Ocean Pollution

Problem: Pollution of the world's oceans is quickly becoming a major problem on Earth. We know very little about the effect that pollution has on the oceans but we continue to dispose of chemicals, sewage and garbage into it.

Toxic Ocean Pollutants Our waste, even in small quantities, have huge effects on ocean communities and species. Toxic pollutants in the ocean ecosystem have massive impacts on the plants and animals.

Some major types of pollutants: garbage sewage chemicals radioactive waste eutrophication heavy metals oil

Marine Garbage Garbage includes junked out fishing nets, plastics, general household garbage In one case an island 300 miles from the nearest inhabited island) had 950 pieces of garbage ranging from plastics to tin cans. Garbage in the oceans is a serious issue as fish entangle themselves in fishing nets and animals sometimes eat trash products and die. There are numerous examples each year of dolphins, sharks and whales entangling themselves in fishing nets and dying from oxygen starvation.

Oceanic Sewage Disposal Typically the problem with sewage is that it causes massive nutrient loading in the ocean ecosystem. When nutrient loading occurs there will often be algae blooms in the water leading to the loss of dissolved oxygen. After the depletion of oxygen levels from sewage, many organisms in the ocean die from being unable to breathe properly.

Oceanic Sewage Disposal Cont’d Other problems associated with sewage include parasites/bacteria that require the closing of coastal beaches and poisoned shellfish fisheries. For the most part cities in the developed world have sewage treatment facilities but many of the cities in poorer areas have little to no sewage treatment.

Chemicals These are toxic substances that are released by the industrialized nations and make their way into ocean systems. Toxic chemicals often enter ocean systems through food chains and affect organisms at different times and places from where they were released.

Example: DDT (Dichlorodiphenyltrichloroethane) DDT was used for years as a pesticide on farms. Later it was found that it does not breakdown, This compound is relatively insoluble in water and bonds strongly to particles. Although DDT is not used in the marine environment it enters marine food webs through land runoff, precipitation and dumping. DDT is absorbed by plankton but cannot be metabolized. Since, it is not metabolized it accumulates in the food chain until it reaches the top carnivore, where more drastic effects are seen. For example, in marine birds, DDT interferes with calcium deposition in the eggshells. The eggs shells are extremely thin and therefore easily broken.

Desalination Plants There are several concerns about the impact of desalination plants on the marine environment. Various chemicals used to clean pipes and to pre-treat the water, are later washed out in the effluent. One of the largest concerns is the release of highly-concentrated salt water, sometimes into estuaries and rivers, where the salt content is obviously much lower than in the open ocean. Estuaries are important breeding and juvenile development habitats for many species, because of their calm waters. Eggs, larvae and juveniles are usually far less tolerant to environmental changes than their adult counterparts, so changes in estuary oceanography could have a large impact of brood stock of various fish and invertebrate species.

Radioactive waste Radioactive waste enters the ocean from nuclear weapon testing, the releasing or dumping of wastes from nuclear fuel cycle systems, and nuclear accidents. Dumping of high-level radioactive waste is no longer permitted in the ocean, but dumping of low-level wastes is still permitted. Low-level waste contains less radioactivity per gram than high-level waste. High-level wastes usually have longer half-lives. For example, one common high-level waste that is produced by spent nuclear fuel has a half-life of 24,100 years! It has been suggested that contained nuclear waste should be disposed in the deep sea. So little is known about the deep sea environment or the consequences of containment leakage and failure, that the effects could be devastating.

Eutrophication: The release of excess nutrients into coastal waters. Fertilizers used on land are washed into the ocean via rivers and streams. High nutrient concentrations cause phytoplankton blooms such as, red tides, various yellow and green foams, slimes, and slicks. Although algal blooms are natural, a higher frequency of their occurrence in the past twenty years indicates an unhealthy ecosystem. The toxicity of recent blooms are increasing, which can have a direct effect on the organisms that feed on them. Also, phytoplankton naturally contains DMS (dimethyl sulfide) which is released from dead phytoplankton into the atmosphere and can be changed to sulfuric acid to eventually contribute to acid rain.

Heavy Metals Heavy metals in the water are dangerous when they have a chance to built up inside organisms. Organisms tend not to get rid of the metals within them, so it accumulates over the coarse of their life Examples: mercury, cadmium, arsenic

Oil Spills (1) The effects of an oil spill of marine life depend on a number of physical and biological factors. The distribution of the oil spill will be affected by currents and wind In addition, the amount of oil spilled will determine the eventual geographic boundaries of the impact area. The physical and chemical properties of the oil will determine the behaviour of the slick, in terms of its thickness and rate of spreading.

Oil Spills (2) Environmental conditions such as salinity, water temperature, and type and slope of shoreline will determine habitat effects and clean-up procedures Some example habitats include sandy beach, mud, cliffs, estuaries and open water. In terms of difficulty of clean-up and relative vulnerability, a salt marsh ranks the highest, followed by eelgrass, mud, mixed-fine sediment, mixed- coarse sediment, rock, sand, algae (kelp) and open water.

Oil Spills (3) Biological characteristics of the organisms affected will determine the severity of impact. These characteristics include the type of species, life stage (larval, juvenile or adult) and size.

Cleaning-up oil spills: 1. Dispersants: Oil can be broken down more quickly by spraying dispersants (chemicals) on the oil slick from boats or planes. This method only works on fresh, small oil spills. 2. Booms: A boom has a floating skirt suspended down in the water and a sail holding it above the water line. The floating skirt stops the oil from passing. These are used to prevent oil from entering delicate and protected areas. 3. Slick-lickers: This method uses a belt of oil absorbing material that sucks up the oil from the ocean water. The oil is then squeezed out of the absorbing material into a collecting bin.