- July 3, 2022
- Posted by: OptimizeIAS Team
- Category: DPN Topics
Section : Climate change
- Ecological service provided by Ocean
- Absorb 90% excess heat generated by GHG
- Produce upto 80% of world’s O2
- Absorb 30% of CO2 emissions
- Climate change impact on Ocean
- 2021 saw record heat absorbed by upper 2000 metres of ocean(epipelagic zone)
- 14% coral lost,30% ocean acidity increase and sea surface temperature
- 50% increase in marine heatwave
- 13% decline in arctic ice cover past decade
- Poleward shift of different marine species
- Most of the ocean species yet to be classified
- Only 20% of sea floors has been explored
- Despite 2021 being la Nina year ocean warming continued
- Deep sea mining will release sediments and other waste from sea floor.
- Ocean basin classification from coast to submarine floor
- Continental shelf, continental slope, continental rise, abyssal plain, trenches
- Special report on the ocean and cryosphere in achanging climate published by IPCC
The open ocean is an enormous place. In fact, more than 99% of the inhabitable space on earth is in the open ocean. In order to better study and understand this huge ecosystem, scientists divide it into different zones:
- The epipelagic zone (or upper open ocean) is the part of the ocean where there is enough sunlight for algae to utilize photosynthesis (the process by which organisms use sunlight to convert carbon dioxide into food). Generally speaking, this zone reaches from the sea surface down to approximately 200 m (650 feet). The epipelagic is home to all sorts of iconic animals, like whales and dolphins, billfishes, tunas, jellyfishes, sharks, and many other groups. Algae that live in the epipelagic zone are responsible for much of the original food production for the entire ocean and create at least 50% of the oxygen in the atmosphere (both through photosynthesis). Organisms that live in the epipelagic zone may come into contact with the sea surface.
- The mesopelagic zone (or middle open ocean) stretches from the bottom of the epipelagic down to the point where sunlight cannot reach. Generally speaking the deep end of the mesopelagic zone is approximately 1000 m (3300 feet) deep. The mesopelagic zone is much larger than the epipelagic, and the most numerous vertebrates on Earth (small bristlemouth fishes) live in this zone. Many of the species of fishes and invertebrates that live here migrate up into shallower, epipelagic depths to feed, but only under the cover of night.
- The next deepest zone is called the bathypelagic zone (or lower open ocean). This zone starts at the bottom of the mesopelagic and stretches down to 4000 m (13,000 feet). The bathypelagic is much larger than the mesopelagic and 15 times the size of the epipelagic. It is the largest ecosystem on earth. The upper bound of this zone is defined by a complete lack of sunlight. Organisms in the bathypelagic live in complete darkness, 24 hours per day. The darkness can be interrupted, however, by some light caused by the organisms themselves. This so called bioluminescence can be used to attract prey or to find a mate. Some species have lost their ability to see anything at all.
- Deeper still is the abyssopelagic zone, which stretches from the bottom of the bathypelagic to the seafloor. This zone is characterized by a relative lack of life. It truly is the abyss.
- A special zone that only exists in certain places around the world is called the hadopelagic zone. Where deep, wide trenches occur in the otherwise flat seafloor, the open water that fills them is the hadopelagic zone. By this definition, all of the deepest parts of the ocean conclude in the hadopelagic. The deepest known ocean depth is nearly 11,000 m (36,000 feet or almost 7 miles).
Finally, organisms that live on the ocean floor (regardless of depth) are part of the benthos. Benthic ecosystems include coral reefs, seagrass beds, and other systems in shallow coastal areas and deep hydrothermal vents, the abyssal plain, and other systems in the deep sea.