Staples to many world economies, and home to millions of species, the ocean has always been a place of mystery and adventure. Sadly, this sense of mystery led industrial-era societies to view the ocean as both fishing grounds, as well as waste disposal sites. This mindset is only now beginning to shift due in part to the rising awareness that our actions have dire consequences, including for us.
Our pollution has caused massive problems for marine ecosystems, but none quite so insidious as the growth of dead zones around the world. Dead zones, or hypoxia, are areas where oxygen no longer mixes in with the water in a marine ecosystem.
Although some dead zones are naturally occurring, pollutants from the human industry have caused a growth in the total area impacted by hypoxia. Mobile fish species will leave the area, and vegetation and localized animal species like coral simply die off as the water stops being breathable.
A. Environmental Pollutants
Environmental pollutants refer to a broad spectrum of chemical and atmospheric substances and conditions which contaminate marine ecosystems. These cause different effects and are best understood in three key categories:
Eutrophication refers to nutrient-rich effluent which flows from land into the water. Most common sources of this effluent agriculture, and lawn maintenance products. Nitrates from fertilizer flow through the water table into rivers, lakes, and eventually to the coastline. This can cause an increase in algae blooms which are more often than not toxic for terrestrial life, as well as deadly to marine life.
As carbon and other molecules build up in the atmosphere, those molecules encounter other materials. This causes new chemicals to be formed, which travel on air currents and accumulate in different biomes around the world. This process can happen either in the atmosphere or in direct contact with water.
3. Global Warming
As the greenhouse effect caused by carbon-heavy gases like carbon dioxide and methane cause global temperatures to rise, the temperature of the ocean rises as well. This warming increases the rate at which water molecules interact with other naturally and unnaturally occurring compounds. The result has been a slow increase in the acidity of the ocean itself. This decrease in pH has shown a significant increase in carbonic acid in marine ecosystems, which directly contributes to the growth of dead zones.
B. Refuse and Domestic Waste
The most obvious pollutant humans produce domestic waste products. These pollutants can be observed in the water near their source, but marine currents spread them all over. They can be best understood in two categories:
1. Sewage and Stormwater Disposal
Many coastal cities around the world pour stormwater and sewage waste directly into the ocean. Chemicals that flow through our sewer systems will invariably end up in the wider ocean. These chemicals have been directly linked to coral bleaching and increased hypoxia in nearby marine ecosystems. Moreover, sewage, whether raw or processed, has the same impacts on aquatic ecosystems as eutrophication does.
We, humans, produce a lot of garbage. While we do our best to dispose of garbage responsibly in most jurisdictions around the world, refuse is still falling into the ocean faster than we or natural processes can remove them. This is everything from plastic pollution to heavy metals from household products like batteries, and the impacts are most noticeable to the naked eye. While plastic waste poses a direct threat to marine animals, organic waste also contributes to eutrophication in coastal ecosystems.
C. Industrial Pollutants
Different industries use water in different ways to help in their operations. Often, runoff and industrial waste end up in the mix before being pushed back out into the natural environment, where these pollutants end up interacting with marine ecosystems in various ways. Different types of Industrial pollution include:
1. Industrial Water
Industries utilize dangerous chemicals to produce their end products, and more often than not freshwater has been used to clean away the leftovers. These include heavy metals like mercury and lead, asbestos, sulfates, nitrates, phosphates, and petrochemicals. The best example of this sort of pollution is Lake Erie, which has ostensibly become one big dead zone after a century of industrial waste.
2. Nuclear Waste
Nuclear industrial products produce some of the most dangerous waste of any industry. Regardless if it is from power generation, medical applications like x-ray machines or just the byproducts of mining for nuclear fuel, the waste products produced from nuclear technologies have devastating and wide-reaching impacts. Irradiated particles introduced into water systems can travel thousands of miles, causing problems for all life in their path.
3. Oil and Gas
The petroleum industry has been widely recognized as the main antagonist of the industrial and post-industrial eras. While the effects of greenhouse gasses are well known, oil and gas contaminate our water systems in a number of different ways beyond the end product of burning them as fuel. Through extraction processes like hydraulic fracturing, spillage from transport, and storage of petroleum, we dump a lot of toxic waste into the earth’s waterways due to oil and gas.