A scientific review has offered advice about trying to plant large-scale underwater grass beds in the Chesapeake: Don't bother. At least not until the Bay's often-murky water gets clearer.

The recent report by the Bay Program's Scientific and Technical Advisory Committee recommended that efforts to replant large underwater grass beds be discontinued until environmental conditions improve, although it said small-scale projects in carefully targeted areas should continue.

The state-federal Bay Program in 2003 had set a five-year goal of planting 1,000 acres of submerged aquatic vegetation, or SAV, in the Chesapeake in the hope of jump-starting the growth of underwater meadows in areas that had often been barren for decades.

But the goal, estimated to cost more than $30 million, was never fully funded. The $5 million which was spent, mostly by federal agencies, resulted in the planting of fewer than 150 acres by 2008, most of which died.

The report nonetheless said that scientists demonstrated they had the technical expertise to harvest large amounts of seeds and plant large, multi-acre projects. Those techniques work: Virginia Institute of Marine Science researchers planted 37.8 million eelgrass seeds on 309 acres in four different bays in the Virginia seaside starting in 1999. These beds are now 4,200 acres.

But in the Chesapeake, almost all of the restoration projects died, apparently because of poor water clarity and high summer water temperatures. Eelgrass, the focus of much of the work, needs clear and cool water to survive.

"Without water quality improvements, SAV restoration in the Bay proper is not yet a viable, large-scale alternative," the report said.

The report did encourage smaller projects in areas where improvements in water quality suggest plants will survive, and to better understand conditions that affect the survival of plantings.

It also called for taking the impact of climate change into account with underwater grass restoration. Warm temperatures can be lethal for eelgrass, the dominant underwater grass in high-salinity areas, especially when coupled with poor water clarity. Eelgrass was the species that got the most focus in restoration efforts because of its importance in the lower Bay.

"Their conclusions are valid," said Lee Karrh, a biologist with the Maryland Department of Natural Resources and chair of the Bay Program's SAV Workgroup, which had requested the review. But since 2008, there has been little funding for underwater grass plantings, and he and others worry that lack of support will keep them from better understanding why so many projects failed.

"We can't learn how to do restoration at all unless we put things in the water," he said.

SAV provides important habitat for fish, shellfish and waterfowl. The Bay Program has goal of restoring 185,000 acres of underwater grass — more than twice what exists today.

Based on the success of some small– and large-scale projects, including two that successfully jump-started significant eelgrass beds in the James River in the late 1990s, it was hoped that a concerted larger-scale planting program could help reach the Bay goal.

Part of the program's problem was bad timing: It began in 2003, a year of high flows, and therefore bad water quality. It was capped by Hurricane Isabel in the fall, which destroyed some beds planted that year. In 2005, a heatwave baked most eelgrass beds in the lower Bay — both established and planted ones — causing a major die-off.

"We proved methodologically we could do it," said Bob Orth, a seagrass researcher at the VIMS. "If the water quality conditions were appropriate, we could have easily restored quite a bit of eelgrass. It's just that the years that we did this were years of exceptional stress."

But the plantings also showed that establishing new beds was more difficult than thought. Planted beds failed to survive in areas where water clarity appeared to be adequate and scientists say it became evident that other factors, such as wave action, may play important roles in limiting plant survival.

Also, water quality considered good enough for adult plants, which was used to help select restoration sites, might not have been good enough for seedlings, scientists say.

Teasing apart exactly why some beds persisted and others did not is difficult. A number of projects were conducted on the St. Mary's River in Maryland and some died while others "within arms' reach" survived, Orth said. Some difference in that short distance was great enough to determine the success or failure of a grass bed, he said. "But we'll never know, because we don't have the funding for it."

Research on some of those issues had just begun when funding for SAV restoration efforts ended. Without that type of knowledge and the ability to successfully plant grass beds, Orth and Karrh said, large areas of the Bay could remain barren even if water quality improves.

While grasses have generally been recovering in freshwater areas where there are multiple species that provide an abundant source of seeds, high-salinity areas rely on eelgrass, which has been declining for two decades. Many areas in the lower Bay have no beds nearby to supply seeds.

The surviving eelgrass beds in the St. Mary's River, Orth noted, remain the only eelgrass documented in the Potomac drainage since 1963. "In some places, where there are no source populations, recovery is not going to happen, or not for a very long time," he added.

Susquehanna Flats' recovery after storm shows resiliency of large beds

Bay scientists had been worried that the deluge from Tropical Storm Lee, which sent a massive plume of sediment-laden water down the Susquehanna River and into the Bay in late summer, might have buried the largest grass bed in the Chesapeake.

But recent aerial photographs show that the bed on Susquehanna Flats survived largely intact.

"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," said Bob Orth of the Virginia Institute of Marine Science and leader of the team that conducts the annual Bay grass survey. That, he said, demonstrates the ability of large, dense and healthy grass beds to survive stresses that would wipe out smaller beds.

Susquehanna Flats was nearly barren little more than a decade ago, but a lush bed covers nearly 10 square miles today.

Nonetheless, the unusually high flows that washed huge amounts of nutrients and sediment into the Bay during the spring and late summer months of 2011, coupled with unusually high summer temperatures, are expected to take a toll on grasses Baywide. Scientists expect final figures for 2011 to show a decline from the 79,675 acres observed in 2010. The Bay Program goal is 185,000 acres.

An aerial photo comparison of Susquehanna flats for 2010 and 2011 can be viewed at: http://thumper-web.vims.edu/bio/sav/wordpress/archives/1458.