Updated December 9, 2022
Global Warming is increasing rapidly day by day due to human activities like burning fossil fuels, Cutting trees (Deforestation), and changing land use.
It results in increasing the atmospheric concentration of greenhouse gases like carbon dioxide(co2) and Methane (CH4).
These Changes affect the whole earth including extreme weather events, glacier retreats, changes in the timing of seasonal events (e.g., earlier flowering of plants), sea-level rise, and declines in Arctic sea ice extent.
There is no doubt that the rapid increase of greenhouse gases like Co2 is changing the physical and chemical environment of the Earth. Rapid environmental changes affect the biological system across the planet.
Coral reef ecosystems have played a vital role in our understanding of how the world’s environments may react to fast anthropogenic environmental change.
The Effects of Global Warming on Coral Reefs
The environmental conditions that deﬁne, where coral reefs exist today, give a significant understanding of how they will change later on under quick natural change.
Coral reefs are already being affected by many other pressures, some human-related and some natural. Coral reefs are distributed in the shallow, sunlit waters of the tropics and subtropics.
They capture the sunlight and convert it into organic energy, which either ﬂows directly through the ecosystem or is used to power important processes such as calciﬁcation.
Coral reefs occupy coastal areas in a band from roughly 30° north and south of the equator. At higher latitudes, calciﬁcation decreases to a point where it decreases below the rate of erosion, reef accretion becomes negative, and carbonate coral reefs no longer persist.
Impacts of Thermal Stress
Rapid climate change impacts the biological systems associated with coral reefs. At the Starting of the 1980s, a new phenomenon called mass coral bleaching entered the scientiﬁc literature.
It is a phenomenon in which the corals lose their special color due to the loss of pigments or cells of their fundamental symbiotic dinoﬂagellates (Symbiodinium).
Bleached corals are likely to have reduced growth rates, decreased reproductive capacity, increased susceptibility to diseases, and elevated mortality rates.
Death of Corals due to bleaching results in a Decline in genetic and species diversity. Degraded coral reefs are less able to provide the ecosystem services on which local human communities depend.
If DHW values are greater than 4 then coral reefs will bleach but recover quickly without a little damage. DHW values greater than 8 can cause coral bleaching on a large- scale with considerable deaths.
If DHW values are greater than 12 then it will be a dreadful impact on coral reefs. In 1998, many sites across the Western Indian Ocean experienced DHW values of over 12, with as much as 95% of corals on some reef systems being killed. Almost 50% of all corals died across the region by the end of the very long warm summers associated with this period.
Ex: Bleaching observed in the Great barrier reef of Australia.
Impacts of Ocean Acidiﬁcation
Increasing ocean temperatures are contributing to coral bleaching and making them more susceptible to diseases. Chemical pollution coming into the oceans from rivers is also making coral habitats very scarce.
The increasing carbon dioxide concentration is the main reason for causing Ocean acidification. When carbon dioxide reacts with water it forms carbonic acid (H2CO3).
Afterward, Carbonic Acid dissociates in water and releases a proton which reacts with carbonate ions and converts them into bicarbonate ions.
Carbonate ion concentrations are often expressed relative to the saturation state of seawater with respect to aragonite, the principal crystal form of calcium carbonate crystals deposited by reef-building corals and many other marine calciﬁers.
It is important to note that changes in pH can have signiﬁcant direct effects on processes other than that of calciﬁcation. There are several other factors that are affecting coral reefs, which may change as the climate changes.
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