top of page

ocean acidification

CO2 in the atmosphere is being absorbed by the oceans, increasing their acidity and threatening marine life. [180] [181]

acidification.png

Source: [182]

CO2 in the atmosphere is also taken-up by the oceans through organic metabolic processes, particularly by phytoplankton in the photic zone. Increasing ocean acidification drives up proton (H+) abundance while decreasing carbonate abundance. Carbonate is used in conjunction with iron in phytoplankton (particularly diatom) protein complexes for metabolism. A doubling of CO2 in the atmosphere has a one-to-one correlation with the reduction of carbonate ions in the upper ocean, restricting phytoplankton growth by 44%. [183] [184]

 

This may represent the beginnings of large-scale ecosystem collapse starting at the base of oceanic food webs. 

Ocean acidification is particularly damaging to corals, whose outer shells begin to dissolve if the concentration of aragonite (a calcium carbonate mineral) in surrounding water is too low. [187] [188]

acidification2.png

Source: [185]

acidification3.png

Observed and predicted Southern Ocean surface acidification conditions for the 21st century. (A) IPCC IS92a atmospheric CO2 scenario (black) and the average oceanic pCO2 level south of 60°S from the CSIRO ocean carbon model (blue line). (B and C) Projections for Southern Ocean (south of 60°S) for surface pH and carbonate ion (CO32−, μmol/kg) for two different methods using the IPCC IS92a atmospheric CO2 scenario. The observed seasonal cycle is represented in the year 1995 with a box-and-whiskers plot. The concentration of CO32− that results in aragonite and calcite saturation is shown by the horizontal dotted lines. The observations were used as the baseline for these two different scenarios. The solid red line represents the average conditions assuming atmospheric equilibrium from the year 1995, and the blue line includes the estimated CO2 disequilibrium from the CSIRO climate model. The shading for red and blue represents the maximum seasonal variability taken from the observations derived here. [186]

Ocean acidification has been variably shown to have impacts on: [189]

​

  • shellfish aquaculture due to directly influencing shell formation

  • fishery aquaculture due to blooms of fish-killing algae such as Heterosigma akashiwo which gain competitive advantage under ocean acidification

  • algal neurotoxicity which is expected to become more potent

  • food web changes as a result of decreasing phytoplankton abundance and declining pteropod numbers

  • wild fisheries that depend on pteropods and echinoderms, which are also expected to decline in number

  • a shift from macroalgae to algal turf, with consequences for juvenile fish that feed on macroalgae

  • coral species that provide vertical reef structure

  • behavioral changes at various trophic levels, including increased downward swimming behavior in phytoflagellates and decreased avoidance of predators in juvenile fish

  • postulated species range movement to refuge areas such as eelgrass meadows

  • crabs and other crustacean growth rates, particularly when juvenile

bottom of page