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Abstract The Von Damm vent field (VDVF) on the Mid-Cayman Rise in the Caribbean Sea is unique among modern hydrothermal systems in that the chimneys and mounds are almost entirely composed of talc. We analyzed samples collected in 2020 and report that in addition to disordered talc of variable crystallinity, carbonates are a major class of mineral at VDVF. The carbonate minerals include aragonite, calcite, magnesium-rich calcite, and dolomite. Talc and carbonate mineral textures indicate that, rather than replacing volcanic host rock, they precipitate from the mixing of hydrothermal fluids and seawater at the seafloor, occurring in chimneys and surrounding rubble. Alternating precipitation of this mineral assemblage is pervasive, with carbonate minerals typically being succeeded by talc, and with indications that in some cases talc and carbonate minerals replace one another. Stable carbon isotopic data indicate the carbonate minerals originate from the mixing of seawater and hydrothermal fluid, which is supported by U-Th data. Radiocarbon calcite ages and talc 234U-230Th isochron ages indicate mineral ages spanning over thousands to tens of thousands of years. Analyses of these samples illustrate a dynamic system that transitions from carbonate-dominated to Mg-silicate–dominated precipitation over time scales of thousands of years. Our observations raise questions regarding the eventual fate of seafloor precipitates and whether carbonate and silicate minerals in such settings are sequestered and represented in the rock record. 

Abstract Staphylococcus aureusis an opportunistic pathogen frequently detected in environmental waters and commonly causes skin infections to water users.S. aureusconcentrations in fresh, brackish, and marine waters are positively correlated with water turbidity. To reduce the risk ofS. aureusinfections from environmental waters,S. aureussurvival (stability and multiplication) in turbid waters needs to be investigated. The aim of this study was to measureS. aureusin turbid fresh and brackish water samples and compare the concentrations over time to determine which conditions are associated with enhancedS. aureussurvival. Eighteen samples were collected from fresh and brackish water sources from two different sites on the east side of Oʻahu, Hawaiʻi.S. aureuswas detected in microcosms for up to 71 days with standard microbial culturing techniques. On average, the greatest environmental concentrations ofS. aureuswere in high turbidity fresh waters followed by high turbidity brackish waters. Models demonstrate that salinity and turbidity significantly predict environmentalS. aureusconcentrations.S. aureuspersistence over the extent of the experiment was the greatest in high turbidity microcosms with T₉₀'s of 147.8 days in brackish waters and 80.8 days in freshwaters. This study indicates that saline, turbid waters, in the absence of sunlight, provides suitable conditions for enhanced persistence ofS. aureuscommunities that may increase the risk of exposure in environmental waters. Practitioner PointsStaphylococcus aureusconcentrations, survival, and persistence were assessed in environmental fresh and brackish waters.Experimental design preserved in situ conditions to measureS. aureussurvival.Higher initialS. aureusconcentrations were observed in fresh waters with elevated turbidity, while sustained persistence was greater in brackish waters.Water turbidity and salinity were both positively associated withS. aureusconcentrations and persistence.Climate change leads to more intense rainfall events which increase water turbidity and pathogen loading, heightening the exposure risk toS. aureus. 

Abstract Single‐celled microbial eukaryotes inhabit deep‐sea hydrothermal vent environments and play critical ecological roles in the vent‐associated microbial food web. 18S rRNA amplicon sequencing of diffuse venting fluids from four geographically‐ and geochemically‐distinct hydrothermal vent fields was applied to investigate community diversity patterns among protistan assemblages. The four vent fields include Axial Seamount at the Juan de Fuca Ridge, Sea Cliff and Apollo at the Gorda Ridge, all in the NE Pacific Ocean, and Piccard and Von Damm at the Mid‐Cayman Rise in the Caribbean Sea. We describe species diversity patterns with respect to hydrothermal vent field and sample type, identify putative vent endemic microbial eukaryotes, and test how vent fluid geochemistry may influence microbial community diversity. At a semi‐global scale, microbial eukaryotic communities at deep‐sea vents were composed of similar proportions of dinoflagellates, ciliates, Rhizaria, and stramenopiles. Individual vent fields supported distinct and highly diverse assemblages of protists that included potentially endemic or novel vent‐associated strains. These findings represent a census of deep‐sea hydrothermal vent protistan communities. Protistan diversity, which is shaped by the hydrothermal vent environment at a local scale, ultimately influences the vent‐associated microbial food web and the broader deep‐sea carbon cycle.