Nutrient Loading

When too much of a good thing is not a good thing

While people scan the ingredients of packages of food to compare which one will give them more nutrients, the life in an aquatic ecosystem has a limit to the amount of nutrients it can digest. While more nutrients are better for people, they are not necessarily better for fish.

Nature balances each aquatic ecosystem to perfection. During different times of the day, algae and other aquatic plants feast on a selection of food in the form of chemical nutrients, such as nitrate and sulfate. Every day, some of those plants die, but others are "born" to take their place. The fish in the ocean have enough oxygen to breathe and food to eat.

When a man-made chemical substance like fertilizer is introduced into the system, it breaks down into individual chemicals as it seeps into the soil and eventually into the water. Some of those chemicals, like nitrate and sulfate, are already present in the water as nutrients. The chemicals add extra nutrients that the watershed must try to absorb, and when it reaches its loading capacity, the watershed allows the excess nutrients to spill into the ocean. The water is now loaded with nutrients.

Too many nutrients causes a chain reaction that eventually ends in death. More nutrients mean more algae. Algae die in mass amounts, multiplying bacteria that feed on detritus (decaying matter). As the bacteria deplete the oxygen, the fish begin to suffocate and eventually die. The decomposition of the dead algae and fish causes the foul odor people smell at a fish kill area.

Nutrient loading is typically caused by human interference in the ecosystem. Besides chemicals in man-made substances, nutrients and contaminants exist in auto exhaust, roads, parking lots, rooftops and other man-made structures.