ANALYZING TRENDS IN BENTHIC MACROFAUNAL BIODIVERSITY IN THE PACIFIC ARCTIC THROUGH TAXONOMINC AND GENOMIC METHODS

Abstract

Trends and environmental parameters that can influence benthic macrofaunal biodiversity were examined at sites in the Distributed Biological Observatory, a group of time-series stations located in the biologically productive shallow Pacific Arctic shelf region. This goal of this study was to better understand the underlying drivers of biodiversity and connectivity, which are important for predicting regional ecosystem resiliency to future warming, especially as sea ice loss and seawater warming have impacted seasonal water column production, carbon export to the benthos, and benthic faunal community structure and composition. A mixed-effects regression analysis was undertaken on taxonomically-based Shannon Index macrofaunal data from 1998-2019 to identify the region-wide environmental parameters influencing benthic macrofaunal biodiversity and any temporal and spatial patterns of variability. An index of the heterogeneity of sediment grain size classes, representing niche space, was found to positively influence biodiversity at both regional and sub-regional scales. There were few temporal trends in sediment heterogeneity, yet both positive and negative biodiversity trends persisted at specific locations, related to other environmental parameters. Specifically, the length of seasonal sea ice persistence influenced biodiversity, but with some regional complexities. A phylogeographic analysis of three benthic macrofaunal species from the northern Bering and Chukchi Seas was conducted using cytochrome c oxidase (CO1) barcode data. The study examined two clam species, Ennucula tenuis (Montagu, 1908) and Macoma calcarea (Gmelin, 1791), along with the polychaete Cistenides hyperborea (Malmgren, 1866), to investigate population-level genetic connectivity in these seasonally productive, shallow-shelf ecosystems. Genetic barcode data were compared with sequences in National Center for Biotechnology (NCBI) from other studies across the Arctic to assess broader population dynamics. E. tenuis specimens belonged to a single population with distinct geographic variation. Analysis of M. calcarea was inconclusive due to technical problems during sample processing that prevented developing a population structure assessment prior to completing this thesis. C. hyperborea specimens from the northern Bering and Chukchi Seas formed a single population with two closely related haplotypes and minimal geographic genetic differentiation. However, sequences from this study differed significantly from Cistenides hyperborea records in the NCBI, suggesting there may be have taxonomic uncertainties associated with available data in the NCBI.