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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.
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 ...
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.
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
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 ...
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.
Water carried into the mantle eventually returns to the surface in eruptions at mid-ocean ridges and hotspots. [131]: 646 Estimates of the amount of water in the mantle range from 1 ⁄ 4 to 4 times the water in the ocean. [131]: 630–634 The deep carbon cycle is the movement of carbon through the Earth's mantle and core.
Changes in ocean circulation triggered by ongoing climate change could also add or magnify other causes of oxygen reductions in the ocean. [11] Anthropogenic causes include use of chemical fertilizers and their subsequent presence in water runoff and groundwater, direct sewage discharge into rivers and lakes, and nutrient discharge into ...