The acidity of the oceans is increasing. CO2, released in great amounts by human activity and partly captured by the world’s seas, is implicated. Scientists are now getting organised in an effort to understand the impact of this phenomenon on marine ecosystems, for they are facing a daunting technological challenge: they must set up a laboratory on the seabed to measure the effect of ocean acidification on the species living there

A quarter of the CO2 released by human activity, which builds up in the atmosphere, is absorbed by the oceans, causing a drop in their pH. This acidification threatens to disrupt the balance of ecosystems. By dissolving the calcium carbonate normally present in ocean waters, it endangers organisms that use it to build their skeletons; at the same time, certain algae that metabolize CO2 to grow could gain the upper hand. Scientists are trying to accurately quantify this impact.

The FOCE concept

Experiments are customarily performed in the laboratory on organisms isolated from their natural environment in aquariums. But these artificial conditions cannot account for the complexity of the exchanges in underwater ecosystems.

A new solution began to take shape in 2003, at the Monterey Bay Aquarium Research Institute (MBARI), in California. Inspired by experiments on terrestrial plants, marine chemistry researcher Peter Brewer invented a new technological concept: the direct study of the effects of acidification on marine organisms on the seabed by enriching the ocean waters locally with CO2, what he calls “FOCE”, for Free Ocean CO2 Enrichment.

An innovative technical solution

Since then, the MBARI team, in a collaborative effort between scientists and engineers led by Peter Brewer and William Kirkwood, has developed a complex submersible system. An open enclosure, placed on the seabed and connected to a submerged relay station, provides a highly regulated local flow of CO2, recreating controlled acidification of the water within its confines. This means that biologists can study the effect produced in situ on marine species in their natural environment.

An open source technology

MBARI is now making its expertise and technology available to the scientific community at large as an open source system known as “xFOCE”, thus giving researchers on various continents, who wish to measure the effects of ocean acidification, a substantial technical head start. It will be up to each of the teams to adapt this basic system to the environment studied (in terms of depth, temperature, salinity, etc.).

An xFOCE community has thus come into being under the leadership of MBARI. Scientists are starting projects in all latitudes: in the United States (deep FOCE), Australia (cp-FOCE), Europe (eFOCE) and Antarctica (Antarctic FOCE). This sharing of experience designed to foster technical advances is already bearing fruit. The initial results, obtained on the Great Barrier Reef and published in the prestigious journal Nature in May 2012, provide a convincing demonstration of the system’s efficacy.

BNP Paribas Foundation Climate Initiative, 12 April 2013. Article.