Soils and vegetation play an important role in the carbon exchange in Maritime Antarctica but little is known on the spatial variability of carbon processes in Antarctic terrestrial environments. The objective of the current study was to investigate (i) the soil development and (ii) spatial variability of ecosystem respiration (ER), net ecosystem CO2 exchange (NEE), gross primary production (GPP), soil temperature (ST) and soil moisture (SM) under four distinct vegetation types and a bare soil in Keller Peninsula, King George Island, Maritime Antarctica, as follows: site 1: moss-turf community; site 2: moss-carpet community; site 3: phanerogamic antarctic community; site 4: moss-carpet community (predominantly colonized by Sanionia uncinata); site 5: bare soil. Soils were sampled at different layers. A regular 40-point (5×8 m) grid, with a minimum separation distance of 1m, was installed at each site to quantify the spatial variability of carbon exchange, soil moisture and temperature. Vegetation characteristics showed closer relation with soil development across the studied sites. ER reached 2.26μmolCO2m(-2)s(-1) in site 3, where ST was higher (7.53°C). A greater sink effect was revealed in site 4 (net uptake of 1.54μmolCO2m(-2)s(-1)) associated with higher SM (0.32m(3)m(-3)). Spherical models were fitted to describe all experimental semivariograms. Results indicate that ST and SM are directly related to the spatial variability of CO2 exchange. Heterogeneous vegetation patches showed smaller range values. Overall, poorly drained terrestrial ecosystems act as CO2 sink. Conversely, where ER is more pronounced, they are associated with intense soil carbon mineralization. The formations of new ice-free areas, depending on the local soil drainage condition, have an important effect on CO2 exchange. With increasing ice/snow melting, and resulting widespread waterlogging, increasing CO2 sink in terrestrial ecosystems is expected for Maritime Antarctica.

During February–March of the austral summers of 2013/14 and 2014/2015, fieldwork was performed on Half Moon Island, South Shetland Archipelago, Antarctica, to evaluate the distribution and abundance of mosses and lichens, as well as to describe and map the plant communities there. The quadrat (20 × 20 cm) sampling method was employed in a phytosociological study that aimed to describe these communities. The area was mapped using an Astech Promark II® DGPS, yielding sub-metric precision after post-processing with software. The number of species totalled 38 bryophytes, 59 lichens, only one flowering plant (Deschampsia antarctica Desv.), and two macroscopic terrestrial algae. Five types of plant communities were identified on the island, as follows: (1) fruticose lichen and moss cushion, (2) moss carpet, (3) muscicolous lichen, (4) crustose lichen and (5) moss turf.

In this study, the organelle genomes of Polytrichum juniperinum Hedw. and Polytrichum strictum Menzies ex Brid. (Polytrichaceae, Bryophyta) from Antarctica were sequenced and compared with the plastomes of the model moss species Physcomitrella patens Brid. The sizes of the cpDNA in P. juniperinum and P. strictum were estimated to be 55,168 and 20,183 bp, respectively; the sizes of the mtDNA were 88,021 and 58,896 bp, respectively. The genomes are very similar to each other, with the possible loss of petN in the cpDNA, which also showed some gene inversions when compared with the cpDNAs of P. patens Brid. In the mtDNA, it is possible that rps10 was lost. In contrast, Antarctic Polytrichaceae species have nad7 and orf187, without the occurrence of rearrangement events. Phylogenomic analyses of the plastid and mitochondria revealed that the majority-rule tree suggests some differences in the plastids ancestry, however, P. juniperinum and P. strictum were grouped in the same clade in chloroplast, but in mitochondria P. strictum was grouped with Atrichum angustatum (Brid.) Bruch & Schimp. This study helped us understand the evolution of plastomes and chondriosomes in the family Polytrichaceae, and suggest a hybridization event with relation to the mitochondrial data.

Prasiola crispa is a macroscopic green algae found in abundance in Antarctica ice free areas. Prasiola crispan-hexaneextract (HPC) induced insecticidal activity in Nauphoeta cinerea cockroaches after 24 h of exposure. The chemical analysis of HPC revealed the presence of the followingphytosterols: β-sitosterol, campesterol and stigmasterol. The incubation of cockroach semi-isolated heart preparations with HPC caused a significant negative chronotropic activity in the heartbeats. HPC affected the insect neuromuscular function by inducing a complete inhibition of the cockroach leg-muscle twitch tension. When the isolated phytosterols were injected at in vivo cockroach neuromuscular preparations, there was a progressive inhibition of muscle twitches on the following order of potency: β-sitosterol > campesterol > stigmasterol. HPC also provoked significant behavioral alterations, characterized by the increase or decrease of cockroach grooming activity, depending on the dose assayed. Altogether, the results presented here corroborate the insecticide potential of Prasiola crispa Antarctic algae. They also revealed the presence of phytosterols and the involvement of these steroidal compounds in the entomotoxic activity of the algae, potentially by modulating octopaminergic-cholinergic pathways. Further phytochemical-combined bioguided analysis of the HPC will unveil novel bioactive compounds that might be an accessory to the insecticide activity of the algae.