Beverly Johnson: Current Research

Coastal Blue Carbon

Coastal “blue” carbon refers to the carbon captured and stored in coastal wetlands (i.e., salt marshes, mangroves and seagrass beds).  These ecosystems provide nursery habitat for fisheries, filter out pollutants, buffer against storm surges and are extremely efficient at capturing and storing carbon.  Approximately 50% of historical salt marshes, mangroves and seagrass beds have been lost due to human activities; current rates of loss are higher than any other ecosystem on the planet (approximately ~1-2% annually).  Because of the high carbon sequestration and storage potential, conservation and restoration of coastal wetlands provide climate mitigation benefits.

Students are involved with many different blue carbon research projects at Bates, including:

  • assessment of carbon stocks in salt marshes and seagrass beds in Maine,
  • analysis of methane emissions in hydrologically altered marshes in Maine, and
  • assessment of carbon stocks in seagrass beds from Brazil.

Some of the data generated by Bates students have been used in the Manual For Measuring Coastal Blue Carbon, a resource generated by myself and others on the Blue Carbon Scientific Working Group and distributed globally.

Changes in Baseline Conditions in Gulf of Maine Coastal Ecosystems over the Last 4,000 Years

Historically, the Gulf of Maine (GoM) was one of the world’s most productive fishing grounds.  Beginning in the early seventeenth century, its coastal codfish stocks attracted European colonists including the Pilgrims at Plymouth, Massachusetts on the shores of Cape Cod.  Today, however, Atlantic cod (Gadus morhua) and virtually all large-bodied fishes are rare and “ecologically extinct” from coastal zones in the GoM.

The focus of this research project is to evaluate the degree to which nearshore ecosystem dynamics have shifted over the last 4,000 years, and how these changes may have impacted the GoM fish stocks.  We use the stable carbon (C), nitrogen (N) and sulfur (S) isotopes preserved in tissues of ancient marine organisms to assess long-term trends in nearshore primary production, trophic connectivity, and foodweb dynamics.