Scuba Diver Australasia + Ocean Planet - - Briefing -

Since the be­gin­ning of the in­dus­trial era, the ocean has ab­sorbed around 525 bil­lion tons of car­bon diox­ide (CO2), which equates to around 22 mil­lion tons a day – a 43 per­cent in­crease from the start of the In­dus­trial Rev­o­lu­tion. This amount is only a third of the CO2 re­leased by burn­ing coal, oil and gas. At this rate, ocean acidification is likely to hit un­prece­dented lev­els not seen in 14 mil­lion years, ac­cord­ing to a study led by Cardiff Univer­sity.

When the ocean ab­sorbs CO2 from the at­mos­phere, the sea­wa­ter be­comes more acidic, with a lower pH. The rapid in­take of CO2 is se­verely threat­en­ing ma­rine life – shells of some an­i­mals are al­ready dis­solv­ing due to high acid lev­els. An­other study con­ducted by re­searchers at the Univer­sity of Ex­eter found that ris­ing acid­ity is caus­ing fish to lose their sense of smell. This is af­fect­ing their abil­ity to find food and re­spond to preda­tors, in ad­di­tion to the im­pact of CO2 on their cen­tral ner­vous sys­tem.

Com­par­ing the chem­istry of fos­sils of tiny sea crea­tures that once lived near the ocean sur­face to the new records of CO2 lev­els, sci­en­tists found that if we con­tinue to emit car­bon at the cur­rent rate, at­mo­spheric CO2 would be reach­ing 930 parts per mil­lion in the year 2100, com­pared to around

400 parts per mil­lion today. Th­ese lev­els were seen 14 mil­lion years ago dur­ing the Mid­dle Miocene Cli­matic Op­ti­mum pe­riod, when global tem­per­a­tures were around three de­grees Cel­sius warmer than today as a re­sult of the Earth’s nat­u­ral ge­o­log­i­cal cy­cle.

Pro­fes­sor Car­rie Lear, co-au­thor of the study, ex­plains, “The cur­rent pH is al­ready prob­a­bly lower than any time in the last two mil­lion years. Understanding ex­actly what this means for ma­rine ecosys­tems re­quires long-term lab­o­ra­tory and field stud­ies as well as ad­di­tional ob­ser­va­tions from the fos­sil record.”

ABOVE A sea snail’s shell that has been dam­aged from high lev­els of sea­wa­ter acid­ity

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