Nutrient Pollution’s Effects on the Fishing Industry

The holidays are nearing, and while for many that means turkey, mashed potatoes, and sweet potato casserole, for others it means lobster dinner and clam bakes. But soon enough, we might not be able to enjoy the sweet meat of red lobsters or the briny bite of oysters rockefeller.

For those who don’t live on the coast, the effects of climate change on salt water bodies is merely a distant and hushed rumor. The soaring prices at the supermarket are merely ploys by food giants to get us to spend more. But really, our fishing industry is suffering due to two factors: climate change and pollution.

Nutrient pollution’s effects on the fishing industry are growing. This past September, Cape Cod Bay discovered a startling scene when lobstermen unearthed several nets of dead lobsters from one section of the bay. That week, more and more fishermen called into the Massachusetts Lobstermen’s Association with stories of dead skate, flounder, and eel. To find out why aquatic life was dying rapidly in this section of the bay, two biologists tested the waters and found that the bay was experiencing hypoxia.


Hypoxia refers to low or depleted dissolved oxygen levels within a body of water. Despite being underwater, aquatic life still needs oxygen to breathe. In fact, lobsters need at least three milligrams of dissolved oxygen per liter of water, and the water tested in the bay showed levels below 2 mg/L. According to Owen Nichols, director of marine fisheries research at the Center for Coastal Studies, such low levels of oxygen have never been seen in the bay before.

So what caused this hypoxia?

According to researchers, climate change is to blame. Unusually hotter weather caused warmer water temperatures over the summer, leading to water stratification. Water stratification refers to a layered column of water, in which colder, more saline waters remain trapped at the bottom of the ocean and warmer, fresher waters rise to the surface. The cold and warm waters cannot mix, meaning the colder water at the bottom of the column loses its dissolved oxygen. Anything at the bottom that cannot swim to the top dies.

Another factor is to blame, however, for the hypoxia in Cape Cod Bay as well as the fish kills and poor water quality around the globe.

Nutrient Pollution’s Effects 

Hypoxia can also occur as a direct effect of nutrient pollution.

Nutrient pollution, also referred to as eutrophication, occurs when chemicals from agricultural and industrial runoff enter water bodies. According to a 2013 EPA estimate, high concentrations of nitrogen are present in 28 percent of the U.S.’s stream length. High concentrations of phosphorous are present in 40 percent of this stream length. (Retweet this!)

Nutrient pollution depletes dissolved oxygen levels in the water, causing hypoxia and dead zones, areas in which there are extremely low levels of oxygen and, therefore, no aquatic life. Over 166 dead zones have been identified in the U.S., especially in the Chesapeake Bay and Gulf of Mexico.

Nutrient pollution also supports the growth of algae, which consumes the available oxygen in the water when it decomposes and blocks light from reaching lower layers of water. This algae can also be toxic, and when one organism consumes it, the toxins will move up the food chain as other organisms consume the contaminated ones.

According to the EPA, “agricultural nonpoint source (NPS) pollution is the leading source of water quality impacts on surveyed rivers and lakes, the second largest source of impairments to wetlands, and a major contributor to contamination of surveyed estuaries and ground water.”

Did you catch that? Agricultural runoff is the leading source of nutrient pollution in rivers and lakes. 

Farmers contribute to nutrient pollution in several ways:

  • Poorly located and managed animal feeding operations
  • Overgrazing
  • Plowing too often or at the wrong time and
  • Improper and excessive use of pesticides, irrigation water, and fertilizer.

That’s right: improper and excessive fertilizer use can pollute our water resources.

Fertilizer Pollution

Whether fertilizer is organic or synthetic, it can be washed away by rainwater and end up polluting rivers and lakes.

Farmers apply fertilizer to their fields in order to increase crop yield. While soil already has the vital nutrients that plants need, fertilizer gives them direct access to nitrogen and phosphorous, which means faster growth and an increased yield. Due to poor agricultural practices fueled by the incentive to make more money, however, the world’s soil has become increasingly infertile. In order to combat this, farmers apply more fertilizer than necessary, which ironically decreases soil fertility, perpetuating this unsustainable cycle.

What farmers either don’t understand or don’t care about is that plants will only absorb 30-50 percent of fertilizer. Plants, unlike humans, know when to stop eating and will only consume what is necessary. So when farmers add excess fertilizer to their fields, it is either washed away by the rain, leading to nutrient pollution, or consumed by soil microbes, who then convert the nitrogen into nitrous oxide, a greenhouse gas.

Sustainable Fertilizers Negate Nutrient Pollution’s Effects 

In order to combat nutrient pollution’s effects on the environment, the EPA suggests sustainable fertilizer use. Here are a few ways farmers can use fertilizer more sustainably:

  • Switching to a natural fertilizer that doesn’t contain chemicals or salts:
    • Chemicals in fertilizers can burn plant roots, decrease soil fertility, and even cause illness for animals who ingest them. Salts can acidify soil, reduce germination, prevent water absorption, weaken growth, and kill plants. When farmers see their plants dying or weakening, they instinctively add more fertilizer, further hurting them.
  • Using a nitrate fertilizer rather than an ammonium-based one:
    • Nitrate fertilizers are healthier for plants and the environment, and they are more efficient at feeding plants than ammonium-based fertilizers. Because they are mobile in the soil, plants can directly absorb them. They also promote the uptake of essential nutrients, whereas ammonium will compete for this uptake, causing the plant to “choose” between ammonium and other essential nutrients. They limit the plant’s uptake of harmful elements. Lastly, nitrate’s are converted to amino acids using sunlight while ammonium is converted to amino acids using carbs. Thus, the plant has to burn energy to use ammonium, making it weaker.
  • Measuring the correct ratio of fertilizer needed for their plants and never overusing fertilizer:
    • Using fertilizer is a science. You can’t simply eyeball it; it must be uniquely measured and applied.

Fortunately, xVital, which contains only nitrate and ionized water, is a sustainable solution for farmers. It contains no chemicals or salts, is nitrate-based, and comes with an online ratio calculator.

Switching to more sustainable fertilizer practices is one way to help reduce nutrient pollution’s effects on the environment. Another way is employing aquaculture.

Aquaculture Saving our Oceans

A recent study of New England’s waters found that when shellfish and seaweed are properly farmed, they improve water quality.

According to Seth Theuerkauf, aquaculture scientist with The Nature Conservancy, seaweed can absorb nutrients from the water column and restore the ocean’s pH by absorbing carbon dioxide in the water. Shellfish absorb nitrogen from water and provide hiding places for fish seeking shelter from predators.

By introducing seaweed to very acidic ocean waters and shellfish to waters contaminated by agricultural runoff, we can begin reversing the nutrient pollution that is decreasing our water’s quality.

There are many ways to reduce our pollution and save the earth. Check out our other articles to see how you can help!



Mysterious Lobster Deaths in Cape Cod Raise Climate Change Concern


Nutrient Pollution

Protecting Water Quality from Agricultural Runoff

Farming Seaweed And Shellfish Can Help Water Quality And Wild Fish Stocks, Report Finds