Elevated CO2 levels cause additional stress on marine life
Mallorca, 8th June 2012. An International research led by the Spanish National Research Council (CSIC) and the Pontifical Catholic University of Chile reveals that elevated levels of carbon dioxide (CO2) aggravate the stress driven by low oxygen levels (O2) in the ocean. This research, placed along the Chilean coast and published in the journal Biogeoscience, is centered in defining the water column in which the conjunction of these parameters limits the presence of marine organisms.
The oceans have absorbed about 25 percent of the CO2 emitted by mankind, and this has altered its chemistry, causing progressive water acidification that represents a threat to calcifying organisms (corals and planktonic calcifiers). However, CO2 also affects the efficiency of marine aerobic respiration, which depends on the relationship between CO2 and O2 levels in the water.
”This work emphasizes the fact that not only hypoxia (low O2 levels) generates breathing problems, but CO2 levels are also a threat to the marine aerobic respiration process. Thus, the bulk of the water column that holds breathing problems could be even greater and, if we consider the predictions of increasing CO2 in the oceans, the tendency is to rise further”, says the researcher from IMEDEA (CSIC-UIB) Eva Mayol.
The results of this work have shown that due to the combined effect of low concentrations of O2 and high levels of CO2, breathing is affected between 200 and 400 meters deep, while the biocalcification remains affected in most of the water column, except in the surface and in small plots under the 600 meters level.
“Viewed this way, acidification not only poses problems of calcification in calcareous organisms, but is also a threat for the breathing process in aerobic organisms. Thus, high levels of CO2 act as a hinge connecting two important challenges: breathing and calcification”, says Carlos Duarte, researcher at the IMEDEA (CSIC-UIB).
The study warns that if CO2 continues increasing, and ocean superficial layers reach critical levels, aerobic marine life, which mainly lives in these waters, could be strongly affected in its breathing process. This marine life includes key species in the fishing industry.
The CSIC and the Pontifical Catholic University of Chile are members of the International Global Change Laboratory (LINCGlobal). This organization facilitates interaction among Latin American researchers in order to understand, predict and develop strategies to tackle the impact of global change on marine and terrestrial ecosystems in the southern cone of South America and the Iberian Peninsula.
Citation: Mayol, E., S. Ruiz-Halpern, C. M. Duarte, J. C. Castilla, and J. L. Pelegrí. 2012. Coupled CO2 and O2-driven compromises to marine life in summer along the Chilean sector of the Humboldt Current System. Biogeosciences 9: 1183-1194.