Beagle Channel Research Articles

Stable isotope spatial patterns for the Southwest Atlantic Ocean towards polar waters

Mapping stable isotope gradients (isoscapes) has become a powerful tool to understand and forecast the status and variability of marine ecosystems at different levels of ecological organization. To differentiate five marine areas from the Southwest Atlantic Ocean towards oceanic and polar waters, a key foraging area for many marine consumers, we built isoscapes at different spatial scales using carbon (δ13C) and nitrogen (δ15N) isotope values of phytoplankton, zooplankton and particulate organic matter in sediment. We analyzed the isotopic variability between marine areas in relation with oceanographic parameters (e.g. temperature, salinity) and geographical sampling site data (e.g. latitude, longitude). We collected samples during 6 oceanographic surveys conducted in spring and autumn between 2014 and 2019 at the Beagle Channel, the Atlantic coast of Tierra del Fuego and Burdwood Bank. We included also published isotopic data of zooplankton from two other oceanic areas (the Polar Frontal Zone and Polar Antarctic Peninsula waters) to construct large-scale isoscapes. We found that the marine areas analyzed have substantially different δ13C and δ15N baselines; some differences exist between spring and autumn but the general pattern of isotopic variability remains similar. Combining different biological components and spatial scale analysis, isotopic variability was found to be related to variables such as seawater temperature, depth, chlorophyll and nutrients. The generated data will enhance the efficacy of isoscapes in long-term monitoring initiatives that documents alterations in attributes and features across marine expanses. This is particularly pertinent to areas under legal protection, such as the oceanic Marine Protected Areas (MPAs) established in Argentine waters.

Phenolics and enzyme inhibitors from the Patagonian Empetrum rubrum berries

The small fruits from Empetrum rubrum were consumed by Native Americans in southern Patagonia. Two samples collected close to the Magellan Street and the Beagle channel in Tierra del Fuego were investigated. Three different extracts from the berries were analyzed, namely: methanol, phenolic-enriched (PEE) and ethyl acetate (EtOAc). The total phenolic, flavonoid, procyanidin and anthocyanin content of the extracts was determined. The effect of the extracts towards the metabolic syndrome-associated enzymes α-glucosidase, α-amylase and pancreatic lipase was assessed. In addition, the antioxidant capacity was measured using DPPH, FRAP, TEAC and ORAC assays. The composition of the extracts was determined by HPLC-MS/MS. Seventy-one compounds were identified for the first time in the berries, including 10 anthocyanins, 35 flavonoids, 11 phenylpropanoids and 13 procyanidins. The main compounds were quantified by HPLC-DAD. The extracts displayed strong activity as α-glucosidase inhibitors, with IC50 values ranging from 0.10 to 0.19 μg/mL for the PEE and 0.82–1.95 μg/mL for the EtOAc extracts, respectively. The results show high chemical diversity and differences with the boreal species E. nigrum.

Evaluation of fish biodiversity in the Beagle Channel (Tierra del Fuego-Argentina) using environmental DNA (eDNA) metabarcoding

The fish biodiversity of the Beagle Channel is insufficiently assessed, poorly managed, and threatened by exotic species. Novel, rapid, and cost-effective DNA-based approaches are valuable for understanding fish communities and biomonitoring in remote areas. Here, we evaluate the potential of environmental DNA (eDNA) metabarcoding for assessing fish species composition by analyzing water samples from three sites along the Beagle Channel in the extreme south of Argentina. Fish biodiversity was estimated using high-throughput sequencing of 12S rRNA amplicons. First, a local reference database was generated, including 12S sequences of 48 spp. In total, 31 environmental sequences were recovered, belonging to 11 families, 15 genera, and 22 species. Six eDNA sequences did not match any species in our database. Multivariate analyses indicated that the relative species composition differed significantly among the sampled sites. However, the most abundant species detected were consistent with historical data on fish species recorded in the sites sampled. In conclusion, eDNA metabarcoding is sensitive, reliable, and suitable for studies on the presence and distribution of fish species in the area. We further strengthen the potential of eDNA metabarcoding as a biomonitoring tool.

First catalogue of benthic marine macroalgae from glacier-influenced environments of the Beagle Channel, deposited in the new Sub-Antarctic Cryptogamic Herbarium (SCH) of the University of Magallanes

The environmental characteristics and geomorphological landscape in the sub-Antarctic Magellanic ecoregion underpin a biological diversity that evolved adapting to the microhabitats produced by these heterogeneous ecological conditions. The high level of endemism found in these biological communities is nowadays protected thanks to the creation of the Cape Horn Biosphere Reserve (CHBR), a natural laboratory at the southern end of the sub-Antarctic Magellanic ecoregion. Studies produced in this region offer a valuable knowledge of its biological, ecological and cultural facets in a state still scarcely impacted by anthropogenic activities. The retreat of glaciers present along the channels and fjords of the CHBR due to global climate change impacts the marine benthic and macroalgae communities hosted in these water bodies. European expeditions in the 18th and 19th centuries pioneered the works which provided our current knowledge about this subantarctic marine flora. Nevertheless, there is still a gap of taxonomic information of macroalgae diversity in the CHBR. To solve this gap, with support of the Cape Horn Internationional Center (CHIC), we created the Sub-Antarctic Cryptogamic Herbarium (SCH) hosted at the Antarctic and Sub-Antarctic Marine Ecosystems Laboratory (LEMAS), University of Magallanes. In 2020, the New York Botanical Garden indexed the SCH in its Index Herbariorum. This indexation granted by this world-renowned institution places the SCH's biological collection as the world's southernmost cryptogamic repository. As such, the SCH's botanical collection is currently the only gateway to the subantarctic ecosystem's biological legacy. The catalogue below provides information about the ecological and morphological characteristics of macroalgae deposited in the SCH, with particular focus on those species present in the CHBR. We identified 54 species. Among them 23 belong to the Rhodophyta division (43%), 19 species to the Chlorophyta division (35%), and 12 species to the Ochrophyta division (22%). In the context of rapid global change, involving increasingly threatened taxa due to human impact, baseline studies and records deposited at the SCH will provide an essential tool for assessing patterns of change and defining conservation practices to protect the rich biodiversity of these sub-Antarctic ecosystems.

THE GENUS PHILOBRYA J.G. COOPER, 1867 (BIVALVIA: PHILOBRYIDAE) IN PATAGONIA AND ADJACENT ANTARCTIC WATERS

The present study provides the first comprehensive revision of the species of Philobrya occurring in the Atlantic and Pacific coasts of Patagonia, the Strait of Magellan, the Beagle Channel, Isla de los Estados, Malvinas/Falkland Islands, Burdwood Bank, the Scotia Arc islands, the Antarctic Peninsula and the Bellingshausen Sea. Based on extensive collections, the identity of all species previously described from these areas is re-evaluated, and species are redescribed and figured, considering their ontogenetic variability. As part of this study, 15 taxa are recognized as valid, including Philobrya delli new species and another possibly new (Philobrya cf. barbata) species. Philobrya crispa Linse is considered a junior synonym of Philobrya blakeana (Melvill & Standen), and Philobrya antarctica (Philippi) is regarded as a nomen dubium. Neotypes for Philobrya sublaevis Pelseneer and Philobrya quadrata (Pfeffer) and a lectotype for Brachidontes (Hormomya) blakeanus are here designated. The clarification of the identity of P. sublaevis allows the revalidation of Philobrya limoides E.A. Smith and Philobrya orbiculata (Hedley), two species regarded as synonyms of P. sublaevis in the last 60 years. Furthermore, the synonymy of Philippiella Pfeffer, Stempelleria Clasing and Stempellia Odhner (non Léger and Hesse) with Philobrya is here confirmed.

Noble hosts: effects of internal parasites on the physiology of an intertidal brooding Sea-star

Introduction: The endoparasite Dendrogaster argentinensis infects the intertidal brooder sea star Anasterias antarctica. This sea-star species is in the highest trophic level in the Beagle Channel.
 Objective: To study the effects of parasitism by D. argentinensis on the fitness and reproduction of A. antarctica.
 Methods: Adults from the brooder sea-star were collected from the rocky intertidal of Ensenada Zaratiegui bay (54°51’ S & 68°29’ W), Argentina. Eight seasonal samplings were performed (four seasons in two years) in the upper and low intertidal. During dissection, parasites were removed, and all organs were extracted and weighed separately.
 Results: Dendrogaster argentinensis prevalence was the highest for the region (20.4 %). Parasitized individuals were more frequent in the low intertidal in all seasons, with a higher difference in summer, where it is likely that the higher temperatures and strong winds could make the upper intertidal more challenging for a parasitized individual. Five parasitized individuals were castrated. Generally, the gonadal (GI) and somatic (pyloric caeca, PCI; stomach, SI; body wall, WI) indexes were lower in parasitized than non-parasitized individuals.
 Conclusions: Parasitism by D. argentinensis negatively affects A. antarctica condition. It affects reproduction because it reduces the GI, and can also produce castration. The parasite competes for the sea-stars’ energetic resources, also decreasing the individual’s capacity for feeding (reduced stomach) and growth (reduced body wall).

Rapid change in plankton community structure during spring along the eastern Beagle Channel

In November 2019, a first joint Chilean–Argentinian research cruise was conducted along the eastern section of the Beagle Channel (BC). Here we present the results of the microbial plankton (2–200 μm cell size) abundance and composition analyses in relation to water masses and environmental variables, along a longitudinal transect characterized by contrasting hydrology. Plankton samples were analyzed within the photic zone along the channel and at two fixed stations during two short time series (a first one of 30 and a second one of 42 h). Results revealed a spatial zonation in the composition and structure of the plankton assemblages, related to bathymetry, water temperature and nutrient availability but also, a small-scale temporal variability due mainly to a rise in air and water temperature. The inner (westernmost) and outer sectors of the sampled area, west and east of Mackinlay Strait, respectively, were characterized by low plankton abundances, mostly dominated by nanoflagellates and some large diatoms. In contrast, the easternmost sector of BC, showed the highest total cell abundances, displaying a high diversity of small and large diatoms. Notably, in the inner BC (fixed station F1), chlorophyll-a (chl-a) concentrations almost doubled in 24 h, along with an increase in total plankton abundance and the dominance of small diatoms and nanoflagellates. Rapid changes in plankton relative abundance were also observed east to Mackinlay Strait. This highlights the large spatial (km) and temporal (hours to days) plankton heterogeneity along the eastern section of the BC, scales which should be considered for further sampling strategies.

Vertically distinct sources modulate stable isotope signatures and distribution of Mesozooplankton in central Patagonia: The Golfo de Penas - Baker Channel connection and analogies with the Beagle Channel

Vertically distinct sources modulate stable isotope signatures and distribution of Mesozooplankton in central Patagonia: The Golfo de Penas - Baker Channel connection and analogies with the Beagle Channel

Benthic foraminifera diversity from the south Atlantic Ocean: Tierra del Fuego and surrounding waters (South America).

The present study provides a detailed record of foraminiferal fauna and their ecological implications from surface sediments from Atlantic shelf of Tierra del Fuego, Argentina. The foraminiferal assemblage is mostly composed by four main hyaline genera, such as Cibicidoides, Cibicides, Globocassidulina and Buccella, which allowed the identification of three environmental zones. Zone 1 (Z1, 37 to 90 m) encompasses the eastern Beagle Channel and San Sebastian Bay. The assemblage reflected well-oxygenated marine inner shelf habitat, adapted to cold temperate waters. Zone 2 (Z2, up to 98.4 m), is located around the southern tip of Tierra del Fuego. The assemblage suggested a deeper marine environment, well oxygenated and with higher energy, probably due to the effect of tides and mainly by the influence of Malvinas Current. Finally, Zone 3 (Z3, up to 195 m) is located furthest from the Atlantic coast and the assemblage suggested an environment characteristic of outer shelf, with well-oxygenated cold waters and high-energy environment, reflected by species adhered to the substrate and coarse sediments. The distribution and abundance of certain species showed the influence of the Malvinas Current, while others evidenced a contribution of the Cape Horn waters.

SNP genotyping revealed a hybrid zone between Mytilus chilensis and M. platensis in southern South America (the Strait of Magellan, Isla Grande de Tierra del Fuego and the Falkland Islands).

Hybrid zones among mussel species have been extensively studied in the northern hemisphere. In South America, it has only recently become possible to study the natural hybrid zones, due to the clarification of the taxonomy of native mussels of the Mytilus genus. Analysing 54 SNP markers, we show the genetic species composition and admixture in the hybrid zone between M. chilensis and M. platensis in the southern end of South America. Bayesian, non-Bayesian clustering and re-assignment algorithms showed that the natural hybrid zone between M. chilensis and M. platensis in the Strait of Magellan, Isla Grande de Tierra del Fuego and the Falkland Islands shows clinal architecture. The hybrid zone can be divided into three different areas: the first one is on the Atlantic coast where only pure M. platensis and hybrid were found. In the second one, inside the Strait of Magellan, pure individuals of both species and mussels with variable degrees of hybridisation coexist. In the last area at the Strait in front of Punta Arenas City, fjords on the Isla Grande de Tierra del Fuego, and at the Beagle Channel, only M. chilensis and a low number of hybrids were found. According to the proportion of hybrids, bays with protected conditions away from strong currents would give better conditions for hybridisation. We do not find evidence of any other mussel species such as M. edulis, M. galloprovincialis, M. planulatus or M. trossulus in the zone.

Littoral meiofauna community structure in San Julián bay, Santa Cruz province, Argentina

For the first time, standing stocks and community structure have been reported in San Julián Bay, located in the Santa Cruz province, toward the southern tip of South America, within the sub-Antarctic region. The mean density of the meiofauna found was 6724 individuals/10 cm2, with a high dominance of nematodes (97.69%). Multivariate studies (PERMANOVA) revealed two distinct meiofauna assemblages: one, in an upper littoral salt marsh habitat and other, in a medium to low soft bare sediment. In the middle of the bay —in front of San Julián city— salt marsh habitats had the highest meiofaunal density, while bare sediments (medium-low levels) were the lowest. The mean average in the salt marsh area was 12246 individuals/10 cm2, with nematodes being dominant followed by oligochaetes as the subdominant taxa. The mean average in bare sediments (medium to low levels) was 3962 individuals/10 cm2, with nematodes as dominant and turbellarians, mastigophorans and maxillopodos (harpacticoid copepods) as subdominant taxa. Bare sediments related to Patagonian mussel’s populations presented the lowest meiofauna densities. Diversity showed an opposite trend, with a maximum in medium-low levels and a minimum in salt-marshes habitat. Richness in number of taxa ranged from 8 to 12, with a total number of 18 taxa. Despite dominance of nematodes in meiofauna assemblages is known, maximum density found in San Julián bay is much higher than previously found for estuaries from north and mid-latitudes littoral sandy beaches and in the nearby region of the Straits of Magellan and Beagle Channel and other sub-Antarctic and Antarctic sites. On the other hand, the number of meiofauna taxa (no nematodes) is low, and its community structure differs from what has been reported in previous studies. The meiofauna taxa assemblages provide evidence that, in salt-marsh habitats, they have the highest densities, but the lowest diversity when compared with lower levels. This is likely due to adaptation problems of meiofauna communities to a semi-terrestrial habitat.

EFECTOS DEL ETIL PARATHION Y DDYP SOBRE LARVAS DE CENTOLLA L IT H O D E S A N T A R C T IC U S JACQUINOT

The tox icity o f two pesticides, ethil - parathion (DNTP) and DDVP, organophosphorous insecticides extensively used in commercial formulations, was evaluated. Standard short-term exposure (108 h) static toxicity bioassays were performed with Southern king crab larvae (1 st. zoeae) obtained from ovigerous females of Beagle Channel (Ushuaia). Each 12 h lethal concentrations for the 50% of the individuáis (LC 50) were estimated by Finney’s formal probit analysis. Three speed computing methods were used furthermore, obtaining not unbiased estimates in case of asymmetrical tolerance distribution. The data show that the two pesticides are acutely toxic at low concentrations. The 96 h of exposure LC50 are 33 /ag/1 for DNTP and 3.6 mg/¡ for DDVP. The DNTP toxicity curve indicates that lethal treshold concentration is smaller than 33 p.g/1. Apparently treshold for acute lethality were not found for DDVP.Both drugs induced suble'thal effects. There are: swimming and appendix inactivity, expansión of the posterior carapace area and rigid abdomen or eontinuously twisted.

Magmatic arc evolution during the tectonic closure of the Rocas Verdes basin: insights from Cretaceous–earliest Paleocene intrusive rocks of Navarino Island (55°S), Fuegian Andes

Navarino Island is located in the southernmost part of the Fuegian Andes, south of the Beagle Channel. Its geological record documents the complex tectonic history of Tierra del Fuego, which includes the opening and closure of the Rocas Verdes basin, Cordillera arc collision and subsequent subduction processes. The geology of the island is mostly composed of the Cretaceous Yahgán Formation, a marine metasedimentary sequence, which is intruded by diverse plutons that are mostly exposed on the northwestern tip of the island. We herein present a new dataset that shows the presence of three Cretaceous–earliest Paleocene magmatic suites of active margin magmatism emplaced during the early stage of the Fuegian Andes, which are referred to as (1) the Dientes de Navarino Microdioritic Sills, a suite of pre-tectonic microdioritic sills that formed at c. 101–97 Ma; (2) the Castores Plutonic Complex, a series of pre- to syntectonic gabbroic to tonalitic plutons emplaced at c. 90–87 Ma, and (3) the Samantha Monzonites, a suite of isolated monzonitic to monzodioritic post-tectonic plutons that formed at c. 66–65 Ma. These distinct magmatic episodes are recognized by field observations, geological mapping, petrography and whole-rock geochemistry integrated with amphibole and biotite 40 Ar/ 39 Ar and U–Pb LA-ICP-MS. The geochemical compositions of these rocks are consistent with a continental arc setting that existed during the interval c. 101–65 Ma. Whereas the three pulses spatially overlap in Navarino Island, the arc magmatism shows a migration (or expansion) throughout the Late Cretaceous. The locus of the arc then migrates at c. 68–66 Ma towards the SW. We suggest that this trenchward migration at c. 68–66 Ma may be associated with a change in the subduction angle. The three Cretaceous–earliest Paleocene plutonic pulses recorded in Navarino Island formed during the early stages of development of the Fuegian Andes, and are pre-, syn- and post-tectonic with respect to a major compressional event caused by the collision and obduction of the back-arc Rocas Verdes oceanic floor. Supplementary material: A detailed dataset is available at https://doi.org/10.6084/m9.figshare.c.6675416

Examination of female energy dynamics and larval quality in the southern king crab, Lithodes santolla: Annual and interannual variability

The southern king crab, Lithodes santolla, constitutes one of the most important fishery resources in the Beagle Channel. In this study, we considered that Lithodes santolla females showing better physiological conditions may produce larvae with higher survival rates. To determine whether this quality may be useful for the enhancement of natural crab stocks, in the present study, we aimed to evaluate several biochemical parameters considering the size and ovigerous condition of the female parent. Primiparous (<80 mm CL) and multiparous (>80 mm CL) females, as well as ovigerous and non-ovigerous females, were evaluated. The patterns of accumulation or use of several macromolecules (glycogen, lipids and proteins) in different organs and development stages (midgut gland, ovary, eggs, larval stages and first crabs) were also evaluated along two reproductive seasons. The possibility that some females could be producing larvae with high survival was evaluated through the relationship between the female midgut gland and ovarian quality and the larvae. The results obtained indicate that the energy content of L. santolla females is highly variable according to the year, season, and month, and between primiparous and multiparous females. We hypothesized that this variability in the energetic quality is explained by differences in the female's diet: food availability or food quality during ovary maturation. Most of the energy reserves of the ovary are transferred to the offspring. The only female parent-brood connection is through the energy reserves transferred to the eggs 10 months earlier, and we hypothesize that this depends on the previous environmental and female feeding conditions during ovarian development. Moreover, zoea I larvae showed high variability in survival, not influenced by their own energy reserves or by the reserves of the eggs or the ovary. The physiological variables here analyzed did not allow identifying better females that can produce larvae with higher survival.

Seasonal and spatial variability of vertical particle flux along the Beagle Channel (Southern Patagonia)

The Beagle Channel is a 300-km long passage connecting the Pacific and Atlantic Oceans at ~55° S, where glaciers and river streams meet subantarctic waters. Here we present the first evaluation of downward fluxes and composition of particulate matter in the channel. Settling particle fluxes were collected by sequential sediment traps deployed in two contrasting areas: one in the western part of the channel, corresponding to an early post-glacial environment (site A) and a second, fully deglaciated, river-dominated environment (site B) in the eastern part. In early summer, fluxes at both sites are driven by organic matter produced in spring, with peak organic carbon fluxes of 289 and 413 mg C m−2 d−1 at sites A and B, respectively (C:N ratios of 7.3 and 6.3, respectively). During winter, the fluxes of fecal pellets, particulate organic carbon (POC) and particulate nitrogen (PON) were at their minimum. At site A (integrated annual POC flux of 74 g C m−2 yr−1), seasonality was weak and the flux was driven by ballast material (>95% of total particle flux) of glacial origin year-around, which also promotes the POC export. According to isotopic and taxonomic analyses performed at site A, the low seasonality in the organic component of the flux appears to be mainly related to autochthonous production of nano- and picophytoplankton during autumn and winter, later replaced by microphytoplankton fluxes during spring and summer. At site B, ballast material accounted for <60% of total mass flux and the POC flux showed a marked seasonality with a well-defined maximum after the spring phytoplankton bloom. Regarding the contribution of zooplankton, fecal pellets of appendicularians dominated at the western sector of the channel (site A) while Munida gregaria pellets dominated the flux at the eastern site (site B). This work is a contribution to ongoing efforts to unveil the physical and biogeochemical variables driving the biological carbon pump and the land-sea connections in this high-latitude ecosystem threatened by climate change.

High-resolution seismic characterization of post-glacial subaqueous mass movements in the Beagle Channel (Tierra del Fuego, Argentina): dynamics and tsunami hazard implications

High-resolution seismic characterization of post-glacial subaqueous mass movements in the Beagle Channel (Tierra del Fuego, Argentina): dynamics and tsunami hazard implications

Unusual occurrence of a mixed pod of false killer whales (Pseudorca crassidens) and common bottlenose dolphins (Tursiops truncatus) in the Beagle Channel (Argentina)

Unusual occurrence of a mixed pod of false killer whales (Pseudorca crassidens) and common bottlenose dolphins (Tursiops truncatus) in the Beagle Channel (Argentina)

Ancient Human Mitogenome of the Beagle Channel (Tierra del Fuego): An Argentine Collaborative Project

AbstractThe increasing use of massively parallel sequencing in the study of current and ancient human populations has enabled new approaches to bioanthropological and archaeological issues; however, its application to archaeological samples requires the use of technologies that are not easily accessible outside US and European research centers. To obtain an ancient mitogenome in Argentina, several institutions collaborated to apply massively parallel sequencing and bioinformatic methodologies on an enriched ancient DNA library of an individual from the Beagle Channel (dated 1504 ± 46 years BP), a region of particular interest for this line of inquiry. Phylogenetic reconstruction showed a close relationship with a Yamana from Navarino Island and an individual from Hoste Island (Chilean Antarctic Province): the three shared an ancestor who lived between 203 and 4,439 years ago. These three have mutations reported only for current and ancient individuals from the Beagle Channel, and their relationship with the rest of the D1g sub-haplogroups is unclear. The results obtained here are consistent with the reduction of mobility in the Fuegian archipelago around 4500 years BP that has been proposed based on archaeological evidence.

Active faulting in the Beagle Channel (Tierra del Fuego)

AbstractIn Tierra del Fuego, the Magallanes‐Fagnano Fault System (MFFS) accommodates a significant portion of the relative motion between the South America and Scotia plates. However, it remains unclear whether some of the deformation is partitioned southwards, along the Beagle Channel Fault System (BCFS). In this paper, high‐resolution seismic reflection profiles were used to identify fault‐related ruptures in the submerged Quaternary sediments of the Beagle Channel. Some faults reach the seafloor, affecting marine sediments, indicating they are Holocene in age. The correlation with outcrop data and lineaments mapped onshore suggests the post‐glacial reactivation of two structures: the E‐W striking BCFS and the NW‐SE‐trending Lapataia Fault Zone (LFZ). Whereas the BCFS displays along‐strike variation in throw, the LFZ shows significant normal displacements. These results imply that deformation occurs in a wider and more complex manner than previously thought and highlight the need for a thorough hazard assessment of the area.

Spatial distribution of zooplankton in the Beagle Channel in relation to hydrographic and biological drivers in different seasons

Spatial distribution of zooplankton in the Beagle Channel in relation to hydrographic and biological drivers in different seasons