02347nas a2200193 4500008004100000022001300041245009200054210006900146260001200215300001200227490000800239520173400247100002101981700001702002700001502019700002402034700002302058856007202081 2018 eng d a0016706100aBiogeochemical weathering of soil apatite grains in the McMurdo Dry Valleys, Antarctica0 aBiogeochemical weathering of soil apatite grains in the McMurdo  c01/2018 a136-1450 v3203 a

The biogeochemical weathering of the mineral apatite links the lithosphere to the biosphere by releasing the essential nutrient phosphorus (P) into the soil ecosystem. In Taylor Valley, Antarctica, faster rates of apatite weathering may be responsible for the higher concentrations of bioavailable soil P that exist in the Fryxell Basin as compared to the Bonney Basin. In this study, we use scanning electron microscopy to quantify the morphology and surface etching of individual apatite grains to determine whether the degree of apatite weathering differs between the Fryxell and Bonney Basins as well as saturated and dry soil sediments. We show that apatite grains from the Fryxell Basin are rounder, have fewer intact crystal faces, and are more chemically etched than grains from the Bonney Basin. In the Bonney Basin, apatite grains from dry soils show few signs of chemical dissolution, suggesting that soil moisture is a stronger control on the rate of apatite weathering in the Bonney Basin than in the Fryxell Basin. In addition, etch-pit morphologies in the Bonney Basin are more clearly controlled by the hexagonal crystal structure of apatite, while in the Fryxell Basin, etch pits demonstrate a wide range of morphologies without clear crystallographic control. Higher rates of apatite weathering in the Fryxell Basin may be due to the legacy of the physical abrasion of apatite grains during transport by a warm-based ice sheet, as well as the higher levels of precipitation and soil moisture closer to the coast. Our grain-scale approach provides a new perspective on P cycling in the McMurdo Dry Valleys and has implications for apatite weathering and P dynamics in the early stages of soil development.

1 aHeindel, Ruth, C1 aLyons, Berry1 aWelch, Sue1 aSpickard, Angela, M1 aVirginia, Ross, A. uhttps://www.sciencedirect.com/science/article/pii/S001670611732069403147nas a2200241 4500008004100000245006800041210006800109260001200177300001400189490000800203520239000211653001102601100002202612700002302634700001702657700002402674700002102698700002402719700002002743700002402763700002102787856009702808 2007 eng d00aBiogeochemical stoichiometry of Antarctic Dry Valley ecosystems0 aBiogeochemical stoichiometry of Antarctic Dry Valley ecosystems c02/2007 aG01010+120 v1123 a

Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–106 years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates.

10aBiggie1 aBarrett, John, E.1 aVirginia, Ross, A.1 aLyons, Berry1 aMcKnight, Diane, M.1 aPriscu, John, C.1 aFountain, Andrew, G1 aWall, Diana, H.1 aMoorhead, Daryl, L.1 aDoran, Peter, T. uhttps://mcm.lternet.edu/content/biogeochemical-stoichiometry-antarctic-dry-valley-ecosystems00429nas a2200145 4500008004100000245003300041210003200074260003000106300001200136490000600148100002200154700002300176700002000199856006400219 2006 eng d00aBiogeochemistry, terrestrial0 aBiogeochemistry terrestrial aNew YorkbRoutledge Press a154-1550 v11 aBarrett, John, E.1 aVirginia, Ross, A.1 aRiffenburgh, B. uhttps://mcm.lternet.edu/content/biogeochemistry-terrestrial00655nas a2200169 4500008004100000245010600041210006900147300001000216490000700226100001800233700002400251700002200275700002000297700002300317700002000340856012500360 2004 eng d00aThe Biodiversity and Biogeochemistry of Cryoconite Holes from McMurdo Dry Valley Glaciers, Antarctica0 aBiodiversity and Biogeochemistry of Cryoconite Holes from McMurd a84-910 v361 aPorazinska, D1 aFountain, Andrew, G1 aNylen, Thomas, H.1 aTranter, Martyn1 aVirginia, Ross, A.1 aWall, Diana, H. uhttps://mcm.lternet.edu/content/biodiversity-and-biogeochemistry-cryoconite-holes-mcmurdo-dry-valley-glaciers-antarctica00448nas a2200145 4500008004100000245004600041210004600087260001900133300001200152490000600164100002300170700002000193700001400213856007500227 2001 eng d00aBasic Principles in ecosystem functioning0 aBasic Principles in ecosystem functioning bAcademic Press a345-3520 v21 aVirginia, Ross, A.1 aWall, Diana, H.1 aLevin, S. uhttps://mcm.lternet.edu/content/basic-principles-ecosystem-functioning