28 Water Pollution-II (Marine Pollution)

Anjali Malan and Hardeep Rai Sharma

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Objectives:

  • To understand the classification of oceans
  • To learn about the composition of oceans
  • To explain the importance of oceans
  • To understand the sources, impacts and control of marine pollution

Concept Map

 

The previous module (WRM/27) discussed the surface and ground water pollution and in this module we will study about the remaining another aspect of water pollution i.e. marine pollution. This module deals with the importance of oceans and the main causes, effects and control of marine pollution.

 

Introduction: Life on Earth originated in the oceans, and oceans are home to many unique ecosystems that are important sources of biodiversity. The oceans are the large masses of water bordering the continents. Oceans cover 71 % of our earth’s surface and contain approximately 97.5% of water. Even though all oceans are interlinked, they are predominantly categorized geographically into five divisions as Atlantic, Pacific, Indian, Antarctic, and Arctic Ocean having distinctive characteristics, area and depth (Table. 1). Sometimes the terms “ocean” and “sea” are used interchangeably because seas are present on the margins of the ocean. The sea is defined as a division of an ocean or a large body of salt water partially enclosed by land. Seas are smaller than oceans and are usually located where the land and ocean meet.

Table 1: Classification of world oceans

Sr. No. Name of the ocean Area (Sq.kms) Max depth (m)
1 Pacific Ocean 161,760,000 10,803
2 Atlantic Ocean 85,133,000 8486
3 Indian Ocean 70,560,000 7906
4 Southern Ocean 21,960,000 7075
5 Arctic Ocean 15,558,000 5567

Source: http://www.ngdc.noaa.gov/mgg/global/etopo1_ocean_volumes.html

 

Composition of seawater: The water in the oceans is very high in salts and dissolved ionic substances and is mainly composed of sodium, magnesium, chloride etc. (Table 2). The oceans are not uniformly mixed but are structured in layers with distinct properties similar to the atmosphere. Pressure increases with depth as the weight of the overlying air and water increase along the depth. Atmospheric pressure at sea level is 101 kPa or 14.7 psi or one atmosphere.

 

Importance of oceans: Oceans and seas are very valuable for us. Oceans cover greater than 70% of the earth’s surface and contain 99% of living space on earth. They are important for ecosystem balance as well as protecting biodiversity as mentioned below:

1.  Water cycle: The oceans are an important part of the water cycle. Vast amounts of water evaporate from the ocean surface, rising into the atmosphere as water vapour. As the air passes over warm waters, it rises due to warming. As it cools, condensation of the water creates rainfall. If the air passes over cooler waters, it cools and sinks. Air moves from high to low pressure areas. .

 

2. Temperature and weather control: The Ocean is the largest solar energy collector on Earth. It can also absorb large amounts of heat without a large increase in temperature. There is marked ability to store and release heat over long periods of time which gives the ocean a central role in stabilizing Earth’s climate system. The surface of the ocean absorbs over half the heat reaching the Earth from the sun. By distributing this heat around the world, ocean currents are extremely important in determining the climate of the world’s continents. For example, the Gulf Stream carries warm water from the Gulf of Mexico all the way to Western Europe. As a result, northwest Europe is much warmer than other lands at the same latitude.

 

3.  Oxygen: There are also photosynthetically active plants and bacteria in the ocean, the primary producers. Photosynthetic production of oxygen is limited, however, to the uppermost, sunlit layer of the ocean. This only extends to a depth of around 100 metres. Scientists believe that phytoplankton contribute between 50‒85 % of the oxygen in Earth’s atmosphere.

 

4. CO2 sink: Ocean waters have the capacity to absorb vast amounts of the greenhouse gas carbon dioxide (CO2), and thus have helped to buffer global warming and climate change. Nearly half the CO2 produced by human activities in the last 200 years has dissolved into the ocean. Like land plants, the microscopic algae known as phytoplanktons use CO2 for growth. After their death this CO2 sinks as organic matter to the bottom of the ocean, keeping it out of the atmosphere. A major factor governing the rate of uptake of CO2 by the oceans is pace at which global CO2 emissions are increasing over time. Approximately 2.5 billion tons of CO2 is absorbed by the oceans annually mainly as bicarbonates (Scripps Institution of Oceanography, 2013).

 

5.  Fisheries: People depend for sea food on oceans and variety of marine food like fishes, crabs, snails are present in marine water. India has more than 10% of the global biodiversity in terms of fish and shellfish species. Indian fisheries constitutes about 6.3% of the global fish production, the sector contributes to 1.1% of the Gross Domestic Product (GDP) and 5.15% of the agricultural GDP. The total fish production of 10.07 million metric tons presently has nearly 65% contribution from the inland sector and nearly the same from culture fisheries (NFDB, 2017). However, coastal waters are much more productive than the open ocean therefore marine fisheries have traditionally been located near the coast.

 

6.  Biodiversity: Coral reefs, estuaries, salt marshes, mangrove and seagrass beds are just a few of the ocean environments which support a large diversity of different types of organisms. Marine biodiversity plays a key role through ecosystem services (provisioning, regulatory and cultural). They provide economic wealth and resources that range from active ingredients for pharmaceuticals and medicine to products from fisheries and aquaculture.

 

7.  Natural resources: The ocean floor is not only a habitat for the organisms that live on the bottom (benthic organisms), commercially important as well. The continental shelves and ocean floor are home to many important minerals including oil and natural gas. The major reserves are found off the Mumbai coast-the richest oil field in India known as Bombay High which is 115 km from the shore. Many thousands of square kilometres of the deep-sea floor are covered by metal-bearing nodules. They contain primarily manganese, but also nickel, cobalt and copper, which makes them economically promising. Gas hydrates in the ocean environment with their abundant resource potential is emerging as a potential fuel resource. When gas molecules are trapped in a lattice of water molecules at temperatures above 0°C and pressures above one atmosphere, they can form a stable solid called gas hydrates (NOAA, 2013). The preliminary assessment of geological condition and limited available seismic data suggest high possibility of occurrence of large quantity of gas hydrates within the Exclusive Economic Zone (EEZ) of India. Gas hydrates are crystalline form of methane and water, and exist in shallow sediments of outer continental margins of India (MoES, 2015). Methane gas hydrate is stable at the seafloor at water depths beneath about 500 m. India’s Oil Ministry and the US Geological Survey made the discovery of large, highly enriched accumulations of natural gas hydrate — an icy form of the fuel — in the Bay of Bengal.

 

8.  Transportation routes: The oceans provide convenient shipping routes. Around 90% of all trade between countries is carried by cargo ships. The transport includes everything from food and fuel to construction materials, chemicals, and household items.

 

9. Economy: The oceans are very important to our economy. Revenue related to the ocean is generated through- kelp (emulsifying agent in food and pharmaceutical products), mining (salt, oyster shells, jade, etc.), food, recreation (hook and line fishing, spearfishing, scubadiving, snorkeling, whale watching, etc.), shipping and biomedical products.

 

Marine pollution: It is a big threat to marine ecosystems, human health, and other food sources. Marine waters are continuously degraded by both point and non point sources. Pollution observed in coastal environments occurs mainly due to anthropogenic activities being conducted on the coast and on land adjoining the ocean environment.

 

According to the Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP, 1991), a United Nations body, defined marine pollution as “The introduction by man, directly, or indirectly, of substances or energy to the marine environment (including estuaries) resulting in deleterious effects such as hazards to human health, hindrance to marine activities, impairment of the quality of seawater for various uses and reduction of amenities”.

 

Sources of marine pollution: Many sources are responsible for the pollution in seas and oceans. The major part of marine pollution comes from the land i.e. dumping of garbage and sewage (30%), through the atmosphere as air pollutants (20%), farm runoff (20%), maritime transportation (10%) as well as industrial wastewater (10%). The consequences of offshore drilling and liter make up for the rest (10%) (Figure 1).

 

1.   Runoff from land: Most of the worlds rivers carry different waste material from the land, which finally ends up in the oceans. The major load of pollutants comes from the urban and industrial sewage systems that are dumped in the rivers. These runoffs contain high amount of phosphorous and nitrogen from agricultural and industrial sources. It can lead to the problem of eutrophication in which influx of nutrients causes ‘algal blooms’ and imbalance in the marine ecosystem. Dust particles coming from metal ore and metal mines, also wash away in the rivers. According to the US Environmental Protection Agency (USEPA), over 40% of watersheds in the western continental United States have been contaminated with metals (Sharma, 2009). Large chunks of plastics dumped in oceans are the main killer of life in the ocean and may take up to 450 years to degrade. Micro‒plastics (size < 5 mm) has been reported in deep-sea sediments and surface waters of Southern Ocean (Waller et al. 2017). Particles and fibres of secondary micro‒plastics resulted from the breakdown of macroscopic plastic ocean debris are common throughout the world’s oceans (Li et al. 2016). The global release of primary micro‒plastics in the world ocean was evaluated in the order of 1.5 Metric tons/year. i.e. between 0.8 and 2.5 Metric tons/year (Boucher and Friot, 2017). These global figure corresponds to a world equivalent per capita of 212 gm or a plastic quantity equivalent to every human tossing one conventional light grocery plastic bag (weighing 5 grams) per week into the ocean.

  • Runoff water contains harmful contaminants including fertilizers, pesticides, petroleum and other forms of soil pollutants that contaminate the ocean.
  • Sewage or other polluting substances flow through the rivers, or drainages directly into the ocean. Minerals and substances from mining activities also move to the oceans through this pathway. The discharge of other chemical nutrients into the ocean’s ecosystem can cause reductions in oxygen levels, affect plant life, decline in the marine water quality itself.
  • Agricultural and industrial waste are directly discharged into the oceans, leading to marine pollution. These wastes are comprised of dust and sand, and several types of anthropogenic wastes such as plastics, debris and trash. It is well known that plastics, cannot be degraded and remain suspended in the ocean waters for years. Animals can become snagged on the plastic or mistake it for food, slowly killing them over a long period of time. Animals that suffer because of plastic debris include turtles, dolphins, fish, sharks, crabs, sea birds, and crocodiles.
  • Some toxic and hazardous liquids are directly disposed in the ocean and affects the marine life and increase the temperature of the ocean. The temperature of these liquids is quite high and therefore causes thermal pollution. Many species of animals and plants cannot survive at higher temperatures and eventually perish. However, as per UN treaty (Basel Convention) 1992 hazardous waste disposal in oceans is banned.

 

2.   Atmospheric pollution: The atmosphere also forms a way for the pollutants to reach the ocean. Lighter dust fractions and debris is blown towards the ocean by wind. A great number of dust particles will carry metal traces, which are spread out this way. The greenhouse gases, which are causing warming of the earth, also raise the temperatures in the oceans. The increased concentration of CO2 in the atmosphere contributes to ocean acidification as a secondary consequence. Combustion processes produce a significant amount of SO2 and NOx which will increase the occurrence of acid rain.

 

3.   Ships: Ship’s engines along with incineration of garbage produce CO2, SO2 and NOx, which also contribute to warming. Cooling systems may still be operating on freons and other chlorofluorocarbons (CFCs), and sometimes halon gases. Therefore, subsequent escape of these gases to stratosphere can cause depletion of ozone layer.

 

Ballast water: During unloading of cargo certain amount of oil remains adhered to the walls of container and this may amount to 800 metric ton in a 200,000 metric ton tanker. The ballast water is contaminated with oil when fresh crag of oil is to be loaded.

 

Bilge water: Bilge is a specific compartment, designed to capture all water (from rough seas, rain, minor leaks) that does not drain off over the side of the deck. Depending on the ship’s design and function, bilge water may contain water, oil, urine, detergents, solvents, chemicals and other materials. Cleaning of this tank releases a vast quantity of pollutants in sea water. The International Maritime Organization, London, United Kingdom, has imposed a number of strict rules to limit the impact of the shipping sector on the marine environment. In this case, no water exceeding 15 parts per million (ppm) of oil can be discharged into sea.

 

Biological contamination: when ballast water is taken up, it is bound to contain a number of microscopic life forms, such as algae and larval forms of invertebrates that belong to the specific region the ship resides in. After a few weeks, when the ballast water is pumped out, possibly organisms may be displaced from the region where they belong naturally. In a process of biofouling, the organisms attach themselves to the ship hull. Calcareous fouling organisms include molluscs, barnacles, tube worms and polychaetes and non-calcareous (soft) are seaweed, hydroids, bacterial biofilms and algae. Together, these organisms form fouling communities on all kinds of maritime objects and their habitat also get destructed due to ship activities.

 

4.   Ship accidents: Oil spills from ships containing crude oil causes marine pollution. An accidental oil spillage can cause large damage as crude oil mainly contains different hydrocarbon molecules. Oil discharged into the sea appears as oil slicks, dissolved/dispersed petroleum hydrocarbons, floating petroleum residues (tar balls) and tar on beaches (Gupta and Singbal, 1988). These aromatic hydrocarbons if difficult to clean up can cause cancer and other health problems on prolonged exposure. Crude oil lasts for years in the sea and is extremely toxic to marine life. Worldwide release of petroleum oils in to the marine ecosystem globally, has been estimated to range from 0.5 to 8.4 million tonnes per year (GPA [Global Marine Oil Pollution Information Gateway] 2008). Seabirds are more vulnerable to oil spills because of their distribution and breeding grounds. The floating crude oil on surface covers their bodies and can result in immediate death due to loss of buoyancy. The oil ingested from feeding by aquatic organisms may cause gastrointestinal disorders. Two tanker routes from the Middle East countries cross the Arabian Sea i.e. Western hemisphere through the Mozambique Channel and the other to the Far East and Japan across the Southern Bay of Bengal causes chronic oil pollution problem in the Northern Indian Ocean. Some of the major accidents of oil spillage across the world are described in Table 3.

 

In addition, many ships lose thousands of crates each year due to storms, emergencies, and accidents. This causes noise pollution (excessive, unexpected noise that interrupts the balance of life, most often caused by modes of transportation), excessive algae, and ballast water. Often times, other species can also invade an ecosystem and do harm to it by interrupting the life cycles of other organisms, causing a clash of nature that has already been damaged by the overflow of pollution (Figure 2).

 

5.   Deep Ocean Mining: Another source of marine pollution is mining in the deep sea. An ocean mining site which drills for silver, gold, copper, cobalt and zinc create sulfide deposits up to 1400– 3700 m down in to the ocean. Deep sea mining causes damage to the lowest parts of the ocean and increase the toxicity of the region. The damage caused by this kind of mining also leads to corrosion, leaking, and oil spills that further inhibit the ecosystem functioning of the region. The Central Indian Basin, for example, is rich in nickel, copper, cobalt and potentially rare-earth minerals, which are highly lucrative and used widely in manufacturing electronics such as mobile phone batteries. India has been exploring deep sea for minerals since 1981. The oceans that surround the Indian peninsula have over 1,300 islands. They give India seven-and-a-half thousand kilometres of coastline and 2.4 million square kilometres of the Exclusive Economic Zone.

 

Effects of Marine pollution: The pollution in the oceans can cause many types of problems to marine organisms as well as human beings and can affect the economy of a country. Many of such effects are described below:

 

1.   Effect of Toxic Wastes on Marine Animals: Oil spill is threatening marine life in one way or the other. It spreads over the surface of the water to form a thin film called as oil slick. It prevents sunlight from reaching to marine plants under the ocean and affects in the process of photosynthesis. Skin irritation, eye irritation, lung and liver problems can impact marine life over long period of time according to the National Oceanic and Atmospheric Administration (NOAA, 2017), the oil spilled in the ocean if get on fur-bearing mammals or birds get oil on their fur or feathers, it causes difficulty for them flying or moving properly, in maintaining body temperature, or feed.

 

The oil washes up on beaches and contaminates nesting areas and feeding grounds. Marine mammals may ingest this oil which can poison them. Birds often clean their plumage by pruning and consume oil during this process which can cause intestinal, renal and liver failure. Although fish and shellfish are not impacted immediately, long-term exposure may lead to organ damage, reduced growth, reduced respiration, and may adversely impact reproduction and larva development and survival. Also, the long term effect on marine life can include failure in the reproductive system, cancer, behavioral changes, and even death. According to some reports, thousands of porpoises and dolphins are dying every year due to the increased human interferences in the oceans.

 

2. Disruption of the Cycle of Coral Reefs

 

The coral reefs are the productive ecosystems and offer many benefits to people. These coral reefs are threatened by the sediments from deforestation carried by the runoffs, and the agricultural and industrial chemicals reaching through river discharges. For example River Ganga is estimated to carry 1.5 billion tons of sediments per year due to deforestation and intensive farming in India, Bangladesh and Nepal through which it flows to Bay of Bengal (WordPress, 2017). Oil floating on the water’s surface can be deposited directly on corals in an intertidal zone when the water level drops at low tide. As heavy oil weathers or gets mixed with sand or sediment, it can become dense enough to sink below the ocean surface and smother corals below. Once oil comes into contact with corals, it can kill them or impede their reproduction, growth, behavior, and development. The entire reef ecosystem can suffer from an oil spill, affecting the many species of fish, crabs, and other marine invertebrates that live in and around coral reefs. Moreover, ocean acidification due to high CO2 absorption causes a reduction in pH levels which decreases coral growth and structural integrity.

 

3. Depletes Oxygen Content in Water

 

The greatest quantity of debris in the ocean remains in the ocean for years as it does not decompose and uses oxygen as it degrades slowly. As a result oxygen levels decreases in the ocean. When oxygen level falls down, it affects the survival of marine animals like sharks, dolphins, whales, turtles and penguins for long time. Most of the plastic debris present on ocean surfaces remains floating for years. As it does not decompose rapidly; it leads to depletion in oxygen level in the marine water. The wastes dumped into the oceans contain toxic substances that soak in all the oceanic oxygen. This leads to depletion of oxygen available in oceans which causes marine animals to die in their natural habitat. Organic waste addition results in end products such as hydrogen sulphide, ammonia and methane which are toxic to many organisms. It results in the formation of an anoxic zone which is low in its oxygen content and threatening to marine life.

 

4. Failure in the Reproductive System of Sea Animals

 

Industrial and agricultural wastes include various toxic and hazardous chemicals that are harmful for marine life. Chemical pesticides from runoff can deposit in the fatty tissue of animals, causing failure in their reproductive system.

 

5. Effect on Food Chain

 

Chemicals used in agriculture and industries are get washed into the rivers from runoff loses and carried into the oceans. These chemicals could not get dissolved or sink at the bottom of the ocean. Small animals ingest these chemicals and are later eaten by large animals, which then affect the whole food chain. Bioaccumulation in food chain can also result in loss of species diversity.

 

6. Affects Human Health

 

Hydrocarbons and benzpyrene gets accumulated in food chain and consumption of such fish by man may cause cancer. Similarly, the presence of harmful wastes in the waters affects the food habits of aquatic organisms and human health. When dumping ground is closer to fishing areas and the toxic substances are consumed by the fishes, they gets accumulated in their fat tissues, then the humans consuming these affected fishes can face unwanted health issues. For example Minamata disease in Japan caused by methylmercury (MeHg) poisoning that occurred in humans who ingested MeHg contaminated fish and shellfish from Minamata Bay.

 

7.   Ocean acidification and Eutrophication: Toxic chemicals make our oceans more acidic. Apart from causing eutrophication, a large amount of organic wastes can also result in the development of ‘red tides’. These are phytoplankton blooms because of which the whole area is discolored. For example: Dead Sea. Despite its name, the sea is home to a variety of microorganisms, like a salt-tolerant unicellular green alga known as Dunaliella and red Archaea. This alga flourishes when the sea is slightly diluted. Therefore, an influx of less-salty water would trigger algal blooms and the effect would be enhanced by the addition of fertilizers containing phosphates. A bloom of Dunaliella would in turn feed Archaea that could turn the sea red.

 

Control of marine pollution: Marine pollution should be controlled to protect the marine animals and to maintain the balance in ecosystem. Here are some ways to remove the marine debris and contaminants from oceans.

 

§  Toxic pollutants from industries and sewage treatment plants should not be discharged in coastal waters.

 

§  Run off from non-point sources should be prevented to reach coastal areas.

 

§  Sewer overflows should be prevented by having separate sewer and rain water pipes.

 

§  Dumping of toxic, hazardous wastes and sewage sludge should be banned.

 

§  Developmental activities on coastal areas should be minimized.

 

§  Oil and grease from service stations should be processed for reuse.

 

§  Oil ballast should not be dumped into sea.

 

§ Double Hull tankers should be adopted. These tanker ship hulls are with double layers of watertight hull surface. The inner and outer layers of the hull are on the bottom as well as the sides of the tanker ships. The double layer construction helps in reducing the risks of marine pollution during collision, grounding, and any other form of ship’s hull damage.

 

§  Ecologically sensitive coastal areas should be protected from drilling. Some methods can be adopted to remove the pollutants like oil from ocean water including:

a. Introduction of sewage treatment plants to reduce BOD of final product before discharging into sea.

 

b. Cleaning oil from surface waters and contaminated beaches can be accelerated through the use of chemical dispersants which can be sprayed on the oil.

 

c.    Load on top system reduces oil pollution cleaned with high pressures jets of water.

 

d.   Crude oil washing: While the cargo is being unloaded.

 

e.    Skimming off the oil surface with a section device.

 

f.     Spreading a high density powder over the oil spill, so that oil can I be sunk to the bottom.

 

 

Indian Scenario: India’s considerable maritime interests include a coastline of 6,100 km extending deep into the Indian Ocean, augmented by about 1,400 km of island and rock territories in the Arabian Sea and the Bay of Bengal (the latter comprising 723 islands and rocks of the Andaman and Nicobar chain). In December 1982, India signed the Law of the Sea Convention, and after it came into force in November 1994, and ratified it (along with the implementation of Part XI) in June 1995. Till June 1997, India was one of 116 countries which had ratified United Nations Convention on the Law of the Sea (UNCLOS) III. In view of the Maritime Zones Act (1976), India began to actively demarcate boundaries with its seven maritime neighbours.

 

In order to effectively cope with the multiplicity of activities relating to the sustainable development of the Indian Ocean, the Department of Ocean Development (DOD) was created in July 1981. The DOD functions under the direct control of the Prime Minister, aiming the sustainable and environment-friendly exploration and exploitation of living and non-living marine resources for the socio-economic benefit of the country. The responsibility for the prevention of marine pollution is shared by the provincial and central governments. The pollution control boards of the maritime provinces/union territories work in close coordination with the central government’s, Ministry of Surface Transport (MST) through the Indian Merchant Shipping Act (1958) (for control of pollution from ships and offshore platforms in the EEZ), and the Indian Ports Act (1963); the Ministry of Petroleum and Natural Gas (MPNG) (concerning pollution upto 500 metres from oil platforms and structures); and the Ministry of Environment and Forests’ (MoEF), Water (Prevention and Control of Pollution) Act (1974) for the control of pollution arising from land-based sources with a jurisdiction of upto 5 km in the sea); and the Central Pollution Control Board (CPCB), in addition to the DOD.

 

In 1996, the Indian Coast Guard formulated National Oil Spill Disaster Contingency Plan (NOS-DCP) also came into force. It contains standard formats for reporting spills as well as forwarding data on equipment holding in the country. Since the late 1970s, the Coast Guard has undertaken 29 oil spill operations. It maintains pollution response equipment, and approximately 20,000 tonnes of chemicals. In addition, it also maintains minor stocks of anti-pollution chemicals.

 

International Cooperation

 

India has ratified the Articles of Association of the South Asian Cooperative Environment Programme (SACEP) of the United Nations Environment Programme (UNEP), which became a legal entity in January 1982. The DOD was designated the nodal Indian agency for its Action Plan in 1995. This plan emphasizes the formulation of integrated coastal zone management, national and regional oil and chemical spill contingency planning, human resource development, and control of land based sources of marine pollution (Sudhakar and Kumar, 1996).

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References

 

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