Rapid observations of ocean dynamics and stratification along a steep island coast during Hurricane María.

Hurricanes are extreme storms that affect coastal communities, but the linkages between hurricane forcing and ocean dynamics remain poorly understood. Here, we present full water column observations at unprecedented resolution from the southwest Puerto Rico insular shelf and slope during Hurricane María, representing a rare set of high-frequency, subsurface, oceanographic observations collected along an island margin during a hurricane. The shelf geometry and orientation relative to the storm acted to stabilize and strengthen stratification. This maintained elevated sea-surface temperatures (SSTs) throughout the storm and led to an estimated 65% greater potential hurricane intensity contribution at this site before eye passage. Coastal cooling did not occur until 11 hours after the eye passage. Our findings present a new framework for how hurricane interaction with insular island margins may generate baroclinic processes that maintain elevated SSTs, thus potentially providing increased energy for the storm.

Isolation and characterization of a psychropiezophilic alphaproteobacterium.

Cultivated psychropiezophilic (low-temperature- and high-pressure-adapted) bacteria are currently restricted to phylogenetically narrow groupings capable of growth under nutrient-replete conditions, limiting current knowledge of the extant functional attributes and evolutionary constraints of diverse microorganisms inhabiting the cold, deep ocean. This study documents the isolation of a deep-sea bacterium following dilution-to-extinction cultivation using a natural seawater medium at high hydrostatic pressure and low temperature. To our knowledge, this isolate, designated PRT1, is the slowest-growing (minimal doubling time, 36 h) and lowest cell density-producing (maximal densities of 5.0 × 106 cells ml⁻¹) piezophile yet obtained. Optimal growth was at 80 MPa, correlating with the depth of capture (8,350 m), and 10°C, with average cell sizes of 1.46 µm in length and 0.59 µm in width. Through detailed growth studies, we provide further evidence for the temperature-pressure dependence of the growth rate for deep-ocean bacteria. PRT1 was phylogenetically placed within the Roseobacter clade, a bacterial lineage known for widespread geographic distribution and assorted lifestyle strategies in the marine environment. Additionally, the gene transfer agent (GTA) g5 capsid protein gene was amplified from PRT1, indicating a potential mechanism for increased genetic diversification through horizontal gene transfer within the hadopelagic environment. This study provides a phylogenetically novel isolate for future investigations of high-pressure adaptation, expands the known physiological traits of cultivated members of the Roseobacter lineage, and demonstrates the feasibility of cultivating novel microbial members from the deep ocean using natural seawater.