Name: Nicholas Silverson
Date: 10/28/2024
Time (EST/EDT): 09:30 am
Location: CBL
Access Link : email mees@umd.edu

Committee Chair: Dr. Jacqueline Grebmeier
Committee Members: Dr. Lee Cooper, Dr. Matthew Galaska

Title: Analyzing trends in benthic macrofaunal biodiversity in the Pacific
Arctic through taxonomic and genetic methods

Abstract: The rapid warming of the Arctic Ocean has consequences for patterns
of biodiversity as altered oceanographic conditions contribute to shifts in
community composition. Trends and the environmental parameters that 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 to better
understand the underlying drivers of biodiversity and connectivity. This
understanding is 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. A mixed-effects regression analysis was performed
on taxonomically-based Shannon Index data from 1998-2019 to identify the
region-wide environmental parameters influencing benthic macrofaunal
biodiversity and any temporal and spatial patterns of variability.
Additionally, a phylogeographic analysis of the dominant nut clam, Ennucula
tenuis (Montagu, 1808), was done using cytochrome c oxidase (CO1) barcode data,
which was then compared with sequences from across the Arctic to identify the
wider population dynamics of this presumed circumpolar species. An index of the
heterogeneity of sediment grain size classes, representing niche space,
positively influenced 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, with regional complexity. Genetically, E.
tenuis had greater diversity within locations than between locations. However,
some geographic structure was identified; the northernmost and southernmost
populations in the study region were significantly different. Furthermore,
Pacific Arctic nut clam populations differed from populations across the
Canadian Arctic seas. This pattern suggests that a barrier to dispersal may
exist between the Chukchi and Beaufort seas, with the northern Chukchi Sea
existing as a zone of admixture. Historical glaciation is most likely
responsible, yet patterns of sediment heterogeneity and sea ice decline could
also influence these genetic differences. As sea ice loss and warming waters
are predicted to continue to increase in coming years, these trends could
become more obvious with further study. Insights into the biodiversity and
population structure of important Arctic species can lead to a deeper
understanding of regional ecosystem structure, which can be useful for
predicting resiliency in response to environmental change.