Ocean Issues: Ocean Pollution – Ocean acidification- Ocean Dead Zone – Geography UPSC Notes

Oceans Issues and Threats – Currently our Oceans are facing the following major problems:

• Over Fishing
• Predation of Top predators
• Ocean Acidification
• Coral Bleaching
• Ocean Dead Zone
• Heavy metal Pollution
• Plastic Pollution

Over Fishing

• Overfishing is having some serious impacts on our oceans. Not only does it work towards wiping out a species, but also the other species of marine animals that are dependent upon those fish for survival. It’s been shown that overfishing can cause marine animals to starve since we’re taking food from their mouths in too large of numbers for them to be able to get their fill. It is also estimated that most seas already need long-term fishing bans if certain species are to recover at all.
• Apart from that, the processes that are being used for fishing are causing more havoc. We use some pretty destructive methods in how we pull catches, including bottom trawling which destroys seafloor habitat and scoops up many unwanted fish and animals that are tossed aside. We also pull far too many fish to be sustainable, pushing many species to the point of being listed as threatened and endangered.
• The main reason for overfishing is a sudden increase in the demand for seafood. We are trying to diversify our food sources and recently more impetus has been given to seafood citing its health benefits.

Predation of Top predators

• Sharks are killed in the tens of millions each year, mainly for their fins. It is a common practice to catch sharks, cut off their fins, and toss them back into the ocean where they are left to die. The fins are sold as an ingredient for soup. And the waste is extraordinary.
• Sharks are top-of-the-food-chain predators, which means their reproduction rate is slow. Their numbers don’t bounce back easily from overfishing. On top of that, their predator status also helps regulate the numbers of other species. When a major predator is taken out of the loop, it’s usually the case that species lower on the food chain start to overpopulate their habitat, creating a destructive downward spiral of the ecosystem.
• Whaling is also a major problem pushing the population of blue whales to the brink.

Ocean Acidification

Ocean acidification is the ongoing decrease in pH of the Earth's ocean water, caused by the absorption of carbon dioxide(CO₂) from the atmosphere. When CO₂ dissolves in seawater, it forms carbonic acid, which increases the acidity of the water. This process of ocean acidification has been ongoing for several decades and is primarily driven by the burning of fossil fuels, which releases large amounts of CO₂ into the atmosphere.

Ocean acidification is no small issue. The basic science behind acidification is that the ocean absorbs CO2 through natural processes, but at the rate at which we’re pumping it into the atmosphere through burning fossil fuels, the ocean’s pH balance is dropping to the point where life within the ocean is having trouble coping.

• “Ocean acidification is more rapid than ever in the history of the earth and if you look at the pCO2 (partial pressure of carbon dioxide) levels we have reached now, you have to go back 35 million years in time to find the equivalents,” said Jelle Bijma, chair of the Euro CLIMATE program Scientific Committee and a biogeochemist at the Alfred Wegener-Institute Bremerhaven.
• You need to understand that the pH of ocean water is basic. It is around 8.1 on average. With ocean acidification, the pH is slightly less. This does not mean that is has come less than 7. If it gets less than seven, then nothing will survive.

Causes of Ocean Acidification

• Increased Carbon Dioxide Concentration in the Ocean: When sea organisms die on the sea floor, their remains accumulate and form corals, which are made up of carbons.
  • These organisms also release calcium into the water. Because they add acidity to the water, these compounds have a far-reaching negative impact on its composition.
• Increased Carbon Dioxide Concentration in Atmosphere: When carbon dioxide is released into the atmosphere as a result of various human activities, it also contaminates the water because the carbon gases dissolve in the seawater, lowering the pH and contributing to acidification.
• Increased Hydrogen Ions Concentration in Water: Some chemical reactions that occur on the sea floor may include an increase in hydrogen ions, which, when combined with other compounds like nitrogen, water, and other gases, cause ocean water acidification.
• Burning of Fossil Fuels: When petroleum, diesel, and coal are burned, they emit a large amount of carbon dioxide. This raises the concentration of carbon dioxide in the atmosphere, which eventually finds its way into the water.
  • Carbon and other atmospheric gases enter the sea via acidic rainfall or direct dissolution into the water.
• Waste Disposal: Many countries that live near seawater masses have been too quick to use the oceans as potential dumping grounds for domestic and industrial waste.
  • Other wastes, in addition to direct sewage waste disposal, increase the acidity of the water.
  • Acidic compounds in industrial and agricultural waste, for example, are extremely dangerous because they lower the PH of ocean water.
• Improper Land Management: Agriculture also plays a role in the problem of ocean acidification.
  • Some of the farmers' methods are ineffective and prone to soil erosion, and the chemicals are washed downstream into the ocean as a result.
  • In short, if the land is not well managed, the impact of acidifying soil mineral content and water pollution can harm water bodies.
• Industrialization: Countries or cities that have embraced industrialization pose serious environmental risks.
  • Their presence can only mean that there is more carbon dioxide in the atmosphere, which, when absorbed by the water, raises the level of acidity.
  • Industries contribute to the release of hazardous gases such as carbon dioxide, sulfur dioxide, nitrogen oxides, and others, which eventually form acid rain or dissolve in the oceans, resulting in acidic conditions.

CO2 Effect on Ocean Acidification

• Carbon dioxide is being absorbed from the atmosphere at a rate that exceeds the ocean's natural buffering capacity.
• Since the beginning of the industrial revolution, the pH of the ocean surface waters has decreased by about 0.1 pH unit (a 26 percent increase in ocean hydrogen ion concentration).
• The ocean currently has a pH of around 8.0 and is thus 'basic,' and it is chemically impossible for all of it to become a pH less than 7.0. But it is still referred to as ocean acidification because acidification is the trend, regardless of the starting point.
• Acidification is the process of lowering the pH of a solution from any starting point to any endpoint on the pH scale.

Influence of Other Factors

Several factors can locally influence CO2 chemical reactions with seawater, contributing to the effects of ocean acidification.

Acid Rain

• Acid rain has an impact on surface ocean chemistry and has a pH range of 1 to 6.
• It has a significant local and regional impact on ocean acidification, but a negligible global impact.

Eutrophication

• Excess nutrient inputs, mostly nitrogen, from agriculture, fertilizers, and sewage also have an impact on coastal waters.
• The resulting eutrophication causes large plankton blooms, and when these blooms collapse and sink to the sea bed, the subsequent respiration of bacteria decomposing the algae causes a decrease in seawater oxygen and an increase in CO2 (a decline in pH).

Effect of Ocean Acidification

• Sea water absorbs CO2 and produces carbonic acid (H2CO3), bicarbonate (HCO3--), and carbonate ions (CO32-).
• These carbonate ions are required for the calcification process, which allows certain marine organisms to build their calcium carbonate shells and skeletons (e.g. hard tropical corals, cold-water corals, mollusks, crustaceans, sea urchins, certain types of plankton, lobsters, etc).
• However, increases in atmospheric CO2 levels cause a decrease in pH, an increase in the concentration of carbonic acid and bicarbonate ions, and a decrease in the concentration of carbonate ions.
• As a result, carbonate ions are less available, making calcification more difficult and possibly impossible.
• The impact of ocean acidification may have potentially disastrous consequences for ocean life and many economically important marine species.

Mitigation of Ocean Acidification

• The primary cause of ocean acidification is the release of CO2 into the atmosphere as a result of human activity. On a global scale, the only known realistic mitigation option is to limit future atmospheric CO2 levels.
• Appropriate land use and land-use change management can increase the uptake of atmospheric CO2 by vegetation and soils through activities such as wetlands restoration, forest planting, and reforestation.
• Proposals for geoengineering that do not reduce atmospheric CO2 levels, such as methods that focus solely on temperature (such as aerosol backscatter or reduction of greenhouse gases other than CO2), will not prevent ocean acidification.
  • Adding alkaline minerals to the ocean would be effective and cost-effective only on a very small scale in coastal areas, and the unintended environmental consequences are unknown.
• Other stressors on ocean ecosystems, such as higher temperatures and deoxygenation, which are also associated with rising CO2, will be mitigated by limiting CO2 levels.
• The shellfish aquaculture industry faces significant threats, and a risk assessment and analysis of mitigation and adaptation strategies may be beneficial.
  • For example, seawater monitoring near shellfish hatcheries can identify when to limit the intake of lower pH seawater, when to relocate hatcheries, or when to select larval stages or strains that are more resilient to ocean acidification for breeding.

Saturation Horizons

• Deep, cold ocean waters are naturally deficient in carbonate ions, causing most calcifying organisms' shells to dissolve.
• Surface waters are oversaturated with carbonate ions and do not dissolve calcifying organism shells easily.
• The saturation horizon is the point at which calcium carbonate minerals dissolve.
• Those organisms that can survive below the saturation horizon do so because they have special mechanisms in place to keep their calcium carbonate from dissolving.
• As ocean acidification causes this horizon to rise vertically in the water column, more and more calcifying organisms will be exposed to undersaturated water, leaving their shells and skeletons vulnerable to dissolution.
• Calcite's saturation horizon is deeper in the ocean than aragonite's, but both horizons have moved closer to the surface in recent years when compared to the 1800s.

Ocean Acidification and the Short and Long-term Fate of Carbon in the System

• On long timescales (>100,000 years), a natural balance between CO2 uptake and release on Earth is maintained; the CO2 produced by volcanoes, the main natural source of CO2, is taken up by the production of organic matter by plants and rock weathering on land.
• However, because rock weathering takes tens of thousands of years, the current anthropogenic CO2 input to the atmosphere and ocean will not be removed quickly enough.
• On shorter time scales (>1,000 years), the ocean has internal stabilizing feedback known as carbonate compensation that connects the ocean carbon cycle to the underlying carbonate-rich sediment.
• Because the upper layers of the ocean are supersaturated with CaCO3, little dissolution occurs, whereas the deep ocean is undersaturated and carbonate dissolves readily.
• The lysocline, or depth at which dissolution strongly increases in the deep ocean, is the first boundary between these two states.
• CaCO3 in the form of dead shells sinks to the ocean floor.
• The majority is buried in the sediment and trapped for a long time in shallow water, but when the shells sink in deep water, nearly all of the CaCO3 is dissolved, preventing the carbon from being locked away for millions of years.
• The current increased rate of atmospheric CO2 dissolution into the ocean causes an imbalance in the carbonate compensation depth (CCD), which is the depth at which all carbonate is dissolved.
• As the pH of the ocean falls, the lysocline and the CCD become shallower, exposing more shells trapped in the sediments to suboptimal conditions and causing them to dissolve, which will help buffer ocean acidification over a thousand years.

Coral Bleaching

Basically, bleaching is when the corals expel certain algae known as zooxanthellae, which live in the tissues of the coral in a symbiotic relationship.

About 90% of the energy of the coral is provided by the zooxanthellae which are endowed with chlorophyll and other pigments. They are responsible for the yellow or reddish-brown colors of the host coral.

When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white. This phenomenon is called coral bleaching.

• The pale white color is of the translucent tissues of calcium carbonate which are visible due to the loss of pigment-producing zooxanthellae.
• Corals can recover if the stress-caused bleaching is not severe.
• Coral bleaching has occurred in the Caribbean, Indian, and Pacific oceans on a regular basis.
• When a coral bleaches, it does not die but comes pretty close to it. Some of the corals may survive the experience and recover once the sea surface temperature returns to normal levels.

Causes of Coral Bleaching?

• The rise in Sea Temperature: Most coral species live in waters close to the warmest temperature they can tolerate i.e., a slight increase in ocean temperature can harm corals. El Nino elevates the sea temperature and destroys coral reefs.
• Ocean Acidification: Due to rising carbon dioxide levels, oceans absorb more carbon dioxide. This increases the acidity of ocean water and inhibits the coral’s ability to create calcareous skeletons, which is essential for their survival.
• Solar radiation and ultraviolet radiation: Changes in tropical weather patterns result in less cloud cover and more radiation which induces coral bleaching.
• Infectious Diseases: Penetration of bacterium like vibrio chili inhibits photosynthesis of zooxanthellae. These bacteria become more potent with elevated sea temperatures.
• Chemical Pollution: Increased nutrient concentrations affect corals by promoting phytoplankton growth, which in turn supports increased numbers of organisms that compete with coral for space.
• Increased Sedimentation: Land clearing and coastal construction result in high rates of erosion and a higher density of suspended silt particles which can
  • smother corals when particles settle out (sedimentation),
  • reducing light availability (turbidity) and
  • potentially reducing coral photosynthesis and growth.
• Human-Induced Threats: Overfishing, pollution from agricultural and industrial runoff, coral mining, and development of industrial areas near coral ecosystems also adversely impact corals.

Consequences

• Changes in coral communities can affect the species that depend on them, such as the fish and invertebrates that rely on live coral for food, and shelter. The loss of such marine animals can disturb the entire food chain.
• Declines in genetic and species diversity may occur when corals die as a result of bleaching.
• Healthy coral reefs attract divers and other tourists. Bleached and degraded reefs can discourage tourism, which can affect the local economy.
• Coral bleaching can cause large shifts in fish communities. This can translate into reduced catches for fishers, which in turn impacts food supply and associated economic activities.
• Coral reefs protect coastlines by absorbing constant wave energy from the ocean, thereby protecting people living near the coast from increased storm damage, erosion, and flooding.

Ocean Dead Zone

• Dead zones are swaths of ocean that don’t support life due to a lack of oxygen, and global warming is a prime suspect for what’s behind the shifts in ocean behavior that cause dead zones. The number of dead zones is growing at an alarming rate, with over 400 known to exist, and the number is expected to grow.
• Dead zone research underscores the interconnectedness of our planet. It appears that crop biodiversity on land could help prevent dead zones in the ocean by reducing or eliminating the use of fertilizers and pesticides that run off into the open ocean and are part of the cause of dead zones.

Heavy metal Pollution

• Mercury is the scariest pollutant that is being added to the ocean water. What makes it harmful is the fact that it is ending up on the dinner table. According to estimates, it is about to increase. Almost all coastal countries are facing the problem of mercury poisoning.
• The long shelf life of mercury allows it to get bioaccumulated and magnified. The main source of mercury in water is Coal based thermal power plants.
• Under Minamata, convention countries are trying to reduce the use and production of mercury.

Plastic Pollution

• Large masses of plastic are swirling in the ocean. A giant patch of plastic soup the size of Texas sitting smack dab in the middle of the Pacific Ocean.
• Many large fishes are choking on plastics. Plastic bags are ingested by the fishes and they get set in the digestive tract. This does not leave any space for the food and fishes die due to starvation.
• Most of the plastic is finding its way to the ocean through drains and rivers.

Marine Pollution - Mitigation

• Limiting off-shore drilling by using renewable energy sources like wind and solar electricity is advisable.
• Pesticides in agriculture should be limited, and organic farming and environmentally friendly pesticides should be encouraged.
• Sewage treatment and investigation of environmentally friendly wastewater treatment options should be done.
• To avoid spills, industry, and manufacturing waste should be reduced and should be contained in landfills.
• Biotechnology is being used to treat oil spills through bioremediation (the use of specialized microbes to digest and eliminate toxic compounds).
• Personal carbon footprint should be reduced by living a "green" lifestyle.
• Having a global convention prohibiting the use of single-use plastics and a cooperative effort to clean up the ocean is mandatory.

Global Initiatives to Combat Marine Pollution

Global Programme of Action (GPA)

• The Global Program of Action for the Protection of the Marine Environment from Land-based Activities (GPA) was established as a one-of-a-kind intergovernmental instrument to combat land-based pollution.
• The GPA is also the first global intergovernmental process that specifically addresses the interconnection of terrestrial, freshwater, coastal, and marine ecosystems.
• At an intergovernmental summit in Washington, D.C. in 1995, 108 governments and the European Commission accepted the GPA.
• Governments, in collaboration with other stakeholders, including international and public organizations, local communities, non-governmental organizations, and the commercial sector, implement the GPA.

MARPOL Convention (1973)

• It includes ship pollution of the marine environment due to operational or unintentional reasons.
• It details the numerous types of maritime pollution caused by oil, toxic liquid chemicals, packaged dangerous substances, sewage, and waste from ships, among other things.

The London Convention (1972)

Its goal is to encourage effective regulation of all causes of marine pollution and to take all reasonable actions to prevent pollution of the sea from waste and other materials dumped into it.

Greenpeace

• It is a non-profit organization dedicated to protecting the seas and marine life around the world.
• Because of its grassroots initiatives, damaging fishing techniques have been banned.
• Numerous companies' fishing strategies have changed, and whale sanctuaries have been established.

• International blue carbon initiative: mitigating climate change through the conservation and restoration of coastal and marine ecosystem
• ‘magical mangroves- join the movement’ highlights the significance of mangrove conservation
• Blue Nature Alliance It is a global partnership with the aim to advance Ocean Conservation Areas. The alliance is working on large-scale efforts in Fiji’s Lau Seascape, Antarctica’s Southern Ocean, and the Tristan da Cunha island group to collectively secure protection over 4.8 million square kilometers of the ocean
• GloLitter Partnerships Project: aims to help the maritime transport and fishing sectors move towards a low-plastics future.
• The Global Programme of Action for the Protection of the Marine Environment from Land-based Activities (GPA)
• International Coral Reef Initiative (ICRI)– preserve coral reefs and related ecosystems around the world.

Other measures:

• • In Southeast Asia: “blue infrastructure development” and approaches such as “building with nature,” are being introduced as part of efforts to harmonize coastal protection and development with habitat and ecological protection
  • Increasing our scientific knowledge base of the ocean: new feats of technology, namely sensors and autonomous observation platforms, are collecting more granular data on oceans, including in remote areas.
  • One Health model that integrates ecosystems, agriculture, wildlife, and urban landscapes into a singular approach to human and planetary health.
  • 2050 vision for biodiversity: biodiversity be valued, conserved, restored, and wisely used.
  • 30X30 target under UN: protecting at least 30% planet by 2030