Study: long-term eelgrass loss due to joint effects of shade, heat

Analysis puts resulting economic losses at $1-2 billion in Chesapeake Bay alone

A new study led by researchers at William & Mary’s Virginia Institute of Marine Science links a long-term decline in Chesapeake Bay’s eelgrass beds to both deteriorating water quality and rising summertime temperatures. It also shows that loss of the habitat and other benefits that eelgrass provides comes at a staggering ecological and economic cost.

Lead scientist Jonathan Lefcheck, a VIMS post-doctoral researcher, says “Not only have we lost a huge ecological resource, there have been real economic and recreational consequences for the Bay area’s nearly 20 million residents. Blue crab fisheries, for example, have probably lost a year or more of catch based on the amount of eelgrass we’ve already lost. For silver perch, it’s 10-20 years. In all, we estimate the potential economic cost to citizens at $1-2 billion.”

The study—based on a comparison of VIMS’ 31-year record of seagrass abundance and the Chesapeake Bay Program’s long-term record of Bay water quality—appeared in the February 3, 2017 issue of Global Change Biology. Co-authors include Professor Robert “JJ” Orth and scientist David Wilcox of VIMS, Dr. Rebecca Murphy of the University of Maryland Center for Environmental Science, and Scott Marion of the Oregon Department of Fish & Wildlife.

Orth, who initiated VIMS’ annual Seagrass Monitoring and Assessment program in 1984, says, “Declining water clarity has gradually reduced eelgrass cover during the past two decades, primarily in deeper beds where lack of light already limits growth. In shallow beds, it’s more that heat waves are stressing the plants, leading to the sharp drops we’ve seen in recent summers.”

It’s the combined effect of these two factors that gives the researchers their greatest concern. Says Lefcheck, “Declining clarity plus these hot summers is a real double-whammy for eelgrass.”



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David Malmquist
News & Media Director | Virginia Institute of Marine Science
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