A Unique Benthic Microbial Community Underlying the Phaeocystis antarctica-Dominated Amundsen Sea Polynya, Antarctica: A Proxy for Assessing the Impact of Global Changes

Abstract

Polynyas in the polar seas are regarded as windows through which ecosystem responses associated with global climate changes are to be noticed. However, little information is available on benthic microbial communities in the Amundsen Sea polynya (ASP), where environmental changes due to global warming are occurring rapidly, from which future climate change-induced ecosystem responses could be assessed. We performed high-throughput sequencing of 16S rRNA genes and quantitative PCR in combination with biogeochemical analyses and metabolic rate measurements to determine the composition, diversity and controls of major microbial communities in sediments of the ASP. A large fraction of the sequenced benthic microbial community (40% on average) in the polynya was uniquely affiliated with the phylum Planctomycetes, whereas Thaumarchaeota (51% on average) predominated in non-polynya areas. The relative abundance of Planctomycetes correlated significantly with organic carbon (C org) content in the polynya sediment underlying the Phaeocystis-dominated water column. These results suggest that Planctomycetes comprise a major bacterial group utilizing relatively recalcitrant C org produced primarily by Phaeocystis blooms. In contrast, the predominance of chemolithoautotrohic Thaumarchaeota in the sea-ice zone was attributed to low C org supply due to low primary productivity in the ice-covered water column. The Planctomycetes-dominated microbial communities in the ASP is in stark contrast to that Proteobacteria (Delta-and Gamma-proteobacteria) occupy ecological niches as primary mineralizers of organic materials in most benthic systems in the Southern Ocean, where organic materials in the sediments mostly originate from diatom blooms. Given that microbial communities respond quickly to environmental changes,

From the Surface Ocean to the Seafloor: Linking Modern and Paleo‐Genetics at the Sabrina Coast, East Antarctica (IN2017_V01)

“…As with the water column, Proteobacteria were the dominant bacterial phylum in the sediments (∼25% on average across all samples) and occurred in all samples except KC06 170 cmbsf. This result is consistent with previous studies on Southern Ocean and Antarctic sediments, which found Proteobacteria to be relatively abundant in sediments (Cho et al., 2020; Learman et al., 2016). Therefore, Proteobacteria seem to be able to survive in both ocean and sediment environments, with the DNA detected in the sediment record possibly being a mix of modern and ancient Proteobacteria DNA.…”

“…Therefore, Proteobacteria seem to be able to survive in both ocean and sediment environments, with the DNA detected in the sediment record possibly being a mix of modern and ancient Proteobacteria DNA. Proteobacteria are often found in diatom‐dominated waters (Cho et al., 2020; Learman et al., 2016), which may be useful for sed aDNA studies in which diatom sed aDNA is difficult to extract, as the Proteobacteria signals may be indirectly reflecting past diatom presence. However, more research is required to confirm whether the apparent co‐occurrence of proteobacteria (or specific proteobacteria orders) could be used as a proxy of primary producers’ presence in surface waters and whether these eukaryote–bacteria associations could be explored as paleo‐composition indicators.…”

“…Phycispherales and Pirurellales (Planctomycetes) are often found in marine anoxic and subsurface marine sediment (Inagaki et al., 2006), even though when cultivated they are known to be facultative aerobes. Some studies have indicated the possibility that these taxa are able to degrade organic matter derived from algae (Cho et al., 2020; Morris et al., 2006) and have hypothesized their ecological role in the remineralization of recalcitrant organic matter of Phaeocystis origins in the benthic ecosystem.…”

Sea Ice Dynamics Drive Benthic Microbial Communities in McMurdo Sound, Antarctica

“…However, much less is known about the effects on benthic microbial communities, the key drivers of organic matter remineralization processes and biogeochemical cycling (Falkowski et al, 2008). Previous polar studies have shown that the quality and quantity of organic matter are major drivers of microbial diversity and community composition, with certain taxonomic groups showing strong affiliations with environmental parameters such as sediment algal pigment concentration and total organic carbon (TOC; Bienhold et al, 2012;Ruff et al, 2014;Learman et al, 2016;Cho et al, 2020). However, few studies in Antarctica have characterized the benthic microbial communities, and none have compared the effects of FYI and MYI, which may provide a unique perspective on marine ecosystem functioning in these difficult to study and rapidly changing polar environments.…”

Seasonal Sampling of a Microbial Community in the Sediment of Geoje-Hansan Bay, Republic of Korea

“…Marine sediment is an important repository of organic matter and nutrients that are deposited mainly from seawater and land ( 3 ). In particular, the microorganisms in sediment play an important role in the biogeochemical cycle of the ecosystem, including the decomposition of organic matter and the circulation of nutrients ( 4 , 5 ). Nevertheless, monitoring of the marine pollution in Geoje-Hansan Bay is mainly focused on water quality management ( 6 ), and the sediment is managed mainly using organic matter ( 1 ).…”