The hydrothermal sediments of Guaymas Basin, an active spreading center in the Gulf of California (Mexico), are rich in porewater methane, short-chain alkanes, sulfate and sulfide, and provide a model system to explore habitat preferences of microorganisms, including sulfate-dependent, methane- and short chain alkane-oxidizing microbial communities. In this study, hot sediments (above 60°C) covered with sulfur-oxidizing microbial mats surrounding a hydrothermal mound (termed “Mat Mound”) were characterized by porewater geochemistry of methane, C2–C6 short-chain alkanes, sulfate, sulfide, sulfate reduction rate measurements, in situ temperature gradients, bacterial and archaeal 16S rRNA gene clone libraries and V6 tag pyrosequencing. The most abundantly detected groups in the Mat mound sediments include anaerobic methane-oxidizing archaea of the ANME-1 lineage and its sister clade ANME-1Guaymas, the uncultured bacterial groups SEEP-SRB2 within the Deltaproteobacteria and the separately branching HotSeep-1 Group; these uncultured bacteria are candidates for sulfate-reducing alkane oxidation and for sulfate-reducing syntrophy with ANME archaea. The archaeal dataset indicates distinct habitat preferences for ANME-1, ANME-1-Guaymas, and ANME-2 archaea in Guaymas Basin hydrothermal sediments. The bacterial groups SEEP-SRB2 and HotSeep-1 co-occur with ANME-1 and ANME-1Guaymas in hydrothermally active sediments underneath microbial mats in Guaymas Basin. We propose the working hypothesis that this mixed bacterial and archaeal community catalyzes the oxidation of both methane and short-chain alkanes, and constitutes a microbial community signature that is characteristic for hydrothermal and/or cold seep sediments containing both substrates.

In the remote polar sea ice environment of the Bellingshausen Sea, the formation and presence of marine tropospheric aerosol is coupled with physical, chemical, and biological processes. Present in both the Antarctic and Arctic, sea ice habitats are among the largest ecosystems on our planet (Arrigo, 2014). They are subject to a number of physical processes due to the inherent temporality of high-latitude environments, from the seasonal dynamics of variable light availability, increases and decreases in sea ice extent and thickness, fluctuations in nutrient availability, and fluctuations in the timing and magnitude of primary

The production of marine tropospheric aerosol in the Bellingshausen Sea of the western Antarctic Peninsula (WAP) is coupled to environmental variability. Distant from most continental sources of anthropogenic pollution and mineral dust, variability in the sources of marine aerosol in this polar sea ice environment is largely driven by the ocean itself. The Bellingshausen Sea is thus a relatively pristine environment to study the impact of primary and secondary sources as drivers of marine tropospheric aerosol. Primary sources contribute to the mechanical production of marine aerosol, most notably wind-driven sea spray aerosol (SSA) (O'Dowd & de Leeuw, 2007). Sea surface temperature (SST) also contributes to SSA production across a wide range of wind speeds, and prior field observations have observed that SST enhances the SSA when wind exceeds 5 m s −1 (S. Liu et al., 2021). Secondary sources are also contributed by the oxidation of precursor compounds (Kroll & Seinfeld, 2008;Lewis & Schwartz, 2004). As such, aerosol production is influenced by physical and biological processes including wind stress, SST, water column stability, sea ice melt, and the timing and magnitude of phytoplankton blooms (Figure 1) (Ardyna et al., 2014;Tremblay & Gagnon, 2009).Prior studies have observed variation in the timing and magnitudes of marine aerosol production in relation to environmental drivers, with studies in high-latitude environments supporting a biogenic component of marine aerosol observations due to the coincident timing of seasonal sea ice melt and phytoplankton production. These processes can foster wind-driven SSA, the formation of primary organic aerosol, and the growth of sea spray from volatile organic compounds (

The Antarctic marine environment is a dynamic ecosystem where microorganisms play an important role in key biogeochemical cycles. Despite the role that microbes play in this ecosystem, little is known about the genetic and metabolic diversity of Antarctic marine microbes. In this study we leveraged DNA samples collected by the Palmer Long Term Ecological Research (LTER) project to sequence shotgun metagenomes of 48 key samples collected across the marine ecosystem of the western Antarctic Peninsula (wAP). We developed an in silico metagenomics pipeline (iMAGine) for processing metagenomic data and constructing metagenome-assembled genomes (MAGs), identifying a diverse genomic repertoire related to the carbon, sulfur, and nitrogen cycles. A novel analytical approach based on gene coverage was used to understand the differences in microbial community functions across depth and region. Our results showed that microbial community functions were partitioned based on depth. Bacterial members harbored diverse genes for carbohydrate transformation, indicating the availability of processes to convert complex carbons into simpler bioavailable forms. We generated 137 dereplicated MAGs giving us a new perspective on the role of prokaryotes in the coastal wAP. In particular, the presence of mixotrophic prokaryotes capable of autotrophic and heterotrophic lifestyles indicated a metabolically flexible community, which we hypothesize enables survival under rapidly changing conditions. Overall, the study identified key microbial community functions and created a valuable sequence library collection for future Antarctic genomics research.