Unlike other marine species, the corals are still capable of adapting under current circumstances of declining sea alkalinity, according to researchers at the Centro de Investigaciones Biológicas del Noroeste S.C. “The first models indicated that the coral reefs would disappear mid-century, but our study reveals that corals are adapting to the ocean’s acidification that has increased since the industrial revolution,” said Eduardo Balart Páez, head of research at the Mexican institution.
The project covers the Gulf of California and the coast of the Mexican Pacific. The scientists analyzed colonies of Porites and Pocillopora, which are the more important species in the reefs of the eastern Pacific Ocean.
Through radiographic plates taken from samples of Porites panamensis of up to 22 years of age, changes in extension, density and calcification were visualized through time in the coral skeleton. DNA was also extracted from both species to learn their genetic diversity.
These studies helped identify that the ocean’s reduction in alkalinity is affecting the coral’s growth but not dramatically. Moreover the impact is different between males and females, said researchers. The corals of the Pocillopora genus are hermaphrodites but not Porites, hence the answer is not the same for all, they added.
“This marine organisms are healthy for the moment because of a bigger energetic expense given by a genetic adaptation. However as the acidification levels rise there can be a disturbance in the sexual proportions,” warned Balart Páez.
The researcher specified that the species Porites panamensis is a massive coral that is frequently found from the shore to a depth of 30 meters. Meanwhile, the Pocillopora, ramified corals, require a great quantity of light given to their great dependence to the photosynthesis of their symbionts, and that is why they are found in shallow waters.
The current decrease in alkalinity of the oceans is a consequence of the rise of carbon dioxide emissions to the atmosphere. The average pH of ocean waters was of 8.15 during preindustrial period, and now it has dropped to 8.05, meaning that, the ocean is turning less alkaline. The level 7.0 is neutral.
Finally, the researcher said that the threat of acidity over the reefs has not diminished. It will be necessary to do more research in order to find which coral species are the most prone to adapt, how the fragmentation of populations is affecting them and study the phenomenon in the laboratory to forecast possible future scenarios.
The center is associated with the Instituto Politécnico Nacional in La Paz, Baja California.