In marine ecosystems, eelgrasses have proven to be influential to their surrounding environments through their many ecosystem functions, ranging from the provisioning of food and shelter to serving as a natural defense against pollution and pathogenic bacteria. In the marine waters of San Diego, CA, USA, eelgrass beds comprised of Zostera spp. are an integral part of the coastal ecosystem. To evaluate the impact of eelgrass on bacterial and archaeal community structure we sequenced the 16S rRNA gene from paired eelgrass-present and eelgrass-absent sites. We applied mixed effects models to the gene sequencing results and bacterial abundance data derived by flow cytometry to test the hypothesis that microbial community structure is influenced by the presence of eelgrass. This approach allowed us to identify specific microbial taxa that were differentially present at eelgrass-present and eelgrass-absent sites. Principal component analysis (PCA) revealed that PC1 and PC2 accounted for a 93.1 % of the variance in microbial community structure among the samples. Microbial taxa that were differentially present between eelgrass present and eelgrass absent sites were identified, along with microbial taxa that were differentially present between samples from the inner and outer San Diego Bay sampling sites. Differentially present bacterial taxa included potential pathogens of order Rickettsiales, family Flavobacteriaceae, Tenacibaculum maritimum and members of the order Pseudomonadales.

Tropospheric marine aerosol presence in the western Antarctic is coupled to physical and biological processes. These aerosols may be biogenic, formed from the activity of primary producers, and can be associated with seasonal dynamics of sea ice melt and phytoplankton blooms. These aerosols may also influence local environments of polar regions by absorbing and scattering solar radiation and by initiating cloud formation. To study tropospheric marine aerosol in the remote marine Bellingshausen Sea environment, we used a specialized instrument onboard the NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) capable of detecting the presence of aerosols at altitudes close to the sea surface. We termed this measurement marine aerosol optical depth (MAOD). To further support these observations, we also examined coarse-mode aerosol optical depth (AODC), often used as a proxy for sea spray aerosol (SSA). We used MAOD and AODC to examine trends in marine tropospheric aerosol and undertook a multi-year remote sensing analysis in the Bellingshausen Sea from 2006-2018.

Across open ocean to coastal regions, daily fluctuations in nighttime and daytime winds, respectively, drove increasing MAOD and AODC. MAOD depicted strong correlations with wind speed across the open ocean and weak correlations in coastal regions, suggesting that daily fluxes in wind speed drive the production of SSA. In the open ocean, we further observed that warmer SST enhanced AODC and the associated production of SSA, supporting prior studies. We also observed seasonal increases in MAOD alongside a seasonal increase in chl-a and the melt of sea ice; these patterns suggest that biological activity of primary producers likely contributed towards magnitudes of marine tropospheric aerosol. This work is also the first to distinguish a late winter to early spring temporal MAOD signal, likely tied to an aerosol source from either venting of biogenic aerosol from breaks in sea ice or to the production of SSA resulting from pulses in wind speed. Our work extends upon previous findings of marine aerosol in polar environments and more fully characterizes interactions during polar winter.

We developed the Multilayered Instrument for Continuous Adaptive Laboratory Evolution (MICALE), a novel apparatus for Adaptive Laboratory Evolution (ALE) of microbial strains with increased stress resistance. MICALE has two distinct media types separated by density. The less-dense top layer media (TLM) is permissive for growth of the wild type. A constant flow of media and removal of waste maintains a continuous culture in the upper region only. The denser bottom layer media (BLM) has an added stressor and remains static, allowing for batch-culture growth of an evolved strain. As they arise, mutants with stress-resistant phenotypes can colonize the lower regions. We tested MICALE’s ability to produce evolved strains by subjecting Escherichia coli MG1655 to high concentrations of sodium chloride (NaCl,) magnesium chloride (MgCl2,) or the antibiotic ciprofloxacin in the BLM. Measurements during experiments show that MICALE functions as intended; density stratification is maintained, and the media flow controls the population size in the upper layer. We tested for stress-tolerant phenotypes by measuring the optical density (OD600) of MICALE samples alongside the ancestor in increasing amounts of stressor. From the resulting OD600 curves, we extracted values representing stress-resistance using a novel analysis developed for atypical growth curves. We then performed whole genome resequencing followed by breseq to identify mutations linked to observed phenotypes. Contamination, however, prevents us from determining whether MICALE is effective at producing strains with increased stress tolerance. Our work provides a foundational methodology and outlines improvements for future ALE experiments to successfully evolve stress tolerant strains using MICALE.

Mangroves offer many important ecosystem services including carbon sequestration, serving as nursery grounds to many organisms, and acting as barriers where land and sea converge. Mangroves exhibit environmental flexibility and resilience and frequently occur in nutrient-limited systems. Despite existing research on mangrove microbiomes, the effects of nutrient additions on microbial community structure, composition, and function in intertidal and landward zones of mangrove ecosystems remain unclear. We utilized a long-term nutrient amendment study in Exmouth Gulf, Western Australia conducted in two zones, the intertidal fringe and supralittoral scrub forests, dominated by Avicennia marina. Root samples were fractionated into rhizosphere, rhizoplane and endosphere compartments and analyzed by 16S rRNA gene amplicon sequencing to determine the effects of nutrient stress on community structure and function. Our data showed species richness and evenness were significantly higher in the scrub forest zone. PERMANOVA analysis revealed a significant effect of nutrient enrichment on beta diversity (p = 0.022, R2 = 0.012) in the fringe forest zone only. Cylindrospermopsis, which has been associated with harmful algal blooms, was found to be significantly enriched in fringe phosphate-fertilized plots and nitrogen-fixing Hyphomicrobiales were significantly depleted in the scrub nitrogen-fertilized plots. Meanwhile, root compartments and forest zone had a greater effect on beta diversity (p = 0.001, R2 = 0.186; p = 0.001, R2 = 0.055, respectively) with a significant interaction between forest zone and root compartment (p = 0.001, R2 = 0.025). This interaction was further observed in the distinct divergence identified in degradative processes of the rhizosphere compartment between the two forest zones. Degradation of aromatic compounds were significantly enriched in the fringe rhizosphere, in contrast to the scrub rhizosphere, where degradation of carbohydrates was most significant. Our results indicate that nutrient enrichment impacts microbial community structure and function, potentially compromising overall mangrove health and ecosystem stability.

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Results

Conclusion

Environmental processes aerosolize bacteria from the seawater and into the atmosphere. In the sea surface-atmospheric boundary layer (SSABL), two very distinct biomes can overlap. The SSABL's microbiota fluctuates between the two environments. Airborne microbiological habitats have few microbes, while the coastal sea surface has one of the most diverse microbial ecosystems.Because of the ecosystem's variability, it is hard to paint the whole picture due to the region's significant daily irregularity, and addressing its criteria is a significant endeavor. We faced challenges in refining our equipment for 21st-century microbiome analysis. Our design addressed equipment sterilization and low abundance in sample collection. Our approach aggregated the data over a month, delivering a glimpse of this dynamic ecological environment. This study aimed to characterize the SSABL community structure by identifying taxa likely to inhabit the interface and determining how similar these populations are to the parent marine community. Using 16S rRNA gene sequencing and flow cytometry, airborne samples were compared to marine samples. We found a link between meteorological conditions and the SSABL community by tracking air masses to the Scripps Pier with NOAA's HYSPLIT model. Oceanic air masses are a component in influencing a site's community composition. Thus, we detected aerosolized marine taxa. We then describe factors influencing microbiome makeup using multiple regression and environmental variable ordination.

Mangrove forests are among the most productive ecosystems globally, offering critical ecosystem services such as coastal protection, carbon sequestration, and support for mangrove-dependent fisheries. These forests host a diverse range of microorganisms that contribute to nutrient acquisition, disease resistance, and adaptation to salinity stress, yet many of these microbes remain uncharacterized. Mangrove forests are increasingly threatened by habitat loss,climate change, and pollution. The impact of these anthropogenic stressors on the microorganisms that sustain these forests, and on the local artisanal fishery communities, remains largely unknown. This research addresses the effects of land use changes, particularly nutrient pollution associated to shrimp aquaculture, on nutrient cycling, water quality, and microbial community function and structure. It also examines the variability and influence of mangrove zones and flow dynamics on microbial community structure and function in less perturbed mangrove forests. Additionally, this work investigates how salinity and pathogenic stress affect mangrove microbial communities and their functions and develops a model to explore plant-microbe interactions to understand how microbes could provide chemical protection to the plant to tolerate stress. Finally, this research focuses on developing methodologies to build just and equitable partnerships with local Afro-Ecuadorian communities to better understand the impact of pollution and threats to mangrove forests and mangrove-dependent fisheries. The findings of this work offer valuable insights for conservation efforts and provide a framework for addressing ecological challenges in vulnerable coastal regions to climate change.