Denser grass beds in the Chesapeake Bay could boost the region’s blue crab population, according to a new report from the Virginia Institute of Marine Science (VIMS).
While researchers have long known that blue crabs use grass beds as sheltered nurseries and feeding grounds, this study is the first to show that denser, higher-quality grass beds hold more crabs than open beds where patches of mud or sand separate plants.
These findings are based on fieldwork conducted between 2007 and 2008, during which scientists used a powerful vacuum to collect blue crabs from 104 sites along the shores of the lower Bay.
Graduate student Gina Ralph led the study and said in a media release that her work suggests “the quality of seagrass habitat can influence the population dynamics of blue crabs on a baywide basis.” But underwater grass abundance has declined in recent years, due to warming waters and sunlight-blocking sediment pollution. Blue crabs, too, have suffered population declines, as pollution, predators and human harvest put pressure on the iconic species.
Learn more about the link between grass beds and blue crabs.
To track the health of the Chesapeake Bay, researchers across the watershed watch so-called “indicator species” for clues about water quality. Bay grasses—sensitive to pollution but quick to respond to water quality improvements—are one such indicator. Bay grasses are monitored each year by a range of experts in the field, from the U.S. Fish and Wildlife Service (USFWS) to the Virginia Institute of Marine Science (VIMS), the latter of which compiles Bay-wide observations in an annual report on bay grass abundance.
Bay grasses, also known as submerged aquatic vegetation or SAV, provide critical habitat and food for wildlife, add oxygen to the water, absorb nutrients, trap sediment and reduce erosion.
During the months of May, July and September, biologists like Chris Guy, who works with USFWS, visit randomly selected sample sites throughout the Bay. Occasionally accompanied by volunteers, their mission is to track the ebb and flow of underwater grass beds in order to gauge the health of the Bay.
Once a sampling site is reached, researchers use a refractometer to determine the salinity of the water. Different bay grass species prefer different salinity levels, and this measurement gives biologists a hint as to what kind of grasses they should expect to find.
Biologists measure water clarity by submerging a black and white Secchi disk until it is no longer visible, at which point it is pulled up and the waterline is measured. Clear water is important to the health of bay grasses. Because they need sunlight to survive, submerged aquatic vegetation is typically not found in water deeper than five feet.
Once the salinity and turbidity are measured, a rake is tossed into the water and allowed to sink to the bottom.
As the rake grips the bottom and the boat moves forward, the line attaching the rake to the boat becomes taught. The thrower hauls it back on board, records the grass species that are found and rates the abundance level on a scale of one to four. A one indicates an empty rake, while a four means that at least 70 percent of the rake is full of grass.
Hundreds of sampling trips allow scientists to amass a set of data that can be used to measure grass abundance across the Bay. Over the past 30 years, this number has fluctuated with changes in weather and water quality. In 2012, a VIMS analysis indicated bay grasses experienced a 21 percent decline, from just over 63,000 acres in 2011 to just over 48,000 in 2012. The Chesapeake Bay Program and its partners hope to restore 185,000 acres of underwater grasses to the Bay, which would approach historic twentieth century averages and bring a dramatic improvement to the entire Bay ecosystem.
View more photos on the Chesapeake Bay Program Flickr page.
Photos by Steve Droter
Close to 15,000 acres of underwater grasses have disappeared from the Chesapeake Bay.
While robust grass beds on the Susquehanna Flats and expanding beds in the James River offer two examples of the Bay’s resilience, an aerial survey conducted by the Virginia Institute of Marine Science (VIMS) showed a 21 percent decline in the Bay’s grasses in 2012. This so-called “alarming” loss—from just over 63,000 acres in 2011 to just over 48,000 in 2012—approaches lows last reported in 1986.
In a report released this week, Chesapeake Bay Program scientists attributed last year's decline in grass beds to warmer-than-normal water temperatures seen in 2010 and strong storms seen in the fall of 2011. The former "cooked" grasses in the Lower Bay, while the latter pushed excess sediment into rivers and streams, clouding the water and creating unfavorable growing conditions for aquatic plants in the Upper and Middle Bay.
These strong storms and episodes of heat stress have occurred alongside a widespread decline in water clarity, said Bob Orth, coordinator of the VIMS Submerged Aquatic Vegetation Survey. While Orth remains "concerned" over the decline in bay grasses, he noted that favorable growing conditions in the future could lead to quick signs of recovery in a species that is fast to respond to water quality changes—both good and bad.
"The best thing we can do [for bay grasses] is to improve water quality," said Lee Karrh, a biologist with the Maryland Department of Natural Resources (DNR) and chair of the Bay Program's Submerged Aquatic Vegetation Workgroup. "If you improve water quality and reduce chronic problems, then the Bay should be able to deal with episodic events easier than it has been able to in the past."
Underwater grasses—also known as submerged aquatic vegetation or SAV—are critical to the Bay ecosystem, offering food and habitat to countless critters while absorbing nutrients, trapping sediment and reducing shoreline erosion. The Bay Program uses underwater grass abundance as an indicator of Bay health, and has this week released a data visualization tool that allows users to track changes in grass abundance over time, as dominant species ebb and flow and grass beds shrink and expand.
Read more about the 2012 Distribution of Submerged Aquatic Vegetation in the Chesapeake Bay.
In 2011, monitoring data collected by the Bay jurisdictions and other partners showed that dissolved oxygen concentrations in the Chesapeake fell to their lowest level in the last four years with 34 percent of the waters meeting the established DO standards for the summer months. This represents a decrease of 4 percent from the 2010 figures according to the Chesapeake Bay Program (CBP) partnership and is almost half of the higher DO values recorded a decade ago.
In spite of lower levels and in the face of many weather challenges, various Bay habitats and creatures that have been the target of restoration efforts showed resilience last year. In CBP news this March, scientists from Virginia Institute of Marine Sciences (VIMS) reported that despite a decrease in Bay grasses overall, the restored, healthy grass beds at Susquehanna Flats remained intact, widgeon grass beds grew (likely due to seed germination stimulated by lower salinities) and new grass beds were found in Virginia’s James River. In terms of fisheries, preliminary data by oyster scientists from Maryland Department of Natural Resources and NOAA showed good news, too. Experts estimate last year’s oyster survival rate was at its highest since 1985, oyster biomass increased 44 percent and oyster disease was at an all time low.
“Last year’s heavy rains and even this year’s early algae blooms and fish kills reinforce the critical importance of controlling polluted runoff reaching the Bay’s waters,” said Nick DiPasquale, Director of the Chesapeake Bay Program. “The survival rates of some oyster and grass beds in 2011 shows us that our efforts are working. By actively restoring and protecting valuable resources we can build a stronger, healthier Bay ecosystem that can withstand the forces of nature. Clearly, while we can’t control the weather, we can restore the watershed’s ability to survive its more extreme events. We know what works; we just need to do more of it.”
Experts were not terribly surprised by the final information on the Bay’s 2011 “dead zones” given the extreme weather. Between the very wet spring that sent excessive nutrients downstream, a hot, dry, early summer and more heavy rains accompanying Tropical Storm Lee and Hurricane Irene, conditions in the Chesapeake were bound to be affected.
Peter Tango, CBP Monitoring Coordinator and U.S. Geological Survey scientists explains, “The Bay ecosystem functions most effectively when fresh and salt water can mix, just like oil and vinegar need to mix to form salad dressing. A large fresh water influx such as that in 2011, along with intense heat, can result in vast differences in quantities of warm fresh and cool salt water in the Bay. These variables make it more difficult for water to mix vertically in the water column.”
In addition to vertical mixing, the dissolved oxygen levels in the Bay are also affected by what happens at the edges. Tango continues: “By the fall of last year, the Upper Bay became mostly fresh water due to rain. The Lower Bay became a hot tub due to heat,” illustrates Tango. “While the initial effects of the Tropical Storm Lee’s arrival was to mix the Bay more than usual in late summer, this combination of salinity and temperature conditions resulted in minimal levels of oxygen in bottom waters that lasted well into the fall. The delay in autumn vertical mixing and the persistent summer-like water quality conditions at the northern and southern boundaries pushed on the mid-Bay waters, resulting in what we scientists call a dissolved oxygen or ‘DO squeeze.’”
All of the Bay's living creatures – from the fish and crabs that swim through its waters to the worms that bury themselves in its muddy bottom – need oxygen to survive, although the amounts needed vary by species, season and location in the Bay. A DO squeeze challenges the health of fish, crabs, and other Bay creatures since they become compacted together – predator and prey, from north to south and bottom to top – in significantly smaller sections of water where and conditions are less-than-ideal for their survival.
Fewer acres of bay grasses grew in the shallows of the Chesapeake Bay and its tidal rivers in 2011, according to scientists with the Chesapeake Bay Program. Bay grass acreage fell to an estimated 63,074 acres in 2011, down from 79,664 acres in 2010. This is the lowest Bay-wide acreage measured since 2006.
Because of heavy rainstorms that led to cloudy, muddy conditions that blocked monitoring efforts, only 57,956 acres of bay grasses were actually mapped in 2011. However, scientists believe about 5,119 acres of bay grasses may have been present during the height of the growing season, leading to the final estimated Bay-wide figure of 63,074 acres.
Bay grasses – also known as submerged aquatic vegetation or SAV – are a critical part of the Bay ecosystem. These underwater meadows provide fish, crabs and other aquatic life with food and habitat, absorb nutrients, trap sediment, reduce erosion, and add oxygen to the water. Bay grasses are also an excellent measure of the Bay's overall condition because their health is closely linked with the Bay’s health.
“2011 was the year that bucked two trends we’ve seen over the last decade,” said Lee Karrh, chair of the Bay Program’s Submerged Aquatic Vegetation (SAV) Workgroup. “The Upper Bay had major decreases after years of increasing or sustained high acreages. On the other hand, the brackish parts of the Middle Bay witnessed dramatic increases in 2011, after prolonged decreases since the turn of the century.”
Experts agree that extreme weather conditions in 2010 and 2011 led to the substantial decrease in bay grasses. According to Bob Orth, scientist with the Virginia Institute of Marine Science (VIMS) and coordinator of the annual bay grass survey:
In the upper Bay (from the mouth of the Susquehanna River to the Chesapeake Bay Bridge), bay grasses covered approximately 13,287 acres, down from 21,353 acres in 2010. This is most likely an underestimate because scientists did not monitor the area until November, once muddy conditions improved but well past the end of the growing season. One bright spot in the upper Bay was the more than doubling of bay grass acreage in the Chester River and near Eastern Neck.
In the middle Bay (from the Bay Bridge to Pocomoke Sound and the Potomac River), bay grasses decreased 4 percent to an estimated 34,142 acres, down from 35,446 acres in 2010. (Only 29,023 acres were mapped, but scientists estimate that an additional 5,119 acres may have been present.) Large eelgrass losses were observed in Tangier Sound. These were offset by widgeon grass gains in many areas, including Eastern Bay and the Choptank River.
In the lower Bay (south of Pocomoke Sound and the Potomac River), bay grasses covered 15,645 acres, down 32 percent from 22,685 acres in 2010. Hot summer temperatures in 2010 led to this significant drop in acreage, which offset any gains that followed in 2011. Eelgrass in many parts of the lower Bay had been recovering from similar heat-related losses that took place in 2005.
Despite Bay-wide losses, there were a few bits of good news for bay grasses last year. The huge, dense bed on the Susquehanna Flats – which has increased threefold in size over the past 20 years – survived the late summer tropical storms, showing how resilient healthy bay grass beds can be to natural disturbances. Also, scientists recorded the first-ever bay grass bed in the mainstem James River since the area was first surveyed in 1998.
Annual bay grass acreage is estimated through an aerial survey, which is conducted from late spring to early autumn. Residents can do their part to help restore bay grasses by not fertilizing in the spring and planting more plants to reduce polluted runoff from backyards.
For detailed information about 2011 bay grasses acreage, including aerial photos and year-to-year comparisons, visit VIMS' SAV blog. For more information about the aerial survey and bay grass monitoring efforts, visit VIMS’ SAV website.
Though the final figures on the overall health of the Bay’s underwater grasses won’t be available for a few months, in late November, scientists with the Chesapeake Bay Program’s (CBP’s) team that monitors the abundance of the Bay’s grasses had a pleasant surprise. Aerial survey images of the vast grass-filled Susquehanna Flats, the circular area where the Susquehanna River meets the Bay, were not pictures of devastation as was feared, but pictures of health, showing that these valuable Bay habitats survived the fall’s deluge of runoff and sediment better than expected.
During Hurricane Irene and Tropical Storm Lee, experts out monitoring the effects of these storms noted large tangles of all varieties of uprooted Bay grasses floating downstream. Based on these visual accounts and their knowledge of the devastation that events such as Tropical Storm Agnes wrought on the Bay’s grass beds almost forty years ago, hopes among scientists were not high for these habitats, which are a critical food source for over-wintering waterfowl at this time of year and that are vital as shelter for juvenile Bay creatures in the spring.
“We were incredibly surprised at how much of the grass bed remained on the Flats,” says Robert Orth of Virginia Institute of Marine Sciences (VIMS) and leader of the team that conducts the annual survey of Bay grasses. “While we did see some declines along the flanks and edges of that big bed, my gut feeling says next year should be ok for grass beds up there. And the fact that we are now seeing overwintering waterfowl in our photographs is a good sign that lots of food is available.”
CBP’s Associate Director for Science Rich Batiuk commented, “Back on those days of Tropical Storm Lee, looking at the deluge of water over the Conowingo Dam, I would’ve bet that we had lost the Flats grasses entirely. Their survival is a good example of how large, dense beds can survive extreme conditions and another indicator of the Bay’s resilience.”
Compare the underwater grass beds on the Susquehanna Flats in VIMS aerial photographs in 2010 and 2011 at http://thumper-web.vims.edu/bio/sav/wordpress/archives/1458
Aerial photos show that the upper Chesapeake Bay’s underwater grasses mostly survived the muddy plume of water that flowed from the Susquehanna River after heavy late summer rainstorms from Hurricane Irene and Tropical Storm Lee.
Scientists with the Chesapeake Bay Program acquired the imagery in early November. It appears that some grasses in the large bed on the Susquehanna Flats were lost, particularly on the eastern edge. The image above shows a comparison of the bay grass bed between 2010 and 2011.
Visit the Virginia Institute of Marine Science’s SAV blog to view an interactive version of this image and learn more about bay grass monitoring in the Chesapeake Bay.
When it became clear that Hurricane Irene would move through the Bay region, the Chesapeake Bay Program’s (CBP) monitoring program coordinators, like Bruce Michael at Maryland’s Department of Natural Resources, adjusted the Bay water quality monitoring cruise schedules to get data just following the hurricane.
Now in the days since the hurricane, recent data from Maryland’s Eyes on the Bay program is showing that the Bay received a short term water quality boost from the hurricane. This is a result of the physical mixing of the Bay’s waters by extreme winds and waves that sent oxygen-rich surface waters into the deeper channels that are normally lacking oxygen at this time of year.
When it comes to hurricanes and their impact on the Bay, it’s the timing that makes the big difference in terms of whether there is a short term (weeks to a month) or a long lasting (months to years) impact on the Bay ecosystem.
In this case, timing is made up of two important components: the point during the hurricane season when the hurricane moves through Bay country and how long the hurricane lingers over the Bay and its surrounding watershed.
When hurricanes strike during important growing seasons for fish, oysters and underwater bay grasses, the results can over longer lasting effects. Hurricane Agnes back in 1972 (a tropical storm by the time it hit the Bay), hit in June at the peak of the underwater Bay grasses growing season, tipping an already declining Bay ecosystem into a tailspin lasting into the early 1980s.
Also, when a hurricane stalls and hangs around the Bay and its watershed for days, the amount of rain and resultant flooding can increase dramatically compared to the effects of Irene who moved all the way through the region over in less than a 24-hour period.
Fortunately in the case of Hurricane Irene, we are at the tail end of the peak growing season for bay grasses, so the clouded water and increased amounts of sediments entering the Bay’s tidal waters via runoff will not have as big of an impact compared to if the hurricane hit us in June or July.
We are also not in prime oyster spawning season (later in the fall to early winter) nor are we in any critical fish spawning period (late winter to late spring) so we missed those opportunities for a bigger, more direct impacts on our fish, crabs, oysters and grasses.
Unlike Hurricane Isabel, Irene’s track and, therefore, wind directions meant that we did not experience a devastating storm surge that resulted in the extreme shoreline erosion the region witnessed in the fall of 2003.
The flood waters will continue to bring in extra nutrient and sediment pollution loads into the Bay for days and even weeks to come. But again, timing is on our side. With cooler temperatures and shorter days coming, those excess nutrients will not feed algal blooms which love hot, sunny, calm days.
Some of the excess nutrients that flowed downstream during the storm will remain in the Bay’s tidal waters and will support next year’s algal growth. However their impact is likely less than if the hurricane had struck later in October or November when the nutrients have a greater opportunity to hang around until the next year.
The bottom line on Hurricane Irene’s impact is that we will have to wait for weeks (mixing up of the water column with good oxygen levels; short term algal blooms), and really months (impact on the next spring’s algal blooms, early summer’s re-growth of underwater Bay grasses, and mid-summer’s dissolved oxygen conditions years), to fully answer the question, “What was the impact of Hurricane Irene (and even the fall 2011 hurricane season) on the Bay?”
Fortunately, the CBP partnership has an extensive monitoring program in place which continues to measure various indicators of the Bay’s health — in this case, prior to the hurricane and in the weeks and months following the storm.
Given the timing of this storm, the Bay likely dodged a potentially serious bullet thanks to Irene’s timing, rapid movement through the region, and track.
For more information about the effects of Hurricane Irene on the Chesapeake Bay, visit these links from our partners:
Scientists with the Virginia Institute of Marine Science and other Bay Program partners have released a mid-year update on bay grass monitoring in the Chesapeake Bay.
Some highlights of the mid-year monitoring update include:
The full results of the Bay Program’s annual bay grass monitoring will be released next spring.
Visit VIMS’s website to learn more about bay grass monitoring.
Underwater bay grasses covered 79,675 acres of the Chesapeake Bay and its tidal rivers in 2010, according to data from scientists with the Chesapeake Bay Program. This is a 7 percent decrease from 2009, when bay grasses covered 85,914 acres of the Bay’s shallows.
Despite the drop, the 2010 bay grass acreage estimate ranks as the third-highest Bay-wide acreage since 1984, when the annual survey began.
"Even with the decreases in the 2010 bay grass coverage, the patterns are similar to previous years,” said Lee Karrh, living resources assessment chief with the Maryland Department of Natural Resources and chair of the Bay Program's SAV Workgroup. “Many of the fresh and low salinity areas have very high abundances, including 16 that have reached their restoration targets. However, the saltier parts of the Bay continue to struggle, with most areas well below the restoration goals, with only the mouth of the James River exceeding the goal.”
Bay grass abundance is currently at 43 percent of the Bay Program’s 185,000-acre goal. This goal is based on approximate historic bay grass abundance from the 1930s to present.
“We were pleased that grasses remain healthy and abundant in two areas where nutrient pollution was reduced: the upper Potomac River and Susquehanna Flats,” said Bob Orth, scientist with the Virginia Institute of Marine Science and leader of the baywide annual survey. “However, the overall condition for bay grasses remains one of concern with many areas still having few, if any, grass beds.”
In the upper Bay (from the Susquehanna Flats to the Chesapeake Bay Bridge), bay grasses covered about 21,353 acres. This is a 10 percent decrease from 2009. Large increases were observed in the Chesapeake and Delaware Canal and part of the Sassafras River. However, these were offset by large decreases in local rivers, including the Bush, Bohemia and Magothy. The massive grass bed in the Susquehanna Flats continues to dominate this area.
In the middle Bay (from the Chesapeake Bay Bridge to the Potomac River and Pocomoke Sound), bay grass acreage decreased 11 percent to 35,446 acres. Most segments in this part of the Bay lost grasses. The largest percentage decreases occurred in the middle and lower central Bay, as well as the Choptank, Honga, Patuxent and Potomac rivers. Increases were seen in Tangier and Pocomoke sounds and the Manokin and Big Annemessex rivers, where eelgrass continued to come back following a 2005 die-off.
In the lower Bay (south of the Potomac River), scientists mapped 22,876 acres, a 1 percent increase from 2009. This is the fourth year that bay grasses in this part of the Bay have increased since 2005, when hot summer temperatures caused a dramatic large-scale eelgrass die-off. Most of the gains were in the upper Rappahannock, lower Piankatank, and the upper section and mouth of the James River. These gains offset losses in other areas.
“In 2010, our big concern arose in the lower Bay where eelgrass appeared to suffer another setback from the incredibly hot summertime temperatures,” said Orth. “Since we had mapped those beds prior to the heat wave, losses there are not reflected in our final figures. We believe the really hot summer temperatures in the early part of the growing season may have just cooked the grasses before we were able to map them, e.g. parts of the Honga River. The changes also occurred in areas dominated by just one species, widgeongrass, which has been shown to be a boom or bust species. 2010 may have been the hottest on record but it was those summer time temperatures in June that may have tipped the scale for SAV in some areas.”
Bay grasses – also known as submerged aquatic vegetation or SAV – are a critical part of the Bay ecosystem. They provide underwater life with food and habitat, absorb nutrients, trap sediments, reduce erosion, and add oxygen to the water.
Bay grasses are also an excellent measure of the Bay’s overall condition. The health of bay grasses is closely linked with Bay health. Annual bay grass acreage estimates are an indication of the Bay’s response to pollution control efforts.
Annual bay grass acreage is estimated through an aerial survey, which is conducted from late spring to early autumn. For more information about the aerial survey, and to view an interactive map of bay grass acreage throughout the Bay and its tidal rivers, visit VIMS’ website.
The Magothy River in Anne Arundel County, Md., received a D-minus on its latest health report card, the same grade as last year but a significant decline from several years ago, according to the Magothy River Association’s latest Magothy River Index.
The index assesses the river’s health according to three indicators: water clarity, dissolved oxygen and bay grasses. Bay grass acreage in the river decreased in 2007 and water clarity diminished in 2008. Scores for both have remained low ever since.
Low dissolved oxygen at the surface of several creeks is also a problem in the river. Upper Mill and Dividing creeks had the worst surface dissolved oxygen, suggesting that pollution problems that lead to low oxygen levels are worse in those areas.
Despite the low scores, the Magothy River Association is looking to the future to help restore the river. The group is working with scientists to explore if any native species of bivalves other than oysters could be used to help clean up the river. Bivalves can help filter algae out of the water as they feed, but oysters can’t live in many parts of the Magothy because the water is too fresh. One species that may help is dark false mussels, which helped improve water clarity and bay grass acreage in one Magothy River creek in 2005 when they were abundant.
The Magothy River Association also encourages its members and area residents to take small steps to help reduce pollution to the river. Planting more native trees and flowers, installing rain gardens, reducing use of lawn fertilizer and maintaining septic systems are a few of the tips the group suggests. These practices will help reduce pollution no matter where you live.
The Magothy River Index is an annual health report developed by Dr. Peter Bergstrom, a NOAA scientist and Magothy River Association member. The index uses scientific data from state agencies and volunteer water quality monitors. The Magothy River Association has released the index each year since 2003.
For more information, visit the Magothy River Association’s website.
Today we’re introducing a new blog feature called “Ask a Scientist.” Each month, we'll take a question submitted through our website or Twitter (@chesbayprogram) and have a scientist from the Bay Program partnership answer it here on our blog.
Today's question is about restoring bay grasses in the Chesapeake Bay. One of our readers wanted to know if he could help restore bay grasses in his local creek by planting bay grass seeds. We turned to Mark Lewandowski, natural resources biologist with the Maryland Department of Natural Resources and member of the Bay Program's Submerged Aquatic Vegetation (SAV) Workgroup, for some expert advice.
Many people who live in the Chesapeake Bay watershed do everything they can to help the environment. They recycle, compost, use rain barrels, or plant native plants and shrubs. But people always want to know what else they can do.
Culturing oysters, growing wetland plants and planting underwater bay grasses all seem like good, easy ways to help. So what’s so hard about planting bay grasses? Isn’t it as simple as getting some seeds, planting them in an aquarium and watching them grow?
Many people have successfully grown grasses in their aquarium. But very few people have had success planting them in the Bay because the grasses do not survive over the long term. Selecting an appropriate site to plant bay grasses requires a lot of research and information.
Water quality is the biggest factor in bay grass survival. All bay grasses need enough light to photosynthesize, so clear water is critical. Each type of bay grass has very specific physiological needs that are different for each species.
The next requirement is proper substrate.; The bottom sediment can't be too sandy or the plant won't root. It can't be too silty or the transplant will just get buried. And it can't have too much clay. In addition, plants need the correct balance of nutrients to grow. Scientists have access to the most comprehensive data available, as well as specialized analytical tools that can pinpoint the sites where grasses might flourish.
In addition to finding the right conditions, you also need a large number of plants for the grasses to take hold. Planting a few square meters of bay grasses off the end of your pier is almost never successful. Bay grasses on the outside of a bed protect the core of the bed. So the grasses that are on the fringe will die back, protecting the center of the bed from waves and animal grazing.
Restoration would be easier if we could just buy seeds from a garden center. However, our experience is that only bay grass seeds collected from grass beds in the Bay have the best chance of survival. Even this is not an ideal or easy approach, though. Collecting seeds from the Bay depletes the seed stock that naturally replenishes bay grass beds. It also requires a permit from resource management agencies and may require specialized equipment to harvest. Additionally, it’s necessary to have specific knowledge of seed development to ensure that the seeds collected are mature and will germinate.
So keep doing the things you are doing to help the Bay already, but it may be best to leave bay grass restoration to the experts.
Visit Maryland DNR's website to learn more about the agency's bay grass restoration efforts.
Welcome to the latest installment of the BayBlog Question of the Week! Each week, we take a question submitted on the Chesapeake Bay Program website or a frequently asked question and answer it here for all to read.
This week’s question came from Raymond, who asked, “Can I get eelgrass planted in Kingscote Creek at my cottage? Would this grow in a sandy bottom?”
We often receive questions about what species of bay grasses and plants would grow best in certain environments at people’s houses. There are a variety of resources out there to help you learn about the growth requirements of different species of bay grasses
As far as eelgrass goes, our field guide entry was helpful in answering Raymond’s question. Eelgrass is found in the middle and lower Bay, south of the Eastern Shore’s Honga River, meaning that Raymond’s location in Virginia’s Kingscote Creek should be a safe place to plant eelgrass. Eelgrass can grow in a variety of areas, from shallow and sandy to deep and muddy bottoms. There does not appear to be any reason Raymond should not be able to plant eelgrass near his cottage in Virginia.
One good resource for finding out about bay grasses is the Virginia Institute of Marine Science. It has a wealth of information about bay grasses in the Chesapeake Bay, the different species found in the Bay, and bay grass restoration. The Maryland Department of Natural Resources also has an extensive bay grasses section on its website.
Do you have a question about the Chesapeake Bay? Ask us and we might choose your question for the next Question ofthe Week! You can also ask us a question via Twitter by sending a reply to @chesbayprogram! Be sure to follow us there for all the latest in Bay news and events.
A new study by the U.S. Geological Survey (USGS) suggests that underwater bay grasses in the Potomac River are increasing due to efforts to reduce nutrient pollution.
The study, which used data from 18 years of river monitoring, shows that fewer nutrients and clearer waters in the Potomac have increased the amount and different types of bay grasses growing in the river.
Bay grasses – also known as submerged aquatic vegetation or SAV – are critical to the ecosystem of the Chesapeake Bay and its tributaries. Bay grasses provide oxygen to the water and food and shelter for fish, crabs, waterfowl and other species.
Excess nutrient pollution in the water fuels the growth of algae blooms, which block sunlight that bay grasses need to grow and survive.
Between 1990 and 2007, the area covered by bay grasses in the lower Potomac River doubled, from 4,207 acres to 8,441 acres.
In addition, the area covered by native grasses has increased tenfold, from 288 acres in 1990 to 3,081 acres in 2007. Meanwhile, the proportion of non-native species to native species has declined. In 1990, more than 80 percent of the total amount of bay grasses in the lower Potomac was the non-native hydrilla; in 2007, hydrilla declined to 20 percent of all bay grasses.
The diversity of bay grass species in this reach of the Potomac has increased. More than a dozen species of bay grasses – including hydrilla – now co-exist in the lower Potomac.
These improvements have occurred “nearly in lock step with decreases in nutrients and sediment in the water” and reductions in nitrogen in treated wastewater from Washington, D.C., according to USGS scientist Dr. Nancy Rybicki.
“Upgrades to the wastewater treatment plant have benefited [bay grass] habitats 50 miles downstream. These findings underscore the benefits of nutrient reduction efforts on a major tributary to the Chesapeake Bay,” said Rybicki, who has been conducting research on the Potomac since 1979.
“People want to know that money spent on ecosystem restoration is having tangible results, but many feel that efforts to clean up Chesapeake Bay have so far had limited success,” said researcher Dr. Henry Ruhl of the National Oceanography Centre, which also contributed to the study. “Our results suggest that widespread recovery of submerged vegetation abundance and diversity can be achievable if restoration efforts are enhanced across the Bay.”
A multi-agency study released in July found similar results to the USGS study, correlating nutrient reductions with gains in bay grass abundance in some Bay tributaries, while noting a negative correlation between bay grasses and nitrogen.
For more information about the USGS study, visit the project website and the USGS Chesapeake Bay Activities page.
Underwater bay grasses covered 85,899 acres of the Chesapeake Bay and its tidal rivers in 2009, about 46 percent of the 185,000-acre baywide abundance goal, according to data from scientists with the Chesapeake Bay Program. This was a 12 percent increase from 76,860 acres in 2008 and the highest baywide acreage since 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, serve as food for animals such as turtles and waterfowl, clear the water, 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.
“The overall increase in SAV acreage in 2009 was strongly driven by changes in the middle and lower Bay zones, including Tangier Sound, the lower central and eastern lower Chesapeake Bay, Mobjack Bay, and the Honga, Rappahannock and lower Pocomoke rivers,” said Bob Orth, scientist with the Virginia Institute of Marine Science (VIMS) and leader of the SAV baywide annual survey.
Bay grass acreage increased in all three of the Bay’s geographic zones – upper, middle and lower – for just the second time since 2001.
Upper Bay Zone (from the Chesapeake Bay Bridge north)
In the upper Bay zone, bay grasses covered about 23,598 acres, just shy of the 23,630-acre goal for this area and a 3 percent increase from 2008.
Large percentage increases were observed in the Northeast River, part of the Sassafras River and the upper central Chesapeake Bay, an area just north of the Bay Bridge. However, bay grass acreage in a few local rivers, such as the Bush and Magothy, decreased significantly and offset increases elsewhere.
Overall, the massive grass bed on the Susquehanna Flats continues to dominate this zone.
“The growth and persistence of the SAV bed in the Susquehanna Flats – including the largest bed in the Bay – continues to be a major success story for bay grass recovery today,” said Lee Karrh, living resources assessment chief with the Maryland Department of Natural Resources and chair of the Bay Program's SAV Workgroup. “Many of the Bay’s lower salinity areas are doing well and seem to be driven by reductions in nutrient pollution entering the Bay. Seventeen segments in this zone have met or exceeded their restoration targets.”
Middle Bay Zone (from the Chesapeake Bay Bridge to the Potomac River and Pocomoke Sound)
In the middle Bay zone, bay grass acreage increased 15 percent to 39,604 acres, 34 percent of the 115,229-acre goal.
Eighty-four percent of the acreage increase in the middle Bay zone occurred in five segments: Eastern Bay, the Honga River, Pocomoke and Tangier sounds, and the lower central Chesapeake Bay. These changes reflect a large expansion of widgeon grass – the dominant SAV species in the middle Bay zone – as well as the continued recovery of eelgrass in Tangier Sound.
Elsewhere in the middle Bay zone, large percentage declines in bay grass acreage were observed in the Severn River and Piscataway Creek, a tributary of the Potomac River.
Lower Bay Zone (south of the Potomac River)
In the lower Bay zone, researchers mapped 22,697 acres of bay grasses – a 17 percent increase from 2008 and 49 percent of the 46,030-acre restoration goal. This is the third year that bay grasses in the lower Bay zone have increased since 2005, when hot summer temperatures caused a dramatic large-scale dieback of eelgrass.
Eighty-two percent of the acreage increase in the lower Bay zone occurred in Mobjack Bay, the lower Rappahannock River and the eastern lower Chesapeake Bay.
None of the 28 segments in the lower Bay zone saw large declines in bay grasses in 2009.
“We are cautiously optimistic about eelgrass recovery now that it is into its third year following the 2005 dieback,” said Orth. “But we are concerned about the long-term absence of eelgrass from areas that traditionally supported large dense beds, such as much of the York and Rappahannock rivers, many of the mid-Bay areas just north of Smith Island, and in the deeper areas of Pocomoke Sound. Declining water clarity noted in much of the lower Bay may be a major impediment to eelgrass recovery.”
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 grass acreage is estimated through an aerial survey, which is flown from late spring to early fall. Visit VIMS’s website for additional information about the aerial survey and an interactive map of bay grass acreage throughout the Bay.
As Aldo Leopold and many other environmental writers have stressed, attachment to "special places" promotes environmental stewardship. For me, two of those special places were underwater. They were submerged aquatic vegetation (SAV) beds in two rivers near where I live and work, the Magothy and the Severn. Those beds were special to me because they were two of the first places that I saw SAV beds, starting in 1992. I use the past tense because as of last summer (2009), those two SAV beds are gone, part of a recent decline of SAV in both rivers.
The special SAV bed on the Magothy was in the lower part of the river on the western shore of Gibson Island. I first visited it in the summer of 1992, before it was mapped in the Virginia Institute of Marine Science (VIMS) SAV survey. I was doing volunteer water monitoring with a lifelong Magothy resident, Dan Zivi. Because he grew up here, Dan remembered when the grasses were abundant in the 1960s, and he knew there was a small remnant SAV bed. We stopped there in his boat to see it. It didn’t look like much; just a few spindly stalks of redhead grass in shallow, murky water. But it held great promise.
The following year, 1993, that bed was large and dense enough to be mapped in the VIMS SAV survey, along with a few nearby beds.
The recovery of SAV in the Magothy had started. That Magothy SAV area would peak in 2005 at 125 hectares (309 acres), which was 53 percent of the restoration goal.
By 2009, the Magothy SAV area was down to only 5 hectares (12 acres), just 2 percent of the goal. The SAV bed I first saw on Gibson Island’s shore was gone.
The first SAV bed I saw on the Severn was also special because it was large and dense right from the start, and it was the first field trip I made with Bob Orth of VIMS, who has boundless energy when SAV is involved. This bed must have been growing for years on a wide shoal outside of Asquith Creek. In the summer of 1994, the plants were tall enough to be visible from the air, and thus they were mapped in the SAV survey.
Bob Orth, a VIMS scientist who supervises the annual aerial SAV survey, wanted to see the “new” bed in the summer of 1994, so several of us went there with him in a small boat. I wasn’t familiar with the Severn’s bottom features, but Bob knew the bed was on a large shoal. As soon as we saw the edge of the bed, he jumped in the water. I was not prepared to jump in the water, so I stayed in the boat, but I leaned over to take a photo of a blue crab doubler that was caught in that bed as we explored it.
I had just started working at the U.S. Fish & Wildlife Service’s Chesapeake Bay Field Office, mainly to study and protect SAV, so I was happy.
Hence my sadness in summer 2009 when I visited this bed to do SAV sampling and found that, just like the bed near Gibson Island, it was almost gone. This was confirmed by the VIMS SAV map that was just completed. There was still a bed north of Asquith Creek in 2009 (labeled J4), but it no longer extends onto the shoal at the mouth of the creek.
What does the loss of these two SAV beds in 2009 mean for the future of SAV in the Bay? For me their loss is partly symbolic, and I know that almost all SAV beds come and go, sometimes returning after they disappear. I’m not that worried about the Severn SAV bed because there were still some large and dense beds nearby, although SAV in the Severn may have declined overall in 2009.
I am worried about the future of SAV in the Magothy, however, because of the large SAV area declines since 2005. It’s also troubling that the river's water clarity got worse again last year; data collected by Magothy River Association volunteers (including myself) showed water clarity was down to the lowest status we’ve measured (14 percent of the goal). Details of these changes will be in the forthcoming Magothy River Index, which I will present at the annual State of the Magothy meeting at Anne Arundel Community College on Wednesday, February 17 at 7:00 p.m.
What can we do about these declines in aquatic health in the Magothy and in other rivers? See this brochure from the Department of Natural Resources for some ideas on what you can do in your yard to improve aquatic health in the rivers near where you live. I’ve done many of these in my yard.
However, I think it will take more than changes in our yards to reverse the declines in aquatic health in the Magothy and in other rivers. The marked improvements in aquatic health that we saw in the Magothy and some nearby rivers in 2004 were caused by millions of tiny dark false mussels filtering the water. We estimated there were 400 million of them in one creek, Cattail Creek, that year. I live in the Cattail Creek watershed and I’ve done water monitoring there for 19 years, and 2004 had the best water clarity and dissolved oxygen status I ever recorded there. To get the same improvements in aquatic health by reducing stormwater runoff, we’ll need more than a few rain gardens. I think a good start would be stormwater retrofits in all of the waterfront communities, including mine, that lack any stormwater management facilities, because the communities were built before these were required. Who would pay for these expensive retrofits, and where would we put them? I’m not sure. One option could be to set up a special taxing district in communities to pay for stormwater retrofits. Crofton and other communities have done this for decades to pay for extra police protection. Taking actions like this directed at improving our environment would really demonstrate commitment to cleaning up the Bay.
You could say the weather was against me that day. I woke up in the morning to pouring rain and a temperature in the 50s. Not exactly the best conditions for planting wetland grasses on an island in the Chesapeake Bay. But nonetheless, the Baltimore Aquarium volunteer packet did say RAIN or shine.
So I hopped in the car with some fellow co-workers and began the hour-and-a-half drive from Annapolis to the planting site at Eastern Neck National Wildlife Refuge. I had never been to Eastern Neck before, but I will surely return, preferably on a warm, sunny day! The refuge, located at the mouth of the Chester River on the Eastern Shore, is one of the top five waterfowl habitats in Maryland.
I arrived at the parking lot to find the hardy Aquarium staff ready to load us onto a boat and shuttle us to the planting site. So I suited up in layers and raingear and prepared for an interesting boat ride. The river was a bit choppy, so the ride was a cross between white water rafting and riding a rollercoaster with a bucket of water dumped over your head every five minutes. Taking a ride in a washing machine might be a similar experience.
Thoroughly drenched, I arrived at the planting site ready to get to work. My mission that day was to plant two species of grass on the eroding sandbar separating Hail Creek from the Chester River. We broke into teams and started planting. My team had a diviler, a feeder and a tucker. The diviler dug the hole, the feeder put fertilizer in the hole, and the tucker planted the plug of grass.
We repeated the process over and over and over until half of the sandbar was planted with new grass. The other half would be planted by more volunteers the next day.
After a long day of planting, we boarded the boat back to the mainland. Soaked to the bone, the Aquarium staff was nice enough to give us some trash bags to sit on or in, depending on our preferences. I went home knowing that through the wind and the driving rain, my blades of grass will remain.
Mid-season monitoring of underwater bay grasses in Virginia’s portion of the Chesapeake Bay is showing beds of eelgrass and widgeon grass that are similar to or slightly denser and larger than 2008, reflecting continued recovery from a large-scale eelgrass die-off in 2005, according to updates from the Virginia Institute of Marine Science (VIMS).
Bay grasses, also known as submerged aquatic vegetation or SAV, provide critical habitat for juvenile fish and molting blue crabs. Bay grasses also help improve the Bay’s health by adding oxygen to the water and reducing erosion.
Based on these mid-season observations, total bay grass acreage in the lower Bay is expected to be higher than in 2008, but still far below the peak seen in the 1990s, according to Dr. Robert Orth with VIMS. The Bay Program will release bay grass acreage figures for the entire Chesapeake Bay in spring.
Along the Bay’s western Virginia shore:
On the Eastern Shore:
Read the full mid-summer monitoring report on VIMS’ SAV observation blog.
Underwater bay grasses increased by 18 percent in 2008 to cover 76,861 acres throughout the Chesapeake Bay and its tidal rivers, according to data collected by scientists with the Bay Program. This is the fourth largest total amount of bay grasses recorded since surveying began in 1984.
Bay grasses are vital to the Bay because they filter pollutants, produce oxygen, prevent erosion, shelter fish and blue crabs and provide food for waterfowl. They are 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.
The 11,943-acre increase from 2007 was driven by the continued expansion of grasses on the Susquehanna Flats in the upper Bay and the steady recovery of eelgrass and widgeon grass in the middle and lower Bay.
Another positive sign for bay grasses is that about 60 percent of bay grass beds were considered “high-density,” the highest percentage since 1984. High-density grass beds are better at removing pollution, producing oxygen and providing shelter for fish and shellfish.
The 2008 bay grass acreage of 76,861 brings the Bay Program to 42 percent of its goal to restore 185,000 acres of grasses.
For the first time since 2001, bay grasses increased in all three geographic zones of the Bay.
In the upper Bay (from the mouth of the Susquehanna River to the Bay Bridge), bay grasses increased 21 percent to 22,954 acres. This is 97 percent of the upper Bay goal of 23,630 acres.
Bay grass increases in the upper Bay are due in part to lower amounts of nitrogen entering the Bay from the Susquehanna River. The Susquehanna Flats, which includes three of the five largest grass beds in the Bay, now filter water so well that plumes of clear water are visible flowing down the Bay.
“Thirteen of the Bay’s fresh water rivers have exceeded their bay grass restoration goals, with another four on the verge of passing benchmarks,” said Lee Karrh, a biologist with the Maryland Department of Natural Resources and chair of the Bay Program’s Submerged Aquatic Vegetation Workgroup.”
In the middle Bay (from the Bay Bridge to the Potomac River), bay grasses increased 15 percent to 34,521 acres. This is 30 percent of the middle Bay goal of 115,229 acres.
One middle Bay segment that continues to show increases is the upper Potomac. At 6,517 acres of bay grasses, the upper Potomac has exceeded its restoration goal by 41 percent. This increase is due in part to improvements in wastewater treatment at the Blue Plains facility in Washington, D.C. in 2000.
However, 21 of the 44 middle Bay segments had no bay grasses in 2008. Additionally, many middle Bay segments saw decreases in bay grass acreage, including:
In the lower Bay (from the Potomac River to the mouth of the Bay), bay grasses increased 21 percent to 19,386 acres. This is 42 percent of the lower Bay goal of 46,030 acres.
Eelgrass, a species only found in the Bay’s saltier waters, continued its comeback from a 2005 baywide die-off. Notable segments include:
“The continuing recovery of eelgrass in the lower portions of the Bay is an extremely positive sign, particularly in light of the dramatic losses in 2005,” said Bob Orth, a professor at the Virginia Institute of Marine Science and leader of the annual survey.
Despite the overall increase, 11 of the 28 lower Bay segments had no bay grasses in 2008, and the Chickahominy River lost 25 percent of its grasses.
Annual bay grass acreage estimates are an indication of the Bay's response to pollution control efforts, such as implementation of agricultural conservation practices 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.
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/.
Over the past five years, the NOAA Chesapeake Bay Office and the U.S. Army Corps of Engineers have led innovative new research to increase the amount of underwater grasses in the Chesapeake Bay.
Bay grasses are vital to the Bay ecosystem because they provide food for migratory waterfowl and habitat for juvenile fish and blue crabs. They also add oxygen to the water, stabilize bottom sediments and slow shoreline erosion.
In recent decades, bay grass growth has been hindered by polluted runoff containing nutrients and sediment, negatively affecting both water quality and the fish and crabs that depend on bay grasses for their survival. The decline of bay grasses spurred the Bay Program to set a goal to restore 185,000 acres of bay grasses by 2010, including an ambitious goal to plant 1,000 acres of bay grasses by the end of 2008.
Traditionally, bay grass restoration efforts focused on hand-planting adult grasses, which was labor-intensive, costly and had mixed results. Furthermore, these earlier restoration projects were often small and uncoordinated, without consistent methods.
As part of efforts to meet the Bay Program’s bay grass restoration goals, NOAA and the Army Corps Engineer Research and Development Center (ERDC) contributed approximately $4 million from 2003 through 2006 to develop procedures for large-scale bay grass restoration. This is the largest coordinated, multi-federal agency effort to date on bay grass restoration.
“We quickly realized that if we were going to be able to plant large acreages of underwater grasses, we needed to take an agricultural approach,” said Deborah Shafer, research marine biologist for the Army Corps ERDC.
Just as farmers plant seeds to grow crops, scattering bay grass seeds instead of planting adult grasses was found to be the most cost-effective way to restore large, self-sustaining bay grass beds.
“The work funded by NOAA and the Army Corps focused on a variety of research topics, starting with developing a basic understanding of seed ecology and germination issues,” said Peter Bergstrom, biologist with the NOAA Chesapeake Bay Office. “We then started applying this knowledge to large-scale restoration, including improved methods for seed collection, storage and dispersal.”
At first, researchers tried two methods of collecting seeds from existing bay grasses: using divers to hand-collect seed shoots, and using a mechanical harvester that cuts off seed shoots, much like a lawn mower cuts grass. The mechanical harvesting proved to be the most cost-efficient method for collecting seeds.
Researchers also compared two different techniques for spreading bay grass seeds. The first involves putting the seed shoots right after they are collected in large, floating mesh bags, which allow the seeds to slowly disperse. These “seed buoys” have been found to yield high seedling rates under some circumstances. But seeds dispersed using this method yield fewer seedlings because many things can happen to the seeds over the summer while they are not growing—including natural predation, burial by sediments and being carried away from favorable areas.
The second method uses a special aquaculture process to separate the seeds from the shoots. The seeds are then stored until fall, when they are scattered by hand and mechanically. The aquaculture method allows seeds to be distributed during the same time of year when natural grass seed germination occurs.
(Learn more about the two methods of planting bay grass seeds.)
From 2003 through 2006, scientists with NOAA, ERDC and other Bay Program partners distributed 133 acres of bay grass seeds, an average of 33 acres per year. In comparison, only 9 acres of grasses were planted per year from 1983 through 2003 using the traditional method of hand-planting adult grasses.
Seeds were planted in select locations throughout the Bay, including 16 million seeds over 101 acres of Virginia’s Piankatank River and Maryland’s Patuxent and Potomac rivers, and more than 1 million seeds over 15 acres at Poplar and Barren islands on Maryland’s Eastern Shore.
While the agricultural method of planting seeds resulted in more acres of bay grasses planted than hand-planting adult grasses, very few seedlings became established. However, because of the large number of seeds distributed, even low seedling establishment rates can mean many seedlings.
“Seed-based restoration does hold promise, though challenges remain, including improving seedling success rates and the long-term survival of seedlings with the Bay’s marginal water quality,” said Robert Orth, scientist with the Virginia Institute of Marine Science.
Just outside of the Chesapeake, bay grass restoration efforts have had more successful results. In Virginia’s coastal bays, scientists with the Virginia Institute of Marine Science are using very similar methods to conduct underwater grass seedings. Since 1998, 30 million seeds have been scattered in four coastal bays over 190 acres that had no seagrass beds. Today, over 1,000 acres of these bays are covered by seagrass, showing the importance of clean water to underwater grass growth.
“Concurrent water quality and environmental monitoring in these bays has shown that parameters such as light attenuation, algae and temperature are within the range necessary for growth and expansion of seagrass beds,” Orth said.
Details about the status of underwater bay grass restoration in the Bay are available in the technical report Large-Scale Submerged Aquatic Vegetation in Chesapeake Bay, published by ERDC.
Other partners involved with the bay grass research and restoration effort include the Virginia Institute of Marine Science, the University of Maryland Center for Environmental Science Horn Point Laboratory, the Maryland Department of Natural Resources and Anne Arundel Community College.
Since 2004, the Maryland Department of Natural Resources (MD-DNR) has been developing and applying large-scale bay grass restoration techniques at its Piney Point Aquaculture Center on the Potomac River in St. Mary's County.
Bay grasses, also known as submerged aquatic vegetation or SAV, once grew in abundance in the shallows of the Bay and its tributaries. The underwater grasses are vital to a healthy Bay ecosystem because they provide protection and nursery habitat for fish and blue crabs, filter and oxygenate the water, and help reduce shoreline erosion.
Currently, there are about 32,000 acres of bay grasses in the Maryland portion of the Chesapeake - approximately 30 percent of the state's 114,000-acre restoration goal. Progress toward the bay-wide goal of 185,000 acres of grasses is similar, at about 32 percent.
While the best way to restore bay grass populations is through water quality improvements, bay grass restoration activities also play an important role. Since 2004, MD-DNR has seeded nearly 70 acres of suitable, unvegetated habitat to help jumpstart natural, established bay grass beds.
MD-DNR staff are currently working to restore bay grasses—specifically eelgrass, a particularly beneficial species—by collecting seeds from healthy eelgrass beds in the spring and distributing them in promising areas of the lower Potomac River.
Each May, scientists and volunteers collect seed-bearing shoots from eelgrass growing in Tangier Sound, near Crisfield on Maryland's Lower Eastern Shore. The seed material is then transported by boat across the Bay to the Piney Point Aquaculture Center to be processed, stored and distributed.
MD-DNR staff members at Piney Point are currently evaluating two eelgrass seed dispersal methods to determine the most cost-effective way to re-establish eelgrass beds.
The first takes place almost immediately following the late spring seed collection, using seed bags.
While this technique is similar to the way eelgrass seeds naturally drift and scatter, the seeds distributed in the spring won't turn into seedlings until the fall. That's because eelgrass is a cool-water species that typically does not thrive during the Chesapeake 's hot summer months. However, many things can happen to the seeds over the summer while they are not growing—including natural predation, burial by sediments and being carried away from favorable areas.
The MD-DNR staff also works actively with researchers from the Virginia Institute of Marine Science (VIMS) and St. Mary's College of Maryland to refine a second method for seed processing, storing and distribution. This method was originally developed by VIMS and is now being carried out on a large scale at the Piney Point facility.
Seed processing begins once seed material is brought from Crisfield in May. Seed shoots are processed to separate the seeds, then stored for the summer. Distribution takes place in the fall, when natural eelgrass seed germination occurs.
The collected material is placed in several 20,000-gallon aerated holding tanks. The eelgrass seeds grow into grasses, then die and decay.
Over a period of about a month, the seeds separate from the grasses and non-seed material and sink to the bottom of the tanks. The seed slurry—a muddy substance—is then pumped through a series of settling tanks and filter screens to remove the non-seed material.
The eelgrass seeds are placed in small temperature- and salinity-controlled tanks until fall, when they are distributed (by hand and mechanically) in suitable areas of the lower Potomac River.
MD-DNR scientists monitor the seeding sites throughout the eelgrass growing season (March through November) to determine the effectiveness of both distribution techniques. In addition, nearby water quality monitoring information is also collected to help explain changes in the overall health of eelgrass beds.
Scientists at VIMS are conducting similar restoration efforts in Virginia waters.
Bay-wide acreage of underwater bay grasses (SAV) decreased by 25 percent in 2006, dropping to 59,090 acres from 78,263 acres in 2005, according to data from scientists with the Bay Program. This loss marks the first setback for SAV after two consecutive years of moderate gains and the lowest total SAV acreage figure since 1989.
Bay grass acreage is broken down into three zones: Upper, middle and lower Bay.
Scientists are attributing acreage declines in the upper and middle Bay to:
The lower Bay is still experiencing the effects of a large eelgrass dieback that took place in late summer 2005 after a period of record high temperatures. Many of the areas affected by the dieback in 2005 did not produce grass at all in 2006, while the remaining SAV beds observed were very thin.
SAV losses in the lower Bay could be particularly hard on blue crabs, which use grass beds as nursery areas where they hide from predators until they grow large enough to migrate up the Bay and its tributaries. This additional habitat loss, among other factors, could contribute to the extended period of low blue crab abundance currently observed in the Bay.
Although SAV acreage decreased bay-wide, there were some bright spots in bay grass restoration in 2006.
Large, dense beds on the Susquehanna Flats area remained healthy and vibrant despite the deluge of sediment following the June rain event.
Widgeon grass spread throughout the lower Rappahannock River.
Hydrilla continued to do well in the Mattaponi, Pamunkey, Chickahominy and upper James rivers.
SAV beds remained very dense in the tidal freshwater areas of the Potomac from Broad Creek down to Aquia Creek.
Researchers on the St. Mary's River also witnessed healthy SAV populations.
SAV is critical to the Bay's ecosystem because the grasses provide habitat for fish and shellfish, help reduce shoreline erosion, absorb excess nutrients and trap sediment. SAV once covered an estimated 200,000 acres along the shallows and shorelines of the Bay.
Bay grasses can only grow if water is clear enough for sunlight to reach its underwater leaves. Since water clarity is reduced by excess nutrients and sediment from the land, the Bay Program looks at annual bay-wide SAV survey results as an indication of the Bay's response to pollution control efforts. Based on long-term trends, significant progress is still needed before the Bay is clean enough for SAV to recover to historic levels.
The health and density of bay grasses is just one indicator of the overall health of the Bay. The Bay Program's 2006 Chesapeake Bay Health and Restoration Assessment, which provides the most current scientific data and tracks restoration progress, is currently in production and will be made public on April 18.
Underwater bay grass acreage increased by seven percent in 2005 to a total of 78,260 acres, according to data gathered by the Virginia Institute of Marine Science for the Chesapeake Bay Program. The 2005 acreage represents about 42 percent of baywide restoration goals.
While this increased acreage is encouraging, scientists are concerned about possible losses in 2006 due to a widespread defoliation of eelgrass in lower and mid-bay areas. This occurred after last summer's unusually high water temperatures and calm conditions. The full extent of the losses will not be known until June, when the aerial survey of key areas is completed.
Abundant bay grasses are essential for a thriving Chesapeake Bay ecosystem. Bay grasses reduce pollution by absorbing nutrients and trapping sediments and provide shelter and nursery areas for juvenile striped bass and crabs.
The Bay has seen a slow increase in bay grass coverage, from 38,000 acres in 1984 to nearly 90,000 acres in 2002. Because of the importance of bay grasses to the Bay ecosystem, the Bay Program partners have committed to protect and restore 185,000 acres by 2010.
Bay Program partners are working to provide optimal water quality conditions for bay grasses by upgrading sewage treatment plants, planting streamside forest buffers and minimizing runoff from developed and agricultural areas. Water clarity improvements are critical to helping the Bay's underwater grasses return to their former abundance.
Some 19,464 acres of underwater grasses were mapped in 2005. While about ten percent lower than last year's record level of 21,673 acres, the average density of the beds increased, providing higher quality habitat for resident aquatic life. The density of grass beds in this area has been steadily increasing since 1999, following almost 15 years of sparse coverage. Bed density has almost tripled since 1999, increasing from about 1,700 acres to nearly 5,000 acres of moderate- to high-density beds in 2005.
Last year's 39,576 acres marked a 17 percent increase, but is far below the previous high of 52,971 acres in 2002. Bay grass acreage in this region is dominated by widgeon grass, a species that shows tremendous inter-annual variability. The middle bay has seen two peaks since 1984, one in 1992-93, and one in 2001-02.
Below the Maryland/Virginia state line, grasses covered 19,220 acres in 2005, a nine percent increase from the unusually low acreage recorded in 2004. After a period of steady increase from 1984 through 1993, bay grass abundance in this region has fluctuated, generally averaging of approximately 21,000 acres. Changes observed between 2004 and 2005 in some areas of the lower and mid-bay were likely a result of these beds beginning a recovery from the effects of Hurricane Isabel in 2003.