Pacific Ocean Threats & Impacts: Pollution

Pollution can smother marine life, cause harmful algal blooms and hypoxic zones, and alter food web dynamics. Pollution can also endanger human health and result in great economic loss for fisheries, tourism operators and others.

Quick Facts

  • Excessive nutrients in the water lead to excessive algal growth. More than 300 recorded cases of paralytic shellfish poisoning and 17 documented human deaths have occurred in Central America alone as a result of toxins produced by these algal blooms.
  • Healthcare costs for illnesses related to beach bacteria from pollution range from an estimated $21 - $414 million each year in Southern California. The state of California spent an estimated $51 million under its Clean Beaches Initiative over six years from 2000-2006.


Organic pollutants from sewage, nutrient pollution from fertilizer run-off, plastic marine debris, toxic dumping and oil spills, urban runoff and dispersed pollutants combine to create one of the most critical classes of ocean threats. Wastewater from aquaculture, offshore oil and mining, radionuclides, oil spills and antifouling chemicals, and toxic dumping compound the problem. Plastics pose a particularly severe threat; an estimated 90% of floating debris in the ocean is plastic, which can take hundreds of years to break down at sea. A section of the North Pacific Ocean (the North Pacific Gyre) is home to the world's largest floating "island" of trash, known as the "Great Pacific Garbage Patch”.  The polluted area covers approximately 8 million square kilometers—larger than the entire United States.

Environmental & Socioeconomic Impacts

Pollution exerts some of the worst impacts on marine and human systems. Nutrient inputs from sewage or fertilizer can cause eutrophication, which increases primary productivity and algal blooms (including harmful algal blooms), oxygen depletion, and reductions in water quality, fish, coral, and other marine populations. These changes, in turn, alter food web dynamics and the entire ecosystem. Nutrient pollution can also lead to disease outbreaks, which can produce massive fish and coral mortality. Chemical pollution from mining or toxic dumping is just as harmful. Toxic chemicals can bioaccumulate in fish, disrupt hormone balances, endanger fish reproduction, and alter food web dynamics, ecosystem functions and biodiversity. Oil spills, which form thin, toxic films over large areas of water, also have far-ranging impacts on multiple levels of marine life. Plastics and floating debris are equally damaging; they absorb persistent organic pollutants like Polychlorinated Biphenyls (PCBs), which then bioaccumulate in fish, marine mammals and seabirds and disrupt ocean food web dynamics.

Pollution also creates problems for human populations. By causing mortality of economically important species, pollution can lower the productivity of fisheries and aquaculture operations, thus threatening livelihood. Nutrient pollution also poses severe health risks, including paralytic shellfish poisoning (PSP), ciguatera, linked with algal blooms, or elevated mercury levels in people. The pollution of coastal waters can also reduce aesthetics, recreation and tourism. As agriculture, mining and industrial activities intensify throughout parts of the Pacific Ocean, and new synthetic compounds are developed, chemical pollution has proceeded unregulated and unmonitored. Many of the impacts upon marine ecosystems and humans are still unknown.

Click here for key readings about pollution's threat to and impact on the Pacific Ocean.