Fluxes of microbes, organic aerosols, dust, sea-salt Na ions, non-sea-salt Ca ions, and methanesulfonate onto Greenland and Antarctic ice

Abstract

Abstract. Using a spectrofluorimeter with 224-nm laser excitation and six emission bands from 300 to 420 nm to measure fluorescence intensities at 0.3-mm depth intervals in ice cores, we report results of the first comparative study of concentrations of microbial cells (using the spectrum of proteinbound tryptophan (Trp) as a proxy) and of aerosols with autofluorescence spectra different from Trp (denoted "nonTrp") as a function of depth in ice cores from West Antarctica (WAIS Divide and Siple Dome) and Greenland (GISP2). The ratio of fluxes of microbial cells onto West Antarctic (WAIS Divide) versus Greenland sites is 0.13±0.06; the ratio of non-Trp aerosols onto WAIS Divide versus Greenland sites is 0.16±0.08; and the ratio of non-sea-salt Ca 2+ ions (a proxy for dust grains) onto WAIS Divide versus Greenland sites is 0.06±0.03. All of these are roughly comparable to the ratio of fluxes of dust onto Antarctic versus Greenland sites (0.08±0.05). By contrast to those values, which are considerably lower than unity, the ratio of fluxes of methanesulfonate (MSA) onto Antarctic versus Greenland sites is 1.9±0.4 and the ratio of sea-salt Na 2+ ions onto WAIS Divide versus Greenland sites is 3.0±2. These ratios are more than an order of magnitude higher than those in the first grouping. We infer that the correlation of microbes and nonTrp aerosols with non-sea-salt Ca and dust suggests a largely terrestrial rather than marine origin. The lower fluxes of microbes, non-Trp aerosols, non-sea-salt Ca and dust onto WAIS Divide ice than onto Greenland ice may be due to the smaller areas of their source regions and less favorable wind patterns for transport onto Antarctic ice than onto Greenland ice. The correlated higher relative fluxes of MSA and marine Na onto Antarctic versus Greenland ice is consistent with the Correspondence to: P. B. Price (bprice@berkeley.edu) view that both originate largely on or around sea ice, with the Antarctic sea ice being far more extensive than that around Greenland.

Microbial cell budgets of anArctic glacier surface quantified using flow cytometry

“…The mean stream water concentrations of ∼ 3 × 10 4 biological particles ml −1 and ∼ 2 × 10 4 cells ml −1 corresponds to published values for bacteria and/or cell abundance in glacial meltwaters at ML (Anesio et al ., ; Mindl et al ., ; Rassner, ); the range of ice core cell concentrations found in the MLSG catchment of 1.83 × 10 4 –2.25 × 10 5 cells ml −1 lie well within published in‐ice concentrations ranging from 7.0 × 10 2 to 1.4 × 10 7 cells ml −1 (Miteva and Brenchley, ; Price et al ., ). The proportion of cells within the aeolian samples was broadly similar to those in ice and stream samples, a finding reiterated by Segawa and colleagues () who reported the delivery and elution of microbes from a mountain snowpack, and Hawes's () indication that the southerly winds, which characterize the ML catchment, deliver organic material to the local terrain surface.…”

“…The latter, here classed as 'residual biological fraction', was suggestive of a particulate population comprising fragmented or degraded cells or nucleic acids (DNA/RNA), or viral particles. Support for this interpretation is given by virus geometries and fluorescence signals (Brussaard et al, 2000), supraglacial viral abundance observed proximate to MLSG (Rassner, 2009) and potential fluorescent 'noise' associated with organic, non-cellular particulates and aerosols found within glacier ice (Price et al, 2009). Setting gates to define cells, these were then differentiated by size: size categories were defined using 0.5, 0.9 and 3 mm Megamix (BioCytex, France) fluorescent beads (Fig.…”

Marine bacteria in deep Arctic and Antarctic ice cores: a proxy for evolution in oceans over 300 million generations

“…From ∼ 20 to ∼ 100 times as many dust grains are deposited in polar ice during glacial maxima as in glacial minima. During the Holocene (the present warm period) the average dust concentration has been 40 to 50 ng g −1 in Greenland ice and ∼ 10 ng g −1 in Antarctic ice (Price et al, 2009). In a detailed study of dust in the NGRIP Greenland core with a laser microparticle detector, Ruth et al (2003) measured log normal modes of 1.3 µm during the Holocene and 1.7 µm during the LGM.…”

“…In the present work we used that same instrument to map Chl in ice cores by analysing the two channels at 670 and 710 nm. Price et al (2009) determined the concentrations of non-microbial aerosols from the deviations of their fluorescence spectra from the spectrum of Trp, which has a peak at ∼ 320 nm when bound in cells. In Table 1 we note that Antarctic ice has a lower concentration of all small particles by a factor of several than Greenland ice.…”

“…Table 1 compares ratios of concentrations in Antarctic ice relative to Greenland ice for Trp-containing microbes, Chl-containing microbes, mineral dust and ash, and nonmicrobial aerosols. Price et al (2009) used the BFS to identify Trp as a proxy for all microbes in ice cores at NICL based on analysis of its emission in five channels at 300, 320, 340, 360 and 380 nm. In the present work we used that same instrument to map Chl in ice cores by analysing the two channels at 670 and 710 nm.…”