Discovering Trophic Interactions in the Ocean Twilight Zone: Metabarcoding Analysis of Mesopelagic Fish Diet Diversity

Melissa Wojcicki1, Sarah G Glancy2, Paola G. Batta-Lona1, Joel Llopiz3, Annette Govindarajan4 and Ann C Bucklin1, (1)University of Connecticut, Marine Sciences, Groton, CT, United States, (2)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (3)Woods Hole Oceanographic Institution, Woods Hole, United States, (4)Woods Hole Oceanographic Institution, United States
Abstract:
The food web dynamics of the ocean twilight zone or mesopelagic (200m-1,000m) are central to the functioning of the ecosystem, determining responses to climate change, and resilience to commercial fishing. Mesopelagic fishes were collected using mid-water trawls from the slope water of the Northwest Atlantic Ocean during summer 2018 and spring 2019. Fishes were removed from samples immediately and frozen in liquid nitrogen. Several species were selected for study including Chauliodus sloani, Hygophum hygomii, and Agyropelecus aculeatus which were partially thawed for species identification and dissection of gut contents. Specimens were paired by species and size for comparative analysis of gut contents by either molecular (metabarcoding analysis) or morphological (microscopic) taxonomic identification. Extracted DNA was sequenced for the V9 hypervariable region of the 18s rRNA gene and the mitochondria cytochrome oxidase I (COI) barcode region using an Illumina MiSeq sequencer. Results were analyzed using custom scripts and reference databases to classify sequences and operational taxonomic units (OTUs). This study will contribute to new understanding of the role of these fishes in the mesopelagic food web and new insights into the trophic dynamics of the ocean twilight zone.
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