A nutrient is any substance that provides nourishment, allowing life to grow and remain healthy. On land, nutrients can boost plant growth in farms and forests. But in the wrong place, in the wrong amount, nutrients can cause severe damage. The problem of having too many nutrients is known as eutrophication.
In Chesapeake Bay and estuaries around the world, nutrients like nitrogen and phosphorus are causing major environmental health problems. These elements are common ingredients in fertilizer and manure put on lawns and farm fields. Some forms of nitrogen are released into the air by power plants and automobiles and come back to earth in rain. Rain can wash nutrients into streams that carry them to coastal waters. Nutrients are also released into streams and coastal waters from sewage treatment plants and septic systems. Microscopic algae called phytoplankton feast on the influx of nutrients, and their growth can explode in a massive algal bloom that clouds the water.
Massive algal blooms make life hard for many other aquatic creatures. They block light to underwater plants, making it difficult or impossible for them to grow. Without those plants, juvenile blue crabs and fish are deprived of food and habitat. Algal blooms also can create zones of hypoxia, or cripplingly low oxygen (“dead zones”). Some low-oxygen zones last only a few hours at night, because algal photosynthesis floods the water with oxygen during the day, but respiration sucks up oxygen at night when photosynthesis stops. This daily cycle of oxygen occurs naturally, but massive algal blooms make the day-night swings far more extreme. Other low-oxygen zones can last for months, years or even longer. The problems caused by massive algal blooms ultimately begin with nutrient pollution.
Scientists at SERC have been studying nutrient pollution since 1971, almost since the organization’s birth. They were among the first to discover that streamside forests and marshes (called riparian buffers) can help absorb nutrient pollution from farms, keeping it from wreaking havoc on coastal waters. They collected a 19-year dataset on phytoplankton communities in the Rhode River, the Chesapeake Bay tributary where SERC is based. Today, they’re exploring denitrification—in which natural bacteria convert a polluting form of nitrogen into harmless nitrogen gas. They’re also testing how nutrient pollution impacts wetlands in Maryland and mangroves in Florida, studying the impacts of low oxygen on fish and oysters, and building models to explore how different ecosystems within the Chesapeake Bay landscape release or absorb nutrients. They’ve discovered nutrient pollution can even transform how plants respond to climate change. Read more about their projects below.
