Quantitative, multi-scalar in-situ imaging of jellyfishes and jelly-derived particles

Jellies play a fundamental role in the oceans, inhabiting the whole ecosystem from the surface down through the midwater (twilight zone, 50-1000m, and the bathypelagic, 1000-4000m). Recent best estimates suggest that gelatinous zooplankton account for 30% of total plankton biovolume. However, these estimates are most likely a drastic underestimate. A barrier to quantifying the role of jellies in biogeochemical cycles are the currently used sampling techniques. There is a pressing need to accurately quantify the contribution of jellies to biovolume, which is the prerequisite to quantifying their role in biogeochemical cycles. We have been developing platform-agnostic, quantitative imaging systems tailored to enable surveys of jellies from ephyrae size to adult medusae. We have also been developing software pipelines to rapidly process the collected data, with a human-in-the-loop approach for quality control, leveraging recent AI developments to quantify jelly abundances, sizes, biovolumes and diversity.

 

Currently, the imaging systems we have been developing are centred on colour stereo and shadowgraph-based imaging systems.  Colour stereo camera systems can provide size and diversity data on  larger animals. Shadowgraphs, on the other hand, can image small plankton and mucoidal/marine snow particles in detail. Since shadowgraphs use collimated light and the recorded images have a generally uniform background, it is easy to detect and quantify particles. Furthermore, internal structures of targets such as jellyfish and mucus can be observed. By using a range of different lenses on shadowgraph systems it becomes possible to simultaneously survey multiple size classes of jellyfishes. We will introduce the hardware prototypes and data processing pipeline as applied to surveys using ROVs and CTD rosettes in deep-sea environments with clear, oceanic water and in the turbid, coastal waters of the Gulf of Thailand from locally-hired fishing vessels and from wharfs.