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ODU, Virginia Aquarium Collaborate in $1 Million Eelgrass Study

Richard Zimmerman

Oceanographers at Old Dominion University and staff at the Virginia Aquarium & Marine Science Center in Virginia Beach are working together on a $1 million project that is designed to predict how climate warming and ocean carbonation will affect the eelgrass that grows submerged in shallow coastal waters.

The hypothesis of the researchers, interestingly enough, is that ocean carbonation - one discrete aspect of our changing global conditions - may help promote the growth of eelgrass (Zostera marina). This would be good news for the seagrasses that have been endangered in the Chesapeake Bay for several decades and are the subject of restoration efforts.

Thriving stands of seagrasses are indicators of healthy waters and provide favorable habitats for marine creatures. But the ribbon-like eelgrass prefers cool, clear waters, which have been in short supply in the bay in recent decades. Nutrient and sediment runoff from coastal lands, extensive algae blooms, unusually warm summers and severe storms have reduced water quality, devastating the eelgrass meadows.

On top of these threats is a problem related to geography. Already, the Chesapeake Bay is near the southern limit for the growth of eelgrasses; not much farther south the water becomes too warm. If global warming continues, the eelgrass boundary could move north.

So climate warming is a negative for eelgrasses, but what about ocean carbonation? Global warming has been linked to increasing amounts of carbon dioxide in the atmosphere, and the abundance of this gas in the air is also bringing about increased carbonation of the oceans (also known as ocean acidification). Scientists have shown that this trend is a threat to many marine organisms, largely because the acidified seawater can eat away at corals and the shells of snails, oysters and clams.

Nevertheless, Richard Zimmerman, professor of ocean, earth and atmospheric sciences at ODU, believes the rising levels of carbon dioxide in marine waters may be a good thing for seagrasses. "My past work indicates that rising carbon dioxide may rescue eelgrass from severe temperature stress, allowing it to persist even in a warmer climate," he explained.

Zimmerman teamed up last year with Victoria Hill, a research assistant professor of ocean, earth and atmospheric sciences at ODU, and Mark Swingle, director of research and conservation at the Virginia Aquarium, to write a proposal for a grant from the National Science Foundation for a collaborative eelgrass study. Early in March, they received formal word that the work had been funded.

The university will receive $912,000 over the next four years to conduct the experiments and mathematical modeling involved in the project. The aquarium gets $167,000 to construct and maintain the experimental facility and to provide outreach services to educate the public about the work.

Nearly 700,000 guests visit the facility each year.

The Virginia Aquarium's experience with the seawater systems that will be needed for the project's experiments helped seal the deal for this first-ever major research collaboration between the aquarium staff and ODU scientists. "Furthermore, the aquarium has space where we could build the project near a source of good water - Owls Creek and they are a natural outlet for the climate science we will be doing," Zimmerman said.

Swingle said, "This National Science Foundation grant is an example of the aquarium's efforts to develop our research programs and to work closely with regional academic partners such as ODU. It really reflects the aquarium's mission of being more than just an attraction but also a marine science center, just as our formal name implies."

Over the next four years, the researchers will grow test beds of eelgrass in seawater at varied temperatures and aqueous-carbonation levels. In addition to manipulative experiments, the research will employ physiological/biochemical investigations and mathematical modeling.

Plants produce the energy they need to survive and grow through photosynthesis, which requires that they take in carbon dioxide. The researchers hypothesize that rising aqueous carbon dioxide will increase the high temperature tolerance of plants by improving the compensatory response of photosynthesis relative to respiration, by which plants give off carbon dioxide.

"In the context of climate change, the some 50 species of seagrasses worldwide represent a unique group of marine organisms that are poised to take significant advantage of rising carbon dioxide concentrations that acidify the ocean and should make life difficult for lots of other organisms," Zimmerman said.

The ODU oceanographer said that although the research will focus on eelgrass in the Chesapeake Bay, the research team hopes to gain insight into how climate change may affect the species in other coastal environments that may be subjected to less temperature stress, but similar levels of ocean carbonation.

Zimmerman has done research over the past 25 years on seagrass-production ecology, focusing on how light, temperature and nutrients affect the plants' growth and reproduction. His work has received external funding because seagrasses are extremely sensitive indicators of changes in the climate or water quality, and, at the same time, are so critical to the well-being of marine ecological systems.

"Historically, eelgrass has been an important ecosystem engineer for the Chesapeake Bay, providing critical habitat for finfish and shellfish such as blue crabs, stabilizing sediments to prevent erosion and providing an important source of food for other organisms," Zimmerman said. "Unfortunately, pollution and reduced water quality nearly extirpated it from the bay, and we will be eager to see it restored, even in modest proportion to its original distribution."

This article was posted on: March 21, 2011

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