Pollution of global marine environment

The oceans are enormous in their size, volume and depth. All oceans and seas are continuous. They are complex, extensive and stable ecosystems, controlled by a variety of physical, chemical and biological processes. They form a largest ecological system. The life on earth first originated in the seas and oceans. The marine environment dominates that of land (70% of the earth’s surface.) The ocean is the giant reservoir of water – water wealth 97.3 % in oceans and 2.7 % on the land. They are complex chemical system – 96.6% of seawater is pure water and only 3.4% contain dissolved solids. Ocean currents distribute heat energy around the globe and moderate earth’s surface temperature. They are the rich reservoir of carbon dioxide (130 trillion tons: 50 times more than air) and mineral wealth (50 million billion tons). The oceans are the richest source of the atmospheric oxygen and large reservoir of momentum and energy. Off-shore waters of marine environment have nearly 20% of world’s oil resources. They are the huge reservoir of biological wealth – 180 thousand species from small bacteria to huge mammals – 25000 varieties of fish. At present 75-80 % of the total global transports by world oceans and seas.

Role  of  Life supporting functions

The ocean absorbs a great amount of carbon dioxide and pollutants. The ocean absorbs 80 percent of the heat added to the Earth’s system by climate change. The oceans provide humans with foods, recreational opportunities, and transportation corridors. The oceans are comprised of diverse habitats that support a wealth of marine wildlife. Humans have been disposing a lot of 'waste into the ocean - trash, sewage, oil, chemicals, heat.

Role as Global carbon sink

The ocean is a natural sink of co2. The net annual uptake of co2 by oceans is estimated to be approx. 2 thousand million tones. The CO2 dissolves in sea water and forms carbonic acid. It hydrolyses into carbonates and bicarbonates. About 90 % of CO2 exists as carbonates and bicarbonates. CO2 is taken up by phytoplankton in photosynthesis and converted into plant material.

Global marine environmental changes

About 390 million tonnes of run-off water enters our marine environment each year. Approx. 7 billion tons of litter enters the world's oceans each year. Approx. 35% of mangrove area has been lost or converted. Approx. 20% of coral reefs have been destroyed globally in the last few decades. Coastal wetland loss in some places has reached 20% annually. Indiscriminate fishing practices kill and waste between 18 - 40 million metric tons of "unwanted" fish, seabirds, sea turtles, marine mammals, and other ocean life annually (FAO - U.N). Oil spills may occur when an ocean oil rig springs a leak or when an oil tanker wrecks. E.g., The Santa Barbara spill in 1969, and the Exxon Valdez spill in Alaska in 1989. In 1991, millions of gallons of oil were released into the Persian Gulf during the Gulf War.

Global and Indian coastal lines

Two-thirds of the world population lives in coastal lines. Over 90% of the world’s living biomass is contained in oceans. Coastal areas produce 80% of the marine resources.Indian coastal line measures about 7500 km and 2000 km wide Exclusive Economic Zone. The Indian coastline supports almost 30% of its human population. India is the 7th largest marine fishing nation in the world. The Bay of Bengal and the Arabian Sea are rich fishing grounds.

Marine biodiversity

Animal life in the sea is very varied and more diversified in terms shape, size, form and weight-right from microscopic plankton to the giant whale. The total number of marine species is ranging from 178,000 species to more than 10 million species.
Total number of marine species described: approx. 3 million, which represent about 15% of all described species. Coral reefs (the high number of species per unit area) have 1 - 9 million species. Deep sea (its enormous area) contains 5 million species.
Ecosystem services of Continental shelf
Continental shelves account for at least 25% of global primary productivity. It provides 90–95% of the world’s marine fish catch. It produces 80% of global carbonate and 50% of global de-nitrification. It carries out 90% of global sedimentary mineralization (UNEP 1992).Composition of Marine Biodiversity

— 
321 species of marine fungi
40000 species of foraminiferans
Of the 28000 fish species , ¾ colonizes marine habitats
More than 2500 macro fauna species
More than 600 species of Benthic algae

Marine physical diversity gradients

—  Depth gradient -dissolved gases decreases with depth. 

—   Salinity gradient-species diversity declines as the concentration of dissolved solutes deviates from normal sea water.

—  Nutrient gradient- species diversity decrease as a function of nutrients from the shore to the open sea.

—  Latitudinal gradient - species  diversity increase  from the poles to the tropics

Diversity of coastal habitats—

• Mangrove swamp ecosystem – water logged saline soil
• —Sea grass ecosystem – highly productive macro algae
• —Coastal lagoon ecosystem – most fertile littoral ecosystems
• —Coral ecosystem – richest in species
• —Estuarine ecosystem - meeting place of river and sea
• —Delta ecosystem –
• —Sandy beach ecosystem – intertidal zone
• —Rocky shore ecosystem – intertidal zone
• —Coastal upwelling ecosystem

Marine life

Marine organisms can be categorized into plankton, nekton and bentos.
Plankton is mostly microscopic size.They have no means of locomotion or self-propulsion. The surface of each plankter is large in relation to bulk and often with elongate body parts. Phytoplankton includes microscopic diatoms, dino flagellates, green algae, blue green algae whereas Zooplankton consist of many protozoans, crustaceans, small mollusks, few worms, a host of larvae copepods and macro-crustaceans.
Nekton – They are actively swimming organisms which include all evolved species of fish.
Small and big organisms including dolphins, porpoises and whales
Benthos- are bottom dwelling organisms. They are categorized into epifauna and infauna.
Those benthic organisms living on the sea floor are called epifauna and those living in the sea floor are called infauna. Sessile benthos includes sea weeds, sponges, anemones, corals, barnacles and oysters. Creeping benthos consists of crabs, lobsters, snails and echinoderms. Burrowing benthos has clams and worms.

Human impacts on marine environment

Direct effects include dredging and dumping (reclamation), removal of biota (through fishing) and construction of marinas, port facilities or breakwaters.
Indirect effects include introduction of foreign diseases or species and discharge of nutrients and toxic pollutants.
Direct human impacts:
Dredging refers to excavation of sediments from the sea bed to make the water deeper. Loss of habitat alters species composition. Dumping (or reclamation) refers to the deposition of sediments in the seas to create new land. Reclamation results in complete physical loss of the natural environment e.g.port expansions, shipping activities, or construction canals. Introducing soil and mud into the water column increases turbidity and sedimentation which alters benthic flora and fauna.
Over-fishing - Over-fishing of a target species removes predator or prey animals. Over-fishing affects the species composition and ecological food chain
Trawling - Trawling results in by-catch of non-target species, such as seals, dolphins, sharks, sea snakes, fish, turtles and invertebrates. Trawling has the potential to devastate benthic habits.
Coastal aquaculture can contribute to degradation of coastal habitat.
Land based discharge (sewage, industrial effluent and urban/river run off etc.) and atmospheric inputs from industry sources account for some 77% of marine pollution.
Maritime transport is responsible for some 12% of the total.Marine environmental problems

Coastal erosion – sand erosion by strong winds, high waves, heavy rains, flooding, and storm waves.
Pollution with toxic substances.
 Eutrophication – over-enrichment with nutrients.
Sedimentation- Land based discharge and deposition of sediments.
Over exploitation of living and non-living resources for  selective commercial exploitation.