How does rising atmospheric CO2 affect marine organisms?

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Substance Not Registered for Use in Australia Threatens Corals There
Scarlett, A., Donkin, P., Fileman, T.W. and Morris, R.J.  1999.  Occurrence of the antifouling herbicide, Irgarol 1051, within coastal-water seagrasses from Queensland, Australia.  Marine Pollution Bulletin 38: 687-691.

What was done
Seagrasses off the east coast of Queensland and within the Great Barrier Reef Marine Park, as well as a green alga from the Outer Barrier Reef, were sampled for the s-triazine herbicide Irgarol 1051, an antifouling agent used in some marine craft paints.

What was learned
Irgarol 1051 was detected at nine of the ten locations sampled, including parts of the Great Barrier Reef Marine Park. Within the Queensland coastal marine environment, it was present at potentially toxic concentrations.

What it means
Irgarol 1051 has been shown to be very toxic to the growth of freshwater and marine microalgae; and its presence within the Great Barrier Reef Marine Park, in the words of the authors, raises the possibility that it "could be affecting the endosymbiotic microalgae of coral polyps, upon which the health of the reef system depends."  Hence, it is logical to expect that the presence of this debilitating substance would weaken various coral components of the Great Barrier Reef and make them more susceptible to other stresses, such as increasing water temperatures, possibly leading to serious coral bleaching.  Two implications of this finding are (1) global warming may not be the major cause of increased coral bleaching over the past few years in this and other such affected areas and (2) elevated levels of atmospheric (and, hence, hydrospheric) CO2 may help to ameliorate this situation through their tendency to enhance photosynthesis within coral symbionts.

Reviewed 15 March 2000