On Flagler College Week: We’re still learning how climate changes will impact aquatic habitats.
Matthew Brown, professor of natural sciences, looks into one such quandary.
Preceded by an undergraduate degree in Chemistry (B.Sc.,Old Dominion University), Dr. Matthew Brown completed an M.Sc.(Oceanography) at the University of Hawaii and a Ph.D. (Ocean Sciences–Marine Chemistry) at the University of California Santa Cruz . Prior to beginning his doctoral work, Dr. Brown worked for 2 years as an oceanographic research specialist at the University of Hawaii where he took part in several major oceanographic cruises related to the US CLIVAR program. To date, Dr. Brown has spent over 300 days at sea, performing shipboard analysis of both macronutrients and dissolved trace metals. As of Fall 2025, Dr. Brown is in his 15th year at Flagler College and teaches courses in oceanography, general chemistry, science methods, and global climate change. He worked for 2 years with researchers at the Guana Tolomato Matanzas National Estuarine Research Reserve on a water quality project in relation to the restoration of the Summerhaven River south of Matanzas Inlet. With the help of undergraduate students, he finds purpose and enjoyment in continuing research in the fields of water quality and marine chemistry, recently in the areas of marine primary productivity and ocean acidification/carbonate chemistry in the Matanzas River estuary. When not teaching or doing research, Dr. Brown enjoys spending time with his wife Rachel and daughters Liliana (8) and Vivian (5), surfing, swimming, meditation, and yoga.
Acidification in a Northeast Florida Estuary: Potential Impacts on Shellfish
How might changes in water chemistry impact oyster and other shellfish in a Florida estuary system? Northeast Florida’s Matanzas River estuary is home to one of the densest populations of the Eastern oyster on the East Coast. These oysters are a valuable fishery and provide significant ecosystem services such as filtering pollutants out of the water.
The impact that carbon dioxide from fossil fuel burning has on open ocean marine ecosystems is well understood. About 25 percent of emitted carbon dioxide gas accumulates in the ocean, leading to an increase in the acidity of the water, or ocean acidification. This increase in acidity makes it harder for organisms with a calcium carbonate shell to form their shell. The impacts of acidification in coastal estuaries are less understood as estuaries are so dynamic, with tidal mixing, freshwater input, and coastal runoff.
My current research, with the help of undergraduate research assistants, monitors two sites in the Matanzas River estuary for changes in pH and alkalinity. Since May 2024, we have measured pH, temperature, salinity, and dissolved oxygen every two weeks. We also collect water samples to measure alkalinity, a measure of the buffering capacity of the estuary, in addition to phytoplankton biomass. Using these variables, we can determine how favorable or not the water is for shell formation.
Our most significant research finding thus far shows that the estuary water becomes much more acidic after major rain events, which are common in Florida particularly during hurricane season. The estuary can actually become corrosive to a shell, meaning that it would be tough for an oyster to actually form its shell. Next, we hope to determine how long these acidic events persist in our estuary, and to what extent these acidification events are related to either the input of fresher water or the decomposition of organic matter in our estuary.
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