Seminar by Christophe Guinet (CEBC, Chizé) on April 1 at 11:30 am

Sea elephants bio-samplers of oceanographic conditions: measurement of new oceanographic parameters and assessment of intermediate biological levels.

Summary: In recent years, Kerguelen elephant seals have become an essential component of the National Observing System: Bio-Sampling Mammals of the Ocean Environment for the observation of oceanographic conditions in the Indian sector of the Southern Ocean. Temperature, salinity, and fluorescence are now recorded continuously and at high frequency (0.5 Hz) over periods of several months. More recently, our efforts have focused on the evaluation of new environmental parameters. First of all, as part of Dorian Cazau’s post-doctoral fellowship at ENSTA-B, we were able to evaluate wind strength and direction and sea state (wave frequency and amplitude) by combining acoustic, acceleration and magnetometry measurements. In addition, our research activities in recent years have focused on studying biological levels: phytoplankton to elephant seal prey, as well as assessing the distribution and density of intermediate levels (zooplankton and micro-nekton). To this end, new generations of recorders have been developed in partnership with the Sea Mammal Research Unit, namely a high-frequency, low-energy micro-sounder that can detect the presence of planktonic and micro-nectonic biological organisms during sea elephant diving. In parallel, high sensitivity bioluminescence sensors sampling light at very high frequencies. By simultaneously measuring continuous and high frequency oceanographic and biological parameters, elephant seals have become essential bio-samplers for assessing the influence of oceanographic conditions on the fine scale structure of the different biological levels in the Southern Ocean.