High cryptic diversity of invertebrates in varying nearshore habitats of the Beaufort Sea

The Alaskan Beaufort Sea lagoon system supports a diverse invertebrate community shaped by a complex glacial and biogeographic history, yet it remains severely understudied relative to the rapid environmental changes it is experiencing. As Arctic amplification accelerates habitat loss, shifts dispersal pathways, and facilitates the introduction of boreal and invasive species, accurately documenting current biodiversity is increasingly urgent. In this study, we used DNA barcoding of the mitochondrial cox1 gene for various invertebrates, and the nuclear 28S rRNA gene for Porifera, to examine invertebrate genera across coastal sites in the Alaskan Beaufort Sea, including the unique Boulder Patch kelp community in Stefansson Sound. We sequenced specimens belonging to five phyla: Annelida, Arthropoda, Mollusca, Porifera, and Priapulida. Specimens were identified by morphology, and their cox1 or 28S rRNA gene sequences were matched against the GenBank and Barcode of Life Data Systems (BOLD) databases. Molecular identification revealed substantially higher species diversity than morphology alone in three of five phyla: Annelida (12 versus six species), Arthropoda (14 versus 11), and Mollusca (five versus four). In Porifera and Priapulida the number of species were the same for morphological and molecular identification; however, we still found different species identifications between the two methods. Other notable findings include the discovery of multiple cryptic species within Terebellides sp., Pontoporeia femorata, Onisimus litoralis, and Micronephthys minuta, as well as the first published sequences for Acanthostepheia incarinata, Haliclona gracilis, Onisimus affinis, and Saduria sibirica. Our results highlight the extent to which morphology-based surveys underestimate invertebrate diversity in Arctic ecosystems and underscore the need for comprehensive surveys and molecular reference databases to support future molecular-based biodiversity monitoring in this rapidly changing region.