Once I thought of the ocean as infinite. The constancy of seawater was taken for granted.\u00a0 But, now as we see evidence of increasing concentrations of mercury in seawater, if seems that the human mobilization and disposal of wastes worldwide is taxing the infinite dilution capacity of the seas.<\/p>\n
And, there is good evidence that the ocean is also getting more acid. Why?\u00a0 When carbon dioxide dissolves in water, it creates a weak solution of carbonic acid.\u00a0 If a lot of carbon dioxide dissolves, as in a bottle of soda, the solution is very acid.\u00a0 When only a small amount dissolves, the solution is weakly acid.\u00a0 But, as carbon dioxide rises in Earth\u2019s atmosphere, more of it enters the oceans and they are becoming more acid.\u00a0 There is no climate model to criticize in this chain of logic.<\/p>\n
In water, acidity is expressed in units of pH. \u00a0Neutral is 7.0 and greater acidity is seen with lower values.\u00a0 Lemon juice has a pH of about 2.0. \u00a0In remote regions, the pH of rainfall is about 5.6, reflecting a small amount of acid-generating CO2<\/sub> that has dissolved in it as rain falls through the atmosphere.<\/p>\n Values above pH = 7.0 indicate increasing levels of alkalinity\u2014that is, less acidic. Older textbook indicate the pH of seawater was uniform at 8.3.\u00a0 Now, in many regions the value is as low as 8.1 and dropping at a rate of about 0.02 units per decade.\u00a0 Can a drop of pH of 0.2 units be a big difference?\u00a0 Unfortunately, yes. Since pH is a logarithmic value, a water sample of pH 8.1 is 37% less alkaline than water at a pH of 8.3.<\/p>\n Why should we care if the pH of seawater is declining, indicating that the oceans are getting less alkaline, or alternatively more acidic?\u00a0 Many ocean organisms use calcium carbonate for their outer skeletal material.\u00a0 This is obvious in clams, oysters, and mussels, but harder to see in the myriad small organisms that are part of the phytoplankton in the seas. Calcium carbonate dissolves in acid, so it is more difficult for these organisms to live in more acid waters.\u00a0 Below a pH of about 7.5, mussels can\u2019t precipitate calcium carbonate at all (Gazeau et al. 2007).<\/p>\n Studies of the oceans\u2019 history, written in marine sediments, show that periods when the CO2<\/sub> content of the atmosphere was very high, the oceans were very acidic, and many marine organisms went extinct.\u00a0 Unfortunately, in the clamor about global climate change, the quiet side of rising CO2<\/sub> in the atmosphere, is that we are making the oceans more acidic every year, with the likelihood of extinction of many of the hard-shelled marine organisms that we all enjoy. Not all areas and not all organisms will be impacted equally. Coastal areas of the Pacific Northwest and the Gulf of Maine are most vulnerable; areas in Massachusetts and southeastern North Carolina are not just vulnerable, but especially dependent on the shellfish economy.<\/p>\n What to do?\u00a0 Short of speeding the transition to energy sources that do not increase the concentration of carbon dioxide in Earth\u2019s atmosphere, there are only a limited number of options. \u00a0Some organisms, such as sea urchins, shift their metabolism to become more tolerant of acid waters. \u00a0Farm-raised shellfish could be reared in pens with additions of crusted limestone, which would help maintain the pH of the water above thresholds of vulnerability. But, it will be almost impossible to protect the ocean\u2019s phytoplankton that are the basis of the food chain for all marine organisms.<\/p>\n What should be most disconcerting is this evidence that the effluent of modern society\u2014from 7 billion humans on the planet\u2014is causing a change in the basic chemistry of our environment.\u00a0 When is enough, enough?<\/p>\n <\/p>\n References<\/p>\n Clarkson, M.O., S.A. Kasemann, K.A. Wood, T.M. Lenton, S.J. Daines, S. Richoz, F. Olmemueller, A. Melxner, S.W. Poulton and E.T. Tipper. 2015.\u00a0 Ocean acidification and the Permo-Triassic mass extinction.\u00a0 Science 348: 229-232.<\/p>\n Ekstrom, J.A., L. Suatoni, S.R. Cooley, L.H. Pendleton, G.G. Waldbusser, J.E. Cinner, J. Ritter, C. Langdon, R. van Hooidonk, S. Gledhill, K. Wellman, M.W. Beck, L.M. Brander, D. Rittschof, C. Doherty, P.E.T. Edwards, and R. Portela.\u00a0 2014. Vulnerability and adaptation of US shellfisheries to ocean acidification.\u00a0 Nature Climate Change\u00a0 doi. 10.1038\/NClimate2508.<\/p>\n Gazeau, F., C. Quiblier, J.M. Jansen, J.-P. gattuso, J.J. Middelburg, and C.H. Heip. 2007.\u00a0 Impact of elevated CO2<\/sub> on shellfish calcification.\u00a0 Geophysical Research Letters doi. 10.1029\/2006GL028554<\/p>\n Hoffman, M. and H.J. Schellnhuber. 2010.\u00a0 Ocean acidification: a millennial challenge.\u00a0 Energy and Environmental Science 3: 1883-1896.<\/p>\n Lauvset, S.K., N. Gruber, P. Landschutzer, A. Olsen, and J. Tjiputra. 2014.\u00a0 Trends and drivers in global surface ocean pH over the past three decades.\u00a0 Biogeosciences Discussion 11; 15549-15584<\/p>\n Meyer, J. and\u00a0 U. Riebesell. 2015.\u00a0 Reviews and syntheses: Responses of coccolithophores to ocean acidification: A meta-analysis.\u00a0\u00a0 Biogeosciences 12: 1671-1682<\/p>\n Pan, T-C., S.L. Applebaum and D.T. Manahan. 2015. Experimental ocean acidification alters the allocation of metabolic energy. Proceedings of the National Academy of Sciences 112: 4696\u20134701.<\/p>\n Thomsen, J., K. Haynert, K.M. Wegner and F. Melzner. 2015.\u00a0 Impact of seawater carbonate chemistry on the calcification of marine bivalves.\u00a0 Biogeosciences 12: 4209-4220.\u00a0 doi: 10.5194\/bg-12-4209-2015<\/p>\n","protected":false},"excerpt":{"rendered":" In the clamor about global climate change, the quiet side of rising CO2 in the atmosphere, is that we are making the oceans more acidic every year,<\/p>\n","protected":false},"author":517,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5,88],"tags":[],"coauthors":[6],"class_list":["post-172","post","type-post","status-publish","format-standard","hentry","category-faculty","category-marine-studies"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p5KxUl-2M","post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts\/172","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/users\/517"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/comments?post=172"}],"version-history":[{"count":3,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts\/172\/revisions"}],"predecessor-version":[{"id":204,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/posts\/172\/revisions\/204"}],"wp:attachment":[{"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/media?parent=172"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/categories?post=172"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/tags?post=172"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.nicholas.duke.edu\/citizenscientist\/wp-json\/wp\/v2\/coauthors?post=172"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}