Rising CO2 Levels - Worse Than You Thought!

A review of: Doney, S.C., Ruckelshaus, M., Emmett Duffy, J., Barry, J.P., Chan, F., English, C.A., Galindo, H.M., Grebmeier, J.M., Hollowed, A.B., Knowlton, N., Polovina, J., Rabalais, N.N., Sydeman, W.J., Talley, L.D., (2012), Climate Change Impacts on Marine Ecosystems, Annual Review of Marine Science, 4, 11 -37

The marine ecosystem is a very large, complex and delicately balanced world process, however, it is primarily driven, and largely made up of primary producing microorganisms. These are essential in all marine food webs and allow for organisms throughout these webs to survive, including humans, however, with an increase in the human population, there is a greater demand for fossil fuels, and as a result, a larger amount of CO2. This rise in atmospheric CO2, is one of the most critical problems facing our planet due to its global and irreversible effects on the environment. It is in the oceans that one of the largest threats is posed, and this is due to the nature of CO2 which can both raise temperatures of the oceans and lower its pH. This rise in temperature can also lead to the the rising of sea levels, with many coastal habitats being lost, including many of the worlds reef systems. The increase in dissolved CO2 also results in hypoxia where oxygen levels haven been lowered, this is vey problematic for higher species, but can be beneficial to some microbes. However, diatoms will suffer from this as literary tests show that the calcification process is severely hindered in the presence of raised CO2 levels. 

One of the largest problems caused by rising CO2 levels is posed to the symbiotic dinoflagellate zooxanthellae found in corals which, when occurring in the tropics, result in a boom in biodiversity density containing one quarter of all marine species. Risks posed by the rising CO2 levels are the acidification preventing normal calcification of the coral, and the rising temperatures causing bleaching due to the highly sensitive nature of the zooxanthellae. So not only is it the coral organisms that are at a very high risk, but the whole ecosystem that is based around and in them is too. Another area of coral reefs that is directly threatened, is that of the coralline algae coverings, forming a biofilm for reproductive purposes and also as a primary producing food source to other organisms.

As the marine microbes are very often the primary producers in a food web, their importance to the whole world process is of dire importance, this becomes evident when looking at the ice dominated polar systems, where a direct effect can be witnessed when zooplankton have a reduced primary production and are seen to have a knock-on effect to many species in the tropic levels above them.

In its current state, the world oceans contain many of the most delicate ecosystems to be found, this is to do with the delicate nature of many of the microbes that dive the main processes found in them. Due to the delicateness of these organisms, they are posed the largest risk by the very small changes that are predicted from the rising levels of atmospheric and dissolved CO2.