Ocean Heating and Acidification: Difference between revisions

=====Climate velocity reveals increasing exposure of deep-ocean biodiversity to future warming=====

<embed> https://www.nature.com/articles/s41558-020-0773-5#article-info </embed>

=====Global alteration of ocean ecosystem functioning due to increasing human CO2 emissions=====

  Ocean warming and acidification have received increasing focus as global change stressors, but marine species will also be impacted in their performance by other emerging stressors such as changes in sea surface height, UV, underwater irradiance, water salinity, and seawater oxygen content (7). Hypoxic zones are becoming widespread in oceanic as well as shelf environments because of climate change and local stressors such as eutrophication (37). Many species will be challenged by the interactive effects of ocean warming, acidification, and deoxygenation, but at present, hardly any (multistressors) studies exist to evaluate the effects of hypoxia on marine species and ecosystems (8, 38). For some species, there are opportunities to move to deeper waters or extend their ranges to higher latitudes, but not all species will be able to keep up with the pace of climate change, leading to alterations in current species distributions (39, 40). Moreover, species that have fewer generations (e.g., k strategists with greater longevity and later maturation) have fewer opportunities to adapt to rapidly changing conditions forecast for the next ∼85 y. Unless longer-lived species relocate to climate refugia

  A study of 632 published experiments of the world’s oceans, from tropical to arctic waters, spanning coral reefs and the open seas, found that climate change is whittling away the diversity and abundance of marine species.

  The paper, published in the Proceedings of the National Academy of Sciences, found there was “limited scope” for animals to deal with warming waters and acidification, with very few species escaping the negative impact of increasing carbon dioxide dissolution in the oceans.

=====Phytoplankton Population Drops 40 Percent Since 1950=====

  Researchers at Canada's Dalhousie University say the global population of phytoplankton has fallen about 40 percent since 1950. That translates to an annual drop of about 1 percent of the average plankton population between 1899 and 2008.

  The scientists believe that rising sea surface temperatures are to blame.

=====Marine heatwaves kill coral instantly=====

  Increasingly frequent marine heatwaves can lead to the almost instant death of corals, scientists working on the Great Barrier Reef have found. Scientists studying coral after a heat event discovered that extreme temperature rises decayed reefs much more rapidly than previously thought.

=====Rapid Coral Decay Is Associated with Marine Heatwave Mortality Events on Reefs=====

  Severe marine heatwaves have recently become a common feature of global ocean conditions due to a rapidly changing climate [1, 2]. These increasingly severe thermal conditions are causing an unprecedented increase in the frequency and severity of mortality events in marine ecosystems, including on coral reefs [3]. The degradation of coral reefs will result in the collapse of ecosystem services that sustain over half a billion people globally [4, 5]. Here, we show that marine heatwave events on coral reefs are biologically distinct to how coral bleaching has been understood to date, in that heatwave conditions result in an immediate heat-induced mortality of the coral colony, rapid coral skeletal dissolution, and the loss of the three-dimensional reef structure.  

=====Heatwaves 'cook' Great Barrier Reef corals=====

  In surveying the 3,863 individual reefs that make up the system off Australia's north-east coast, scientists found that 29% of communities were affected. In some cases up to 90% of coral died, in a process known as bleaching.

  This occurs when the stress of elevated temperatures causes a breakdown of the coral's symbiotic relationship with its algae, which provide the coral with energy to survive, and give the reef its distinctive colours.

=====Coral reefs head for 'knock-out punch'=====

  A study of 100 reefs, published in Science Magazine, shows the interval between bleaching events in recent decades has shortened dramatically. It has gone from once every 25-30 years in the early 1980s to an average of just once every six years today.Bleaching is caused by anomalously warm water, which prompts coral polyps to eject their symbiotic algae.This drains the corals of their colour and is fatal unless conditions are reversed in a reasonably short time. But even if temperatures fall back quickly, it can still take many years for damaged reefs to fully recover.

=====Climate Change is Weakening an Ocean Current=====

  Both studies found that melting ice from Greenland has spilled huge quantities of freshwater into the North Atlantic, diluting the dense salinity of North Atlantic currents and weakening the AMOC by 15 percent. However, the results disagree on when the changes started.

  For decades, scientists have worried that human-caused global warming could weaken this system and drastically alter weather patterns. It’s an idea best known from the scientifically and cinematically awful 2004 film The Day After Tomorrow.

=====Heatwaves sweeping oceans ‘like wildfires’, scientists reveal=====

  The number of heatwaves affecting the planet’s oceans has increased sharply, scientists have revealed, killing swathes of sea-life like “wildfires that take out huge areas of forest”.

  The damage caused in these hotspots is also harmful for humanity, which relies on the oceans for oxygen, food, storm protection and the removal of climate-warming carbon dioxide the atmosphere, they say.

=====Historical photographs revisited: A case study for dating and characterizing recent loss of coral cover on the inshore Great Barrier Reef=====

  Monitoring programs within the Great Barrier Reef World Heritage Area (GBRWHA) have recently revealed dramatic losses in coral cover on the mid-shelf and offshore reefs1. Declining water quality as a result of rapid coastal development since European settlement (c.1850) in conjunction with crown-of-thorns starfish outbreaks and coral bleaching, is believed to have also resulted in a decline in coral cover and changes in community composition on inshore reefs2,3,4,5. This rather austere outlook is further exacerbated by the Great Barrier Reef (GBR) contentiously being argued as not the best managed reef in the world, with delays in water quality improvement programs and the threat of increased port development along the Queensland coastline6,7. The seriousness of the current state of the GBR has manifested in its potential delisting from World Heritage to World Heritage in Danger by the United Nations Educational, Scientific and Cultural Organisation (UNESCO).

=====Ocean acidification is already harming the Great Barrier Reef’s growth=====

  It was clear from our results that reef calcification was around 7% higher under pre-industrial conditions than those experienced today.

  Our work provides the first strong evidence from experiments on a natural ecosystem that ocean acidification is already causing reefs to grow more slowly than they did 100 years ago. Ocean acidification is already taking its toll on coral reef communities. This is no longer a fear for the future; it is the reality of today.