Is the marine environment threatened?

Oceans are the largest ecosystem of the planet earth. They are the lifeblood of planet earth. Oceans cover greater than 70% of the earth’s surface. About 70% of the earth’s oxygen is produced by oceanic phytoplankton. Ocean is crucial for the maintenance of oxygen-carbon dioxide balance of the biosphere. About 97% of world’s water resides in oceans. Oceans provide a sixth of the animal protein people eat. They are the essential source new medicines to combat cancer, pain and bacterial diseases. Oceans absorb carbon dioxide from the atmosphere and reduce the impact of climate change. About half of the world’s population lives within the coastal zone. About 80% of non-biological marine pollution comes from land based activities.

Definition

Marine pollution is the introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries), resulting in such deleterious effects as; harm to living resources: hazards to human health; hindrance to marine activities including fishing; impairing the quality for use of sea water and reduction of amenities (The Inter-Governmental Oceanographic Commission, -UNESCO).

Causes of coastal marine pollution

The dominant driving factors of marine pollution are population growth, industrialization and urbanization. Marine pollutants include sewage, oil, garbage, nutrients, pesticides, and toxic chemicals, and heavy metals, thermal and radioactive wastes.

Categories of marine pollutants

The wastes can be divided into two major categories such as domestic and industrial wastes. The domestic wastes include municipal sewage, agricultural and urban runoff, garbage, plastic debris and land clearing wastes. Industrial wastes include heavy metals, radioactive nuclides, inorganic chemicals and heated water.

Marine eutrophication/ Nutrient pollution

It is the over-enrichment of nutrients which may of two types: natural eutrophication and anthropogenic eutrophication
Natural eutrophication is the upwelling of nutrient inputs, river-borne nutrients (not polluted). It is a slow process (time scale 10³-10 years) and induces ecosystem adaptations.
Cultural eutrophication results in the disposal of sewage, solid wastes, industrial effluents and agricultural fertilizers. The Mississippi river carries an estimated 1.5 million tons of nitrogen pollution into the Gulf of Mexico each year.This anthropogenic eutrophication add excessive amounts of plant nutrients primarily P,N and C. This leads to excessive algal growth and decay.
Features of Eutrophication- Eutrophication is characterized by high concentration of nutrients, high phytoplankton densities, and frequent incidence of red tides, high densities of herbivores and predators and mass mortalities of near –shore organisms. The oxygen level in bottom waters is depleted by the decomposition of organic matter. Near -bottom anoxia leads to the loss of benthic organisms.

Eutrophication – induced changes

Increased input of nutrients results in deterioration of water quality. There is a large scale incidence of red tides, a bloom of red colored phytoplankton (typically dinoflgellates) or growth of coastal macro algal vegetation. These marine algae produce toxins that are poisonous to vertebrates like birds, mammals and humans. Filter feeders like clams and shellfish strain the algae out of sea water during a bloom. Illnesses caused by toxins are being passed through food chain and cause Ciguatera fish poisoning (CFP), diarrhetic shellfish poisoning (DSP) and paralytic shellfish poisoning (PSP). The water transparency is decreased due to mineral turbidity and cloudy detritus which reduces light penetration in euphotic layers. Hazards to Human health hazards are caused by industrial or domestic effluents with toxic metals, detergents, pesticides, phenols, ammonia, H2S etc. This may also reduce aquaculture opportunities or impairing quality of its products. There is a reduction in species and tropic diversity which may cause loss of fisheries resources. Loss of water clarity, dead animals on shore, foul smells, toxic shell fish etc. damage recreational value.

Garbage and plastics disposal

Solid wastes are generally garbage and rubbish which present the most visible form of pollution (visual pollution). About 14 billion pounds of garbage are dumped into the ocean every year. Disposal such wastes pose a major threat to marine communities. Plastics thrown into the sea can stay there for many years and harm marine life. A huge number of marine animals die every year from either ingesting or become entangled in plastic trash. More than 180 species of animals have been documented to ingest plastic debris. Seals and sea lions starve after being entangled by disposed nets. Plastic debris kills 100,000 marine mammals and 2 million sea birds per year.

Negative impact of sewage disposal

Sewage disposal cause turbidity of sea water which depresses phytoplankton production. Sedimentation changes benthic environment and induces hypoxia/anoxia (oxygen demand). This oxygen depletion pollution causes loss of biodiversity, changes in the species composition and dominance which leads to species – poor communities. This pollution related makes the habitat unsuitable for benthic organisms of commercial importance. The contamination of sewage leads to offensive odor,bacterial and viral enteric infections. The consumption of contaminated shell fish leads to human health problems.

Pesticide contamination

Pesticides are chemicals used to kill insect pest, weeds and pathogenic microorganisms that might damage crops. Pesticides can enter the sea water through urban and agricultural land runoff (nonpoint source). Pesticide contamination of sea water results in fish kills, reduction of growth and impairment of reproduction fish and invertebrates. Poisoning of DDT induces egg-shell thinning in marine birds, which drastically reduces their population. Poisoning in humans leads to potential toxic effects, neurological disorders and reproductive and birth defects.

Contamination of petroleum hydrocarbons

Oil spills cause huge damage to the marine environment but are responsible for about 12% of the oil entering the seas each year. Tankers and cargo ships discharge petroleum hydrocarbons either deliberately or accidentally. In 1992, more than 4 million tons of oil was released into the world’s oceans. In 1992, there are 611 incidents of oil pollution in UK coastal waters alone. Many of the major oil spillages during the last 20 years have been caused or made worse by human error. Exposure to oils causes smothering and clogging of organs which interferes with feeding, reproduction, growth and behavior. The tainting sea foods lead to un-marketability. Human health effects include cancer risks.

Contamination of heavy metals

Heavy metals are of great concern because they enter animal and human food chain. Most dangerous metals include mercury, cadmium, lead and copper. Copper is dangerous to marine organisms and has been used in marine antifouling paints. Exposure to heavy metals causes mortality of juvenile stages of marine organisms and toxicity to phytoplankton, invertebrates and fish. Heavy metal exposure may affect morphology, physiology and behavior of marine organisms. Heavy metals cause potential mammalian toxicity and skeletal, muscular and neurological problems.

Contamination of radio nuclides

The term “nuclear waste” is generally used to represent all radioactive waste materials regardless of their origin, material form or radioactivity levels. Exposure to radioactive waste cause both somatic and genetic effects. The somatic effects include acute lethality and skin allergies. The genetic effects are mutations and cancers.

Impact of Global Climate Change

Climate change damages plant and animal physiology, abundances, and distributions. It has altered bio-productivity and species interactions. It may decreased or increased precipitation, thereby altering coastal and estuarine ecosystems. Species that are unable to migrate or compete with other species for resources may faced extinction. Changes in precipitation and sea-level rise affected the water balance of coastal ecosystems. The increases in precipitation and runoff may caused the risk of coastal flooding. Climate change affected the structure (e.g., plant and animal composition) and function (e.g., plant and animal production, nutrient cycling) of estuarine and marine systems.

Critical coastal ecosystems

Wetlands, estuaries, and coral reefs are particularly vulnerable to climate change. Such ecosystems are among the most biologically productive environments in the world. Climate change may degrade these valuable ecosystems, threatening their ecological sustainability and the flow of goods and services they provide to human populations

Conservation of global oceanic environment

The ocean is international property or global commons. No nation has any right, moral or legal to pollute any part of it, including territorial waters. Habitat protection is the most serious need for coastal and marine biodiversity. The presence of toxic wastes in offshore waters must be curtailed by stricter laws. There should be an optimum exploitation of living and non-living resources. There is a need for co-ordinated, centralized and highly sophisticated research programmes to identify various pathways by which pollutants enter the ocean and to analyze the behavior of individual pollutants. The damaged habitats are restored by re-vegetation of mash grasses, mangroves and sea-grasses. International and national bodies should be initiated to monitor the growth of marine pollution.