Five Major Marine Pollutants


The world’s oceans are so vast that they might seem immune to the influence of human waste. Unfortunately, this is not the case. Marine pollutants are a problem, and despite regulation and laws like the Clean Water Act, marine pollutants continue to be a problem. Marine pollutants, like urban runoff, biostimulants, petroleum, plastics, other debris and thermal pollution, severely harm our waterways and the life they contain.

Major Marine Pollutants: Urban Runoff

Human activity concentrates naturally occurring compounds until they become hazardous. When rainwater or wastewater from homes runs into storm drains, it picks up these hazardous compounds and deposits them into waterways. Man-made compounds like DDT and cleaners are also introduced into the marine environment this way. Much of human runoff results from individuals’ day-to-day activities.

Major Marine Pollutants: Biostimulants and Sewage

Biostimulants do not stimulate life, as their name might mislead one to believe; instead, they do more harm than good. Sewage is organic and breaks down via bacterial decay. The decay process depletes available oxygen and suffocates local animal life. Additionally, the chemical breakdown produces ammonia and hydrogen sulfide. These chemicals are toxic to fish, even in low concentrations. Bacteria and other contaminants may be consumed by shellfish, which then become hazardous to humans or other animals if consumed. Some forms of algae thrive on the nutrients created by biostimulants and can overgrow into algae blooms or “red tides.”

Marine Pollutants: Oil

Oil is introduced into waterways through spills like the massive Deepwater Horizon spill in the Gulf of Mexico on April 20, 2010. Oil production also leads to the seepage of oil into the marine ecosystem, as does rainwater runoff. Oil floats on the surface of the water, coating and suffocating any marine life that touches the water’s surface. Oil also prevents oxygen from permeating from the air into water, and thereby suffocates life that may not even directly touch the oil.

Marine Pollutants: Plastics and Other Debris

As humans travel the earth’s waters, we leave our mark. Despite regulation, we toss debris over the sides of ships, and lose things like containers and fishing nets overboard. This debris is eaten by fish and water mammals and can eventually kill them.


Marine Pollutants: Thermal Pollution

Nuclear power plants and other industrial outlets use water as a coolant. The heated water is disposed of directly into waterways where it increases the temperature of the body of water. This, again, stimulates the dangerous growth of algae blooms.