Tara is back in the Mediterranean Sea to track pollution from rivers

© François Aurat / Tara Ocean Foundation

5 September 2019

Tara is once again studying plastic waste in the Mediterranean Sea. The Tara Ocean Foundation’s long-lasting interest in plastics is fully justified. The issue has become so important that the word “continent” is often used when referring to the billions of tons of plastic fragments scattered in the oceans. Five years after Tara’s first expedition dedicated to plastic pollution at sea, research is still under way. The behavior of plastics and their impact on marine biodiversity are still poorly understood.

2014: Assessing the amount of plastic and studying its relationship with living organisms

For almost 10 years, Tara scientists have been investigating the problem of plastics at sea. After observing that plastic litter is absolutely everywhere, the 2014 Tara Mediterranean expedition revealed that microplastics in this semi-enclosed sea are 4 times more concentrated than in the North Pacific Gyre. Tara scientists also studied the living organisms associated with these tiny fragments.

Today, they define plastic material as “a new ecosystem because “some microorganisms that are a minority in the water column have found a new habitat where they feel particularly good and therefore proliferate”, explains Jean-François Ghiglione, a CNRS ecotoxicologist and scientific director of the new 2019 Microplastics mission.

2019_07_28_Hoedic_Huitre-plastique©Lucas_Blijdorp_Fondation_Tara_OceanA piece of polystyrene found inside an oyster © Lucas Blijdorp / Tara Ocean Foundation

2019: Studying plastic flux to combat its dispersion

Building upon the early work quantifying and qualifying microplastics from the Mediterranean Sea, the schooner has returned to study this semi-enclosed sea. Tara is, of course, navigating in the open sea, but also sailing up 3 major rivers that flow from Spain (Ebro), Italy (Tiber) and France (Rhone) into the Mediterranean Sea. Motivating the Tara Ocean Foundation’s new 2019 Microplastics mission is the fact that 80% of plastic material at sea comes from land and microplastics represent 60 to 80% of all plastic debris present in rivers.

DCIM101MEDIADJI_0007.JPGSampling of microorganisms and microplastics in the Ebro River (Spain) using a Manta net © François Aurat / Tara Ocean Foundation

Given the severity of plastic pollution and the lack of research on the problem, the urgency is all the more pressing. “Since the problem of plastics has no solution at sea, we need to understand the sources represented by rivers and identify the unique characteristics of each of them”, Jean-François Ghiglione says.

Scientists aboard Tara are taking samples of water, microplastics and plankton, at sea, in estuaries, as well as in key locations along the rivers to assess the impact of major cities.

“We will also investigate the microorganisms living on microplastic debris, and other organisms, such as mussels, oysters, sea urchins and bass, to understand the bioaccumulation of pollutants attached to plastics.” In addition to these measurements, a model will be designed on the scale of the Mediterranean basin allowing scientists to describe and compare the influences of these 3 rivers regarding plastic influx to the Mediterranean Sea.

Margaux Gaubert, journalist

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