SEM-REV, a support structure for plankton observation

SEM-REV has been a member of the Phenomer network since July 2020. Initiated in 2013 by Ifremer and rolled out throughout Brittany, this exploratory participatory science project invites members of the public to report coloured water phenomena due to the proliferation of microorganisms. Last March, red water was observed on the SEM-REV site and samples were taken to help identify the species responsible.

on June 29, 2021

Eau colorée au SEM-REV | Photo : Thomas Latreuille-BW IDEOL
Eau colorée au SEM-REV | Photo : Thomas Latreuille-BW IDEOL
The main objective of Phenomer is to gain a better understanding of the marine micro-algae capable of such proliferation that they colour the sea. Thanks to the general observations reported, Ifremer and its partners, including Centrale Nantes, via the SEM-REV test site, can report these phenomena and take samples of sea water which will be analysed and compared with all the available environmental data. This data provides:
  • a better understanding of the ecology of the micro-algae species present and their succession over the seasons
  • insight into the impact of human activity and climate change on these blooms
  • a list of the species that may present risks for marine fauna and human health along the French coast.

On 23 March, the BW Ideol team observed red-coloured water near the FLOATGEN wind turbine currently under test on the SEM-REV test site. Thanks to the collaboration between the BW IDEOL and Centrale Nantes teams, this observation was passed on to the Phenomer network. Samples were taken in order to determine which species of micro-algae was responsible for this event.

Satellite pictures at medium resolution (1 km) also confirmed the presence of high primary production in the Bay of Biscay. Thanks to its high spatial resolution (10 m), the European satellite Sentinel-2 detected these red waters off the Loire estuary on 22 March 2021. The SEM-REV team sent two samples (one live, the second frozen) to the Roscoff Biological Station and to the Ifremer Laboratory in Nantes, for morphological determination and to decide on the actions to be taken for research purposes. On 26 March 2021, the organism responsible for the colouring of the water was identified by the Roscoff Biological Station: a small ciliate, Mesodinium rubrum, the favourite prey of the micro-alga Dinophysis, known to induce the diarrhoeal toxin in shellfish. On 27 March, red water was also observed in the Vendée, off the coast of Saint-Gilles by the boat hire company Voile & Vie. On 28 March 2021, amateur sailors reported "blood red" water in the port of Les Sables d'Olonne. On 29 March 2021, the University of Nantes sampled dark red water in the Vendée. Taxonomic analysis of the samples by Ifremer Nantes confirmed the presence of M. rubrum, accompanied by a dinoflagellate of the genus Scrippsiella.

The trail of coloured water then disappeared, perhaps pushed out to sea... or following the break down of Mesodinium cells, whose life cycle is quite short.

Learn more on the PHENOMER website (in French):
Published on October 11, 2021 Updated on October 11, 2021