Unique Technical Innovations for Plankton Collection

Between the periods of diving on coral reefs, such as during the 15 days at sea between Colombia and Easter Island, science doesn’t stop on Tara. Every morning during the crossings, the scientific team is active for several hours on the back deck of the schooner, taking dozens of filtration samples to recover valuable plankton that will complement the data. We focus on 2 unique technical innovations. 

Un échantillon d’eau de mer prélevé à l’aide du filet haute vitesse, contenant du plancton mais aussi du plastique.
A seawater sample collected with the High Speed Net, containing plankton but also plastic © Maéva Bardy / Tara Expeditions Foundation

As often happens in science, the development of protocols was dictated by logistical reasons. “From the beginning, we knew we would have to take samples without stopping the boat or even slowing down,” recalls Fabien Lombard, lecturer at the Université Pierre et Marie Curie. With the ambitious course of this expedition across the Pacific and time schedules, it was not possible to consider sampling stations while drifting for several hours as in previous Tara expeditions.

“We had to find a technical solution and that’s what is amazing with Tara because researchers are constantly looking for solutions and innovations – we had never sampled at such a speed, and that’s what Gaby Gorsky achieved with his team!” says Maria Luiza Pedrotti from the Villefranche Oceanographic Laboratory.

Guillaume Bourdin, ingénieur de pont, et David Monmarché, chef opérateur hyperbare, mettent à l’eau le « Dauphin », un système de pompage d’eau de surface permettant d’analyser l’eau et de prélever le plancton.
Guillaume Bourdin, deck officer, and David Monmarché, divemaster, immerse the “Dauphin”, a surface water pumping system © Yann Chavance / Tara Expeditions Foundations

With these unprecedented constraints, Gaby Gorsky, one of the scientific coordinators of Tara Pacific, has indeed imagined 2 new devices that can be towed at a speed over 7 knots (about 13 km/h) behind Tara without dislocating under the water force. These 2 prototypes are unique in the world: the “Dauphin”, a system pumping surface water via an impressive pipe, and the High Speed Net (HSN). Two instruments specifically designed to take up sea water via a thin metal slot which gradually widens. “The idea is to create a vacuum to prevent the water pressure from tearing the hose or net, but also not to crush the organisms,” explains Fabien Lombard.

Le filet haute vitesse permettant de récupérer des échantillons d’eau de mer afin d’étudier le plancton.
The High Speed Net, with its collector (below) for recovering sea water samples © Maéva Bardy / Tara Expeditions Foundation

Every morning on Tara’s back deck, the scientific team immerse the 2 metal giants: the Dauphin is positioned alongside the hull and the HSN – weighing nearly a 100 kilos – is towed at the back. Collecting water from the net or gushing from the Dauphin’s pipe, the researchers then race to filter, mix and decant the precious liquid into dozens of carefully labeled tubes. The protocols are complex and require intense concentration: in one morning, the team should collect 30 samples, each intended for a specific laboratory and for a particular research objective.

Yann Chavance