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Marine scientist visiting SCCF Marine Lab to study seagrasses and global warming

By Staff | Mar 18, 2009

Dr. Tom Arnold, a marine scientist from Dickinson College, visited the SCCF Marine Laboratory earlier this month for a small-scale test of an experiment to determine the impact of raised CO2 levels in oceans caused by global warming.

Our oceans are carbon dioxide sponges. They have absorbed nearly half of the 250 billion tons of CO2 emitted into the atmosphere since the dawn of the industrial revolution. This has slowed the process of global warming, but at a price: the excess CO2 absorbed by the oceans is changing the pH of seawater.

While marine animals – particularly shell-forming animals – may be adversely affected, marine plants and seaweeds may enjoy ocean acidification. Carbon dioxide is, after all, plant food and many types of marine plants may grow faster – and longer each season – with added carbon dioxide.

However, it should be also noted that seagrasses need clear water to grow; highly turbid water or water with a heavy algal bloom will reduce the amount of light that reaches the seagrasses for photosynthesis and can kill them, as happened locally in 2005-06.

Arnold is using a system called Free Ocean Carbon Enrichment, or F.O.C.E., which mimicks high CO2 conditions as they are likely to exist in the future for tiny areas of the sea bottom. In March, he conducted a small test to see if the area would be appropriate for larger-scale testing.

The system, which will be deployed in local seagrass meadows, consists of a series of clear plastic domes connected to a system of hoses, pumps, and gas exchange equipment.

“It’s a relatively small system compared to others that have been envisioned,” said Arnold. “But as far as we know, it is the first operational F.O.C.E. system. And it’s perfect for studying seagrass responses to acidification.”

Arnold, who has been studying seagrasses and their pathogens for about 10 years, thinks that high CO2 will not only cause the grasses to be more productive but may also increase their resistance to the sea grass wasting disease, caused by slime-mold like organisms called Labyrinthula. The wasting disease pathogen attacks many seagrasses – especially turtlegrass – at the end of the summer, causing black necrotic spots on leaves and, occasionally, widespread die-offs.

If more carbon dioxide means more photosynthesis in turtlegrass, he reasons, the plants are likely to produce more compounds called phenolics, which are antimicrobial substances, which could protect them from the disease. This may make seagrass restoration efforts more successful.

“The SCCF Lab is a perfect location for this type of work because the grass beds are easily accessible and the SCCF staff is really knowledgeable,” he added. “The SCCF lab could become a popular place to do this type of research.”

How will other marine organisms respond to ocean acidification? That’s something that Arnold hopes to uncover using the F.O.C.E. system. Scientists working in other locations are using onshore tanks, or mesocosms, to study acidification on specific species. One group at MBARI, the Monterey Bay Aquarium Research Institute, is developing a large deep-water F.O.C.E. system.

The March Pine Island Sound test went so well that Arnold will be returning in June to begin work on the actual project. He is also planning to apply for a National Science Foundation grant for additional work on climate change, which would be conducted with SCCF’s Marine Lab.

As Arnold points out, “We need all of these studies. Marine organisms are going to respond to ocean acidification differently, and that’s the challenge for us: predicting how whole communities are likely to change.”

SCCF’s Marine Lab conducts ongoing research into many of the issues affecting our estuaries including:

Studying the impact of the re-opening of Blind Pass on water quality and seagrasses

Oyster and scallop restoration projects

Seagrass and other SAV restoration

Studying the linkage between nutrients and nuisance macroalgae blooms


A CCP project funded through the TDC monitoring nearshore waters of Captiva and northern Sanibel.

The Lab also manages the almost-90-mile deployment of the RECON (River, Estuary & Coastal Observing Network) network of six water quality sensors (real-time data available at www.recon.sccf.org).