Salinity is a critical environmental parameter governing ocean circulation, biogeochemical processes, and ecosystem health, yet existing conductivity-based sensors remain costly and sensitive to variations in ionic composition. Here, we present a low-cost, scalable potentiometric chloride (Cl^–)-sensing platform for salinity monitoring in dynamic marine environments. The system integrates a chemically welded ion-selective membrane (ISM) fabricated via capillary-bridge printing using controlled meniscus deposition and a miniaturized Ag/AgCl reference electrode. This printing process is modeled as a function of contact angle, tip speed, and viscosity, enabling precise control of membrane thickness and interfacial bonding. The meniscus-driven deposition is coupled with polymer–substrate interpenetration, ensuring strong adhesion and structural uniformity. The resulting ISM suppresses the formation of an interfacial water layer and exhibits enhanced resistance to delamination under prolonged aqueous exposure. The Cl^–-selective electrodes exhibit a stable response at environmentally relevant concentrations, with low variability and reduced drift, while the custom reference electrode achieves stable performance with minimal concentration dependence. Ocean deployment demonstrates robust performance under strong salinity gradients and tidal dynamics. Differences between Cl^–-derived and conductivity-derived salinity measurements are analyzed in relation to ionic composition, demonstrating the complementary roles of selective and non-selective sensing.

"Rotten" sea ice, ice in an advanced stage of melt, represents an important but understudied habitat in the rapidly changing Arctic. As Arctic warming accelerates, this late-season ice type will become more prevalent, yet little is known about its microbial inhabitants or their roles in Arctic marine biogeochemical cycles. We examined microbial communities (prokaryote and algal abundance, 16S and 18S rRNA gene and transcript sequencing) and biogeochemical properties of rotten sea ice and earlier-season ice near Utqiaġvik, Alaska, USA. Rotten ice was comparatively warm, isothermal, and largely drained of brine, with extensive, interconnected pore networks linked to melt ponds above and seawater below. Unlike earlier-season ice, fluids saturating rotten ice were vertically homogeneous in pH, dissolved inorganic carbon, prokaryote and phytoplankton abundance, and microbial community composition. However, particulate carbon and nitrogen exhibited strong vertical gradients, with the highest concentrations near the surface. Microbial communities in rotten ice were significantly different from those in earlier-season ice and varied between individual floes. These findings indicate that rotten ice constitutes a distinct microbial habitat and may serve as an important source of nutrient-rich particulate matter in the future Arctic Ocean during the summer melt season.

Since the discovery of perchlorates in martian soils, astrobiologists have been curious if and how life could survive in these low-water, high-salt environments. Perchlorates induce chaotropic and oxidative stress but can also confer increased cold tolerance in some extremophiles. Though bacterial survival has been demonstrated at subzero temperatures and in perchlorate solution, proteomic analysis of cells growing in an environment like martian regolith brines–perchlorate with subzero temperatures–has yet to be demonstrated. By defining biosignatures of survival and growth in perchlorate-amended media at subzero conditions, we move closer to understanding the mechanisms that underlie the feasibility of life on Mars. Colwellia psychrerythraea str. 34H (Cp34H), a marine psychrophile, was exposed to perchlorate ions in the form of a diluted Phoenix Mars Lander Wet Chemistry Laboratory solution at –1°C and –5°C. At both temperatures in perchlorate-amended media, Cp34H grew at reduced rates. Mass spectrometry-based proteomics analyses revealed that proteins responsible for mitigating effects of oxidative and chaotropic stress increased, while cellular transport proteins decreased. Cumulative protein signatures suggested modifications to cell–cell or cell–surface adhesion properties. These physical and biochemical traits could serve as putative identifiable biosignatures for life detection in martian environments.