80 percent of the oxygen supply that living things breathe comes from the sea and phytoplankton plays a role in this process because oxygen is produced from their photosynthetic activity.
The oxygen produced is then used for respiration of living things, but due to climate change factors, plankton becomes sensitive and the carrying capacity of the environment causes a decrease in dissolved oxygen concentrations in the sea. This decrease is called deoxygenation.
Sea Trouble Breathing
Approximately 71% of the earth's surface is covered by oceans and in addition to providing a source of food, the sea also provides oxygen for all living things, but since the mid-20th century it is estimated that the oceans have lost 1-2 percent of their oxygen supply (Limburg, 2020).
This loss is the result of an increase in temperature and the flow of nutrients from residential, agricultural, industrial areas, which are carried by water flows to the sea.
The flow of oxygen in the ocean is influenced by physical, chemical, and biological processes where when climate change occurs, the stratification of the water column increases and reduces the solubility of oxygen in seawater thereby encouraging deoxygenation in the oceans.
Simultaneously the waters around the coast are filled with waste that contains a lot of nutrients causing eutrophication or enrichment of nutrients and organic matter thereby increasing oxygen demand.
In other words, the waste that we produce, as well as the increasing temperature due to climate change, causes low levels of dissolved oxygen in the water resulting in marine organisms experiencing oxygen deficiency and tissue death or hypoxia.
The Effect of Climate Change on Deoxygenation
When the sea becomes the last place of "disposal" of waste, the sea becomes rich in nutrients contained in the waste so that the growth of some organisms becomes very fast, for example algae that utilize nutrients, especially nitrogen to grow and develop, then die and their "carcasses" are remodeled by bacteria. or decomposing microbes. The microbes will then decompose the algae and utilize the oxygen present during the process.
In addition to the available factors, the nutrients in the waste, there are also climatic influences as previously existed. So what does deoxygenation have to do with climate?
So climate change greatly affects deoxygenation because there is a relationship between physical physical properties, microbial respiration, respiration of marine animals and temperature. If on land oxygen is utilized by living things, in the sea there is a free process to make oxygen dissolved in the air so that it can be utilized.
The increase in sea water temperature causes two things, namely a decrease in density and dissolved oxygen levels. Density is related to the ocean currents themselves, for example, when there is a difference in heating on the sea surface, the resulting ocean currents will be very large.
While the increase in water temperature will reduce the ability of water to bind oxygen, so that the level of oxygen saturation in the water will also decrease.
An increase in temperature will also accelerate the rate of respiration and thus the rate of use of oxygen increases. The problem is that when the oxygen consumption exceeds the filling through photosynthesis and the mixing of the water column, a condition called hypoxia occurs.
In other words, when seawater warms, dissolved oxygen is low while respiration of organisms increases as a result, the organism's body lacks oxygen to complete its physiological processes.
That is why the issue of climate change is of concern to all parties because without realizing it, climate change has an impact on the survival of several species.
Effects of Deoxygenation on the Sustainability of Marine Ecosystems
The function of life or biological function is strongly influenced by the state of oxygen in the body as well as for marine or aquatic organisms. When dissolved oxygen is low, several processes are slowed down, such as reproduction, growth, and susceptibility to disease.
It is true that some marine organisms are able to adapt to oxygen-deprived conditions and metabolize anaerobically, but metabolism utilizing oxygen is much more energy efficient than anaerobic.
This deoxygenation condition causes organisms that are unable to adapt to conditions of lack of oxygen, including those cultivated, ponds, and other types of marine cultivation to suffocate or even die. In addition, this condition can disrupt the existing food web.
Hypoxic conditions due to lack of oxygen also have an impact on the destruction of coral reefs, where as marine organisms, corals are very sensitive to oxygen and temperature. The coral bleaching event is one of the effects of the lack of oxygen that occurs in the ocean.
The impact of a warm climate is very visible in coastal areas, in the past we could still find seagrass when the sea water receded, now it is very rare to find even though seagrass plays a role in oxygen production so that when the quality of the place of life or habitat is lost, it also decreases.
In the end, the hardest homework faced by us humans is reducing greenhouse gases because it is likely that as a country that has many coastal areas, Indonesia will feel the impact of deoxygenation, so adaptive planning is needed to assess and deal with the changes that occur.
Lead image from kumparan.com