Pollution

There are many kinds of pollution in the ocean which threaten human and ecosystem health.

Plastic Pollution

Plastics, a major portion of the chemicals industry, are of particular concern from a pollution standpoint. There are 75-150 million tons of plastic in the ocean today, of which an estimated 4.8-12.7 million tons entered the ocean in 2010 ¹. The World Wildlife Fund estimates that oceanic plastic pollution does $3.1 trillion of damage each year, or about $280,000 per ton of plastic in the ocean ², while Beaumont et al. estimate damages at 3300-33,000 per ton per year based on lost ecosystem services ¹.

The WWF cost translate into a cost of $0.68-1.36 per pound of wild-caught fish ³, in contrast to prevailing retail market fish prices of around $6-19 per pound ⁴.

Poor waste management practices, rather than the absolute volume of plastic waste generated, is the main factor that determines how much oceanic pollution occurs.

Source: Ritchie and Roser ⁵, who draw upon Jambeck et al. ⁶ and Li et al. ⁷.

Fishing Gear

The share of discarded fishing gear as a share of all oceanic plastic has been estimated at 20% ⁵, though lower estimates of 0.5 to 1 million tons are made ⁸, and there is limited reliable data on the subject ⁹. Beyond sheer mass, discarded fishing gear is of particular concern because of the potential to continue catching sea life after discard, a phenomenon known as "ghost fishing" ¹⁰. Furthermore, discarded nets have been observed to disrupt ship propellers, having caused at least one major shipwreck ¹¹.

A deposit-refund system is suggested to reduce the level of fishing gear discard. Under such a system, a deposit would be assessed with the sale of fishing gear, and that deposit would be refunded upon returning used gear to a facility at a port. The system is analogous to the beverage container deposit system that exists in many parts of the world ¹².

Improved recycling can increase the economic incentive for fishers to avoid loss of equipment ¹³.

There is ongoing work to develop biodegradable fishing nets ¹⁴.

Persistent Organic Pullutants

Persistent organic pollutants (POPs) refer, as the name suggests, to organic compounds that break down slowly. Most POPs are pesticides, as well as solvents, pharmaceuticals, and some industrial chemicals ¹⁵. Evidence is that since the 1970s, when heavier regulations on POPs were instituted, the level of POP concentration in the ocean has been decreasing, though it remains high enough to cause health problems for sea life, particular life higher on the food chain, and for humans who consume seafood ¹⁶.

The main regulatory tool on POPs the Stockholm Convention on Persistent Organic Pollutants, an international agreement which bans or restricts many classes of POPs ¹⁷. Methods to remove POPs from the ocean, such as with certain nanomaterials, are active areas of research ¹⁸.

Metals

Accumulation of three metals in the ocean in particular--mercury, cadmium, and lead--are of particular concern due to their toxic natures.

Source: U.S. EPA ¹⁹.

Anthropogenic sources constitute about 30% of total mercury emissions, but many of the natural resources are the result of mercury absorption and re-emission, and not the cause of new mercury into the biosphere ¹⁶. The bioaccumulation of mercury and resulting human exposure, from eating seafood, can cause neurological, heart, and nervous system problems, and it is advised that pregnant or child-bearing-age women, and young children, avoid certain kinds of seafood as a result ²⁰.

In addition to mercury, cadmium, and lead, phosphate mining leads to chromium, nickel, copper, arsenic, thorium, and uranium pollution into coastal waters ¹⁶. Rare earth element pollution is also an emerging concern ¹⁶.