Marine bacterial, archaeal and eukaryotic diversity and community structure on the continental shelf of the western Antarctic Peninsula

Abstract

The classic view of polar ocean foodwebs emphasizes large predators sustained by energy and material flow through short, efficient diatom−krill−predator food chains. Bacterial activity is generally low in cold polar waters compared to that at lower latitudes. This view appears to be changing, with new studies of microbial foodwebs in Arctic and Antarctic oceans. We characterized bacterial, archaeal, and eukaryotic community diversity and composition from 2 depths (near surface and below the euphotic zone) at 4 sites, including the inshore and offshore, and north and south corners of a sampling grid along the western coast of the Antarctic Peninsula (WAP). We detected up to 2-fold higher richness in microbial eukaryotes at surface and deep inshore northern stations as compared to southern stations, but offshore northern and southern stations revealed either no trend or higher richness at depth in the south. In contrast, bacterial and archaeal richness showed no significant differences either inshore or offshore at northern versus southern extents, but did vary with depth. Archaea were virtually absent in summer surface waters, but were present in summer deep and winter surface samples. Overall, winter bacterial and archaeal assemblages most closely resembled summer sub-euphotic zone assemblages, reflecting well-established seasonal patterns of water column turnover and stratification that result in an isolated layer of 'winter water' below the euphotic zone. Inter-domain heterotroph− phototroph interactions were evident from network analysis. The WAP is among the most rapidly warming regions on earth. Our results provide a baseline against which future change in microbial communities may be assessed.

Seasonal Succession of Free-Living Bacterial Communities in Coastal Waters of the Western Antarctic Peninsula

“…Previous studies of temperate systems have also reported richness maxima in the winter and minima in the summer (Gilbert et al, 2012; Ladau et al, 2013). Similar seasonal trends in bacterial OTU richness have been reported in Antarctic waters (Murray and Grzymski, 2007; Ghiglione and Murray, 2012; Grzymski et al, 2012; Luria et al, 2014). Gilbert et al (2012) observed relatively gradual changes, reporting that day length and serial day alone explained over 66% of the observed variance in richness during a 6-year time series study of the English Channel.…”

“…Previous analyses in the WAP, based either on community fingerprinting techniques (i.e., denaturing gradient gel electrophoresis) over one or more seasons, or on high-throughput DNA sequencing from only few mid-winter and mid-summer sampling dates, hint at a relationship between bacterial community succession and phytoplankton blooms similar to that observed in more temperate regions (Murray et al, 1998; Murray and Grzymski, 2007; Grzymski et al, 2012; Luria et al, 2014). However, the intervening time period between winter and summer is severely under-sampled in the WAP, as it is throughout the Southern Ocean, making comparisons to other systems difficult.…”

A Decadal (2002–2014) Analysis for Dynamics of Heterotrophic Bacteria in an Antarctic Coastal Ecosystem: Variability and Physical and Biogeochemical Forcings

“…on a variety of processes, including bacterial responses to environmental gradients, coupling with phytoplankton, and community structures (e.g., Morán et al, 2001;Morán and Estrada, 2002;Ducklow et al, 2012;Luria et al, 2014Luria et al, , 2016Nikrad et al, 2014;Bowman and Ducklow, 2015). However, these studies are mostly short-term and usually constrained to just 1 or 2 years.…”

Wind-driven distribution of bacteria in coastal Antarctica: evidence from the Ross Sea region

“…These conditions favor bacteria capable of an autotrophic lifestyle (Alonso-Sáez et al 2010;Grzymski et al 2012), such as the sulfur-oxidizing gammaproteobacterial clades SUP05 (Marshall and Morris 2013), the closely related clade Arctic96B-1, and the (putatively) OMZ-associated clade ZA2333c (Wright et al 2012). The abundance of Sva0853 and SUP05, typically associated with deeper waters (Shi et al 2010;Kim et al 2013), suggests upwelling or the colonization of carbon-poor surface waters by deep clades during winter, a phenomenon observed elsewhere in Antarctica (Luria et al 2014;Bowman and Ducklow 2015). Although all of these clades were present within frost flowers, they were present at lower abundance than in seawater.…”