Distributions of metazoans in low oxygen systems revealed through eDNA

Marine ecosystems are changing due to climate-driven deoxygenation, yet community responses to these shifts remain poorly resolved. Next-generation DNA sequencing allows us to explore metazoan ecosystem composition from water column samples. Using environmental DNA (eDNA), I analyzed metazoan communities above, within and below the anoxic zones in the Eastern Tropical South Pacific (ETSP) Oxygen Deficient Zone (ODZ), comparing them to a suboxic station. Results indicated that metazoan DNA concentrations peaked within the low-oxygen zones and that oxygen strongly structured the community. Additionally, using samples from Hood Canal, WA, we compared COI eDNA amplicons to COI from metagenomes of the same samples, revealing how taxonomic identification varied between these complementary approaches. Finally, we highlight a novel long-read COI amplicon approach by sequencing net tows to help improve reference databases. Together, these results show how modern sequencing approaches can reveal ecological responses across environmental gradients, improving our understanding of a changing ocean.