Marine bioluminescence, in situ spatio-temporal observations using gliders – BIOLUMOPS

In the ocean, the distribution of communities is largely influenced by light. This area of the ocean between 200 and 1000 m deep, where sunlight hardly penetrates anymore. The importance of this area in the functioning of the ocean is major, it has a key role in the carbon cycle by absorbing part of the atmospheric carbon, which will be partially sequestered at the bottom of the ocean. The twilight zone is strongly linked to the illuminated area of the ocean, between the surface and 200 m depth, by the export of organic matter from the surface to the depths and via the migrations of marine organisms. In these dark depths, bioluminescence, the emission of light produced by living organisms, is therefore a widespread means of communication in the marine environment and shaping the spatial distribution of communities. About 75% of the organisms in the water column have this capacity, from the surface to the abyssal depths. Because of its ubiquity, bioluminescence represents a proxy of the presence of organisms and their interactions, especially for small organisms. However, there is little quantitative data on bioluminescence, and these often stop at a few tens of metres above the surface, which limits the understanding of processes and spatial organization related to this capacity of organisms. (impact in nycthemeral migrations, thin layers of plankton, organization around whirlpools...). BIOLUMOPS will rely on an innovative technology in oceanography, the underwater gliders, to answer scientific questions that have been only little explored in the Mediterranean and up to 600 m of depth. Signal processing methods are currently widely developed in oceanography on spatio-temporal measurements and will make it possible to lift new locks. For national defence, the realization of underwater mapping in the first 600 m of the water column is of interest for the stealth of submarine gear. Another example is the direct in situ measurement of bioluminescence, which helps to inform combat swimmers about their potential visual indiscretion at night. Indeed, the mechanical stimulation activating the light emission of plankton is a risk of indiscretion of the Navy’s night operations, involving divers or vessels (submersible or surface vessels).

The main hypothesis of BIOLUMOPS is that bioluminescence is a proxy of the distribution of organisms. BIOLUMOPS will seek to answer scientific questions: What is the spatio-temporal variability of bioluminescence? What are the associated environmental conditions? And what are the characteristics of bioluminescent organisms (size, taxonomic group… ) of major importance in the recorded light signal? Building on technological innovation in oceanography, BIOLUMOPS proposes i) to improve, implement and deploy two bioluminescence sensors on autonomous underwater gliders (glider), ii) to deploy these vehicles in the Mediterranean (northwest) to obtain spatio-temporal mapping along a radial, environmental variables (chlorophyll, temperature, salinity) as well as fine-scale bioluminescence (< 1m) between 0 and 600 m of depth, iii) develop methods for processing the bioluminescence signal in conjunction with environmental variables in order to classify the different groups of organisms present and their variability, and to establish a typology of the recorded profiles between biological light and environmental variables, iv) To obtain a subsurface mapping of phytoplankton compositions and the chlorophyll-a bioluminescence correlation.