Rapid shifts in circulation and biogeochemistry of the Southern Ocean during deglacial carbon cycle events.

The Southern Ocean plays a crucial role in regulating atmospheric CO on centennial to millennial time scales. However, observations of sufficient resolution to explore this have been lacking. Here, we report high-resolution, multiproxy records based on precisely dated deep-sea corals from the Southern Ocean.

Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age.

The Southern Ocean regulates the ocean's biological sequestration of CO and is widely suspected to underpin much of the ice age decline in atmospheric CO concentration, but the specific changes in the region are debated. Although more complete drawdown of surface nutrients by phytoplankton during the ice ages is supported by some sediment core-based measurements, the use of different proxies in different regions has precluded a unified view of Southern Ocean biogeochemical change. Here, we report measurements of the N/N of fossil-bound organic matter in the stony deep-sea coral , a tool for reconstructing surface ocean nutrient conditions.

Low rates of nitrogen fixation in eastern tropical South Pacific surface waters.

An extensive region of the Eastern Tropical South Pacific (ETSP) Ocean has surface waters that are nitrate-poor yet phosphate-rich. It has been proposed that this distribution of surface nutrients provides a geochemical niche favorable for N2fixation, the primary source of nitrogen to the ocean. Here, we present results from two cruises to the ETSP where rates of N2fixation and its contribution to export production were determined with a suite of geochemical and biological measurements.

Multiple B-vitamin depletion in large areas of the coastal ocean.

B vitamins are some of the most commonly required biochemical cofactors in living systems. Therefore, cellular metabolism of marine vitamin-requiring (auxotrophic) phytoplankton and bacteria would likely be significantly compromised if B vitamins (thiamin B(1), riboflavin B(2), pyridoxine B(6), biotin B(7), and cobalamin B(12)) were unavailable. However, the factors controlling the synthesis, ambient concentrations, and uptake of these key organic compounds in the marine environment are still not well understood.