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The leading cause of coral bleaching is rising ocean temperatures due to climate change caused by anthropogenic activities. [3] A temperature about 1 °C (or 2 °F) above average can cause bleaching. [3] The ocean takes in a large portion of the carbon dioxide (CO2) emissions produced by human activity.
A lake in Westgate Park, Melbourne, Australia, was coloured pink in March 2017 [10] and then again in September 2019, but since then and as of January 2022 had taken on a dark green hue. Warmer weather and lower rainfall appears to make it turn pink. [1] As water evaporates, the salinity increases, but salinity is not the only factor at work.
The concept of the oceanic anoxic event (OAE) was first proposed in 1976 by Seymour Schlanger (1927–1990) and geologist Hugh Jenkyns [9] and arose from discoveries made by the Deep Sea Drilling Project (DSDP) in the Pacific Ocean. The finding of black, carbon-rich shales in Cretaceous sediments that had accumulated on submarine volcanic ...
After reducing some other minor elements, the bacteria will turn to reducing sulfate. This results in the byproduct of hydrogen sulfide (H 2 S), a chemical toxic to most biota and responsible for the characteristic "rotten egg" smell and dark black sediment color: [12] [13] 2 CH 2 O + SO 2− 4 → 2 HCO − 3 + H 2 S + chemical energy
Ocean warming causes water stratification, deoxygenation, and the formation of dead zones. Dead zones and OMZs are hotspots for anammox and denitrification , causing nitrogen loss (N 2 and N 2 O). Elevated atmospheric carbon dioxide acidifies seawater, decreasing pH-dependent N-cycling processes such as nitrification, and enhancing N 2 fixation .
Euxinia or euxinic conditions occur when water is both anoxic and sulfidic.This means that there is no oxygen (O 2) and a raised level of free hydrogen sulfide (H 2 S). Euxinic bodies of water are frequently strongly stratified; have an oxic, highly productive, thin surface layer; and have anoxic, sulfidic bottom water.
With primary causes being warming ocean waters, ocean acidity, and pollution. [3] In 2008, a worldwide study estimated that 19% of the existing area of coral reefs had already been lost. [ 4 ] Only 46% of the world's reefs could be currently regarded as in good health [ 4 ] and about 60% of the world's reefs may be at risk due to destructive ...
Carbon emissions cause ocean surface waters to warm and acidify. [17] The combustion of fossil fuels results in the emission of greenhouse gases, such as carbon dioxide into the atmosphere. The ocean uptakes some of the emitted carbon dioxide, injurious to the natural processes that occur in the ocean.