Ocean Water Contaminants

Our oceans, which cover 71% of the planet, are under constant stress from a wide variety of contaminants which are mostly introduced by human activity. Effluent pollution from industry, landfill seepage, oil spills, runoff from agricultural chemicals, and raw sewage is altering the chemistry of ocean water and creating toxic �dead zones� all over the world.

Unless a beach is closed due to high levels of bacteria, very few of us give much thought to the pollutants that plague our oceans. But as human populations rise worldwide and the populations of marine species collapse from over fishing and compromised food chains, it is clear that we are not going to be able to ignore these problems for much longer.

This article will focus on the most common ocean water contaminants and the effects that they have on our oceans. Perhaps the most disturbing aspect of these pollutants is that it takes them a very long time to degrade through natural processes. Once they settle into ocean sediment, they are consumed by small creatures which then pass the pollutants on to larger and larger creatures higher in the food web, including humans.

Agricultural Chemicals

Pesticides, herbicides, and fertilizers that are applied to farmland across the world enter the oceans as rainwater rinses these chemicals from our fields and into streams and rivers. These waterways then carry these chemicals into our oceans where they wreak havoc in a number of different ways. Perhaps the best example of this is the Dead Zone in the Gulf of Mexico. Each spring, a nutrient rich layer of freshwater lays on top of the salt water which promotes the growth of vast algae blooms which consume virtually all of the oxygen in the water. As the level of oxygen decreases, fish and other marine species are literally suffocated and die off in vast numbers.

Another phenomenon from agricultural runoff is the explosive growth of toxic phytoplankton which leads to �Red Tide.� As nitrogen and phosphorous enter the Gulf, they foster the growth of these pathogens. These paralyze the respiratory systems of fish and either kill the fish or store neurotoxins in the flesh which then are ingested by birds and other animals.

Bacteria from Sewage

Consider this: A single gram of dog feces contains 23 million fecal coliform bacteria. One gram. Then consider the millions of gallons of raw sewage that are vented into the ocean when older public water systems are overwhelmed by heavy rainfall. In some countries, sewage is vented directly into the sea without any effort to filter it at all.

Bacterial contamination in our oceans has far greater consequences than a few closed beaches. Fecal coliform and other bacteria in high concentrations can kill off marine mammals like whales, otters, and dolphins from organ failure and the sheer toxicity of the water.

Oil Spills

Huge oil tanker spills get a lot of news coverage all over the world, but the sad fact is that only 5% of oil pollution in our oceans results from tanker spills. The other 95% results from offshore oil drilling rigs, naturally occurring seeps from oil under the ocean floor, and businesses that deliberately dump waste oil into the sea to avoid having to pay for proper disposal.

Oil smothers all sorts of marine life. As birds attempt to clean their feathers and mammals try to get it out of their fur, they ingest oil and are killed by the toxicity. Fish absorb oil through their gills and by direct contact which often leads to massive die-offs and beaches strewn with carcasses which then may be eaten by animals and cause additional deaths. Sadly, there are even more repercussions. Oil damages or kills fish eggs, larva, and fry, and several generations can be wiped out by one single spill. Furthermore, it takes decades for nature to break down oil and recover from the effects of one spill.

Industrial Pollutants

Industrial pollutants like PCBs, mercury, and dioxin create a wide range of health problems in humans and marine animals. What�s more, they are very slow to degrade and once introduced into the ocean, they remain toxic and create health hazards for many, many years.

PCBs (polychlorinated biphenyls) get into our oceans via rainfall from air pollution. Used in a wide variety of electronics, hydraulic fluid, and many other applications, they cause cancer, birth defects, and damage the immune systems of all living things.

Mercury pollution mostly comes from industrial emissions into the air, especially coal-fueled power plants. Once introduced into the ocean by rain, it is changed by microbes into methyl mercury which is a nerve toxin that affects the nervous systems of fetuses, young children and animals.

Dioxins enter our environment from both man-made activities like trash incineration and manufacturing and natural processes such as forest fires and volcano eruptions. Exposure to high levels of dioxins can cause organ damage, increased risk of cancer, severe skin rashes, and a whole host of other problems in humans and animals.


These are but a few examples of the contaminants in our oceans that threaten not only humans, but nearly every living thing. In the U.S. and Europe, legislation has been passed that has cut down on the amount of these pollutants, but in other countries there are no such laws to protect the environment. One thing remains clear. In the last 150 years, human activity and the resulting pollution from manufacturing worldwide has had a dramatic and very serious effect on our ocean�s ability to sustain life. Unless we make a very sober assessment of what we have done to our oceans and soon, there will be repercussions that no one will be able to ignore.