Deep Sea Ecology: Various Perspectives

The deep sea is usually defined as waters and seafloor deeper than 200 metres. Deep sea ecosystem is the largest ecosystem on earth. But it is also one of the least studied ecosystems on the earth.

Characteristic features

Deep sea is characterized by very high barometric pressure, absence of light and extremes of temperature. So, deep sea offers a vast, dark, remote and inhospitable environment.

However, a significant biodiversity exists in deep sea. There are many smaller habitats in the deep sea which adds to its diversity and heterogeneity. Such important habitats include seamounts, canyons and channels, methane vents, fjords and hydrothermal vents.

Role played by deep sea in Ecology

Deep sea plays a significant role in nutrient regeneration and driving various biogeochemical cycles for sustaining primary and secondary production in the oceans.

Nutrient regeneration and cycling

Deep sea supports a high diversity of habitats and species, many of which are microbes. These microbes carry out nutrient regeneration and cycling. One of such processes is the biological pump, which ultimately results in sequestration of carbon from the atmosphere to the deep sea.

Mechanism of Biological Pump

This biological pump is a part of the oceanic carbon cycle and responsible for cycling of organic matter in deep sea. Deep sea heavily relies on this primary production that occurs in surface waters. Photosynthesis by phytoplankton occurs in the surface and helps in its growth. Subsequently, dead particles from the surface sink through the deep pelagic zone. These are degraded by microbes present in the deep sea and also by the higher trophic levels, such as zooplanktons. Hence, nutrient cycling and the biological pump helps in supporting the biomass production and carbon sequestration thus performing the supporting services and regulating services respectively.

Furthermore, the thermohaline circulation helps in returning the recycled nutrients which are regenerated at the seafloor to the surface of the ocean and the process of nutrient cycling begins again.

Carbon and methane sequestration

It is a well known fact that industrial revolution has released huge amount of greenhouse gas such as CO2 into the atmosphere. The dissolution of atmospheric carbon in the ocean surface and its subsequent transportation in to the deep sea through the thermohaline circulation has resulted in the mediation of global temperature. The transported carbon gets separated over longer periods and reduces the impact of anthropogenic carbon release. The deep sea currently has huge reserves of stored carbon and is estimated that it has absorbed nearly a quarter of the carbon released by anthropogenic activities. This function of CO2 absorbance is a very crucial in influencing climate and similar deep-sea functions and services.

Microbial oxidation of methane helps to prevent yet another greenhouse gas entering the atmosphere.

Detoxification of waste products

The deep sea also helps in detoxification of waste products through biotic and abiotic processes. Sinking of particles and deliberate human activities transport pollutants such as persistent organic pollutants, sewage, oil etc., from surface waters in to the deep sea. These pollutants are sometimes removed by bioremediation, which is defined as a waste management technique that uses organisms to remove or neutralize pollutants.

Each of these processes though occurring on a very small scale have great impact keeping in mind the vast area over which they occur. Thus, they become important for the global functioning of the ocean.

What are the uses of deep sea?

The deep sea also provides us with treasure trove of resources, which includes fish stocks, elements and energy reserves, huge bioprospecting potential and holds a great potential to fulfil our needs in the near future.

Ocean thermal energy conversion (OTEC) technology, which produces electricity by harnessing the temperature differences between surface water and colder deep sea water have been in existence since 1980s.

Mining materials

With dwindling terrestrial supplies, deep sea mineral resources are the promising alternative in the near future. Huge concentrated metal reserves occur on the abyssal floor, hydrothermal vents etc. Precipitation of phosphate, magnesium and other metals around seed particles under specific temperature and pressure over millions of years has resulted in the deposits of polymetallic nodules. These nodules lie as sea-bottom sediment. Polymetallic nodules have significant amount of manganese, cobalt, nickel, copper and other minerals.

Bioprospecting

Bioprospecting involves search, discovery and commercialization of new natural products based on biological resources. Resources in the deep sea are exploited by bioprospecting as it offers isolated natural products which may be absent on the terrestrial surface. These can be particularly found at hydrothermal vents. These natural products are known to have pharmaceutical applications and are widely used as antibiotics and anti cancer compounds.

Dumping of waste products

The deep sea surface has been widely used as a dumping ground for various types of waste products such as radioactive substances, animal carcasses, sewage sludge, plastics, wastes from mining activities, disposal of munitions etc.

Cultural services

Some of the main cultural services provided by the deep sea can be classified in to two: educational and scientific. It provides valuable scientific knowledge about various processes and deep sea environments. The educational value generated by exploration and discovery is numerous. In addition, it also provides aesthetic and inspirational services such as tourism, spiritual well being, entertainment etc.

Threats that deep sea ecosystems face

Scientists have identified activities like reckless fishing, overexploitation of mineral resources, science and exploration have negatively impacted the deep sea region.

In addition anthropogenic activities such as waste disposal, cable lays associated with telecommunications, bioprospecting, oil and gas explorations, tourism etc., leads to global climate change, increasing water temperatures, decreasing oxygen concentrations and reduced pH of the ocean waters.

Unsustainable mining of minerals at extreme depths have adverse effects on the deep sea ecosystem as it affects the life of organisms at the deep sea, where these organisms often grow very slowly.

Deepwater Horizon incident and the subsequent oil spill, which affected a large area in the Gulf of Mexico is a classic example of the threat posed by the human activities on these fragile ecosystems.

What steps can be taken to protect deep sea organisms?

Protecting deep-sea habitats receive much less attention than needed because of the remoteness of its location and the inhospitable environment it provides to humans.

Ecological restoration efforts should be carried out to restore the components of the deep sea ecosystem. Ecological restoration can be defined as a process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed intentionally by the human activities. As the stakeholders of the deep sea are not limited to one country or area, all the countries and the whole global population should take part in ecological restoration.

Regulations on existing deep ocean industries must be strengthened. Technology must be improved to minimize or repair the resulting and existing damages to the deep sea environments. More number of marine sanctuaries and protected areas needs to be established for the spatial management of the deep sea and protection of this fragile ecosystem.

Role played by UNCLOS towards Deep Sea

The 1982 United Nations Convention on the Law of the Sea (UNCLOS) has a significant role in promoting equitable and efficient utilization of resources, conservation of living resources and the study, protection and preservation of marine environment and the ecosystem. According to article 192 of the UNCLOS, there is a general obligation on its members to protect and preserve the marine environment. Further, article 194(5) provides for the duty of the member nations to protect and preserve rare or fragile ecosystems, and the habitat of depleted, threatened or endangered species and other forms of marine life. Furthermore, article 197 vests upon States to cooperate on a global or regional basis in formulating and elaborating international rules, standards and recommended practices and procedures for the protection and preservation of the marine environment. UNCLOS also has agreements related to the management of sea floor and mining in international waters.