Protists in Arctic drift and land‐fast sea ice

Abstract

Global climate change is having profound impacts on polar ice with changes in the duration and extent of both land-fast ice and drift ice, which is part of the polar ice pack. Sea ice is a distinct habitat and the morphologically identifiable sympagic community living within sea ice can be readily distinguished from pelagic species. Sympagic metazoa and diatoms have been studied extensively since they can be identified using microscopy techniques. However, non-diatom eukaryotic cells living in ice have received much less attention despite taxa such as the dinoflagellate Polarella and the cercozoan Cryothecomonas being isolated from sea ice. Other small flagellates have also been reported, suggesting complex microbial food webs. Since smaller flagellates are fragile, often poorly preserved, and are difficult for non-experts to identify, we applied high throughput tag sequencing of the V4 region of the 18S rRNA gene to investigate the eukaryotic microbiome within the ice. The sea ice communities were diverse (190 taxa) and included many heterotrophic and mixotrophic species. Dinoflagellates (43 taxa), diatoms (29 taxa) and cercozoans (12 taxa) accounted for ~80% of the sequences. The sympagic communities living within drift ice and land-fast ice harbored taxonomically distinct communities and we highlight specific taxa of dinoflagellates and diatoms that may be indicators of land-fast and drift ice.

Mesoscale distribution and functional diversity of picoeukaryotes in the first-year sea ice of the Canadian Arctic

“…Picoeukaryotes are among the least known protistan groups in the sea ice. The first studies on the diversity of sea-ice protists (not only picoeukaryotes) have shown sea-ice communities to consist of various phylotypes (Eddie et al, 2010;Bachy et al, 2011;Majaneva et al, 2012;Comeau et al, 2013). Our study complements these recent results with the first report on the quantitative distribution of particular groups of picoeukaryotes in first-year sea ice, including percentage of cells actively feeding by phagocytosis.…”

“…Cryptophytes were the second most numerous group (Figure 4). Cryptophyte phylotypes related to Teleaulax and Hemiselmis were found in first-year sea ice in the Canadian Beaufort Sea (Comeau et al, 2013) and the Baltic Sea (Majaneva et al, 2012), but not in multiyear ice close to the North Pole (Bachy et al, 2011). Sequences of cryptophytes have been recovered from size-fractionated (0.2-3 mm) Arctic waters (Terrado et al, 2011).…”

“…Chlorophytes and cryptophytes were the most numerous groups (Figure 4). Sequences of chlorophytes were also retrieved from multi-year sea ice close to the North Pole (Bachy et al, 2011), and first-year sea ice in the Beaufort Sea (Eddie et al, 2010;Comeau et al, 2013) and the Baltic Sea (Majaneva et al, 2012). These phylotypes were related to Chlamydomonas, Mantoniella, Bathycoccus, Pyramimonas and Microsomonas.…”

“…In result, they have received substantially less attention than sea-ice diatoms, and their composition and role are largely understudied. The phylogenetic diversity of pico-(cell size o3 mm) and nano-(cells size 3-20 mm) eukarytoes in the sea ice has been studied only recently (Eddie et al, 2010;Bachy et al, 2011;Majaneva et al, 2012;Comeau et al, 2013), but reliable identification and enumeration is still lacking. Knowledge on the distribution and abundance of sea-ice protists is essential to understand and predict possible changes in microbial communities that will have profound impacts on Arctic marine food webs (Davidson et al, 2010).…”

Status and trends in the structure of Arctic benthic food webs

“…Increased impact of algal viruses and parasites would decrease the amount of food available for pelagic and benthic grazers. How these processes affect current blooms in the Arctic Ocean remains largely unknown, but both viruses and parasitic Syndiniales have been reported from sea ice (Wells & Deming 2006;Bachy et al 2011;Collins & Deming 2011;Comeau et al 2013;Piwosz et al 2013) and the water column (HowardJones et al 2002;Lovejoy et al 2006;Bachy et al 2011;Comeau et al 2011;Payet & Suttle 2013).…”