02770nas a2200241 4500008004100000245007200041210006900113260001200182300000800194490000700202520208300209653001502292653001902307653001902326653001302345653002202358653002102380100002902401700002002430700001302450700002102463856004402484 2023 eng d00aTemperature response of metabolic activity of an Antarctic nematode0 aTemperature response of metabolic activity of an Antarctic nemat c01/2023 a1090 v123 a

Because of climate change, the McMurdo Dry Valleys of Antarctica (MCM) have experienced an increase in the frequency and magnitude of summer pulse warming and surface ice and snow melting events. In response to these environmental changes, some nematode species in the MCM have experienced steady population declines over the last three decades, but Plectus murrayi, a mesophilic nematode species, has responded with a steady increase in range and abundance. To determine how P. murrayi responds to increasing temperatures, we measured metabolic heat and CO2 production rates and calculated O2 consumption rates as a function of temperature at 5 °C intervals from 5 to 50 °C. Heat, CO2 production, and O2 consumption rates increase approximately exponentially up to 40 °C, a temperature never experienced in their polar habitat. Metabolic rates decline rapidly above 40 °C and are irreversibly lost at 50 °C due to thermal stress and mortality. Caenorhabditis elegans, a much more widespread nematode that is found in more temperate environments reaches peak metabolic heat rate at just 27 °C, above which it experiences high mortality due to thermal stress. At temperatures from 10 to 40 °C, P. murrayi produces about 6 times more CO2 than the O2 it consumes, a respiratory quotient indicative of either acetogenesis or de novo lipogenesis. No potential acetogenic microbes were identified in the P. murrayi microbiome, suggesting that P. murrayi is producing increased CO2 as a byproduct of de novo lipogenesis. This phenomenon, in conjunction with increased summer temperatures in their polar habitat, will likely lead to increased demand for carbon and subsequent increases in CO2 production, population abundance, and range expansion. If such changes are not concomitant with increased carbon inputs, we predict the MCM soil ecosystems will experience dramatic declines in functional and taxonomic diversity.

10aAntarctica10acarbon cycling10aclimate change10anematode10arespiration rates10asoil temperature1 aRobinson, Colin, Michael1 aHansen, Lee, D.1 aXue, Xia1 aAdams, Byron, J. uhttps://www.mdpi.com/2079-7737/12/1/10902485nas a2200229 4500008004100000245009100041210006900132260001200201490000600213520181500219653001302034653002802047653001102075653001302086653001002099653002102109653002102130653002502151100001702176700002002193856004202213 2019 eng d00aBiotic interactions in experimental Antarctic soil microcosms vary with abiotic stress0 aBiotic interactions in experimental Antarctic soil microcosms va c08/20190 v33 a

Biotic interactions structure ecological communities but abiotic factors affect the strength of these relationships. These interactions are difficult to study in soils due to their vast biodiversity and the many environmental factors that affect soil species. The McMurdo Dry Valleys (MDV), Antarctica, are relatively simple soil ecosystems compared to temperate soils, making them an excellent study system for the trophic relationships of soil. Soil microbes and relatively few species of nematodes, rotifers, tardigrades, springtails, and mites are patchily distributed across the cold, dry landscape, which lacks vascular plants and terrestrial vertebrates. However, glacier and permafrost melt are expected to cause shifts in soil moisture and solutes across this ecosystem. To test how increased moisture and salinity affect soil invertebrates and their biotic interactions, we established a laboratory microcosm experiment (4 community × 2 moisture × 2 salinity treatments). Community treatments were: (1) Bacteria only (control), (2) Scottnema (S. lindsayae + bacteria), (3) Eudorylaimus (E. antarcticus + bacteria), and (4) Mixed (S. lindsayae + E. antarcticus + bacteria). Salinity and moisture treatments were control and high. High moisture reduced S. lindsayae adults, while high salinity reduced the total S. lindsayae population. We found that S. lindsayae exerted top-down control over soil bacteria populations, but this effect was dependent on salinity treatment. In the high salinity treatment, bacteria were released from top-down pressure as S. lindsayae declined. Ours was the first study to empirically demonstrate, although in lab microcosm conditions, top-down control in the MDV soil food web.

10abacteria10abiological interactions10adesert10anematode10apolar10asoil communities10atop-down effects10atrophic interactions1 aShaw, Ashley1 aWall, Diana, H. uhttps://www.mdpi.com/2571-8789/3/3/57