7 research outputs found
Development and testing of a prototype respiration analyzer Final report
Respiration analyzer for in-flight monitoring of human respiratory function
Character and environmental lability of cyanobacteria-derived dissolved organic matter
Autotrophic dissolved organic matter (DOM) is central to the carbon biogeochemistry of aquatic systems, and the full complexity of autotrophic DOM has not been extensively studied, particularly by high-resolution mass spectrometry (HRMS). Terrestrial DOM tends to dominate HRMS studies in freshwaters due to the propensity of such compounds to ionize by negative mode electrospray, and possibly also because ionizable DOM produced by autotrophy is decreased to low steady-state concentrations by heterotrophic bacteria. In this study, we investigated the character of DOM produced by the widespread cyanobacteriaMicrocystis aeruginosausing high-pressure liquid chromatography-electrospray ionization-high-resolution mass spectrometry.M. aeruginosaproduced thousands of detectable compounds in axenic culture. These compounds were chromatographically resolved and the majority were assigned to aliphatic formulas with a broad polarity range. We found that the DOM produced byM. aeruginosawas highly susceptible to removal by heterotrophic freshwater bacteria, supporting the hypothesis that this autotroph-derived organic material is highly labile and accordingly only seen at low concentrations in natural settings
South American Hydrological Balance and Paleoceanography during the Late Pleistocene and Holocene (SAMBA) â Cruise No. M125, March 21 â April 15, 2016 - Rio de Janeiro (Brazil) â Fortaleza (Brazil)
R/V METEOR expedition M125 (âSAMBAâ) focused on the influence of paleoceanographic
changes off NE Brazil on the continental hydrological cycle. For this purpose, we obtained 202 m
of gravity (24 stations) and piston cores (9) at seven sections on the shelf and continental slope
close to river mouths from Cabo Frio in the south to the Rio Sao Francisco in the north. Coring
stations were determined after intensive echosounder surveys (total: 1221 NM). On-board
foraminiferal biostratigraphy, as well as color and XRF-scanning already provided first
stratigraphic constraints, indicating the preservation of different regional paleoclimatic signals at
the respective sections. Based on the preliminary stratigraphy, we retrieved high-resolution
archives, covering Holocene sediments on the shelf and late Pleistocene sediments on the slope.
These high-resolution archives are complemented by long-term records covering up to 900 ka of
continuous sedimentation at deeper sites at smaller rivers. For proxy-calibration and the study of
present-day sedimentation dynamics and biogeochemical processes, surface sediments were
sampled via multicorer (47), Van Veen Grab (6) and box corer (3). Water samples for
determination of the water chemistry (trace elements, stable and radiogenic isotopes) and nutrient
composition were retrieved by 55 CTD/Rosette casts. In addition, we run multinet-hauls at seven
stations to investigate the planktonic foraminiferal communities in the water column down to 700
m water depth, complemented by filtering water from the shipâs pump twice a day