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Several studies reported that gametophytes and tetrasporophytes of Gigartinaceae produce different carrageenan types, as observed in Sarcopeltis species although they have isomorphic haploid and diploid phases. Cystocarpic and non-fertile plants of Sarcopeltis (ex Gigartina) skottsbergii produced kappa-carrageenans, while tetrasporophytes produced lambda-carrageenans, and yields were higher in cystocarpic and sterile specimens than in tetrasporophytes. However, comparison on the other primary metabolites among different life history phases still needed to be investigated. Then, we tested the hypothesis if the variation on primary metabolites (pigments, proteins and carbohydrates) are related to the life history phases of Sarcopeltis antarctica and Sarcopeltis skottsbergii, and/or are influenced by abiotic factors. Primary metabolites of S. antarctica varied according to the life-history phases: non-fertile specimens presented higher phycobiliprotein concentrations, tetrasporophytes presented higher chlorophyll a concentrations, and cystocarpic specimens presented higher concentrations of proteins, polysaccharides and floridean starch. However, primary metabolites of S. skottsbergii varied in response to some abiotic factors (nutrients, temperature and salinity), since principal component analysis evidenced two groups; one was related by the higher nitrate and phosphate concentrations, and the other was related to the higher temperatures and lower salinities. Concentrations of floridean starch, low molecular weight carbohydrates, and polysaccharides are higher in S. antarctica than in S. skottsbergii, which could be related to the protective role of these compounds against salinity variation and low temperatures faced in the Antarctic extreme environments.

The agarophyte Ahnfeltia (Ahnfeltiales, Rhodophyta) is a globally widespread genus with 11 accepted species names. Two of the most widespread species in this genus, A. plicata and A. fastigiata, may have diverged genetically due to past geographic changes and subsequent geographic isolation. To investigate this genomic and genetic diversity, we generated new plastid (ptDNAs) and mitochondrial genomes (mtDNAs) of these Ahnfeltia species from four different regions (A. plicata - Chile and UK and A. fastigiata - Korea and Oregon). Two architecture variations were found in the Ahnfeltia genomes: in ptDNA of A. fastigiata Oregon, the hypothetical pseudogene region was translocated, likely due to recombination with palindromic repeats or a gene transfer from a red algal plasmid. In mtDNA of A. fastigiata Korea, the composition of the group II intronic ORFs was distinct from others suggesting different scenarios of gain and loss of group II intronic ORFs. These features resulted in genome size differences between the two species. Overall gene contents of organelle genomes of Ahnfeltia were conserved. Phylogenetic analysis using concatenated genes from ptDNAs and mtDNAs supported the monophyly of the Ahnfeltiophycidae. The most probable individual gene trees showed that the Ahnfeltia populations were genetically diversified. These trees, the cox1 haplotype network, and a dN/dS analysis all supported the theory that these Ahnfeltia populations have diversified genetically in accordance with geographic distribution.

Palmaria decipiens (Reinsch) R.W.Ricker is a ecologically important red seaweed restricted to high latitudes of the southern hemisphere. Here, we contribute to the bioinformatics and evolutionary systematics of the Palmariales by performing high throughput sequencing analysis on a specimen of P. decipiens from the western Antarctic Peninsula. The P. decipiens mitogenome is 26,645 base pairs (bp) in length and contains 49 genes (GenBank accession MN967053) and the plastid genome is 193,007 bp and contains 245 genes (GenBank accession MN967052). The mitogenome and plastid genome of P. decipiens are similar to P. palmata from Japan in pairwise genetic distances (93.71% and 98.14%, respectively), and P. palmata from the Maine, USA (87.45% and 94.57%, respectively). The genomes of P. decipiens showed high gene synteny with P. palmata, however several tRNA differences are documented. Organellar genome content and phylogenetic analyses of P. decipiens supports its placement in the genus Palmaria.

Lessonia spicata (Suhr) Santelices is the most ecologically and economically important kelp from Pacific South America. Here, we contribute to the bioinformatics and evolutionary systematics of the species by performing high throughput sequencing on L. spicata from Valparaiso, Chile. The L. spicata complete mitogenome is 37,097 base pairs (bp) in length and contains 66 genes (GenBank accession MK965907), the complete plastid genome is 130,305 bp and has 173 genes (accession MK965908), and the data assembled 7,630 bp of the nuclear ribosomal cistron (accession MK965909). The organellar genomes are similar in structure and content to others published from the Laminariales.

The generitype Lessonia flavicans Bory is an endemic and important kelp from Sub-Antarctic Magellanic ecoregion that shows affinity to extreme salinity, temperature, and photoperiod conditions. Genomic analysis of L. flavicans from Rinconada Bulnes, Punta Arenas, Chile, resulted in the assembly of its organellar genomes. The L. flavicans complete mitogenome is 37,226 base pairs (bp) in length and contains 66 genes (GenBank accession number MN561186), the complete plastid genome is 130,085 bp and has 173 genes (MN561187) and the data assembled 8205 bp of the nuclear ribosomal cistron (MN561188). The organellar genomes are similar in structure and content to L. spicata (Suhr) Santelices and other Laminariales.

Abstract The paradigm of past climate-driven range shifts structuring the distribution of marine intraspecific biodiversity lacks replication in biological models exposed to comparable limiting conditions in independent regions. This may lead to confounding effects unlinked to climate drivers. We aim to fill in this gap by asking whether the global distribution of intraspecific biodiversity of giant kelp (Macrocystis pyrifera) is explained by past climate changes occurring across the two hemispheres. We compared the species’ population genetic diversity and structure inferred with microsatellite markers, with range shifts and long-term refugial regions predicted with species distribution modelling (SDM) from the last glacial maximum (LGM) to the present. The broad antitropical distribution of Macrocystis pyrifera is composed by six significantly differentiated genetic groups, for which current genetic diversity levels match the expectations of past climate changes. Range shifts from the LGM to the present structured low latitude refugial regions where genetic relics with higher and unique diversity were found (particularly in the Channel Islands of California and in Peru), while post-glacial expansions following ~ 40% range contraction explained extensive regions with homogenous reduced diversity. The estimated effect of past climate-driven range shifts was comparable between hemispheres, largely demonstrating that the distribution of intraspecific marine biodiversity can be structured by comparable evolutionary forces across the global ocean. Additionally, the differentiation and endemicity of regional genetic groups, confers high conservation value to these localized intraspecific biodiversity hotspots of giant kelp forests.

Measurement(s) microbial diversity • microbial abundances • cations and anions • trace elements Technology Type(s) MiSeq sequencing 16S rRNA gene • Real Time PCR • HPLC • ICP-MS Sample Characteristic - Organism bacteria • archaea Sample Characteristic - Environment lake water • lake sediment • wetland • peatland • soil • pond Sample Characteristic - Location Western Siberia • Alaska • Patagonia • Cape Horn province • Magellanic subantarctic ecoregion

These extensive kelps forest are among the most productive and diverse habitats on the planet, playing an important ecological role in marine ecosystems. These habitats have been affected by anthropogenic factors worldwide and directly by environmental variations resulting from climate change. The Magellan ecoregion has the southernmost kelp forests in the world, dominated by the species Macrocystis pyrifera. This species presents high ecophysiological plasticity being able to inhabit heterogeneous environments, characteristic of the fjord and channel systems of the region, and has high ecological, sociocultural, and economic importance for local coastal communities. To understand the ecophysiological acclimation strategies of M. pyrifera, samples from different blades were collected at different depths at four locations in the Magellan Ecoregion: Possession Bay, Skyring Sound, Otway Sound, and Puerto del Hambre seasonally. Abiotic measurements (salinity, temperature, and PAR light) were carried out for each location sampled. Measurements of photosynthetic parameters, Fv/Fm, rETRmax, Ek and α; pigment analysis of Chl a, Chl c, and fucoxanthin; and fecundity analysis of the sporophylls of each population studied were carried out on the M. pyrifera sporophytes. Significant differences were observed between seasons, locality, and depth of blades. Each population generally showed different photoacclimation processes, depending on the local conditions such as salinity values and probably tidal cycles. This is reflected in the photosynthetic, pigment, and fecundity values obtained during this study. The higher Fv/Fm values in all populations during the winter and autumn seasons and the differences in Chl c and fucoxanthin concentration during the winter period in Otway Sound and Puerto del Hambre population suggest the marked seasonal acclimation of M. pyrifera. In addition, the coastal environmental heterogeneity observed in the Magellan ecoregion related to salinity gradients (Skyring Sound) or wide tidal amplitudes (Possession Bay) influences the acclimation strategy of each population of M. pyrifera. Therefore, the characteristics of each population should be considered in order to promote its sustainability in times of social and climate change.

The giant kelp Macrocystis pyrifera is a cosmopolitan species of cold-temperate coasts. Its South-American distribution ranges from Peru to Cape Horn and Argentina, encompassing a considerable temperature gradient, from 3 to 20°C. Temperature is known to strongly affect survival, growth and reproduction of many kelp species, and ongoing global warming is already eroding their range distribution. Their response to thermal variability was shown to vary among genetically differentiated regions and populations, suggesting a possible adaptive divergence in thermal tolerance traits. This study aimed at testing the existence of local adaptation in the giant kelp, in regions separated by up to 4000km and strong thermal divergence. Two complementary experiments mimicked reciprocal transplants through a common garden approach, each habitat being represented by a given temperature corresponding to the regional average of the sampled populations. Several proxies of fitness were measured in the haploid stage of the kelp, and sympatric versus allopatric conditions (i.e. individuals at the temperature of their region of origin versus in a different temperature and versus individuals from other regions in that temperature) were compared. Additionally, a heat wave at 24°C was applied to measure the tolerance limits of these gametophytes. A significant interaction between experimental temperature and region of origin revealed that temperature tolerance varied among regions. However, depending on the fitness parameter measured, high latitude populations from the sub-Antarctic region were not always less heat resilient than populations from the warmer region of Peru. Even at 24°C, a temperature that is exceptionally reached in the southernmost part of the kelp’s natural habitat, all the gametophytes survived, although with strong differences in other traits among regions and populations within regions. This large range of temperature tolerance supports the idea of kelp gametophytes being a resistant stage. Finally, local adaptation sensu stricto was not detected. Fertility was more influenced by the geographic origin than by temperature, with possible effects of marginal conditions at the extremes of the distribution range. The latter results also suggest that stochastic dynamics such as genetic drift restricts adaptive processes in some populations of M. pyrifera.

Abstract Two species of scallop, Austrochlamys natans (“Ostión del Sur”) and Zygochlamys patagonica (“Ostión patagonico”) are presently exploited in the southern part of the Magallanes Province (MP). The lack of clarity in taxonomic identification and ecological aspects is generating both erroneous extraction statistics and an unperceived harvesting pressure on A. natans and Z. patagonica. We aim to discriminate these Magallanes scallops accurately, improve our understanding of their complex natural history and discuss possible implications for their management and conservation status, given the current fisheries statistics. To achieve these goals, we present a complete review of the historical identification of the Magallanes scallop and a multi-locus molecular phylogeny which allowed us to recover the phylogenetic position of A. natans. We sampled 54 individuals from five localities across the southern Pacific coast of the MP. We calculated the depth of the byssal notch (BND) and shell height (VH) ratio from morphological characters and conducted phylogenetic reconstructions with mitochondrial (12S and 16S) and nuclear markers (28S) using Bayesian and maximum likelihood analyses. Both morphology and molecular phylogeny identified two distinct entities, Z. patagonica and a distinct, highly divergent lineage that corresponds to A. natans. Our study provides integrative evidence to alert the current fishery management and the need for further conservation studies.

The COVID-19 pandemic has caused an unprecedented health and economic crisis, highlighting the importance of developing new molecular tools to monitor and detect SARS-CoV-2. Hence, this study proposed to employ the carrageenan extracted from Gigartina skottsbergii algae as a probe for SARS-CoV-2 virus binding capacity and potential use in molecular methods. G. skottsbergii specimens were collected in the Chilean subantarctic ecoregion, and the carrageenan was extracted —using a modified version of Webber’s method—, characterized, and quantified. After 24 h of incubation with an inactivated viral suspension, the carrageenan’s capacity to bind SARS-CoV-2 was tested. The probe-bound viral RNA was quantified using the reverse transcription and reverse transcription loop-mediated isothermal amplification (RT-LAMP) methods. Our findings showed that carrageenan extraction from seaweed has a similar spectrum to commercial carrageenan, achieving an excellent proportion of binding to SARS-CoV-2, with a yield of 8.3%. Viral RNA was also detected in the RT-LAMP assay. This study shows, for the first time, the binding capacity of carrageenan extracted from G. skottsbergii, which proved to be a low-cost and highly efficient method of binding to SARS-CoV-2 viral particles.

Freshwater ecosystems are responsible for an important part of the methane (CH4) emissions which are likely to change with global warming. This study aims to evaluate temperature-induced (from 5 to 20 °C) changes on microbial community structure and methanogenic pathways in five sub-Antarctic lake sediments from Magallanes strait to Cape Horn, Chile. We combined in situ CH4 flux measurements, CH4 production rates (MPRs), gene abundance quantification and microbial community structure analysis (metabarcoding of the 16S rRNA gene). Under unamended conditions, a temperature increase of 5 °C doubled MPR while microbial community structure was not affected. Stimulation of methanogenesis by methanogenic precursors as acetate and H2/CO2, resulted in an increase of MPRs up to 127-fold and 19-fold, respectively, as well as an enrichment of mcrA-carriers strikingly stronger under acetate amendment. At low temperatures, H2/CO2-derived MPRs were considerably lower (down to 160-fold lower) than the acetate-derived MPRs, but the contribution of hydrogenotrophic methanogenesis increased with temperature. Temperature dependence of MPRs was significantly higher in incubations spiked with H2/CO2 (c. 1.9 eV) compared to incubations spiked with acetate or unamended (c. 0.8 eV). Temperature was not found to shape the total microbial community structure, that rather exhibited a site-specific variability among the studied lakes. However, the methanogenic archaeal community structure was driven by amended methanogenic precursors with a dominance of Methanobacterium in H2/CO2-based incubations and Methanosarcina in acetate-based incubations. We also suggested the importance of acetogenic H2-production outcompeting hydrogenotrohic methanogenesis especially at low temperatures, further supported by homoacetogen proportion in the microcosm communities. The combination of in situ-, and laboratory-based measurements and molecular approaches indicates that the hydrogenotrophic pathway may become more important with increasing temperatures than the acetoclastic pathway. In a continuously warming environment driven by climate change, such issues are crucial and may receive more attention.

Interactions between algae and herbivores can be affected by various factors, such as seasonality and habitat structure. Among herbivores inhabiting marine systems, species of the order Patellogastropoda are considered key organisms in many rocky coasts of the world. Nacella species are one of the most dominant macro-herbivores on the rocky shores of the sub-Antarctic ecoregion of Magellan. However, the importance of its key role must be associated with its trophic ecology. The objective of this work was to evaluate spatial and temporal variabilities in the dietary composition of two intertidal Nacella species, considering grazing on macro- (macroalgae) and microscopic (periphyton) food. The composition of periphyton and the availability of macroalgae in the winter and summer seasons were examined at two localities of the Magellanic province, alongside the gut contents of N. magellanica and N. deaurata. The dietary composition differed between the two Nacella species, as well as between seasons and locations. The differences observed in the diet of the two species of Nacella may be mainly due to their respective distributions in the intertidal zone. Both species presented a generalist strategy of grazing, which is relationed to the seasonality of micro- and macroalgae availability and to the variability of the assemblages between the localities. This research was the first to perform a detailed study of the diet of intertidal Nacella species.

The southern South American inland waters have many endemic species and some of them are considered as endangered for IUCN, that inhabits in unpolluted ecosystems, one of these ecosystems are the sub-Antarctic perennial forests located in the Cape Horn Biosphere Reserve at 54° S. The aim of the present study is to analyze the spatial patterns of Pisidium chilense Ituarte, 1999 (Mollusca Bivalvia) and Hyalella patagonica (Cunningham, 1871) (Crustacea, Amphipoda) in an unpolluted stream. Both species had aggregated spatial distribution, both have a negative binomial distribution pattern, and both are associated. The present results would agree with similar patterns in Patagonian rivers where both species coexist.

The Katalalixar National Reserve (KNR) lies in an isolated marine protected area of Magellan Sub-Antarctic channels, which represent an important area for marine biodiversity and macroalgal conservation. The present study is the first report of the species Lessonia spicata, “huiro negro”, in the Magellan Sub-Antarctic channels. This finding has implications for macroalgal biogeography and conservation concerns in the Chilean coast. In the ecological assessments of the KNR in 2018 we found populations of L. spicata, specifically on rocky shores of Torpedo Island and Castillo Channel. The morphological identification and molecular phylogeny based on nuclear (ITS1) sequences revealed that these populations of Lessonia are within the lineage of L. spicata of central Chile. This report increases the species richness of kelps for the Magellan Sub-Antarctic Channels from two to three confirmed species (L. flavicans, L. searlesiana and L. spicata), and it also extends the southern distribution range of L. spicata. This species has high harvest demand and is moving towards southern Chile; thus, these populations should be considered as essential for macroalgal conservation in high latitudes of South America.

Photosynthesis at high latitudes demands efficient strategies of light utilization to maintain algal fitness and performance. The fitness, and physiological adaptation, of a plant or algae species depends in part on the abundance and efficiency of the pigments it can produce to utilize the light resource from its environment. We quantified pigment composition and concentration in six species of the brown macroalgal genus Desmarestia, collected from sub-Antarctic sites (Strait of Magellan, Beagle Channel–Cape Horn Province) and sites on the Antarctic Peninsula and adjacent islands. Sub-Antarctic Desmarestia species exhibited lower concentrations of chlorophyll a, chlorophyll c and fucoxanthin than endemic Antarctic species. Antarctic samples of D. menziesii and D. antarctica collected along a decreasing latitudinal gradient showed spatial and interspecific differences in light-harvesting pigment composition. Our results suggest distinct physiological adjustments in Desmarestia species in response to heterogeneous abiotic environmental conditions. The marine sub-Antarctic and Antarctic ecosystems are characterized by harsh environments (e.g., extreme irradiance, photoperiod, temperature, salinity) to which the physiology of macroalgal species must adapt.

In this paper we evaluated the composition and abundance of molluscs associated with beds of the red algae Gigartina, located in the South Shetland Islands (Antarctic Peninsula) and the Strait of Magellan (southern Chile). During the summer season of 2013, samples were obtained by scuba diving using a 0.25 m2 quadrat, arranged randomly within the bed. We extracted a total of 15 quadrats per sampling site. For Antarctic Peninsula beds the most abundant species were the bivalve Lissarca miliaris (233 individuals) and the gastropod Laevilacunaria antarctica (94 individuals), while for Strait of Magellan beds the most abundant species was the polyplacophoran Callochiton puniceus (36 individuals). Comparative analysis between the two molluscan assemblages showed significant differences in the faunal composition between the Antarctic Peninsula and Strait of Magellan (f = 64.474; p = 0.0001). Therefore, molluscs reported in both areas are characteristic of their respective biogeographic area. Finally, Gigartina species play an important role in the formation of patterns of abundance and diversity of the communities associated with them.

Egg masses of the Patagonian squid Doryteuthis (Amerigo) gahi attached to giant kelp (Macrocystis pyrifera) in the Magellanic channels of the sub-Antarctic ecoregion in southern South America is documented for the first time. Of seven egg masses observed between 2008 and 2011, one was taken to the laboratory to be analysed and photographed. Comprising long transparent capsules containing eggs, the masses were strongly attached to the stipes of M. pyrifera. This macroalgae is a potentially important economic resource due to its multiple industrial uses; this study shows that it also serves an important ecological role as a spawning substrate for D. gahi.

Glacial episodes of the Quaternary, and particularly the Last Glacial Maximum (LGM) drastically altered the distribution of the Southern-Hemisphere biota, principally at higher latitudes. The irregular coastline of Patagonia expanding for more than 84.000 km constitutes a remarkable area to evaluate the effect of Quaternary landscape and seascape shifts over the demography of near-shore marine benthic organisms. Few studies describing the biogeographic responses of marine species to the LGM have been conducted in Patagonia, but existing data from coastal marine species have demonstrated marked genetic signatures of post-LGM recolonization and expansion. The kelp-dweller limpet Nacella mytilina is broadly distributed along the southern tip of South America and at the Falkland/Malvinas Islands. Considering its distribution, abundance, and narrow bathymetry, N. mytilina represents an appropriate model to infer how historical and contemporary processes affected the distribution of intraspecific genetic diversity and structure along the southern tip of South America. At the same time, it will be possible to determine how life history traits and the ecology of the species are responsible for the current pattern of gene flow and connectivity across the study area. We conducted phylogeographic and demographic inference analyses in N. mytilina from 12 localities along Pacific Patagonia (PP) and one population from the Falkland/Malvinas Islands (FI). Analyses of the mitochondrial gene COI in 300 individuals of N. mytilina revealed low levels of genetic polymorphism and the absence of genetic differentiation along PP. In contrast, FI showed a strong and significant differentiation from Pacific Patagonian populations. Higher levels of genetic diversity were also recorded in the FI population, together with a more expanded genealogy supporting the hypothesis of glacial persistence of the species in these islands. Haplotype genealogy, and mismatch analyses in the FI population recognized an older and more complex demographic history than in PP. Demographic reconstructions along PP suggest a post-LGM expansion process (7.5 ka), also supported by neutrality tests, mismatch distribution and maximum parsimony haplotype genealogies. Migration rate estimations showed evidence of asymmetrical gene flow from PP to FI. The absence of genetic differentiation, the presence of a single dominant haplotype, high estimated migration rates, and marked signal of recent demographic growth, support the hypothesis of rapid post-glacial expansion in N. mytilina along PP. This expansion could have been sustained by larval and rafting-mediated dispersal of adults from northernmost populations following the Cape Horn Current System. Marked genetic differentiation between PP and FI could be explained through differences in their respective glacial histories. During the LGM, Pacific Patagonia (PP) was almost fully covered by the Patagonian Ice Sheet, while sheet coverage in the FI ice was restricted to small cirques and valleys. As previously recorded in the sister-species N. magellanica, the FI rather than represent a classical glacial refugium for N. mytilina, seems to represent a sink area and/or a secondary contact zone. Accordingly, historical and contemporary processes, contrasting glacial histories between the analyzed sectors, as well as life history traits constitute the main factors explaining the current biogeographical patterns of most shallow Patagonian marine benthic organisms.

Se realiza una revisión de las especies de anfípodos del género Hyalella en aguas continentales de la Patagonia, isla Tierra del Fuego, Reserva de la Biosfera de Cabo de Hornos e islas adyacentes (38-54°S). Esta zona austral presenta numerosos tipos de ambientes acuáticos continentales como lagos, humedales y arroyos, y las principales especies en ambientes bentónicos corresponden a anfípodos del género Hyalella. La bibliografía menciona la presencia de H. costera, H. chiloensis, H. falklandensis, H. franciscae, H. neonoma, H. patagónica, H. rionegrina y H. simplex. La distribución de estas especies concuerda con estudios biogeográficos sobre la presencia de especies endémicas y de amplia distribución en el sur de la Patagonia y zona subantárticas. A pesar de la presencia de especies depredadoras introducidas, sobre la base de la literatura, los anfípodos serían más abundantes debido a la presencia de materia orgánica particulada.This study reviews the amphipod species of the genus Hyalella in the inland waters of Patagonia, Tierra del Fuego Island, Cape Horn Biosphere Reserve, and adjacent islands (38-54°S). This southern zone has numerous kinds of continental water bodies such as lakes, wetlands, and streams, and the main species in benthic assemblages are amphipods of the genus Hyalella. The literature mentions the presence of H. costera, H. chiloensis, H. falklaidensis, H. franciscae, H. neonoma, H. patagonica, H. rionegrina, and H. simplex. The distribution of these species agrees with biogeographical studies about the presence of widespread, endemic species in southern Patagonia and the sub-Antarctic zone. In spite of the presence of introduced predatory species, the literature indicates that the amphipods are more abundant due to the presence of particulated organic matter.

Long-distance dispersal is one of the main drivers structuring the distribution of marine biodiversity. This study reports the first occurrence of Macrocystis pyrifera and Durvillaea antarctica rafts on the southwestern warm temperate coast of the Atlantic Ocean. Our results indicate that an extreme meteo-oceanographic event, characterized by a northward, displacement of cold sub-Antarctic oceanic waters driven by an extratropical cyclone, could account for these unusual occurrences. A niche model based on known current distribution and maximum entropy principle (MAXENT), revealed the availability of suitable habitats at lower latitudes, outside their actual distribution edges. The distributional boundaries, mainly driven by temperature and irradiance, suggest the existence of environmental suitability in warm temperate areas, as well as in the Northern Hemisphere off Atlantic and Asian coasts. These theoretical edges and respective environmental drivers agree with the physiological affinities of both species, supporting the hypothesis that these variables act as limiting factors for their occurrences in tropical or warmer areas. Emerging regions can function as refuges and stepping-stones, providing substrate with adequate habitat conditions for recruitment of propagules, allowing eventual colonization. Long dispersal events reinforce the need for an extensive discussion on selective management of natural dispersion, biological invasions, refuge mapping and conservation initiatives in a transnational perspective.

For the first time, the photosynthetic performance of field-grown macroalgae from the Magellan Strait was evaluated with respect to their photoadaptation in the field and acclimation potential to ultraviolet radiation. Five macroalgal species were collected in the eulittoral and the upper sublittoral: Ulva intestinalis, Porphyra columbina, Adenocystis utricularis, Desmarestia confervoides and D. ligulata. Photosynthesis vs. irradiance (P-I) curves of macroalgae cultivated in the laboratory under low white light intensities more than a week were used to assess the acclimation potential to irradiance conditions in the field. Both, photosynthetic parameters referred to as maximum electron transport rate (ETRmax) and light saturation points of photosynthesis (Ik) were species-specific and did not correlate with the position on the shore. Ik ranging between 80 and 215 μmol photons m-2 s-1 was indicative of moderate sun-adaptation in all studied species. The acclimation potential to UV-radiation was determined as the extent and the rates (m inh) of PSII inhibition (resulting from decreased maximum PSII-quantum yield (Fv/Fm)) after four hours of UV-exposure and as the subsequent rates of recovery (m ) in dim PAR. The results suggest that photosynthesis of each species during UV-exposure was transiently down regulated rather than damaged. Furthermore, no reductions in ETRmax were detected after 4 h exposure to UV-A and UV-B-radiation, and consequently the Calvin cycle could not be affected. Thus, Fv/Fm was a more sensitive parameter than ETRmax explaining the photosynthetic UV acclimation. Both, the rates of inhibition and the rates of recovery were not correlated with the morpho-functional groups of macroalgae nor to their vertical distribution. Thus, although the capacity to acclimate to UV-radiation varied among the different species, data suggest that such responses are based on metabolic adjustments or possibly photoprotective strategies. In conclusion and taking into account the light adaptation characteristics, all species collected in the midlittoral and the upper sublittoral at the Strait of Magellan seem to be well acclimated to UV-B doses occurring at their habitat, which might be a pre-requisite to withstand enhanced solar UV-B during ozone depletion or summertime irradiance conditions.La actividad fotosintética de algas provenientes del Estrecho de Magallanes fue medida por primera vez con el propósito de determinar su fotoadaptación en terreno y su potencial de aclimatación a la radiación ultravioleta. Cinco especies fueron recolectadas desde la zona eulitoral y sublitoral superior: Ulva intestinalis, Porphyra columbina, Adenocystis utricularis, Desmarestia confervoides y D. ligulata. Curvas de fotosíntesis versus irradiancia (P-I) medidas en algas cultivadas en el laboratorio por más de una semana fueron usadas para determinar la aclimatación potencial de las algas en su habitat. Tanto las capacidades fotosintéticas, determinadas a través de la tasa máxima de transporte de electrones (ETRmax), como los puntos de saturación de fotosíntesis (Ik) fueron especies-específicas, no observándose correlaciones con la distribución vertical de las algas. Valores de Ik con rangos entre 80 y 215 μmol m-2 s-1 indicaron una moderada adaptación a la luz en todas las especies estudiadas. La aclimatación a la radiación UV fue determinada a través del grado de disminución del rendimiento cuántico máximo del PSII (Fv/Fm) y su subsiguiente tasa de recuperación. Los resultados sugieren que bajo exposición a la radiación UV, la fotosíntesis no es dañada sino más bien regulada a la baja de forma transitoria. Además, no se observaron reducciones en ETRmax después de 4 h de exposición a la radiación UV-A y UV-B, y por consiguiente el ciclo de Calvin pudo no ser afectado. De este modo, Fv/Fm fue un parámetro mucho más sensitivo que ETRmax para explicar la aclimatación de fotosíntesis a la radiación UV. Tanto las tasas de inhibición como las tasas de recuperación no estuvieron correlacionadas con grupos morfofuncionales ni con la distribución vertical. Por tanto, aunque la capacidad para aclimatar a la radiación UV varió entre las diferentes especies, los resultados sugieren que estas respuestas están basadas en ajustamientos metabólicos o posiblemente estrategias fotoprotectoras. En conclusión, y tomando en cuenta las características de adaptación a la luz, todas las especies colectadas en el mesolitoral y sublitoral del Estrecho de Magallanes están bien aclimatadas a las dosis de UV-B que ocurren en su habitat, lo cual es un prerrequisito para tolerar aumentos de UV-B durante disminución de ozono o durante condiciones de alta radiación en verano.

Se realizó un estudio poblacional sinóptico en poblaciones de Macrocystis pyrifera considerando distintos regímenes de exposición al oleaje en el Estrecho de Magallanes. Para un mejor manejo y análisis de la información obtenida, se utilizó el análisis SIG (Sistema de Información Geográfica). Los estudios se llevaron a cabo en Bahía Porvenir (53º 18' S; 70º 24' W), Tierra del Fuego. Los muestreos se realizaron en transectas perpendiculares a la línea de costa, utilizándose tres cuadrantes de 1 m² de área. Se estudiaron dos poblaciones, una localizada en una zona expuesta al oleaje y la otra en una zona protegida. Entre ambas poblaciones se compararon los siguientes parámetros biológicos: biomasa húmeda (kg m-2), densidad de estipes m², porcentaje de individuos juveniles y adultos, y longitud de los individuos (m). La población situada al interior de la bahía presentó mayores valores de biomasa (p< 0,037), pero de igual forma una gran variabilidad entre individuos, marcándose diferencia dentro de una misma población, situación que no se observó en la población expuesta (p> 0,995), donde existió una uniformidad de relación a la biomasa por m². La utilización de SIG en estudios de esta naturaleza facilita la visualización, monitoreo y análisis de la distribución de las poblaciones, en contraste con los métodos utilizados convencionalmente en estudios de campo.This study was carried out on populations of Macrocystis pyrifera in the Strait of Magellan found under different regimes of wave exposure. To better manage and analyze the data, GIS analysis was used. The study was carried out in Porvenir Bay (53º 18' S; 70º 24' W), Tierra del Fuego Island. The samples were collected in transects perpendicular to the shore, using three quadrats of 1 m². Two populations were studied, one located in the area exposed to wave action and the other in a protected area. Between both populations the following biological parameters were compared: wet weight (kg m-2), density of stipes (m-2), percentage of juvenile and adult individuals, and the length of individuals (m). The population situated at the interior of the bay showed higher values of biomass (p< 0.037), but at the same time a large variability between individuals, large differences within the same populations was not observed in the exposed population (p> 0.995), where there was a uniformity with regards to biomass per m². Using GIS in the study of natural resources facilitates the visualization, monitoring and analysis of the populations, in contrast with methods conventionally used in field studies.

A ceramiaceous red alga, Ceramium stichidiosum J. Agardh was found for the first time in waters of Magellanic Strait, Chile. Thalli are usually epiphytic on other macroalgae such as Mazzaella laminarioides (Bory) Fredericq and Sarcothalia crispata (Bory) Leister. They have fully corticated axes with alternate to dichotomous branches, straight tips and six periaxial cells per each axial cell. This report extends the distribution limit of C. stichidiosum from the X Región de los Lagos (42º 58'S; 74º 19'W) to the XII Región de Magallanes (53°37'S; 70°59'W).La alga roja Ceramium stichidiosum fue encontrada por primera vez en aguas del Estrecho de Magallanes, Chile. Los talos son frecuentemente encontrados epifitando otras macroalgas como Mazzaella laminarioides (Bory) Fredericq y Sarcothalia crispata (Bory) Leister. Se caracteriza por presentar ejes completamente corticados y ramificaciones alternadas a dicótomas, ápices rectos y seis células periaxiales por cada célula central. Este reporte extiende el límite de distribución sur de C. stichidiosum desde la X Región de los Lagos (42º 58'S; 74º 19'W) hasta la XII Región de Magallanes (53°37'S; 70°59'W).