Publications by authors named "Elizabeth K Robertson"

Diatoms can survive long periods in dark, anoxic sediments by forming resting spores or resting cells. These have been considered dormant until recently when resting cells of Skeletonema marinoi were shown to assimilate nitrate and ammonium from the ambient environment in dark, anoxic conditions. Here, we show that resting cells of S.

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Colony formation in phytoplankton is often considered a disadvantage during nutrient limitation in aquatic systems. Using stable isotopic tracers combined with secondary ion mass spectrometry (SIMS), we unravel cell-specific activities of a chain-forming diatom and interactions with attached bacteria. The uptake of C-bicarbonate andN-nitrate or N-ammonium was studied in Chaetoceros affinis during the stationary growth phase.

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Understanding the biogeochemical controls on the partitioning between nitrogen (N) removal through denitrification and anaerobic ammonium oxidation (anammox), and N recycling via dissimilatory nitrate (NO ) reduction to ammonium (DNRA) is crucial for constraining lacustrine N budgets. Besides organic carbon, inorganic compounds may serve as electron donors for NO reduction, yet the significance of lithotrophic NO reduction in the environment is still poorly understood. Conducting incubation experiments with additions of N-labeled compounds and reduced inorganic substrates (HS, Fe, Mn), we assessed the role of alternative electron donors in regulating the partitioning between the different NO -reducing processes in ferruginous surface sediments of Lake Lugano, Switzerland.

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The planktonic marine diatom Skeletonema marinoi forms resting stages, which can survive for decades buried in aphotic, anoxic sediments and resume growth when re-exposed to light, oxygen, and nutrients. The mechanisms by which they maintain cell viability during dormancy are poorly known. Here, we investigated cell-specific nitrogen (N) and carbon (C) assimilation and survival rate in resting stages of three S.

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Growth of large phytoplankton is considered to be diffusion limited at low nutrient concentrations, yet their constraints and contributions to carbon (C) and nitrogen fluxes in field plankton communities are poorly quantified under this condition. Using secondary ion mass spectrometry (SIMS), we quantified cell-specific assimilation rates of C, nitrate, and ammonium in summer communities of large phytoplankton when dissolved inorganic nitrogen concentrations are low in temperate coastal regions. Chain-forming diatoms composed 6% of total particulate organic carbon, but contributed 20% of C assimilation, 54% of nitrate assimilation and 32% of ammonium assimilation within the plankton community.

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