Date of Completion

Spring 6-9-2021

Thesis Advisor(s)

Ann Bucklin; Claudia Koerting

Honors Major

Marine Sciences

Abstract

This study uses molecular approaches to investigate evidence of climate adaptation of a marine zooplankton species in the Arctic Ocean. Euphausiids (krill) are abundant and ecologically important members of the ocean ecosystems and play key roles in pelagic food webs. The specific goal is to analyze patterns of gene expression, which is measured as RNA concentration for all genes across the entire transcriptome and also for specific target genes of known function, for the euphausiid Thysanoessa longicaudata. Gene expression can reveal responses to thermal stress associated with exposure to temperatures outside the normal range for the species. Specimens of T. longicaudata were collected and flash frozen, to preserve RNA, from the relatively warmer waters in the Fram Strait, in Atlantic waters west of Svalbard, Norway, and from the colder waters north of Svalbard. First, the samples were sequenced for the DNA barcode region of mitochondrial cytochrome oxidase I (COI) to confirm species identification. RNA was extracted from individual specimens and prepared for sequencing. RNA sequencing provides a snapshot of gene expression in the organisms within their present conditions. Differential gene expression analysis (comparison of RNA concentration between specimens) indicates environmental stress responses and possible adaptation of the species to varying conditions, including temperature. Bioinformatics reveals the function of the selected genes (i.e., gene annotation), and genes with functional roles hypothesized to be important for thermal adaptation can be selected and analyzed for differential expression using quantitative PCR (qPCR). The Arctic Ocean is experiencing rapid climate change and evaluating the capabilities of key species to adapt may allow better prediction of their survival and ecosystem resilience for the future.

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