Eugenio Rico

Soil trampling in an Antarctic Specially Protected Area: tools to assess levels of human impact.

Abstract Research in extremely delicate environments must be sensitive to the need to minimize impacts caused simply through the presence of research personnel. This study investigates the effectiveness of current advice relating to travel on foot over Antarctic vegetation-free soils. These are based on the concentration of impacts through the creation of properly signed and identified paths. In order to address these impacts, we quantified three factors - resistance to compression, bulk density and free-living terrestrial arthropod abundance - in areas of human activity over five summer field seasons at the Byers Peninsula (Livingston Island, South Shetland Islands). Studies included instances of both experimentally controlled use and natural non-controlled situations. The data demonstrate that a minimum human presence is sufficient to alter both physical and biological characteristics of Byers Peninsula soils, although at the lowest levels of human activity this difference was not significant in comparison with adjacent undisturbed control areas. On the other hand, a limited resilience of physical properties was observed in Antarctic soils, thus it is crucial not to exceed the soils natural recovery capability.

Decomposition of Juncus maritimus in two shallow lakes of Doñana National Park

Santa Olalla and Dulce are two shallow natural eutrophic lakes (lagunas) located in Donana National Park (south of Spain). Both lagunas have high algal biomass and pH and are surrounded by a macrophyte fringe of Juncus spp. and Scirpus spp. The effect of the macroinvertebrate community on decomposition rates (k) of Juncus maritimus was measured in both lagunas using the litter bag method over a one year period after which less than 10% of the original litter bag material remained. Two different mesh sizes, coarse (5 mm) and fine (0.25 mm), were used to evaluate macroinvertebrate community effects on decomposition. Decomposition rates were rapid, with k values of 0.0162 day -1 in coarse bags and 0.0094 day -1 for fine bags at Santa Olalla and 0.0095, 0.0088 day -1 for coarse and fine bags, respectively, at Dulce. Both lagunas had similar densities of macroinvertebrates, with a dominance of shredder-gatherer chironomids. However, densities of scrapers (Ancylidae) increased in Santa Olalla in spring but were almost absent in Dulce. The influence of different physical and chemical parameters and of the macroinvertebrate community on the decomposition process is studied. In spite of some potential confounding effects in the use of fine mesh bags in standing water systems, it is concluded that morphometrical characteristics of the lagunas are important in controlling decomposition rates.

A new freshwater oligochaete species (Clitellata: Enchytraeidae) from Livingston Island, Antarctica

The new enchytraeid species Lumbricillus healyae sp. n. is described from freshwater streams, with well-oxygenated and poorly mineralised waters, situated in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica). Lumbricillus healyae sp. n. is morphologically close to L. antarcticus and L. incisus, and it is mainly distinguished by the structure of the spermatheca with a short, distinct ectal duct, the oval penial bulb (greatest diameter in the transverse body axis) associated with strong dorso-ventral muscular fibres, and a protrusible pseudopenis. A second undetermined Lumbricillus species is described from a small stream. Study specimens are not fully mature; however, the highly irregular form and size of the testis-sac lobes and the absence of a penial bulb encapsulated under a muscular layer are remarkable. It is probably related to a small group of Lumbricillus species reported from the Antarctic maritime region (L. colpites, L. griseus and L. aestum), characterised by the structure of the male duct, which ends in a simple pore surrounded by glands.

Structure of planktonic microbial communities along a trophic gradient in lakes of Byers Peninsula, South Shetland Islands

Abstract A systematic limnological survey of water bodies of Byers Peninsula (Livingston Island, South Shetland Islands) was carried out during the summer of 2001/02. Abundances of microbial plankton were determined which allowed a delineation of the pelagic food web structure. We also report the nutrient status of these lakes. We demonstrate the occurrence of a trophic gradient that extended from upland lakes (oligotrophic) to the coastal ones (eutrophic). The study shows that a lakes morphology regulates the relative importance of the pelagic and benthic habitats, whereas nutrient loads mainly determine its trophic status. Yet, some of the variability observed could be also a legacy of the landscape. Photosynthetic pigments analyses by high-performance liquid chromatography of the lake waters revealed a major occurrence of chlorophytes, chrysophytes and diatoms. The chlorophyll a concentrations in lakes in the central plateau were consistently lower (< 2.5 μg l-1) than coastal sites, which were one order of magnitude higher. Numbers of both bacterioplankton and autotrophic picoplankton also increased from inland to coastal sites. However, the relative role of autotrophic picoplankton in the total phytoplankton assemblage decreased with the increase in nutrients loads. Our results show that the trophic status clearly plays a significant role in structuring the pelagic communities of these lakes despite climatic constraints.

Phylogeographic analysis of filterable bacteria with special reference to Rhizobiales strains that occur in cryospheric habitats

Abstract Although the lower size limit of microorganisms was previously believed to be c. 0.2 μm, there is evidence for the existence of microorganisms that can pass through 0.2 μm-pore-size filters called ultramicrobacteria or nanobacteria. However, information on the phylogeny and biogeography of these bacteria is limited. We obtained 53 isolates of 0.2 μm-passable bacteria from 31 samples collected at 26 locations worldwide, including the Arctic Svalbard Islands, deserts, and Maritime Antarctica. Phylogenetic analysis of near full-length 16S rRNA gene sequences revealed that 18 of the 53 isolates were < 97% homologous with previously cultured isolates, representing potentially novel species. Two isolates (order Rhizobiales) (100% identical) collected from Byers Peninsula, Livingston Island in Maritime Antarctica, were closely related (99.8% similarity) to an isolate collected from intertidal sediments in East Antarctica. In addition, the sequence of this Antarctic isolate showed ≥ 97% similarity to 901 sequences derived from known isolates and samples collected at geographically disparate locations under various environmental conditions. Interestingly, among 13 sequences showing ≥ 99% similarity, ten were isolated from cryospheric habitats such as Arctic, Antarctic, and alpine environments. This implies that such Rhizobiales strains occur in the cryospheric regions, however, their abundance and biomass may be scarce depending on the geographic location.

Community structure and photosynthetic activity of benthic biofilms from a waterfall in the maritime Antarctica

Abstract High-energy flowing water habitats such as waterfalls are uncommon in Antarctica, though they may become more regular as temperature increase. Both high spatial and temporal environmental variability is expected on them. The extent of their biological colonization will depend on the amount of ecological strategies displayed by the surrounding biota. We report here a study on phototrophic microbenthic communities inhabiting such environment in a stream on the Byers Peninsula of Livingston Island. Five different biofilms were distinguished by colour, and were located in specific microhabitat types in the waterfall, which flowed down a steep canyon. Photosynthetic pigment content and microscopic observations demonstrated a different assemblage of chlorophytes, cyanobacteria and diatoms among them. Biofilms were not randomly distributed in the stream channel, which may be related to water flow, nutrient availability and moisture. The exopolymeric substances content, stoichiometry and pigment composition varied among biofilms, likely reflecting differences in the water and nutrients availability. The photosynthetic rates were in the range of the observed in previous studies in the site and varied according to the habitat within the stream. Communities dominated by chlorophytes were restricted to the central channel, suggesting adaptation to faster flow regime. However, cyanobacterial biofilms appeared in a great range of environmental conditions. They were rare in the central channel where water flow was greatest, but achieved large biomass stocks on submerged and even exposed sites in the splash zone at the edge of the flowing water. This study shows how Antarctic biofilms can have a large variability in community structure and biomass over short length scales, reflecting the range of microhabitats in this Antarctic waterfall ecosystem, and the potential occurrence of different strategies to overcome fluctuating conditions.

Maritime Antarctic Lakes As Sentinels Of Climate Change

Remote lakes, such as lakes from the Maritime Antarctica, can be used as sentinels of climate change, because they are mostly free of direct anthropogenic pressures, and they experience climate change as a main stressor capable of modifying the ecosystem structure and function. In this paper, the content of a lecture that has been presented at the First Conference of Lake Sustainability, which has been centred in our studies on lakes from Byers Peninsula (Maritime Antarctica), are summarized. These included physical, chemical and biological studies of these lakes and other freshwater ecosystems, which highlighted the relevance of biotic interactions for these ecosystems and its sensibility to temperature variations and to biological invasions, which is of relevance given the acute regional warming occurring during the last decades in the area, concomitant with the enhancement of dispersion of alien species linked to the increased presence of humans.

Trophic interactions in microbial mats on Byers Peninsula, maritime Antarctica

Cyanobacteria-based microbial mats are common in Antarctic terrestrial freshwater ecosystems such as the extensive wetland seepages that cover Byers Peninsula on Livingston Island (South Shetland Islands), maritime Antarctica, where they play an important role in biomass generation and productivity. Although cyanobacteria, microfauna and fungal communities have been described for such microbial mats, to date, little is known about trophic interactions within the mats, which are likely important to overcome nutrient constraints in oligotrophic polar freshwater ecosystems. We therefore carried out a biomass assessment of the different taxonomic components and their trophic interactions using DNA analysis and stable isotope analysis, as well as physiological activities such as primary and secondary production and nitrogen uptake within the mat food web throughout an austral spring and summer season. Our results suggested, based on a Bayesian mixing model, that carbon flow from cyanobacteria to upper trophic levels was limited to tardigrades and rotifers, whereas fungal and bacterial activity were likely the main connectors between consumers and producers via a heterotrophic loop. This suggests that homeostatic state displayed in freshwater microbial mats from maritime Antarctica provides stability to the microbial mats under the fluctuating environmental conditions commonly found in permanently cold shallow terrestrial aquatic ecosystems in Antarctica.

Distribution and ecology of chironomids (Diptera, Chironomidae) on Byers Peninsula, Maritime Antarctica

Abstract This study describes the ecology and distribution of the only two native Antarctic insects, the chironomid species Parochlus steinenii and Belgica antarctica, both found on Byers Peninsula (Livingston Island, South Shetland Islands). Parochlus steinenii inhabits lakes of the central plateau of Byers Peninsula associated with aquatic mosses on the bottom of lakes and in some streams of the South Beach area. Some streams have stable populations which are able to complete their life cycle while other streams have temporary, unstable populations. Belgica antarctica also inhabits streams running through mosses located in the South Beach area. Our data indicate that this species has a limited dispersal capability which is positively light activated for both adults and pupae. Both Antarctic midge species coexists on Byers Peninsula and share some stretches of streams. Isotopic studies show a non-selective feeding regime for both species with mixed carbon sources associated with both biofilm/microbial mats and mosses.