Abstract. Over recent decades the highest rates of water column warming and sea ice loss across the Arctic Ocean have been observed in the Barents Sea. These physical changes have resulted in rapid ecosystem adjustments, manifesting as a northward migration of temperate phytoplankton species at the expense of silica-based diatoms. These changes will potentially alter the composition of phytodetritus deposited at the seafloor, which acts as a biogeochemical reactor, pivotal in the recycling of key nutrients, such as silicon (Si). To appreciate the sensitivity of the Barents Sea benthic system to the observed changes in surface primary production, there is a need to better understand this benthic-pelagic coupling. Stable Si isotopic compositions of sediment pore waters and the solid phase from three stations in the Barents Sea reveal a coupling of the iron (Fe) and Si cycles, the contemporaneous dissolution of lithogenic silicate minerals (LSi) alongside biogenic silica (BSi) and the potential for the reprecipitation of dissolved silicic acid (DSi) as authigenic clay minerals (AuSi). However, as reaction rates cannot be quantified from observational data alone, a mechanistic understanding of which factors control these processes is missing. Here, we employ reaction-transport modelling together with observational data to disentangle the reaction pathways controlling the cycling of Si within the seafloor. Processes such as the dissolution of BSi are active on multiple timescales, ranging from weeks to hundreds of years, which we are able to examine through steady state and transient model runs. Steady state simulations show that 60 to 98 % of the sediment pore water DSi pool may be sourced from the dissolution of LSi, while the isotopic composition is also strongly influenced by the desorption of Si from metal oxides, most likely Fe (oxyhydr)oxides (FeSi), as they reductively dissolve. Further, our model simulations indicate that between 2.9 and 37 % of the DSi released into sediment pore waters is taken up with a fractionation factor of approximately −2 ‰, most likely representing reprecipitation as AuSi. These observations are significant, as the dissolution of LSi represents a source of new Si to the ocean DSi pool and precipitation of AuSi an additional sink, which could address imbalances in the current regional ocean Si budget. Lastly, transient modelling suggests that at least one-third of the total annual benthic DSi flux could be sourced from the dissolution of more reactive, diatom-derived BSi deposited after the surface water bloom at the marginal ice zone. This benthic-pelagic coupling will be subject to change with the continued northward migration of Atlantic phytoplankton species, northward retreat of the marginal ice zone and the observed decline in DSi inventory of the subpolar North Atlantic Ocean over the last three decades.

<p>Giant icebergs can greatly impact the mass, freshwater and nutrient budgets of the ocean. They can deposit large amounts of freshwater at great distances from their origins, impacting upper-ocean stratification and mixing, and they can be important vectors for micronutrient delivery with impacts on primary production and carbon drawdown. Their impacts on advection, productivity and blocking of flows can be critical for zooplankton and regional ecosystem functioning, with consequences for higher trophic levels and local fisheries. Their breakouts from ice shelves create new opportunities for biological colonisation and carbon sinks and their collisions with the seabed (iceberg scour) can shape local and regional benthic biodiversity patterns and influence carbon sequestration.</p><p>In 2017, the A68 iceberg (around 6000 km<sup>2</sup>) calved from the Larsen C Ice Shelf on the Antarctic Peninsula. It subsequently moved eastward and northward, crossing the Scotia Sea to move, virtually intact, to within 300 km of the island of South Georgia (SG) in late 2020. This caused concern, following the impact of a previous iceberg, A38, on the SG ecosystem in 2003-2004. Further, given the advances in observing technology since the time of the previous iceberg, it afforded an unparalleled opportunity to study in detail the impacts of giant bergs on the ocean physical, biogeochemical and biological systems.</p><p>Diverse datasets were collected in response to this event. A research cruise on RRS James Cook was mobilised, to study the iceberg as it approached SG and fragmented into multiple smaller pieces. These measurements included physical parameters (including oxygen isotopes to inform on freshwater sources), dissolved inorganic nutrients, biosilica concentration, and composition of the phytoplankton community to inform bloom dynamics and primary production by the input of terrigenous material. Ocean gliders, deployed from the ship, surveyed the largest iceberg fragment in extremely close proximity and followed this for the remainder of its life, deconvolving the iceberg influence from frontal dynamics and assisting in understanding meltwater influence. Concurrently, Earth Observation (EO) techniques were employed including Sentinel-1 SAR imagery, Planet Labs very high-resolution optical imagery, MODIS Aqua and Terra imagery and satellite radar and laser altimetry. A sediment trap deployed on a mooring downstream of SG will be utilised to investigate the carbon export from the cruise period to that of the previous 10 years while enhanced observations on higher predator colonies will compare their foraging paths and breeding performance to those of previous years.</p><p>This presentation will discuss preliminary findings from the study of A68, including EO-derived quantifications of changing iceberg morphology, ice loss from fragmentation and basal melting, and the significance of fractures in dictating collapse fissures. Physical oceanographic data from the ship and gliders are used to determine the impact on water column stability, mixing and circulation on a range of scales. Biogeochemical and biological data reveal the impact of interacting processes on phytoplankton community biomass and species composition. Ecosystem implications and future directions of investigation will be outlined.</p><p> </p>

The year 2020 represents a historically turbulent period for the United States marked by the COVID-19 pandemic, a contentious political season, and heightened awareness of racism among citizens. This intersection of medicine, politics, and social unrest generated a demanding clinical environment for healthcare workers, including understudied groups such as physical therapists, occupational therapists, and speech-language pathologists. This descriptive qualitative study focused on experiences and perspectives of clinical rehabilitation therapists working in inpatient rehabilitation and acute-care units from September to November, 2020. Thirteen participants completed individual, semi-structured interviews focused on clinical practice and coping strategies. The analysis included a multi-step, inductive process. Four interconnecting factors chronicling participants’ experiences emerged: sociopolitical, institutional, hospital unit, and personal. Stressors and buffers were noted that further shaped individual experiences. Utilization of an ecological framework provided a way to recognize the impact of a complex range of social and environmental factors affecting participants’ experiences on personal and professional levels. Awareness of rehabilitation therapists’ experiences enriches understanding of the pandemic’s effect on healthcare workers and presents clinical implications for healthcare systems to promote therapist well-being.

<div><span>The silicon isotopic composition of sedimentary biogenic opal can be used to track shifts in the balance between silicon inputs to the ocean and outputs by burial. In addition to biosilicification and opal burial, the global cycles of climate (hydrology, weathering, glaciation, etc.), tectonics (volcanoes, LIPs, mountain building, etc.) and geochemistry (reverse weathering, inorganic Si precipitation, etc.) have driven variations in the global Si cycle over geologic time. Prior to the start of the Phanerozoic it is thought that burial in the global oceans was controlled inorganically through chert formation. The evolution of the Si depositing organisms, radiolarians and sponges, reduced oceanic dissolved Si, but the largest reductions occurred with the evolution of the diatoms bringing dissolved Si to the low concentrations (relative to saturating concentrations) observed today. However, the timing of the depletion of dissolved Si by diatoms is currently under debate.</span></div><div><span> </span></div><div><span>Our understanding of the biological components of the Si cycle has grown enormously. In the last decade, silicon isotope ratios (expressed as δ30Si) in marine microfossils are becoming increasingly recognised for their ability to provide insight into silicon cycling. In particular, the δ30Si of deep-sea sponge spicules has been demonstrated to be a useful proxy for past dissolved Si concentrations. However, more recent studies find anomalies in the isotopic fractionation of sponge spicules that relate to skeletal morphology: reliable reconstructions of past dissolved Si can only be obtained using silicon isotope ratios derived from sponges with certain spicule types. We are applying δ30Si proxies from biosiliceous material contained in sediments to generate robust estimates of the timing and magnitude of dissolved Si drawdown. We will provide fundamental new insights into the drawdown of dissolved Si and other key events, which reorganized the distribution of carbon and nutrients in seawater, with implications for productivity of the biological communities within the ancient oceans. </span></div>

No abstract