Cryoresistance of Antarctic endemic lichen Himantormia lugubris: Analysis of photosystem II functionality using a constant-rate cooling approach

It is well established that lichens from polar regions of the Earth are capable to perform photosynthesis at sub-zero temperatures. Majority of them show a high degree of cryoresistance, however, species-specific differences exist. Therefore, the aim of our study was to evaluate behaviour of primary photochemical processes of photosynthesis in Antarctic endemic species Himantormia lugubris at sub-zero temperature. For the purpose, the method of constant rate (2°C min-1) cooling (from +20 to -40°C) with simultaneous measurements of chlorophyll fluorescence parameters related to photosystem II (PSII) was used. During the cooling, potential yield of photosynthetic processes in PSII (FV/FM), and effective quantum yield of PSII (ΦPSII) were measured in 30 s interval. From the FV/FM and ΦPSII data sets, S-curves reflecting temperature dependence of the two chlorophyll fluorescence parameters were constructed and analyzed. The S-curves were found tri-phasic in response to sample temperature decline: (1) slight or no decline phase, (2) rapid decline phase, followed by (3) slow change reaching critical temperature at which the primary photosynthetic processes were fully inhibited. Critical temperature was found -30 and -20°C for FV/FM, and ΦPSII, respectively. The latter critical temperature was accompanied by an increase in background chlorophyll fluorescence (F0) indicating inhibition of energy transfer from light-harvesting complexes to core of PSII. A newly-designed chlorophyll fluorescence parameter (a differential, i.e. the difference between the maximum value-normalized FV/FM, and ΦPSII) was used in order to evaluate the temperature at which the processes related to photosynthetic electron flow through thylakoid membrane carriers (ΦPSII) and the energy flow through PSII (FV/FM) differed to a largest extent. This parameters proved to be temperature-dependent and useful in the evaluation of cryoresistance.  Based on our study, H. lugubris, its primary photosynthetic processes in particular, might be considered as higly resistant to sub-zero temperature

Soluble carbohydrate content variation in Sanionia uncinata and Polytrichastrum alpinum, two Antarctic mosses with contrasting desiccation capacities

Additional file 1: Table S1. Non structural carbohydrate content (mg g−1 DW) of two Antarctic moss species expossed to desiccation and rehydration treatment under controlled conditions

Geoecology and historical heritage in the Ice-Free Area of Elephant Point (Antarctica): proposal for future environmental protection

The Antarctic Treaty provides the general environmental policies for all areas south of parallel 60° S. In addition, some enclaves have a higher degree of environmental protection regulated by three categories: Antarctic Specially Protected Areas (ASPA), Antarctic Specially Managed Areas and Historic Sites or Monuments. Most of the protected areas in Antarctica have been designated based on the national geopolitical strategies, giving special attention to those areas where access and logistics are easier. This paper focuses on Elephant Point (Livingston, South Shetland Islands), an ice-free area of 1.16 km2 where activities are only regulated by the Antarctic Treaty System and no further environmental protection exists. By using a geoecological approach based on the geomorphology together with the distribution of the fauna and flora existing in the area, we have distinguished six geoecological environments in Elephant Point: Rotch glacier, proglacial environment, moraine system, bedrock plateaus, marine terraces and present-day beach. The distribution of fauna and flora is highly conditioned by the age of deglaciation as well as by the glacial, paraglacial and periglacial geomorphological landforms and processes. Besides this, five well preserved archaeological sites have been found in Elephant Point. These sites were used for sealers and whalers who sailed across the Maritime Antarctic during the eighteenth and nineteenth centuries. The rich biodiversity together with the high geomorphological and historical significance of this peninsula within the Maritime Antarctic constitutes the scientific basis to propose Elephant Point to be designated an ASPA in order to preserve the unique scientific heritage existing in this small peninsula.info:eu-repo/semantics/publishedVersio

Compensatory Transcriptional Response of Fischerella thermalis to Thermal Damage of the Photosynthetic Electron Transfer Chain

Key organisms in the environment, such as oxygenic photosynthetic primary producers (photosynthetic eukaryotes and cyanobacteria), are responsible for fixing most of the carbon globally. However, they are affected by environmental conditions, such as temperature, which in turn affect their distribution. Globally, the cyanobacterium Fischerella thermalis is one of the main primary producers in terrestrial hot springs with thermal gradients up to 60 °C, but the mechanisms by which F. thermalis maintains its photosynthetic activity at these high temperatures are not known. In this study, we used molecular approaches and bioinformatics, in addition to photophysiological analyses, to determine the genetic activity associated with the energy metabolism of F. thermalis both in situ and in high-temperature (40 °C to 65 °C) cultures. Our results show that photosynthesis of F. thermalis decays with temperature, while increased transcriptional activity of genes encoding photosystem II reaction center proteins, such as PsbA (D1), could help overcome thermal damage at up to 60 °C. We observed that F. thermalis tends to lose copies of the standard G4 D1 isoform while maintaining the recently described D1INT isoform, suggesting a preference for photoresistant isoforms in response to the thermal gradient. The transcriptional activity and metabolic characteristics of F. thermalis, as measured by metatranscriptomics, further suggest that carbon metabolism occurs in parallel with photosynthesis, thereby assisting in energy acquisition under high temperatures at which other photosynthetic organisms cannot survive. This study reveals that, to cope with the harsh conditions of hot springs, F. thermalis has several compensatory adaptations, and provides emerging evidence for mixotrophic metabolism as being potentially relevant to the thermotolerance of this species. Ultimately, this work increases our knowledge about thermal adaptation strategies of cyanobacteria

Non-structural carbohydrate content in cryptogamic Antarctic species after two years of passive warming on the Fildes Peninsula

Cryptogamic vegetation dominates the ice-free areas of the maritime Antarctic. This particular flora grows slowly due to extreme environmental conditions, typically low temperature that may limit growth during a short summer. Over the last 50 years, the Antarctic Peninsula has undergone the highest registered temperature increases in Antarctica. As a consequence of higher temperatures, we hypothesized that lichens and mosses would produce more carbohydrates. To test this, open top chambers (OTCs) were installed in an Usnea-Himantormia community on Fildes Peninsula of King George Island. After two years, lichen thalli and plant tissues were collected to quantify non-structural carbohydrates in three lichens and two mosses. Responses contrasted between species. While non-structural carbohydrates were higher in the OTC for the lichen Himantormia lugubris, the values decreased in the moss Polytrichastrum alpinum. No marked responses to experimental warming were observed in the other three species. A significant species-specific increase in soluble sugar was observed inside the OTCs, while polyols content were not markedly different due to OTC treatment. In general, the obtained results indicate that warming does not increase carbohydrate content in all cryptogams, instead suggesting a strong species-specific response to a scenario of global warming. Further long-term warming experiments are needed to assess the responses of target species in the terrestrial Antarctic ecosystem

Competition between native Antarctic vascular plants and invasive Poa annua changes with temperature and soil nitrogen availability

Over the last decades human have introduced non-native organisms to Antarctica, including the grass species Poa annua. This non-native grass under constant growth temperatures has been shown negatively affect the growth of the only two native Antarctic vascular plants, Deschampsia antarctica and Colobanthus quitensis, under constant growth temperatures. However, whether there are changes in the interaction between these species under warmer conditions is an important question. In cold ecosystems, soil nutrient status directly affects plant responses to increases in temperature and Antarctic soils are highly variable in nutrient supply. Thus, in this study we experimentally assessed the interaction between the non-native Poa with the two native Antarctic vascular plant species at two different temperatures and levels of nutrient availability. Individual mats of the study species were collected in King George Island, and then transported to Concepcion where we conducted competition experiments. In the first experiment we used soil similar to that of Antarctica and plants in competition were grown at two temperatures: 5 degrees/2 degrees and 11 degrees/5 degrees C (day/ night temperature). In a second experiment plants were grown in these two temperature regimes, but we varied nitrogen (N) availability by irrigating plants with Hoagland solutions that contained 8000 or 300 mu M of N. Overall, Poa exerted a competitive effect on Deschampsia but only at the higher temperature and higher N availability. At 5 degrees/11 degrees C the competitive response of Deschampsia to Poa was of similar magnitude to the competitive effect of P. Deschatnpsia, and the competitive effect was greater with at low N. The competitive effect of Poa was similar to the competitive response of Colobanthus to Poa at both temperatures and N levels. Thus, at low temperatures and N soil content the native Antarctic species might withstand Poa invasion, but this might change with climate warming

Diversidad de musgos en comunidades vegetales asociadas a una pingüinera en la isla decepción, antártica marítima.

[spa] Con el objetivo de determinar la influencia de las pingüineras sobre la diversidad de la vegetación en la Isla Decepción, se estudió la composición de briófitas de un transecto de aproximadamente 2 km entre el Lago Irízar y la pingüinera (Pygoscelis antarcticus) de Punta La Descubierta. Fueron detectados un total de 39 carpetas de vegetación formadas principalmente por briófitos, distribuidas en tres sectores principales, aledaño al Lago Irízar, en Collado Vapor y en Punta La Descubierta. Los briófitos registrados corresponden a 15 especies de musgos y sólo 2 hepáticas, con 11 familias representadas. Se detectó que dos musgos, Sanionia uncinata y Politrychastrum alpinum, con 31 y 9 registros, dominaban las carpetas, con mayor abundancia y frecuencia. Además, se encontró un nuevo registro para la isla del musgo Bryum orbiculatifolium, el cual crece directamente asociado a la pingüinera. Además, se encontró que hay 5 especies de musgos comunes a los tres sectores, aunque otras 5 especies crecen solo en el sector de la pingüinera, diferenciándose esta comunidad de las otras dos. No se detectaron plantas vasculares en todo el sitio de estudio, por lo que se discute la posibilidad de que estos sitios se encuentran en estados de colonización temprana y donde su biota está marcada por la presencia de musgos pioneros que crecen alrededor de las pingüineras, influenciadas probablemente por el aporte de nutrientes del guano depositado.[eng] In order to determine the influence of a penguin rookery on the diversity of the vegetation on Deception Island, Maritime Antarctica, the composition of bryophytes along a transect of approximately 2 km between Lake Irízar and the penguin rookery (Pygoscelis antarcticus) of La Descubierta Point was studied. A total of 39 vegetation carpets formed mainly by bryophytes were detected, distributed between three main sectors, next to Lake Irízar, in Vapour Coil and at La Descubierta Point. The bryophytes correspond to 15 moss species and only 2 liverworts, with 11 moss families represented. Two mosses, Sanionia uncinata (31 records) and Polytrichastrum alpinum (9 records), were found to dominate the moss carpets, being also the most frequent species. In addition, a new site on the island was found with presence of the moss Bryum orbiculatifolium, which grows directly associated with the penguin rookery. Our results also show that there are 5 species of mosses common to the three sectors, another 5 species grow only in the penguin area, differentiating this community from the other two sectors. Vascular plants were not detected, indicating that the studied sites are in state of early colonization where their biota is marked by the presence of pioneer mosses associated to the penguin colony, which probably benefit from the nutrient input derived from the deposited guano

Do new records of macrofungi indicate warming of their habitats in terrestrial Antarctic ecosystems?

Relatively few macrofungi have been historically described from terrestrial environments of the Antarctic Peninsula and its associated archipelagos which are characterized by a moss-dominated vegetation, most of them preferentially or obligatorily associated with bryophytes. During the study of the influence of penguin rockeries to moss communities on the South Shetland Islands, the bryophilous basidiomycetes Rimbachia bryophila and Arrhenia cf. lilacinicolor were found for the first time on King George Island, growing on carpets of Sanionia uncinata. Other bryophilous fungi previously recorded in the same region are Arrhenia antarctica, Omphalina pyxidata and the rare Simocybe antarctica. The detection of the supposedly parasitic R. bryophila, together with other new observations of macrofungi on different hosts in the Antarctic bryoflora could indicate increased sexual reproduction. The likely increase of reproduction as an effect of warming on the terrestrial antarctic tundra should be proven by follow up field studies

Species-Specific Effects of Passive Warming in an Antarctic Moss System

Polar systems are experiencing rapid climate change and the high sensitivity of these Arctic and Antarctic ecosystems make them especially vulnerable to accelerated ecological transformation. In Antarctica, warming results in a mosaic of ice-free terrestrial habitats dominated by a diverse assemblage of cryptogamic plants (i.e. mosses and lichens). Although these plants provide key habitat for a wide array of microorganisms and invertebrates, we have little understanding of the interaction between trophic levels in this terrestrial ecosystem and whether there are functional effects of plant species on higher trophic levels that may alter with warming. Here, we used open top chambers on Fildes Peninsula, King George Island, Antarctica, to examine the effects of passive warming and moss species on the abiotic environment and ultimately on higher trophic levels. For the dominant mosses, Polytrichastrum alpinum and Sanionia georgicouncinata, we found species-specific effects on the abiotic environment, including moss canopy temperature and soil moisture. In addition, we found distinct shifts in sexual expression in P. alpinum plants under warming compared to mosses without warming, and invertebrate communities in this moss species were strongly correlated with plant reproduction. Mosses under warming had substantially larger total invertebrate communities, and some invertebrate taxa were influenced differentially by moss species. However, warmed moss plants showed lower fungal biomass than control moss plants, and fungal biomass differed between moss species. Our results indicate that continued warming may impact the reproductive output of Antarctic moss species, potentially altering terrestrial ecosystems dynamics from the bottom up. Understanding these effects requires clarifying the foundational, mechanistic role that individual plant species play in mediating complex interactions in Antarctica\u27s terrestrial food webs