasses in the upper Potomac River increased from 4,234 acres in 2006 to 6,246 acres in 2007, exceeding Maryland and Virginia’s restoration goals for that area. However, grasses in the lower central Bay in Virginia decreased from 2,017 acres in 2006 to 1,342 acres in 2007.

Unusually high salinities due to dry conditions during summer 2007 may have contributed to declines in the Chester and Magothy rivers and in Eastern Bay, where bay grass acreage fell from 565 acres in 2006 to 80 acres in 2007. Low river flows during drought conditions allow saltier waters to move up from the Atlantic, negatively impacting certain bay grass species that are adapted to growing in fresher waters.

In the lower Bay zone (from the Potomac River south), researchers mapped about 16,000 acres of grasses — an increase from a record low of 13,000 acres in 2006 and 35 percent of the 46,030-acre restoration goal. Many beds dominated by eelgrass, which dramatically died back during the hot summer of 2005, showed some modest recovery in 2007. Grass beds in the eastern lower Bay, for example, increased from 3,740 acres in 2006 to 5,134 acres in 2007 — still far short of the 15,107-acre goal for this segment.

“The overall picture for eelgrass — one of the two dominant SAV species in the lower Bay zone — remains bleak due to multiple stressors, including declining water clarity, warmer summertime temperatures and cownose rays,” said Orth.

Bay grasses continue to show a strong presence in many of the low-salinity and freshwater areas in the lower Bay zone, such as the Mattaponi, Pamunkey and Chickahominy rivers and creeks off the upper mainstem James River. These tributary segments are far enough from the Bay that the drought did not raise their salinity enough to cause diebacks of the low-salinity grass species that grow there.

“Over the past five to 10 years we have witnessed large increases of SAV in many of the freshwater tributaries and segments of the Bay,” said Lee Karrh, scientist with the Maryland Department of Natural Resources and chair of the Bay Program’s SAV Workgroup. “However, middle- and high-salinity areas, such as Eastern Bay and Tangier Sound, are well below their peaks.”

Because of their importance to the Bay ecosystem, in 2003 Bay Program partners committed to protect and restore 185,000 acres of bay grasses by 2010.

Annual bay grass acreage estimates are an indication of the Bay’s response to pollution control efforts, such as implementation of agricultural best management practices (BMPs) and upgrades to wastewater treatment plants. Bay watershed residents can do their part to help bay grasses by reducing their use of lawn fertilizers, which contribute excess nutrients to local waterways and the Bay, and participating with their local tributary teams or watershed organizations.

Bay managers are supplementing pollution reduction efforts with experimental bay grass plantings where predicted improvements in water quality would support bay grasses where none currently exist. These newly planted grasses act as seed sources which, in turn, produce more grass beds as water quality improves.

Bay grasses acreage is estimated through an aerial survey, which is flown from late spring to early fall. For additional information about the aerial survey and survey results, go to www.vims.edu/bio/sav/.

source: MD DNR press release