Biogeography of microbial communities in high-latitude ecosystems: Contrasting drivers for methanogens, methanotrophs and global prokaryotes.

Methane-cycling is becoming more important in high-latitude ecosystems as global warming makes permafrost organic carbon increasingly available. We explored 387 samples from three high-latitudes regions (Siberia, Alaska and Patagonia) focusing on mineral/organic soils (wetlands, peatlands, forest), lake/pond sediment and water. Physicochemical, climatic and geographic variables were integrated with 16S rDNA amplicon sequences to determine the structure of the overall microbial communities and of specific methanogenic and methanotrophic guilds. Physicochemistry (especially pH) explained the largest proportion of variation in guild composition, confirming species sorting (i.e., environmental filtering) as a key mechanism in microbial assembly. Geographic distance impacted more strongly beta diversity for (i) methanogens and methanotrophs than the overall prokaryotes and, (ii) the sediment habitat, suggesting that dispersal limitation contributed to shape the communities of methane-cycling microorganisms. Bioindicator taxa characterising different ecological niches (i.e., specific combinations of geographic, climatic and physicochemical variables) were identified, highlighting the importance of Methanoregula as generalist methanogens. Methylocystis and Methylocapsa were key methanotrophs in low pH niches while Methylobacter and Methylomonadaceae in neutral environments. This work gives insight into the present and projected distribution of methane-cycling microbes at high latitudes under climate change predictions, which is crucial for constraining their impact on greenhouse gas budgets.

Past climate-driven range shifts structuring intraspecific biodiversity levels of the giant kelp (Macrocystis pyrifera) at global scales.

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.

Carrageenan from Gigartina skottsbergii: A Novel Molecular Probe to Detect SARS-CoV-2.

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.

Revised classification of the Cyanidiophyceae based on plastid genome data with descriptions of the Cavernulicolales ord. nov. and Galdieriales ord. nov. (Rhodophyta).

The Cyanidiophyceae, an extremophilic red algal class, is distributed worldwide in extreme environments. Species grow either in acidic hot environments or in dim light conditions (e.g., "cave Cyanidium"). The taxonomy and classification systems are currently based on morphological, eco-physiological, and molecular phylogenetic characters; however, previous phylogenetic results showed hidden diversity of the Cyanidiophyceae and suggested a revision of the classification system. To clarify phylogenetic relationships within this red algal class, we employ a phylogenomic approach based on 15 plastomes (10 new) and 15 mitogenomes (seven new). Our phylogenies show consistent relationships among four lineages (Galdieria, "cave Cyanidium", Cyanidium, and Cyanidioschyzon lineages). Each lineage is distinguished by organellar genome characteristics. The "cave Cyanidium" lineage is a distinct clade that diverged after the Galdieria clade but within a larger monophyletic clade that included the Cyanidium and Cyanidioschyzon lineages. Because the "cave Cyanidium" lineage is a mesophilic lineage that differs substantially from the other three thermoacidophilic lineages, we describe it as a new order (Cavernulicolales). Based on this evidence, we reclassified the Cyanidiophyceae into four orders: Cyanidiales, Cyanidioschyzonales, Cavernulicolales ord. nov., and Galdieriales ord. nov. The genetic distance among these four orders is comparable to, or greater than, the distances found between other red algal orders and subclasses. Three new genera (Cavernulicola, Gronococcus, Sciadococcus), five new species (Galdieria javensis, Galdieria phlegrea, Galdieria yellowstonensis, Gronococcus sybilensis, Sciadococcus taiwanensis), and a new nomenclatural combination (Cavernulicola chilensis) are proposed.

A combined microbial and biogeochemical dataset from high-latitude ecosystems with respect to methane cycle.

High latitudes are experiencing intense ecosystem changes with climate warming. The underlying methane (CH4) cycling dynamics remain unresolved, despite its crucial climatic feedback. Atmospheric CH4 emissions are heterogeneous, resulting from local geochemical drivers, global climatic factors, and microbial production/consumption balance. Holistic studies are mandatory to capture CH4 cycling complexity. Here, we report a large set of integrated microbial and biogeochemical data from 387 samples, using a concerted sampling strategy and experimental protocols. The study followed international standards to ensure inter-comparisons of data amongst three high-latitude regions: Alaska, Siberia, and Patagonia. The dataset encompasses different representative environmental features (e.g. lake, wetland, tundra, forest soil) of these high-latitude sites and their respective heterogeneity (e.g. characteristic microtopographic patterns). The data included physicochemical parameters, greenhouse gas concentrations and emissions, organic matter characterization, trace elements and nutrients, isotopes, microbial quantification and composition. This dataset addresses the need for a robust physicochemical framework to conduct and contextualize future research on the interactions between climate change, biogeochemical cycles and microbial communities at high-latitudes.

Methane and carbon dioxide cycles in lakes of the King George Island, maritime Antarctica.

Freshwater ecosystems are important contributors to the global greenhouse gas budget and a comprehensive assessment of their role in the context of global warming is essential. Despite many reports on freshwater ecosystems, relatively little attention has been given so far to those located in the southern hemisphere and our current knowledge is particularly poor regarding the methane cycle in non-perennially glaciated lakes of the maritime Antarctica. We conducted a high-resolution study of the methane and carbon dioxide cycle in a lake of the Fildes Peninsula, King George Island (Lat. 62°S), and a succinct characterization of 10 additional lakes and ponds of the region. The study, done during the ice-free and the ice-seasons, included methane and carbon dioxide exchanges with the atmosphere (both from water and surrounding soils) and the dissolved concentration of these two gases throughout the water column. This characterization was complemented with an ex-situ analysis of the microbial activities involved in the methane cycle, including methanotrophic and methanogenic activities as well as the methane-related marker gene abundance, in water, sediments and surrounding soils. The results showed that, over an annual cycle, the freshwater ecosystems of the region are dominantly autotrophic and that, despite low but omnipresent atmospheric methane emissions, they act as greenhouse gas sinks.

Organelle Genome Variation in the Red Algal Genus Ahnfeltia (Florideophyceae).

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.

Type specimen sequencing, multilocus analyses, and species delimitation methods recognize the cosmopolitan Corallina berteroi and establish the northern Japanese C. yendoi sp. nov. (Corallinaceae, Rhodophyta).

A partial rbcL sequence of the lectotype specimen of Corallina berteroi shows that it is the earliest available name for C. ferreyrae. Multilocus species delimitation analyses (ABGD, SPN, GMYC, bPTP, and BPP) using independent or concatenated COI, psbA, and rbcL sequences recognized one, two, or three species in this complex, but only with weak support for each species hypothesis. Conservatively, we recognize a single worldwide species in this complex of what appears to be multiple, evolving populations. Included in this species, besides C. ferreyrae, are C. caespitosa, the morphologically distinct C. melobesioides, and, based on a partial rbcL sequence of the holotype specimen, C. pinnatifolia. Corallina berteroi, not C. officinalis, is the cosmopolitan temperate species found thus far in the NE Atlantic, Mediterranean Sea, warm temperate NW Atlantic and NE Pacific, cold temperate SW Atlantic (Falkland Islands), cold and warm temperate SE Pacific, NW Pacific and southern Australia. Also proposed is C. yendoi sp. nov. from Hokkaido, Japan, which was recognized as distinct by 10 of the 13 species discrimination analyses, including the multilocus BPP.

Unveiling the unknown phylogenetic position of the scallop Austrochlamys natans and its implications for marine stewardship in the Magallanes Province.

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.

Temperature differently affected methanogenic pathways and microbial communities in sub-Antarctic freshwater ecosystems.

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.

A novel biodegradable film based on κ-carrageenan activated with olive leaves extract.

This research focused on the development of carrageenan based biodegradable films incorporated with olive leaves extract (OLE). OLE microbial inhibition and its total phenolics (TP) were evaluated. Carrageenan films were produced by casting technique and were characterized by thickness, water vapor permeability (WVP), color, mechanical properties, and infrared spectroscopy. In order to apply as lamb meat packaging, the antimicrobial effect of the films was investigated. Results showed that OLE inhibited E. coli growth and presented excellent TP (41.40 mgGAE/g). Thicknesses of the film with OLE (CAR-OLE) were approximately 28% higher than film without OLE. Addition of OLE reduced the WVP by approximately 54%. CAR-OLE was less resistant to breakage and more flexible showing darker color. FTIR showed interaction of carrageenan with OLE. Results revealed that CAR-OLE promoted 167-fold reduction in initial count of aerobic mesophiles indicating shelf-life extension of lamb meat and promising use as antimicrobial food packaging.

A new record of kelp Lessonia spicata (Suhr) Santelices in the Sub-Antarctic Channels: implications for the conservation of the "huiro negro" in the Chilean coast.

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.

Long-term persistence of the floating bull kelp Durvillaea antarctica from the South-East Pacific: Potential contribution to local and transoceanic connectivity.

Current knowledge about the performance of floating seaweeds as dispersal vectors comes mostly from mid latitudes (30°-40°), but phylogeographic studies suggest that long-distance dispersal (LDD) is more common at high latitudes (50°-60°). To test this hypothesis, long-term field experiments with floating southern bull kelp Durvillaea antarctica were conducted along a latitudinal gradient (30°S, 37°S and 54°S) in austral winter and summer. Floating time exceeded 200d in winter at the high latitudes but in summer it dropped to 90d, being still higher than at low latitudes (<45d). Biomass variations were due to loss of buoyant fronds. Reproductive activity diminished during long floating times. Physiological changes included mainly a reduction in photosynthetic (Fv/Fm and pigments) rather than in defence variables (phlorotannins and antioxidant activity). The observed long floating persistence and long-term acclimation responses at 54°S support the hypothesis of LDD by kelp rafts at high latitudes.

Analysis of the complete organellar genomes of the economically valuable kelp Lessonia spicata (Lessoniaceae, Phaeophyceae) from Chile.

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.

Next-generation sequencing yields the complete organellar genomes of kelp Lessonia flavicans (Lessoniaceae, Phaeophyceae) from the Sub-Antarctic ecoregion of Magallanes, Chile.

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.

Trophic ecology of two co-existing Sub-Antarctic limpets of the genus Nacella: spatio-temporal variation in food availability and diet composition of Nacella magellanica and N. deaurata.

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.

Initial report on methane and carbon dioxide emission dynamics from sub-Antarctic freshwater ecosystems: A seasonal study of a lake and a reservoir.

The sub-Antarctic Magellanic ecoregion is a part of the world where ecosystems have been understudied and where the CH4 cycling and emissions in lakes has not ever been reported. To fill that knowledge gap, a lake and a reservoir located at 53°S were selected and studied during three campaigns equally distributed over one year. Among the parameters measured were CH4 and CO2 emissions, as well their dissolved concentrations in the water column, which were determined with high spatial resolution. No ebullition was observed and the CH4 flux ranged from 0.0094 to 4.47mmolm-2d-1 while the CO2 flux ranged from -22.95 to 35.68mmolm-2d-1. Dissolved CH4 concentrations varied over more than four orders of magnitude (0.025-128.75µmolL-1), and the dissolved carbon dioxide ranged from below the detection limit of our method (i.e., 0.15µmolL-1) to 379.09µmolL-1. The high spatial resolution of the methods used enabled the construction of bathymetric maps, surface contour maps of CH4 and CO2 fluxes, and transect contour maps of dissolved oxygen, temperature, and dissolved greenhouse gases. Overall, both lakes were net greenhouse gas producers and were not significantly different from temperate lakes located at a similar northern latitudes (53°N), except that ebullition was never observed in the studied sub-Antarctic lakes.

Genetics, Gene Flow, and Glaciation: The Case of the South American Limpet Nacella mytilina.

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.

Chiroptical characterization of homopolymeric block fractions in alginates.

Homopolymannuronic and homopolyguluronic fractions were obtained by partial hydrolysis of the alkaline extracts from the brown seaweeds Ascoseira mirabilis, Desmarestia menziessi, Desmarestia ligulata and Durvillaea sp. collected in southern Chile. Full characterization of the fractions was achieved by FT-IR and NMR spectroscopy. Total hydrolysis with 90% formic acid of the homopolymeric fractions allowed the preparation of mannuronic and guluronic acids. Both monomers and homopolymeric fractions as neutral salts were studied by CD and ORD. Chiroptical spectra were similar in shape and sign to those previously published in the literature, and permitted to assign D configuration to mannuronic acid and L configuration to guluronic acid in alginic acids. Specific optical rotation values at the sodium D light for the homopolymannuronic (∼-100°) and homopolyguluronic (∼-110°) acid fractions were obtained. These high negative values are proposed for the assignment of the absolute configuration of monomers in homopolymeric fractions.

Differential responses of tetrasporophytes and gametophytes of Mazzaella laminarioides (Gigartinales, Rhodophyta) under solar UV radiation.

The effects of solar UV radiation on mycosporine-like amino acids (MAAs), growth, photosynthetic pigments (Chl a, phycobiliproteins), soluble proteins (SP), and C and N content of Mazzaella laminarioides tetrasporophytes and gametophytes were investigated. Apical segments of tetrasporophytes and gametophytes were exposed to solar radiation under three treatments (PAR [P], PAR+UVA [PA], and PAR+UVA+UVB [PAB]) during 18 d in spring 2009, Punta Arenas, Chile. Samples were taken after 2, 6, 12, and 18 d of solar radiation exposure. Most of the parameters assessed on M. laminarioides were significantly influenced by the radiation treatment, and both gametophytes and tetrasporophytes seemed to respond differently when exposed to high UV radiation. The two main effects promoted by UV radiation were: (i) higher synthesis of MAAs in gametophytes than tetrasporophytes at 2 d, and (ii) a decrease in phycoerythrin, phycocyanin, and SPs, but an increase in MAA content in tetrasporophytes at 6 and 12 d of culture. Despite some changes that were observed in biochemical parameters in both tetrasporophytes and gametophytes of M. laminarioides when exposed to UVB radiation, these changes did not promote deleterious effects that might interfere with the growth in the long term (18 d). The tolerance and resistance of M. laminarioides to higher UV irradiance were expected, as this intertidal species is exposed to variation in solar radiation, especially during low tide.