The Impacts of Ocean Acidification on Marine Ecosystems and Reliant Human Communities

Abstract

Rising atmospheric carbon dioxide (CO2) levels, from fossil fuel combustion and deforestation, along with agriculture and land-use practices are causing wholesale increases in seawater CO2 and inorganic carbon levels; reductions in pH; and alterations in acid-base chemistry of estuarine, coastal, and surface open-ocean waters. On the basis of laboratory experiments and field studies of naturally elevated CO2 marine environments, widespread biological impacts of human-driven ocean acidification have been posited, ranging from changes in organism physiology and population dynamics to altered communities and ecosystems. Acidification, in conjunction with other climate change–related environmental stresses, particularly under future climate change and further elevated atmospheric CO2 levels, potentially puts at risk many of the valuable ecosystem services that the ocean provides to society, such as fisheries, aquaculture, and shoreline protection. This review emphasizes both current scientific understanding and knowledge gaps, highlighting directions for future research and recognizing the information needs of policymakers and stakeholders. Expected final online publication date for the Annual Review of Environment and Resources, Volume 45 is October 19, 2020. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Coastal processes modify projections of some climate-driven stressors in the California Current System

“…The oceans have become warmer and stratification patterns have been modified (Talley et al, 2016). These changes are occurring in tandem with biogeochemical alterations, including O2 declines, productivity changes, and increased dissolved inorganic carbon content due to the uptake of anthropogenic carbon dioxide (Doney et al, 2009(Doney et al, , 2020Feely et al 2004Feely et al , 2009. The ocean uptake of anthropogenic carbon dioxide influences the ocean's buffering capacity, reduces calcium carbonate saturation states (Ω), and lowers pH causing a https://doi.org/10.5194/bg-2020-279 Preprint.…”

Nordic Seas Acidification

“…Although the oceanic uptake of carbon dioxide (CO 2 ) mitigates immediate effects of global warming, it also has a more serious downside, namely a reduction of the seawater pH (e.g., Doney et al, 2009;Gattuso and Hansson, 2011). This ocean acidification imposes a serious threat to many marine organisms, in particular to those having shells and skeletons consisting of calcium carbonate, such as corals and pteropods (Doney et al, 2020;Doo et al, 2020). Since 1750, the global surface ocean pH has dropped by approximately 0.1 units (Doney et al, 2009;Gattuso and Hansson, 2011;Jiang et al, 2019).…”

Progressive seawater acidification on the Great Barrier Reef continental shelf

“…Over a quarter of the rising atmospheric CO 2 is being taken up by the oceans. This lowers the pH and changes the carbon chemistry in surface seawaters, a process called ocean acidification 2 . Due to human CO 2 emissions, surface seawater pH is now lower than it has been for more than 800,000 years 3 , and the associated chemical changes are considered to be irreversible on centennial to millennial time scales 4 , 5 .…”

“…Rates of changes in seawater carbon chemistry vary substantially across regions, and depend not only on atmospheric CO 2 concentrations, but also on local physical and biological factors 2 , 11 – 13 . In coastal, shelf and marginal seas the variation in seawater carbon chemistry is typically much higher than in the open oceans due to regional metabolic processes (photosynthesis/respiration and calcification).…”

“…These are sometimes accentuated by terrestrial inputs of carbon, alkalinity, nutrients, freshwater and sediments that directly alter the seawater carbon chemistry and also stimulate biological productivity 14 . In a process called ‘coastal acidification’, acidification may accelerate in areas of eutrophication 2 , 15 . Coastal CO 2 concentrations are also affected by the upwelling of CO 2 rich deeper waters, thermocline shallowing, stratification, freshening and El Niño–Southern Oscillation (ENSO) dynamics.…”