Diversity of Microbial Eukaryotes Along the West Antarctic Peninsula in Austral Spring

Abstract

During a cruise from October to November 2019, along the West Antarctic Peninsula, between 64.32 and 68.37°S, we assessed the diversity and composition of the active microbial eukaryotic community within three size fractions: micro- (> 20 μm), nano- (20–5 μm), and pico-size fractions (5–0.2 μm). The communities and the environmental parameters displayed latitudinal gradients, and we observed a strong similarity in the microbial eukaryotic communities as well as the environmental parameters between the sub-surface and the deep chlorophyll maximum (DCM) depths. Chlorophyll concentrations were low, and the mixed layer was shallow for most of the 17 stations sampled. The richness of the microplankton was higher in Marguerite Bay (our southernmost stations), compared to more northern stations, while the diversity for the nano- and pico-plankton was relatively stable across latitude. The microplankton communities were dominated by autotrophs, mostly diatoms, while mixotrophs (phototrophs-consuming bacteria and kleptoplastidic ciliates, mostly alveolates, and cryptophytes) were the most abundant and active members of the nano- and picoplankton communities. While phototrophy was the dominant trophic mode, heterotrophy (mixotrophy, phagotrophy, and parasitism) tended to increase southward. The samples from Marguerite Bay showed a distinct community with a high diversity of nanoplankton predators, including spirotrich ciliates, and dinoflagellates, while cryptophytes were observed elsewhere. Some lineages were significantly related—either positively or negatively—to ice coverage (e.g., positive for Pelagophyceae, negative for Spirotrichea) and temperature (e.g., positive for Cryptophyceae, negative for Spirotrichea). This suggests that climate changes will have a strong impact on the microbial eukaryotic community.

Diversity and distribution of small-sized planktonic ciliate communities in the East China Sea

“…To date, many surveys by metabarcoding have shown ciliate sequences in the pico-sized fraction (Romari and Vaulot, 2004;Wu et al, 2017;Xu et al, 2017;Grattepanche et al, 2022;Flegontova et al, 2023). Canals et al (2020) indicated that these sequences provided useful information about ciliate communities where over 94% of Ciliophora abundance from the Tara Ocean expedition in each size fraction corresponded to operational taxonomic units (OTUs) detected in the three fractions.…”

Water masses shape pico-nano eukaryotic communities of the Weddell Sea

“…Although polar oceans belong to one of the most productive and rapidly changing ecosystems on Earth 13 , the Southern Ocean remains poorly represented in these large surveys of marine protists. With the exception of a single small-scale study that examined protists in several deep-ocean water masses 14 , most studies of protists in the Southern Ocean focused on the photic layer [15][16][17][18][19][20][21] . Given the unique conditions during the polar winter, it is reasonable to assume that the heterotrophic lifestyle is of particular importance in the polar environment.…”