INTERVIEW. Elvira Pulido is the leader of WP3 dedicated to nutrients in the ocean. She describes the importance of measuring nutrients concentration in the ocean – as they ultimately control biological activity and diversity – and how they are going to measure them in the BioSWOT-Med campaign.
THE RESEARCH THEMES: Elvira Pulido is a marine biogeochemist with a general interest on nutrient cycling at the surface ocean. She’s particularly interested on the oligotrophic ocean where nutrient scarcity limits biological activity and, thus, carbon export is highly dependent on nutrient availability. Currently, she uses high-sensitive techniques to measure phosphate concentration in seawater in order to gain further insight of the phosphorus cycle in the surface ocean, particularly concerning the mechanisms involved in phosphate supply to the euphotic zone and the bioavailability of the organic phosphorus pool. Elvira Pulido is a CNRS researcher and she works at the Mediterranean Institute of Oceanography (MIO) in Marseille, France.
In the BioSWOT-Med campaign you are in charge of WP3 dedicated to nutrients in the ocean. What are the chemical substances that you will be measuring? Why is it important to measure them in the ocean?
The availability of nutrients may ultimately control biological activity and diversity. This is particularly true in nutrient-depleted oceanic regions like the Mediterranean Sea. One of the main objectives of the BioSWOT-Med cruise is to explore how and to which extent fine scale ocean dynamics impact nutrient distribution and fluxes. The study of nutrient dynamics during the BIOSWOT-Med cruise needs to face two challenges: first, the study area is characterized by very low nutrient concentrations and, second, fine scale oceanic circulation shall provoke small (i.e. nanomolar) and rapid changes in nutrient concentration. Both challenges will be undertaken by conducting nutrient measurements (nitrate, nitrite, and phosphate) at both high frequency and precision.
The Mediterranean Sea is called “oligotrophic”. What does it mean? What are the differences with other seas/ other regions of the ocean?
The term oligotrophic comes from the Greek oligos, meaning ‘small’ or ‘few’ and trophe, meaning nutrition. The oligotrophic marine regions are thus characterized by low nutrient concentration and low biological productivity due to a more or less pronounced thermal stratification which delimits a warm surface mixed layer. They cover up to 60% of the global ocean including regions like the Mediterranean Sea and the large sub-tropical gyres in the Atlantic and Pacific Oceans, and play a key role in the regulation of climate by sustaining one third of total marine carbon fixation. In addition, oligotrophic regions are currently expanding due to increase in sea surface temperature and stratification. Studying the functioning of these regions is thus crucial to understand the current and future role of the ocean in climate regulation.
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