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We have designed, built, tested, and deployed a novel device to extract porewater from deep‐sea sediments in situ, constructed to work with a standard multicorer. Despite the importance of porewater measurements for numerous applications, many sampling artifacts can bias data and interpretation during traditional porewater processing from shipboard‐processed cores. A well‐documented artifact occurs in deep‐sea porewater when carbonate precipitates during core recovery as a function of temperature and pressure changes, while porewater is in contact with sediment grains before filtration, thereby lowering porewater alkalinity and dissolved inorganic carbon (DIC). Here, we present a novel device built to obviate these sampling artifacts by filtering porewater in situ on the seafloor, with a focus near the sediment–water interface on cm‐scale resolution, to obtain accurate porewater profiles. We document 1–10% alkalinity loss in shipboard‐processed sediment cores compared to porewater filtered in situ, at depths of 1600–3200 m. We also show that alkalinity loss is a function of both weight % sedimentary CaCO₃and water column depth. The average ratio of alkalinity loss to DIC loss in shipboard‐processed sediment cores relative to in situ porewater is 2.2, consistent with the signal expected from carbonate precipitation. In addition to collecting porewater for defining natural profiles, we also conducted the first in situ dissolution experiments within the sediment column using isotopically labeled calcite. We present evidence of successful deployments of this device on and adjacent to the Cocos Ridge in the Eastern Equatorial Pacific across a range of depths and calcite saturation states.

 

It is challenging to design effective drug delivery systems (DDS) that target metastatic breast cancers (MBC) because of lack of competent imaging and image analysis protocols that suitably capture the interactions between DDS and metastatic lesions. Here, we integrate high temporal resolution of in vivo whole-body PET-CT, ex vivo whole-organ optical imaging, high spatial resolution of confocal microscopy, and mathematical modeling, to systematically deconstruct the trafficking of injectable nanoparticle generators encapsulated with polymeric doxorubicin (iNPG-pDox) in pulmonary MBC. iNPG-pDox accumulated substantially in metastatic lungs, compared to healthy lungs. Intratumoral distribution and retention of iNPG-pDox varied with lesion size, possibly induced by locally remodeled microenvironment. We further used multiscale imaging and mathematical simulations to provide improved drug delivery strategies for MBC. Our work presents a multidisciplinary translational toolbox to evaluate transport and interactions of DDS within metastases. This knowledge can be recursively applied to rationally design advanced therapies for metastatic cancers. 

Present estimates of the biogeochemical cycles of calcium, strontium, and potassium in the ocean reveal large imbalances between known input and output fluxes. Using pore fluid, incubation, and solid sediment data from North Pacific multi‐corer cores we show that, contrary to the common paradigm, the top centimeters of abyssal sediments can be an active site of authigenic precipitation of clay minerals. In this region, clay authigenesis is the dominant sink for potassium and strontium and consumes nearly all calcium released from benthic dissolution of calcium carbonates. These observations support the idea that clay authigenesis occurring over broad regions of the world ocean may be a major buffer for ocean chemistry on the time scale of the ocean overturning circulation, and key to the long‐term stability of Earth's climate.

 

The cycling of biologically produced calcium carbonate (CaCO₃) in the ocean is a fundamental component of the global carbon cycle. Here, we present experimental determinations of in situ coccolith and foraminiferal calcite dissolution rates. We combine these rates with solid phase fluxes, dissolved tracers, and historical data to constrain the alkalinity cycle in the shallow North Pacific Ocean. The in situ dissolution rates of coccolithophores demonstrate a nonlinear dependence on saturation state. Dissolution rates of all three major calcifying groups (coccoliths, foraminifera, and aragonitic pteropods) are too slow to explain the patterns of both CaCO₃sinking flux and alkalinity regeneration in the North Pacific. Using a combination of dissolved and solid‐phase tracers, we document a significant dissolution signal in seawater supersaturated for calcite. Driving CaCO₃dissolution with a combination of ambient saturation state and oxygen consumption simultaneously explains solid‐phase CaCO₃flux profiles and patterns of alkalinity regeneration across the entire N. Pacific basin. We do not need to invoke the presence of carbonate phases with higher solubilities. Instead, biomineralization and metabolic processes intimately associate the acid (CO₂) and the base (CaCO₃) in the same particles, driving the coupled shallow remineralization of organic carbon and CaCO₃. The linkage of these processes likely occurs through a combination of dissolution due to zooplankton grazing and microbial aerobic respiration within degrading particle aggregates. The coupling of these cycles acts as a major filter on the export of both organic and inorganic carbon to the deep ocean.