25 years to save the marine ecosystem, climate change, is there a different mechanism?
Howard Dryden
25 years to save the marine ecosystem, climate change, is there a different mechanism?
by Howard Dryden
Nature 2010 and Nature 2011 reported that there has been a 40% drop in primary productivity in the North Atlantic since the
1950s. At the same time oceanic pH
started to decline sharply. This may be
related to an increase in industrial out-put and carbon dioxide emissions. However, as a marine biologist specialising in
some of the largest aquarium life support systems in the world, carbon dioxide is used to increase primary productivity. Woods Hole also reported that, an increase in carbon dioxide increased photosynthetic productivity, yet over the last 60 years there may have been a reduction by 40%. A slight increase in temperature would also be expected to increase productivity.
From the IPCC report 2014, anthropogenic carbon dioxide emissions only account for 3% of all the carbon dioxide emission entering the atmosphere. The oceans are responsible for between 50% and 80% of all atmospheric carbon dioxide fixation, yet if we have lost 40% (or even if it were only 5%) of this capacity, the reduction in primary productivity would account for the increase in atmospheric carbon dioxide and ocean acidification.
Carbon dioxide and minor increase in ocean temperature should increase productivity but given that there has been a reduction, could there be another reason for drop in pH, primary productivity and climate change?
From MARBEF we know that priority chemicals such as PCBs are over 1 ug/l in the Southern Oceans. We also know that concentrations over 1 ug/l will impact on protists (plankton) by reducing photosynthetic activity. When we factor in all of the other priority chemicals such as PBDE and methyl mercury, then perhaps priority chemicals are responsible for the reduction in primary productivity and indirectly responsible for the increase in atmospheric carbon dioxide and fall of pH?
From the IPCC and MIT it is evident that atmospheric carbon dioxide will continue to increase for the next 50 years. If the current hypothesis is correct that carbon dioxide dissolution into the oceans accounts for ocean acidification, then acidification will continue and the pH will fall below 7.9. Plankton such as carbonate based coccolithophores can not survive, or the eggs of most species of fish and crustacea. Without fish and crustacea we lose all the whales, seals, penguins and polar bears, and without coccolithophores we lose around 50% of the capacity of the oceans to sequester carbon dioxide.
At the current rate of change, pH 7.9 will be reached in 25 to 40 years. If we accept the current hypothesis concerning climate change, then it is inevitable that we will lose the marine ecosystem, there will be a huge shift in marine biodiversity and reduction in carbon dioxide fixation that will accelerate climate change. If we lose the marine ecosystem then ultimately the terrestrial system will follow.
However if there is a different mechanism then in addition to reducing carbon dioxide from the burning of fossil fuels we put our effort into preventing priority chemicals from entering the ecosystem there is a chance that we can reverse the trend, otherwise it will be impossible. By taking the brakes of the marine ecosystem, it can recover in a matter of a few years. The protists will be able to increase the pH and sequester atmospheric carbon dioxide, but this has to happen before the pH falls below pH 8.0.
The GOES Foundation is about debating the issues and raising the awareness regarding the delicate nature of the marine ecosystem and the inevitability of a cascade failure of the marine ecosystem over the next 25 to 40 years if nothing is done.