Microzooplankton grazing on the coccolithophore and its role in the global calcium carbonate cycle.

Identifying mechanisms driving the substantial dissolution of biogenic CaCO (60 to 80%) in surface and mesopelagic waters of the global ocean is critical for constraining the surface ocean's alkalinity and inorganic carbon budgets. We examine microzooplankton grazing on coccolithophores, photosynthetic calcifying algae responsible for a majority of open-ocean CaCO production, as a mechanism driving shallow dissolution. We show that microzooplankton grazing dissolves 92 ± 7% of ingested coccolith calcite, which may explain 50 to 100% of the observed CaCO dissolution in supersaturated surface waters.

Zinc stimulation of phytoplankton in a low carbon dioxide, coastal Antarctic environment: evidence for the Zn hypothesis.

The ocean acts as a carbon sink, absorbing carbon from the atmosphere and resulting in substantial uptake of anthropogenic CO emissions. As biological processes in the oceans such as net primary production (NPP) contribute significantly to this sink, understanding how they will shift in response to increasing atmospheric CO is necessary to project future ocean carbon storage capacity. Macronutrient and micronutrient resource limitation within the oceans regulates NPP, and while some micronutrients such as zinc (Zn) are present at very low concentrations, their ability to limit NPP has remained unclear.

Ultrahigh-precision noble gas isotope analyses reveal pervasive subsurface fractionation in hydrothermal systems.

Mantle-derived noble gases in volcanic gases are powerful tracers of terrestrial volatile evolution, as they contain mixtures of both primordial (from Earth's accretion) and secondary (e.g., radiogenic) isotope signals that characterize the composition of deep Earth.

Adaptive responses of marine diatoms to zinc scarcity and ecological implications.

Scarce dissolved surface ocean concentrations of the essential algal micronutrient zinc suggest that Zn may influence the growth of phytoplankton such as diatoms, which are major contributors to marine primary productivity. However, the specific mechanisms by which diatoms acclimate to Zn deficiency are poorly understood. Using global proteomic analysis, we identified two proteins (ZCRP-A/B, Zn/Co Responsive Protein A/B) among four diatom species that became abundant under Zn/Co limitation.

The Dissolution Rate of CaCO in the Ocean.

The dissolution of CaCO minerals in the ocean is a fundamental part of the marine alkalinity and carbon cycles. While there have been decades of work aimed at deriving the relationship between dissolution rate and mineral saturation state (a so-called rate law), no real consensus has been reached. There are disagreements between laboratory- and field-based studies and differences in rates for inorganic and biogenic materials.

Catalysis and chemical mechanisms of calcite dissolution in seawater.

Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric [Formula: see text] on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms responsible for calcite dissolution in seawater. In this paper, we dissolve C-labeled calcites in natural seawater.

Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation.