Postglacial expansion of the Arctic keystone copepod Calanus glacialis

Agata Weydmann,Artur Burzyński,Gareth A Pearson,Marek Lubośny,Katarzyna S Walczyńska,Aleksandra Przyłucka,Ester A Serrão

doi:10.1007/s12526-017-0774-4

Abstract

Calanus glacialis, a major contributor to zooplankton biomass in the Arctic shelf seas, is a key link between primary production and higher trophic levels that may be sensitive to climate warming. The aim of this study was to explore genetic variation in contemporary populations of this species to infer possible changes during the Quaternary period, and to assess its population structure in both space and time. Calanus glacialis was sampled in the fjords of Spitsbergen (Hornsund and Kongsfjorden) in 2003, 2004, 2006, 2009 and 2012. The sequence of a mitochondrial marker, belonging to the ND5 gene, selected for the study was 1249 base pairs long and distinguished 75 unique haplotypes among 140 individuals that formed three main clades. There was no detectable pattern in the distribution of haplotypes by geographic distance or over time. Interestingly, a Bayesian skyline plot suggested that a 1000-fold increase in population size occurred approximately 10,000 years before present, suggesting a species expansion after the Last Glacial Maximum.

Highlights

A large part of zooplankton biomass in the Arctic shelf seas is formed by Calanus glacialis (Fleminger and Hulseman, 1977; Blachowiak-Samolyk et al 2008; Weydmann et al 2013), a lipid-rich calanoid grazer
The diversity indices showed overall high haplotype diversity (Hd), which was apparently associated with low nucleotide diversity (π) in the studied population of C. glacialis (Table 2)
There was no genetic differentiation between tested pairs of populations; there was no evidence of any population genetic structure among the compared samples (p > 0.05; Table 3)

Summary

Introduction

A large part of zooplankton biomass in the Arctic shelf seas is formed by Calanus glacialis (Fleminger and Hulseman, 1977; Blachowiak-Samolyk et al 2008; Weydmann et al 2013), a lipid-rich calanoid grazer. The areas of its occurrence, including peripheral seas of the Arctic Ocean and adjacent regions of the North Atlantic and Pacific Oceans (Jashnov 1970; Conover 1988), are facing intensive modifications from an unprecedented combination of environmental changes, such as increasing ocean temperatures and reduction in sea ice extent, caused by climate warming (IPCC 2014), with the record high Atlantic Water temperature and salinity in 2006 (Walczowski et al 2012). With the Arctic region likely to continue warming more rapidly than the global mean (IPCC 2014), changes are expected to affect Arctic marine biota. Major changes in the function of the Arctic marine ecosystem are anticipated

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