When you think of the environmental obstacles facing New Bedford Harbor, a heightened level of nitrogen isn’t the first thing that comes to mind. With toxic contaminants like polychlorinated biphenyl (PCBs) and heavy metals already the focus of major remediation efforts, it’s difficult to imagine how nitrogen, an element found in nature, could further deteriorate the harbor’s health.

Nitrogen is a colorless, odorless chemical element found in organic compounds like plants or urine. Aquatic life needs some amount of nitrogen to survive, but too much can drastically change an ecosystem’s delicate balance.

When nitrogen levels are too high, green algae and phytoplankton populations increase, overloading the ecosystem. The algae and phytoplankton suck oxygen needed by shellfish out of the water and block light from eel grass, impairing the entire habitat.

The algae can become so thick in summer months that it sticks to the sides of boats, and washes ashore in green waves. When the algae dies, it is decomposed by bacteria, which suck more oxygen from the harbor and create a stench that smells of rotten eggs.

“Most people are worried about polychlorinated biphenyl (PCBs) in the harbor,” President of the Buzzards Bay Coalition Mark Rasmussen said. “But when they complain about brown water, odor and floating algae, all of that is from too much nitrogen. The PCBs have nothing to do with it.”

In fact, toxic pollution in the bay has improved during the past four years (in part due to the ongoing PCB remediation process). Nitrogen levels, on the other hand, have deteriorated.

In the 2011 State of Buzzards Bay report published by the coalition, the bay’s toxics score went from 47 to 52 between 2007 and 2011, while the bay’s nitrogen score fell from 56 to 53. Generally, areas of the bay near towns that use sewer systems, like New Bedford and Fairhaven, are less nitrogen polluted than those on septic systems that barely treat wastewater. In New Bedford Harbor, however, a unique combination of geography and out-dated waste handling systems makes it far less healthy than the bay at large.

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