02127nas a2200217 4500008004100000245010900041210006900150260001200219300001600231490000700247520142800254100001501682700001801697700003301715700001601748700002001764700002001784700002101804700001601825856006801841 2017 eng d00aNiche specialization of bacteria in permanently ice-covered lakes of the McMurdo Dry Valleys, Antarctica0 aNiche specialization of bacteria in permanently icecovered lakes c06/2017 a2258 - 22710 v193 a

Perennially ice‐covered lakes in the McMurdo Dry Valleys, Antarctica, are chemically stratified with depth and have distinct biological gradients. Despite long‐term research on these unique environments, data on the structure of the microbial communities in the water columns of these lakes are scarce. Here, we examined bacterial diversity in five ice‐covered Antarctic lakes by 16S rRNA gene‐based pyrosequencing. Distinct communities were present in each lake, reflecting the unique biogeochemical characteristics of these environments. Further, certain bacterial lineages were confined exclusively to specific depths within each lake. For example, candidate division WM88 occurred solely at a depth of 15 m in Lake Fryxell, whereas unknown lineages of Chlorobi were found only at a depth of 18 m in Lake Miers, and two distinct classes of Firmicutes inhabited East and West Lobe Bonney at depths of 30 m. Redundancy analysis revealed that community variation of bacterioplankton could be explained by the distinct conditions of each lake and depth; in particular, assemblages from layers beneath the chemocline had biogeochemical associations that differed from those in the upper layers. These patterns of community composition may represent bacterial adaptations to the extreme and unique biogeochemical gradients of ice‐covered lakes in the McMurdo Dry Valleys.

1 aKwon, Miye1 aKim, Mincheol1 aTakacs-Vesbach, Cristina, D.1 aLee, Jaejin1 aHong, Soon, Gyu1 aKim, Sang, Jong1 aPriscu, John, C.1 aKim, Ok-Sun uhttps://onlinelibrary.wiley.com/doi/pdf/10.1111/1462-2920.1372102591nas a2200193 4500008004100000245013100041210006900172260001200241300001100253490000700264520191200271100002202183700002402205700002402229700003302253700002402286700001702310856007002327 2016 eng d00aNutrient treatments alter microbial mat colonization in two glacial meltwater streams from the McMurdo Dry Valleys, Antarctica0 aNutrient treatments alter microbial mat colonization in two glac c03/2016 afiw0490 v923 a

Microbial mats are abundant in many alpine and polar aquatic ecosystems. With warmer temperatures, new hydrologic pathways are developing in these regions and increasing dissolved nutrient fluxes. In the McMurdo Dry Valleys, thermokarsting may release both nutrients and sediment, and has the potential to influence mats in glacial meltwater streams. To test the role of nutrient inputs on community structure, we created nutrient diffusing substrata (NDS) with agar enriched in N, P and N + P, with controls, and deployed them into two Dry Valley streams. We found N amendments (N and N + P) to have greater chlorophyll-a concentrations, total algal biovolume, more fine filamentous cyanobacteria and a higher proportion of live diatoms than other treatments. Furthermore, N treatments were substantially elevated in Bacteroidetes and the small diatom, Fistulifera pelliculosa. On the other hand, species richness was almost double in P and N + P treatments over others, and coccoid green algae and Proteobacteria were more abundant in both streams. Collectively, these data suggest that nutrients have the potential to stimulate growth and alter community structure in glacial meltwater stream microbial mats, and the recent erosion of permafrost and accelerated glacial melt will likely impact resident biota in polar lotic systems here and elsewhere.

1 aKohler, Tyler, J.1 aVan Horn, David, J.1 aDarling, Joshua, P.1 aTakacs-Vesbach, Cristina, D.1 aMcKnight, Diane, M.1 aWagner, Dirk uhttp://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiw04902696nas a2200217 4500008004100000022001400041245013900055210006900194260001200263300000900275490000800284520194700292100002102239700002402260700001802284700002202302700002502324700001902349700003302368856007702401 2015 eng d a0962-845200aNiche and metabolic principles explain patterns of diversity and distribution: theory and a case study with soil bacterial communities0 aNiche and metabolic principles explain patterns of diversity and c05/2015 a26300 v2823 a

The causes of biodiversity patterns are controversial and elusive due to complex environmental variation, covarying changes in communities, and lack of baseline and null theories to differentiate straightforward causes from more complex mechanisms. To address these limitations, we developed general diversity theory integrating metabolic principles with niche-based community assembly. We evaluated this theory by investigating patterns in the diversity and distribution of soil bacteria taxa across four orders of magnitude variation in spatial scale on an Antarctic mountainside in low complexity, highly oligotrophic soils. Our theory predicts that lower temperatures should reduce taxon niche widths along environmental gradients due to decreasing growth rates, and the changing niche widths should lead to contrasting α- and β-diversity patterns. In accord with the predictions, α-diversity, niche widths and occupancies decreased while β-diversity increased with increasing elevation and decreasing temperature. The theory also successfully predicts a hump-shaped relationship between α-diversity and pH and a negative relationship between α-diversity and salinity. Thus, a few simple principles explained systematic microbial diversity variation along multiple gradients. Such general theory can be used to disentangle baseline effects from more complex effects of temperature and other variables on biodiversity patterns in a variety of ecosystems and organisms.

 

 

1 aOkie, Jordan, G.1 aVan Horn, David, J.1 aStorch, David1 aBarrett, John, E.1 aGooseff, Michael, N.1 aKopsova, Lenka1 aTakacs-Vesbach, Cristina, D. uhttp://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2014.2630