Ocean acidification

Summary

• More than 2,000 species of coral have been identified and described. jump to section
• Most coral reefs are found in the tropics and subtropics. jump to section
• More than 200 coral species are listed as threatened with extinction on the IUCN Red List. Although recent research suggests this figure could be an overestimate. jump to section
• Corals face multiple threats, including mass bleaching, overfishing, pollution of local waters, and ocean acidification. jump to section
• Mass bleaching events are becoming more common and severe. jump to section
• The time between bleaching events is getting shorter – often too short for corals to recover from. jump to section
• Large bleaching events used to be reserved for warm El Niño years. Now they even occur in La Niña years, the ‘cold’ phase of the ENSO cycle. jump to section
• Some corals die immediately when exposed to warming. Others bleach, then either recover or die. jump to section
• Some corals are much more resilient to warming than others. jump to section
• It’s unclear how corals will respond to ocean acidification over the next century. jump to section
• More experiments of coral responses at lower levels of warming and acidification are needed. jump to section

A group of whistleblowers has asked three funding agencies for a misconduct investigation into a series of 22 research papers, many of them on the effects of ocean acidification on fish behavior and ecology. The request, which they shared with a Science reporter, rests on what they say is evidence of manipulation in publicly available raw data files for two papers, one published in Science, the other in Nature Climate Change, combined with remarkably large and “statistically impossible” behavioral effects from carbon dioxide reported in many of the other papers. The papers’ two main authors emphatically deny making up data, and James Cook University, Townsville, in Australia has dismissed the fabrication allegations against one of them after a preliminary investigation. But multiple independent scientists and data experts who reviewed the case flagged what they said were serious problems in the two data sets, as well as in two additional ones co-authored by one of the accused scientists. The case isn’t just about data and the future of the oceans. It highlights issues in the sociology, psychology, and politics of science, including pressure on researchers to publish in top-tier journals, the journals’ thirst for eye-catching and alarming findings, and the risks involved in whistleblowing.

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This story was supported by the Science Fund for Investigative Reporting.

Enserink M., 2021. Sea of doubts. Science 372(6542): 560-565. doi: 10.1126/science.372.6542.560

Martin Enserink, AAAS, 6 May 2021. Full article.

Libby Jewett, Ph.D., Director of the NOAA Ocean Acidification Program, provides insight into ocean acidification. Jewett highlights how she became involved in ocean acidification work, how NOAA’s Ocean Acidification Program (OAP) started, and how we all can personally contribute to combatting this threat to our ocean.

What brought you to this position?

After receiving my Ph.D. from the University of Maryland in biology, focusing on marine ecology in the Chesapeake Bay, I was hired by NOAA to work on harmful algal blooms and hypoxia, or low oxygen levels in seawater. Colleagues started talking about ocean acidification around 2006 as a new important topic that was not well understood and a considerable potential threat to marine ecosystems.

In 2007, I became a founding member of NOAA’s Ocean Acidification Steering Committee. I also became the point of contact for ocean acidification in the National Ocean Service, where I was at the time, and initiated, with other members of the Steering Committee, drafting NOAA’s first comprehensive ocean acidification research plan. When NOAA’s OAP was created, I applied and became the founding director, where I have been since May 2011.

What is ocean acidification? How has the field grown since its discovery?

Ocean acidification refers to the change in ocean chemistry — specifically, a reduction in the pH of our ocean over an extended period caused primarily by the uptake of carbon dioxide from the atmosphere. Ocean acidification was first discovered in the early 1900s when scientists realized that rising levels of atmospheric carbon dioxide would be taken up by the ocean, causing changes in the ocean’s chemistry. We’ve known that this had the potential to happen for a long time — however, it wasn’t until the early 2000s that NOAA, with other international scientists, detected a change in chemistry in the open ocean, documented with data.

The climate crisis and the chemistry of the oceans are inextricably connected. The oceans have absorbed close to a third of our carbon dioxide emissions since the beginning of the Industrial Revolution, leading to an increasingly acidic environment and making it more difficult for organisms such as corals, molluscs, and plankton to form their shells and skeletons. Mapping future changes in ocean chemistry is the first step in developing mitigation strategies. However, our knowledge of the future state of the oceans relies on mathematical models that are often not calibrated with modern ship-based observations. Dr Li-Qing Jiang of the University of Maryland and his collaborators are improving ocean acidification predictions by coupling millions of past and present ocean chemistry measurements with the best model projections at each location of the global ocean.

The Ocean as a Carbon Sink

The global oceans have absorbed about 30% of the carbon dioxide released by human activity over the past 200 years. As it dissolves in seawater, carbon dioxide reacts with water to form a weak acid called carbonic acid. Therefore, as atmospheric carbon dioxide increases, so does the acidity of the oceans – a process called ocean acidification.

When ocean acidity rises, calcium carbonate saturation – which describes the tendency of calcium carbonate minerals to form or dissolve – decreases. As many marine organisms need calcium carbonate minerals to build their protective shells and skeletons, they can suffer from slow growth and even dissolution when the ocean is too acidic. Ocean acidification is already having catastrophic effects on coral reefs, some of the world’s most important and biodiverse ecosystems.

NJ signed an agreement yesterday to join the Ocean Acidification Alliance.

This decision was informed by work done by Rutgers –

see report and infographic here.

Professor Grace Saba is a national expert on this topic and has led work in NJ and the Mid-Atlantic.

The ocean, an essential element in the evolution of the climate, currently accumulates 93% of the excess heat and 31% of the excess CO2 generated by human activity. The European climate in general, and the Iberian Peninsula in particular, is influenced in a very relevant way by the southern return circulation (CRM), which transports the warm surface waters to the north and the cold deep waters #face the south and play a crucial role in the climate system, as it facilitates the redistribution of the planet’s heat, water and carbon dioxide. In fact, the southern return circulation significantly amplifies the uptake of anthropogenic CO2 (generated by human activity), exceeding the mean oceanic value by more than 50%. But there are several studies that confirm the recent weakening of this circulation, a phenomenon that according to the report of the Intergovernmental Panel for Climate Change (IPCC, 2019) is expected to be more pronounced in the coming decades.

However, the IPCC itself recognizes that there is a lack of observations to be able to quantify the magnitude of this reduction and it is in this context that the subproject Bocats2 arises (Biennial observation of carbon, acidification, transport and sedimentation in the North Atlantic) , led by CIM researchers Guillermo Francés (Geological and Bioxeochemical Oceanography group) and Gabriel Rosón (Physical Oceanography Group). The main objective of this initiative is “to continue with the observational monitoring (recent and past) of ocean circulation and acidification in the North Atlantic, essential to advance in the accurate detection of anthropogenic impact and to improve the projections of the adjusted climate models that support the IPCC reports for the subpolar turn of the North Atlantic (SPNA), a region known for its strong influence on the European climate.

A new policy handbook, launched today, will help Commonwealth governments put in place strategies to tackle ocean acidification – a key aspect of climate change.

Ocean acidification happens when the sea absorbs excess carbon dioxide in the atmosphere, primarily caused by human activities such as the burning of fossil fuels and deforestation.

This leads to an increase in the acidity of the ocean, affecting the lifecycles and biology of certain marine species, and in turn, threatening the entire food web as well as the lives and livelihoods of communities that depend on these ocean resources.