A team of scientists from the Marine Research Center of the University of Vigo and the Institute of Marine Sciences (CSIC) of Barcelona have just made public the results of a study in which they reveal that marine photosynthesis is more sensitive to nutrients than to temperature. The study is led by professor from the Department of Ecology and Animal Biology, Emilio Marañón, and has just been published in one of the Nature group journals, The ISME Journal.
A fundamental principle in biology is that increasing temperature accelerates metabolic activity, which means that organisms capture and use resources more quickly. Of particular relevance is determining the relationship between temperature and metabolic rate in marine phytoplankton, since these microorganisms are the true ‘green engine’ of the ocean: they carry out half of all the CO2 capture by photosynthesis that occurs on the planet each year, and their photosynthetic activity not only sustains fishing resources, but also contributes to climate regulation. In this new article, the teachers reveal the response of phytoplankton to temperature and the supply of nutrients.
“In optimal conditions, with high nutrient availability, the rate of phytoplankton photosynthesis is stimulated by temperature,” explains Emilio Marañón, professor at the University of Vigo and director of the study, in which researchers María Pérez Lorenzo and Beatriz Mouriño, from the same department, also participated. This led the team of researchers to predict that the photosynthetic activity of phytoplankton could accelerate in the ocean, which has recorded in certain regions an increase in surface temperature of more than 2° C in the last 100 years. “The problem is that in most ocean regions the availability of nutrients, especially nitrogen, is very low, which limits the capacity of phytoplankton to grow. That is why we decided to investigate the response of phytoplankton to temperature under nutrient-limited conditions,” emphasizes the researcher.
The response to warming will vary geographically in the ocean
To test the interactive effect of temperature and nutrient availability on phytoplankton metabolism, the research team measured photosynthesis and respiration of three cosmopolitan and highly abundant ocean species (a cyanobacterium, a diatom, and a coccolithophore) maintained in laboratory cultures under different combinations of temperature and nitrogen supply. The results showed that both photosynthesis and respiration responded strongly to increasing nitrogen supply, while the effect of temperature was almost negligible.
These results suggest that the response of phytoplankton to warming will vary geographically in the ocean. As Pedro Cermeño, a researcher at the Institute of Marine Sciences of the CSIC in Barcelona and a participant in the study, indicates, “the increase in temperature will have a stimulating effect in productive areas, but will hardly affect phytoplankton metabolism in regions with a strong shortage of nutrients, which account for 80% of the ocean surface.” The response of the ocean’s biological productivity to global change processes will be dominated, they indicate, by changes in nutrient supply rather than temperature.
Source:DUVI
