THE TRACE HUNTER Nicolas Sanchez is a Nansen Legacy postdoctoral fellow at NTNU. In this interview, Nicolas explains his tedious search for traces.

Nicloas, on cruises you often go in a white bunny suit and work in a plastic bubble. Why is that?

This is one of the most interesting and at the same time challenging aspects of working with trace elements in marine environments. Trace elements are chemical elements which are present in such low concentrations, that it was not possible to accurately measure the concentrations of these elements for decades.

Most working platforms at sea are metal structures, which means that the risk of contamination for elements, such as iron, copper, or zinc, is high. By using plastic instead of metal structures, clean air filters, and antistatic lab suits, we avoid most of suspended particles in the working environment and therefore minimizing the risk for contamination.

Could you give us a feeling for what kind of concentrations we are talking about for trace elements in the sea?

Iron and other bio-essential trace elements have extremely low solubility in seawater, which is why their concentrations are extremely low in the sea, expressed as parts per billion (ppb). For comparison, five drops of ink in about 200 L of water is the equivalent of 1 part per million (ppm). One ppb is 1000 times less than that.

If trace elements are only found in such infinitesimal amounts in the sea, why should we care about them?

Elements like iron are vital for photosynthetic organisms and limit primary production in 30-40 % of marine environments. Through the evolution of marine life, living organisms have favored several transition elements, mainly because of the versatile biological functions, but also because these elements were abundant in the physic-chemical conditions of early oceans (reductive environments). In today’s ocean (oxygenic environments), these elements are very scarce and therefore marine life (i.e. marine microbes) is faced with the challenge to constantly acquire elements that perform essential functions.

The Nansen Legacy is an interdisciplinary project. Have you in your work profited from the other disciplines?

There is definitive benefit from the other disciplines. The field of marine trace metal biogeochemistry is a cross-disciplinarily domain, as its name suggests. Although trace metals in the ocean have a relevant role of its own - as tracers for geo-physical processes - we are most focused on the role of these elements for the basis of marine life, i.e. all the processes which trace elements affect the uptake of nutrients, ecosystem structure (bacteria and phytoplankton), and ultimately primary production. Therefore, there is definitely a benefit to share data and information with the other scientists.

You have been part of the Nansen Legacy almost from its start. What is your best experience with the project so far?

The Nansen Legacy is a project covering most, if not all domains of oceanography within one of the most contingent topic of our time, so it is exciting to be taking part in such broad endeavor. It also means that you get to share and connect with scientist nationwide. This integrates the best of this experience.

[Work pictures: Christian Morel / christianmorel.net; Phytoplankton picture: NFH Marine microalgae group]