Summer phyto- and bacterioplankton communities during low and high productivity scenarios in the Western Antarctic Peninsula

Abstract

Phytoplankton blooms taking place during the warm season drive high productivity in Antarctic coastal seawaters. Important temporal and spatial variations exist in productivity patterns, indicating local constraints influencing the phototrophic community. Surface water in Chile Bay (Greenwich Island, South Shetlands) is influenced by freshwater from the melting of sea ice and surrounding glaciers, however it is not a widely studied system. The phyto-and bacterioplankton communities in Chile Bay were studied over two consecutive summers; during a low productivity period (Chlorophyll a < 0.05 mg m -3) and an ascendant phototrophic bloom (Chlorophyll a up to 2.38 mg m -3 ). Microbial communities were analyzed by 16S rRNAincluding plastidialgene sequencing. Diatoms (mainly Thalassiosirales) were the most abundant phytoplankton, particularly during the ascendant bloom. Bacterioplankton in the low productivity period was less diverse and dominated by a few operational taxonomic units (OTUs), related to Colwellia and Pseudoalteromonas. Alpha diversity was higher during the bloom, where several Bacteroidetes taxa absent in the low productivity period were present. Network analysis indicated that phytoplankton relative abundance was correlated with bacterioplankton phylogenetic diversity and the abundance of several bacterial taxa. Hubsthe most connected OTUs in the networkwere not the most abundant OTUs and included some poorly described taxa in Antarctica, such as Neptunomonas and Ekhidna. In summary, the results of this study indicate that in Antarctic Peninsula coastal waters, such as Chile Bay, higher bacterioplankton community diversity occurs during a phototrophic bloom. This is likely a result of primary production, providing a source of fresh organic matter to bacterioplankton.

Elucidating Viral Communities During a Phytoplankton Bloom on the West Antarctic Peninsula

“…Total DNA and RNA were obtained from the 0.22 μm filters collected on February 14th and March 4th, which represent samples collected at low and high Chl- a content periods (L-C and H-C), respectively as described in Alcamán-Arias et al (2018) and Fuentes et al (2018). DNA and RNA extractions were performed with the method of Díez et al (2001), as described in Alcamán-Arias et al (2018).…”

“…Briefly, 16S rRNA gene sequences present in the metagenomes were identified and extracted using Ribopicker (Schmieder et al, 2012), then annotated using Blastn (Camacho et al, 2009) with Silva 123 SSU database (Quast et al, 2013) and displayed with MEGAN 6 (Huson et al, 2016). For the photosynthetic eukaryotic community composition, sequences matching chloroplast 16S rRNAs from 20–8 to 8–0.22 μm filter fractions sequenced with Illumina TAGs (iTAGs) from the study of Fuentes et al (2018) were extracted, combined and reassigned against Phytoref database (Decelle et al, 2015), and analyzed for their relative abundance and composition. The activity of the phytoplankton community was assessed with total transcripts as well as metabolic genes such as rubisco (rbcL) and photosystem a (psbA) as described in Alcamán-Arias et al (2018).…”

“…Chile Bay (South Shetland Islands), is a representative site of coastal environments in the WAP where the activities and composition of the eukaryotic and prokaryotic communities have been previously studied during the austral summer (Alcamán-Arias et al, 2018; Fuentes et al, 2018). In particular, during the summer of 2014, metagenomic and metatranscriptomic measurements revealed changes in these communities represented by two contrasting samples of low and high chlorophyll periods in the waters of Chile Bay (Alcamán-Arias et al, 2018).…”

Planktonic microbial eukaryotes in polar surface waters: recent advances in high-throughput sequencing

“…Moreno-Pino et al (2016) also found that in surface waters around the South Shetland Islands, the environmental filtering effect had a significant impact on the composition of the phytoplankton communities. Based on data collected at different sites in Chile Bay (Greenwich Island, South Shetlands) during the spring bloom, it was postulated that autotrophic organisms were affected by preceding blooms during spring (Alcamán-Arias et al 2018;Fuentes et al 2019). Diatoms, especially Thalassiosirales, were the most abundant phytoplankton group in this period.…”

“…Investigations conducted by using high-throughput sequencing on 18S rRNA gene of planktonic microbial eukaryote community in Arctic Ocean (a) and Southern Ocean (b)(Bachy et al 2011;Balzano et al 2012;Comeau et al 2011;Fuentes et al 2019;Hyoung et al …”