Lichen response to ammonia deposition defines the footprint of a penguin rookery

Ammonia volatilized from penguin rookeries is a major nitrogen source in Antarctic coastal terrestrial ecosystems. However, the spatial extent of ammonia dispersion from rookeries and its impacts have not been quantified previously. We measured ammonia concentration in air and lichen ecophysiological response variables proximate to an Adèlie penguin rookery at Cape Hallett, northern Victoria Land. Ammonia emitted from the rookery was 15N-enriched (δ15N value +6.9) and concentrations in air ranged from 36–75 µg m−3 at the rookery centre to 0.05 µg m−3 at a distance of 15.3 km. δ15N values and rates of phosphomonoesterase (PME) activity in the lichens Usnea sphacelata and Umbilicaria decussata were strongly negatively related to distance from the rookery and PME activity was positively related to thallus N:P mass ratio. In contrast, the lichen Xanthomendoza borealis, which is largely restricted to within an area 0.5 km from the rookery perimeter, had high N, P and 15N concentrations but low PME activity suggesting that nutrient scavenging capacity is suppressed in highly eutrophicated sites. An ammonia dispersion model indicates that ammonia concentrations sufficient to significantly elevate PME activity and δ15N values (≥0.1 µg NH3 m−3) occurred over c. 40–300 km2 surrounding the rookery suggesting that penguin rookeries potentially can generate large spatial impact zones. In a general linear model NH3 concentration and lichen species identity were found to account for 72 % of variation in the putative proportion of lichen thallus N originating from penguin derived NH3. The results provide evidence of large scale impact of N transfer from a marine to an N-limited terrestrial ecosystem

The evaluation of time-resolved Raman spectroscopy for the suppression of background fluorescence from space-relevant samples

One of the primary goals in space research is the search for signs of extant or extinct extraterrestrial life, and Raman spectroscopy can play a role in this field. Raman spectrometers are planned for future missions to Mars and possibly the Moon to identify the mineralogical surface composition and potentially existing organic compounds (especially on Mars). However, a major challenge in Raman spectroscopy, especially in the visible range, is the strong fluorescence background. Time‐resolved Raman spectroscopy (TRRS) can provide selective detection of Raman signals over the generally longer living fluorescence. This study investigates the potential of a TRRS system, using 3‐ps, 440‐nm laser pulses and time‐gated detection with an intensified charge‐coupled device (CCD) camera. Test samples were the lichen Xanthoria elegans as an extraterrestrial life analogue, and a lunar regolith analogue material (LRS) as a planetary surface analogue. The TRRS technique is evaluated by comparing gated to nongated Raman spectroscopy using different detectors but with otherwise the same instrument and identical measurement conditions. The gated spectra of X. elegans showed significant signal‐to‐noise ratio (SNR) improvements compared to the nongated spectra. The visible Raman lines could be assigned to the photoprotective pigment parietin. For the LRS sample, measurement spots with a good SNR in the nongated spectrum were not significantly improved by measuring in gated mode. However, spots dominated by fluorescence showed significant improvement in gated mode because of fluorescence suppression. Minerals such as plagioclase, diopside, olivine, apatite, and a carbonate mineral were detected. In most cases, TRRS provided better results compared to nongated measurements, demonstrating the suitability for future space‐exploration missions

Lichen and moss communities of Botany Bay, Granite Harbour, Ross Sea, Antarctica

Antarctic soils are extremely cold, dry, and oligotrophic, yet harbour surprisingly high bacterial diversity. The severity of environmental conditions has constrained the development of multi-trophic communities, and species richness and distribution is thought to be driven primarily by abiotic factors. Sites in northern and southern Victoria Land were sampled for bacterial community structure and soil physicochemical properties in conjunction with the US and New Zealand Latitudinal Gradient Project. Bacterial community structure was determined using a high-resolution molecular fingerprinting method for 80 soil samples from Taylor Valley and Cape Hallett sites which are separated by five degrees of latitude and have distinct soil chemistry. Taylor Valley is part of the McMurdo Dry Valleys, while Cape Hallett is the site of a penguin rookery and contains ornithogenic soils. The influence of soil moisture, pH, conductivity, ammonia, nitrate, total nitrogen and organic carbon on community structure was revealed using Spearman rank correlation, Mantel test, and principal components analysis. High spatial variability was detected in bacterial communities and community structure was correlated with soil moisture and pH. Both unique and shared bacterial community members were detected at Taylor Valley and Cape Hallett despite the considerable distance between the sites

The cosmopolitan moss Bryum argenteum in Antarctica: Recent colonisation or in situ survival?

Since the onset of glaciation following the Oligocene (30–28 Ma), the prevalence of increasingly cold conditions has shaped the evolution of the Antarctic biota. Two hypotheses, postglacial recruitment from extra-regional locations and in situ persistence, have been proposed to explain the biogeography of the contemporary species-poor terrestrial Antarctic biota. Bryophytes, which form a major group of the Antarctic flora, exhibit a strong, inherent ability to survive cold conditions but also have high long-distance dispersal capacities, which are compatible with both hypotheses. Here, we test these hypotheses by means of population genetic and phylogeographic analyses of the cosmopolitan moss Bryum argenteum. We find evidence for at least three independent colonisation events of the species in Antarctica. Ancestral area reconstruction coupled with molecular dating suggests colonisation times of the different Antarctic clades ranging from four million years for the oldest lineage to half a million years for the youngest lineage. This suggests multiple colonisation events of Antarctica by this species during several glacial cycles within the Pleistocene, Pliocene and possibly late Miocene. This is the first study to demonstrate in situ persistence of bryophytes in Antarctica throughout previous glaciations