The occurrence of Nematoda in coastal sea ice on Svalbard (European Arctic) determined with the 18S small subunit rRNA gene

Vanessa Pitusi,Miriam Marquardt,Brandon T Hassett,Magnus Heide Andreasen,Janne E Søreide

doi:10.1007/s00300-021-02863-y

Vanessa Pitusi, Miriam Marquardt + Show 3 more

Open Access

https://doi.org/10.1007/s00300-021-02863-y

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Abstract

Understanding the diversity and functioning of Arctic sea ice ecosystems is vital to evaluate and predict the impact of current and future climate change. In the microscopic communities inhabiting the brine channels inside sea ice, nematodes often dominate numerically and act as bacterivores and herbivores. Despite nematodes great abundances and known ecological roles, molecular tools have not been applied to investigate their species diversity in sea ice. In an attempt to begin establishing a molecular baseline for species diversity of sea ice nematodes, we Sanger sequenced 74 specimens from four locations around Svalbard (European Arctic), using the 18S rRNA barcode. Currently available nucleotide reference databases are both underpopulated with representative marine nematode taxa and contain a substantial number of misidentified organisms. Together, these limitations inhibited the ability to identify marine specimens collected in this study with certainty. Nevertheless, our molecular data indicate the presence of two genera in sea ice on Svalbard—Theristus and Halomonhystera. While it is possible that the latter represents a novel ice nematode species, future studies, including morphometric analysis, are needed to verify our molecular findings. We leverage the assignment of molecular information to robustly identify nematodes and provide the first insight into the diversity of sea ice nematodes in the European Arctic. We advocate for an intensified cooperation between molecular and morphological taxonomists to expedite the establishment of baseline surveys that are required to predict biological consequences of the diminishing sea ice habitat in the future.

Highlights

Nematodes are among the most abundant and species-rich metazoans on earth, comprising taxonomic and functionally diverse communities in terrestrial, freshwater and marine habitats (Heip et al 1985; Yeates 2007; Moens et al 2013)
Despite their broad distribution and functionality, only 30,000 species have been described globally (Hugot et al 2001), which is assumed to present only 3% of the estimated 1 million species that are thought to exist (Creer et al 2010). Much of this undiscovered diversity is thought to be hidden in the marine environment from which only around 6000 species have been described far (Bezerra et al 2020). It is even less with only five described species so far: Theristus melnikovi from the Central Arctic Ocean, Laptev Sea, and Fram Strait (Tchesunov 1986; Riemann and Ngando 1997), Cryonema crassum (Tchesunov and Riemann 1995; Tchesunov and Portnova 2005) and Cryonema tenue (Tchesunov and Riemann 1995) from the White Sea, off the coast of Siberia, and the Fram Strait, and Hieminema obliquorum (Tchesunov and Portnova 2005) from the White Sea
This study presents the first insight into the genetic diversity of coastal sympagic nematodes in the Arctic and foremost in Svalbard

Summary

Introduction

Nematodes are among the most abundant and species-rich metazoans on earth, comprising taxonomic and functionally diverse communities in terrestrial, freshwater and marine habitats (Heip et al 1985; Yeates 2007; Moens et al 2013). Nematodes are commonly the most abundant meiofauna group in aquatic systems (Platt and Warwick 1980; Semprucci 2013), Despite their broad distribution and functionality, only 30,000 species have been described globally (Hugot et al 2001), which is assumed to present only 3% of the estimated 1 million species that are thought to exist (Creer et al 2010) Much of this undiscovered diversity is thought to be hidden in the marine environment from which only around 6000 species have been described far (Bezerra et al 2020).

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