During austral summer 1997, satellite imagery revealed enhanced chlorophyll associated with the Antarctic Polar Front at 170°W. Phytoplankton growth conditions during the early stages of the spring increase were investigated on the Antarctic Environment and Southern Ocean Process Study Survey I cruise using flow cytometry (FCM) and microscopy to characterize...
Microbial communities in Arctic coastal lagoons drive biogeochemical cycles at the terrestrial-marine interface and help to determine the fate and form of resources like nitrogen (N) and carbon (C) as they are delivered to the Arctic Ocean. Though rising rates of primary production in the Arctic Ocean are well-characterized, the...
The deep sea is often viewed as a vast, dark, remote,
and inhospitable environment, yet the deep ocean and
seafloor are crucial to our lives through the services that
they provide. Our understanding of how the deep sea functions
remains limited, but when treated synoptically, a diversity
of supporting, provisioning,...
Soil moisture strongly affects the balance between nitrification, denitrification and N2O reduction and therefore the nitrogen (N) efficiency and N losses in agricultural systems. In rice systems, there is a need to improve alternative water management practices, which are designed to save water and reduce methane emissions but may increase...
Di-nitrogen (N₂) fixation plays a well-recognized role in the enhancement of primary production
and arguably particle export in oligotrophic regions of the subtropical and tropical oceans.
However, recent evidence suggests that N₂ fixation may also be significant in regions of the
surface ocean proximate to or overlying zones of intense...
The discovery on Mars of recurring slope lineae (RSL), thought to represent seasonal brines, has sparked interest in analogous environments on Earth. We report on new studies of Don Juan Pond (DJP), which exists at the upper limit of ephemeral water in the McMurdo Dry Valleys (MDV) of Antarctica, and...
Nitrogen isotopes are an important tool for evaluating past biogeochemical cycling from the paleoceanographic record. However, bulk sedimentary nitrogen isotope ratios, which can be determined routinely and at minimal cost, may be altered during burial and early sedimentary diagenesis, particularly outside of continental margin settings. The causes and detailed mechanisms...
Nitrification is a critical step in the global nitrogen cycle involving the biological oxidation of ammonia (NH₃) to nitrite (NO₂⁻ ) and then to nitrate (NO₃⁻). The first step in nitrification is carried out by NH₃-oxidizing bacteria (AOB) and archaea (AOA), and the second by NO₂⁻-oxidizing bacteria (NOB). In addition...
The boundary between ice and basalt on Earth is an analog for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from...
Full Text:
Methods
55:541–555.
Benzerara, K., Barakat, M., Menguy, N., Guyot, F., De Luca, G.,
Audrain, C., and
Continental shelf sediments are sinks for dissolved oxygen and sources of many major and minor nutrients required for oceanic surface primary production, resulting in a strong coupling between benthic and pelagic biogeochemical cycling. However, the influence and spatiotemporal variability of benthic remineralization on bottom-water chemistry and the supply of nutrients...