Some of the most powerful ecosystem players are not biological, but chemical. Many elements and compounds that cycle through the soil, water and air also cycle through organisms, impacting their health and their environments.

Nutrients like nitrogen and phosphorus boost plant growth, but can have dangerous consequences when levels get too high—a phenomenon known as eutrophication. Nitrogen is the element that most often controls plant growth.  Humans introduce nitrogen into watersheds through fertilizers, sewage or even air pollution. But when nitrogen compounds like nitrate (NO₃) wash off land and enter the water, they fertilize the growth of algae. Too much nitrogen can cause algal blooms that cloud the water and create areas where dissolved oxygen is scarce or absent. Excess nitrogen can also change the ability of tidal marshes to gain elevation and keep pace with sea-level rise. Agriculture and urbanization have raised nutrient pollution in many coastal ecosystems. However, riparian buffers like streamside marshes or woodlands can turn dissolved nitrogen compounds into harmless nitrogen gas (N₂). SERC scientists study how nitrogen and phosphorus flow among and within ecosystems, and how human activities are changing these flows.

The carbon cycle is another powerful environmental shaper. All living things contain carbon as well as nitrogen and phosphorus. Much of SERC research explores the fate of the planet-warming greenhouse gases carbon dioxide (CO₂) and methane (CH₄) through ecosystems. SERC scientists perform decades-long studies and journey across continents to discover which ecosystems store carbon and which emit it. In the process, they’re also tracking how ecosystems react to rising levels of carbon in the atmosphere and to the many environmental changes caused by greenhouse gases acting on the climate.

Mercury—and its more toxic cousin methylmercury—are key on ecologists’ radar as well. Most mercury pollution begins as pure, elemental mercury (Hg) from coal-burning power plants, exhaust fumes and other sources. Microbes are responsible for turning it into methylmercury, the neurotoxin in some high-level seafood like tuna. SERC’s microbial ecologists seek to uncover where those microbes live, and how to keep methylmercury out of the water.