Fieldwork, including work done at sea, is a key component of many geoscientists' careers. Recent studies have highlighted the pervasive sexual harassment faced by women during fieldwork. However, transgender and gender diverse scientists face unique obstacles, which have not yet been studied. We partially fill this gap by sharing our experiences as transgender and gender diverse people. We have experienced sexual harassment, misconduct, privacy issues, and legal and medical struggles as we conduct seagoing work. We provide recommendations to make seagoing work safer to our communities. These recommendations are a starting point to make seagoing work more inclusive for all.

In combination with dramatic and immediate CO2 emissions reductions, net-negative atmospheric CO2 removal (CDR) is necessary to maintain average global temperature increases below 2.0 °C. Many proposed CDR pathways involve the placement of vast quantities of organic carbon (biomass) on the seafloor in some form, but little is known about their potential biogeochemical impacts, especially at scales relevant for global climate. Here, we evaluate the potential impacts and durability of organic carbon storage specifically within deep anoxic basins, where organic matter is remineralized through anaerobic processes that may enhance its storage efficiency. We present simple biogeochemical and mixing models to quantify the scale of potential impacts of large-scale organic matter addition to the abyssal seafloor in the Black Sea, Cariaco Basin, and the hypersaline Orca Basin. These calculations reveal that the Black Sea in particular may have the potential to accept biomass storage at climatically relevant scales with moderate changes to the geochemical state of abyssal water and limited communication of that impact to surface water. Still, all of these systems would require extensive further evaluation prior to consideration of megatonne-scale CO2 sequestration. Many key unknowns remain, including the partitioning of breakdown among sulfate-reducing and methanogenic metabolisms and the fate of methane in the environment. Given the urgency of responsible CDR development and the potential for anoxic basins to reduce ecological risks to animal communities, efforts to address knowledge gaps related to microbial kinetics, benthic processes, and physical mixing in these systems are critically needed.

A document by Natalya Evans. Click on the document to view its contents.

Models and observations suggest that particle flux attenuation is lower across the mesopelagic zone of anoxic environments compared to oxic environments. Flux attenuation is controlled by microbial metabolism as well as aggregation and disaggregation by zooplankton, all of which also shape the relative abundance of differently sized particles. Observing and modeling particle spectra can provide information about the contributions of these processes. We measured particle size spectrum profiles at one station in the oligotrophic Eastern Tropical North Pacific Oxygen Deficient Zone (ETNP ODZ) using an underwater vision profiler (UVP), a high-resolution camera that counts and sizes particles. Measurements were taken at different times of day, over the course of a week. Comparing these data to particle flux measurements from sediment traps collected over the same time-period allowed us to constrain the particle size to flux relationship, and to generate highly resolved depth and time estimates of particle flux rates. We found that particle flux attenuated very little throughout the anoxic water column, and at some time-points appeared to increase. Comparing our observations to model predictions suggested that particles of all sizes remineralize more slowly in the ODZ than in oxic waters, and that large particles disaggregate into smaller particles, primarily between the base of the photic zone and 500 m. Acoustic measurements of multiple size classes of organisms suggested that many organisms migrated, during the day, to the region with high particle disaggregation. Our data suggest that diel-migrating organisms both actively transport biomass and disaggregate particles in the ODZ core.

Marine Oxygen Deficient Zones serve as hotspots for the loss of fixed nitrogen for the world’s oceans, and fixed nitrogen limits primary productivity in large expanses of the ocean. This fixed nitrogen loss occurs primarily through denitrification, where the stepwise reduction of nitrate to nitrite and ultimately to dinitrogen gas is coupled to organic matter oxidation. Nitrite, the first intermediate in denitrification, can also be re-oxidized back to nitrate in a reaction by chemoautotrophic microbes. Nitrite’s partitioning between reduction and oxidation determines if marine fixed nitrogen is lost or recycled. Nitrite oxidation in anoxic waters has been previously studied through stable and tracer isotope experiments, but the difficulty of these measurements has limited their geographical distribution and therefore requires extrapolation to understand their impact on the nitrogen cycling. Using basin-scale data, we analyze the progression of nutrients within the three water masses that feed the Eastern Tropical North Pacific Oxygen Deficient Zone. Significant deviations from the expected stoichiometry for denitrification demonstrate that 79% of the nitrite produced in the upper region of the Oxygen Deficient Zone is re-oxidized, whereas only 54% of the nitrite produced in the lower region of the Oxygen Deficient Zone is re-oxidized. These large estimates for nitrite re-oxidation reveal significant fixed nitrogen recycling across the Eastern Tropical North Pacific.