By: Jean-Louis JAMET, Dominique JAMET, Kévin SUGIER, Christophe BRACH-PAPA, Céline DUFFA, Jérôme GHERSI, Daniela BANARU, François CARLOTTI and Flora DROUET
The EMBIO team at the UM 110 MIO Laboratory has been regularly monitoring the Rade de Toulon since 1995, with monthly trips out to sea. This project has made it possible to collect time series of the various plankton communities evolving in these ecosystems, which are unique in France. These are currently stored and analysed at the Toulon Laboratory (zooplankton since 1995, phytoplankton since 2003, pico-nanoplankton and bacteria since 2013). Data on the associated environmental parameters (i.e. temperature, salinity, dissolved oxygen, pH, etc.) are also available. Following the pandemic caused by the emergence and spread of the Sars-Cov-2 virus and the resulting containment, it would appear that coastal marine ecosystems have been less impacted by human activities. Historically, this is the first time in the modern era that there has been little or no human activity over a period of 2 to 3 months in these environments.
As part of the monitoring of the ecosystem in place since 1995 and the various collaborative projects underway with Ifremer's LERPAC laboratory and IRSN (DROPLETT and NEEDS projects led by Christophe Brach-Papa and Céline Duffa respectively) and the European SHAREMED project, the EMBIO team's plankton group has decided to resume its coastal research activities as soon as possible after the confinement in order to take water and plankton samples. These samples will enable us to identify any changes in the structure, biodiversity and functioning of plankton communities that have occurred as a result of the reduction in human activity during the confinement.
The outings were carried out at the Toulon Bay workshop site, which brings together various DCSMM, RESOMAR and SOMLIT sites (in the process of being labelled) on 20 May and 8 June 2020, the latter corresponding to World Oceans Day. The Rade de Toulon is a particularly instructive study site, presenting two ecosystems that are connected but differently impacted by human activities. It is divided into two roadsteads by a breakwater. The Petite Rade is semi-enclosed and heavily impacted by human activities, notably the presence of military, yachting and commercial harbours, as well as numerous aquaculture sites. The Grande Rade, on the other hand, is less impacted by human activity, open to the sea and subject to the Liguro-Provençal current. During these outings, CTD measurements were also taken to assess classic water quality parameters such as temperature, salinity, dissolved oxygen and pH. Seawater samples were taken using a Niskin bottle at various depths to measure the nutrient salts present in the environment, chlorophyll levels and to characterise the pico-nano plankton and bacterial communities using flow cytometry. Microphytoplankton were also collected at depths of 3 m. Zooplankton samples were collected vertically from the bottom to the surface using Apstein-type plankton nets with different mesh sizes (90 and 200 mm).
Some of the samples collected during these two outings were analysed and stored on returning to the laboratory in the afternoon, and the plankton samples are currently being analysed. With a wealth of temporal information on the structure and diversity of the various plankton communities before and after confinement, the EMBIO team hopes to be able to identify changes in these communities following the reduction in human activity during confinement. The results obtained will provide a better understanding of the general functioning of these sensitive ecosystems in a coastal environment subject to different levels of human activity. Our results will also be compared with those obtained by our colleagues in the Bay of Marseille (Daniela Banaru and François Carlotti). Finally, in a much more general way, these projects will help environmental managers and political decision-makers to manage the conservation of marine biology and marine coastal systems.
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