Zooplankton are important taxa that help marine ecosystems function. Herbivorous copepods serve as a primary prey source for many consumers, including commercial fish species. Copepods support some of the largest, charismatic megafauna via a short, and therefore energetically-efficient, food chain (phytoplankton -> zooplankton ->  predator). These megaplanktivores include the endangered basking shark (Cetorhinus maximus) and the critically endangered North Atlantic right whale (Eubalaena glacialis). Calanoid copepods make up the majority of the diet of both of these species, who have been known to seek out patches with high densities of large, late-stage, lipid-rich copepods in the genus Calanus. Due to their dietary importance, calanoid copepods are strong bottom-up drivers of many marine food webs, including those that exist in the Bay of Fundy. Understanding their populations and how they are changing is, therefore, crucial for the preservation of species that support various industries in the area, such as tourism and fish harvesting.

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Conventionally, zooplankton monitoring utilizes the ship-based deployment of nets and pumps by trained personnel during research cruises. This type of sampling can destroy useful identifying features of the zooplankton and has coarse vertical resolution. Acoustic and imaging tools enable the monitoring of zooplankton without damaging them in most cases and, when mounted on autonomous platforms, can drastically improve the vertical and time-space resolution of the areas they are sampling. Autonomous underwater vehicles (AUVs) are self-propelled, unmanned platforms controlled via an onboard computer. Gliders are a type of AUV that can profile the water column and can be fitted with additional sensors for monitoring oceanographic conditions, tagged fish, and/or animal vocalizations.  Cameras are another group of sensors that can be mounted on gliders. Shadowgraph cameras utilize light path disturbance to produce silhouette images and are particularly useful for resolving fine-scale differences in object transparency and have already proven a useful glider-mounted tool to resolve the taxonomic composition of zooplankton populations.

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The short-term objective of this project is to evaluate a glider-mounted shadowgraph camera’s ability to accurately measure zooplankton abundance and taxonomic composition while deployed in the ocean. The evaluation will be accomplished by comparing the shadowgraph data with co-located data collected with gold-standard oceanographic instruments (MultiNet Midi and Underwater Vision Profiler 6).