As part of the MaHeWa Project, a team from the Louis Malardé Institute (ILM) is currently conducting fieldwork in the Gambier Islands, French Polynesia.
This mission takes place within Work Package 2 – Task 2.2, dedicated to studying the impacts of Harmful Algal Blooms (HABs), and more specifically ciguatera, a marine food poisoning caused by microalgae of the genus Gambierdiscus.
The goal: to understand how marine heatwaves influence the presence, growth, and toxicity of these microalgae in Polynesian lagoons. This work contributes to the assessment of the costs of thermal tolerance and affected physiological functions.
On October 21, 2025, we organized a co-construction workshop at Ifremer in Vairao focused on possible responses to marine heatwaves. This event was part of the ongoing work carried out under the MaHeWa project and brought together around thirty participants, including municipal representatives, environmental associations, staff from the Directorate of Marine Resources, members of the Interministerial Delegation for Climate and Sustainable Development, and several researchers involved in the project. The goal was to engage in concrete discussions about the impacts of ocean heatwaves and to identify collective actions to reduce their effects on ecosystems and human activities. As a reminder, a first workshop of this kind was previously held in Nouméa, New Caledonia.
On October 5th, Alexandre Ganachaud, Research Director at IRD (Laboratoire d’Études en Géophysique et Océanographie Spatiales – LEGOS) and member of the MaHeWa project, represented the consortium at the “Cycles for the Climate” event organized by Météo-France at the Lac de la Ramée in Toulouse.
This friendly and engaging day dedicated to climate change awareness brought together many institutional, scientific, and citizen actors around activities, talks, and workshops.
The recent data from the HOPE buoy, deployed in New Caledonia, are enriching MaHeWa’s analyses on the effects of marine heatwaves (MHWs) by revealing very high-frequency dynamics of surface planktonic biomass — capable of quadrupling within hours — which in turn accelerates the formation of carbon-rich “marine snow” that sinks toward the deep ocean.
Illustration: Awareness seminar for healthcare staff.
Our colleague Cyril Dutheil worked with the middle school class (3ème B) of Collège Olympe de Gouges in Cadaujac to make a complex scientific study about marine heatwaves more accessible. This science outreach work was published in the journal DECODER, which is dedicated to making research available to everyone.
