Abstract

The survival and fitness of marine mammals is influenced by their environment. Most species display some level of plasticity in terms of their acclimatization to changes in climatic patterns. However, some climatic events may be so abrupt or excessive that they may exceed the limits of such plastic responses.¹ During the boreal winter of 2013 an anomalous increase in sea surface temperature was observed off the coast of Alaska. This phenomenon, nicknamed “the Blob”, expanded rapidly, and by 2015 had altered the primary productivity of the northeastern Pacific Ocean, with a marked reduction in fish abundance and an increase in marine mammal stranding events.² The SST was further increased by the 2015 El Niño event. Adult female California sea lions (CSL) modified their foraging patterns,^3,4 and CSL pups born during the anomaly, had lower body condition, altered erythrocyte morphologies,⁵ low blood glucose, and reduced immunocompetence.⁶ Here, we conducted an RNAseq analysis of blood samples collected from adult female CSL at San Benito Archipelago during 2014 (n=3; atypical SST conditions) and 2017 (n=3; normal SST conditions). We conducted a de novo assembly of the transcriptome using the dog (Canis lupus familiaris) and Weddell seal (Leptonychotes wedelli) genomes available in the NCBI genome database. We used stringent quality control criteria according to length and annotation of the contigs. 65% homology was found with the combined reference genomes. A conservative comparison of differentially expressed genes found a marked pattern of up-regulation of genes during 2014 compared to 2017. Mainly, genes associated with regulation responses to stimulus and stress, defense responses, inflammatory, and adaptive immune responses, were significantly upregulated. On the other hand, some cellular and DNA metabolic and cell regulation process were downregulated. While preliminary, these observations suggest that females from 2014 were undergoing marked cellular stress processes and had altered immune responses. Our results add further evidence to the notion that sudden and unpredictable climatic anomalies can impact the physiology, and health of marine mammals.⁷

* Presenting author
+ Student presenter

Literature Cited

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