High-resolution sampling of plankton diversity using fluorescence and bioluminescence sensors

Autonomous sensors routinely measure physical (temperature, salinity), chemical (oxygen, nutrients) and some biological (fluorescence) parameters. However while fluorescence provides a proxy for autotrophic phytoplankton, heterotrophic plankton remain challenging to monitor in real-time and at high resolution. Bathyphotometers provide the capability to identify bioluminescent dinoflagellates, zooplankton, and jellies by measuring the light emitted by these organisms when mechanically stimulated. Highly abundant dinoflagellates emit low-intensity flashes that blend together, generating a continuous background bioluminescence signal. By contrast, rarer zooplankton and jellies emit strong flashes that can be individually resolved by high-frequency sensors. In-situ counts of plankton and jellies (bioluminescent or not) were matched with concurrent datasets of fluorescence and bioluminescence to develop proxies for diatoms, autotrophic and heterotrophic dinoflagellates, zooplankton, and small jellies. Because bioluminescent and non-bioluminescent organisms are often correlated, these proxies are representative of plankton communities. Applying this approach to concurrent fluorescence and bioluminescence sensors onboard autonomous underwater vehicles (AUVs) provides a novel and high-resolution view of plankton diversity and phytoplankton/zooplankton interactions in the sea.