Chris Gobler, a professor and foremost expert on harmful algal blooms at Stony Brook University’s School of Marine and Atmospheric Sciences, says the problem lies in the chemical level within the food source for the clams.
Clams eat algae, but algae eat nitrogen. Ground water carries high levels of nitrogen into the bay from a variety of sources, such as septic systems and lawn fertilizers. Nitrogen is an important food source for algae and helps sustain eelgrass, which provides safe reproductive beds for the clams.
“Nitrogen is an essential part of a marine ecosystem,” said Gobler. However, nitrogen becomes a problem when it enters the bay in excess.
The problem with having too much nitrogen can be compared to having too much food on a table. Eventually the food will rot and will no longer be fit for consumption. Much in the same way, large amounts of nitrogen will feed large amounts of algae. If the clams do not readily consume these algae, as they did in the 1970s, the algae decay and release a form of nitrogen known as dissolved organic nitrogen, commonly referred to as DON, which promotes brown tide growth.
It is important to distinguish DON from the initial form of nitrogen entering the bay that is known as dissolved inorganic nitrogen, or DIN, which can feed brown tide. However, healthier tides vigorously process DIN before brown tide can feed on it.
Brown tides have been studied for the past twenty years by The Nature Conservancy, according to Carl Lobue, one of the head researchers at the conservancy in Suffolk County.