Southern Tip Of South America Research Articles

Correction: Chondrichthyans from the southern tip of South America with emphasis on the marine protected area Namuncurá-Burdwood Bank: exploring egg nursery grounds

Correction: Chondrichthyans from the southern tip of South America with emphasis on the marine protected area Namuncurá-Burdwood Bank: exploring egg nursery grounds

Spatio-temporal variations in the mesozooplankton assemblages off Clarence Island, Magellan Strait, Chile

The seasonality in the light regime from subpolar regions impinges on limitations in the zooplankton dynamics. However, knowledge about seasonal variations in the mesozooplankton assemblages is limited in the southern tip of South America and around the Magellan Strait. Here, we studied the seasonal variation (summer vs. winter) and the spatial distribution (dozens of kilometers) of the mesozooplankton on the occidental shore of Clarence Island, Magellan Strait, Chilean Patagonia. A total of 69 taxonomic groups were identified in the samples, varying from 65 in summer (early March 2020) to 50 in winter (June 2020). Copepods numerically dominated the plankton, particularly Drepanopus forcipatus and Clausocalanus brevipes, although chaetognaths were also abundant in winter. The similarity in the composition was higher for samples collected in summer, whereas in winter there was larger variability in the zooplankton structure. At spatial scale, a large sound at the eastern coast of the island, Dyneley sound showed different composition of copepods compared to other channels both in summer and winter. Seasonal variation was five times larger than the spatial variation in the similarity of the mesozooplankton composition. Finally, higher richness and lower evenness were detected in austral summer, while the opposite was noticed in winter, with differences in alpha-diversity indices between seasons but not among locations. Understanding the drivers of seasonal variability in the zooplankton composition of this extreme ecosystem is essential for predictions of the impacts of salmon farming and climate change in southern Patagonia.

What if there is no further south to go: Assessing the vulnerability of Nacella species to climate change

In the current context of climate change, southern South America and the Southern Ocean are undergoing profound environmental transformations that impose challenges to marine species. Shifts in species distribution ranges will occur through expansions or contractions of the range edges. Invertebrates such as Nacella spp., that being template-cold water species, will be more vulnerable to increasing temperature and will therefore suffer range contraction as temperatures increase southward. To understand the future of this sensitive group of gastropods, the potential impact of future climate on the distribution ranges of six species of the genus Nacella was studied using ensemble ecological niche models and representative concentration pathway 8.5 scenarios for the years 2050 and 2100. The results indicate that all the species studied will undergo a shift in their distribution in response to the projected changes in climate with a decline in habitat suitability. Particularly, the species will lose suitable areas mainly in the northern edge of their current distribution. Nevertheless, the species may not change their distribution equally. Our study suggests that N. magellanica, N. clypeater, and N. concinna appear to exhibit vulnerability, albeit with potentially lesser impact. Nacella magellanica is the limpet that shows the least distribution change in 2100. Both species, N. clypeater and N. concinna, will move southward while the Antarctic species will expand their distribution to other Antarctic areas. The most significant impact is expected for three Magellanic species (N. deaurata, N. flammea, and N. mytilina), currently distributed across the southern tip of South America. With restricted geographical ranges, these species face increased vulnerability to habitat loss as they cannot migrate southward. This comprehensive analysis offers invaluable insights into how Nacella species could tackle the challenges of climate change. The emphasis on specific species' vulnerabilities and the differential impacts on their distribution enhances our understanding of the potential consequences of climate change in the studied region. Furthermore, it will aid in formulating effective conservation and management strategies to protect Antarctic and sub-Antarctic ecosystems.

How Racism and "Tropical Medicine" Built the Panama Canal.

At the turn of the 20th century, the physician William Gorgas led work that substantially mitigated mortality from mosquito-borne diseases among workers building the Panama Canal. The waterway launched the United States to political and economic superpower status by eliminating the need for risky maritime travel around the southern tip of South America, expediting exportation of US goods in international markets. Yet, as this article explains, innovations that curbed malaria and yellow fever were deeply rooted in racist foundations of capital and empire.

Niche partitioning among demersal marine fishes at the southern tip of South America

Niche partitioning among demersal marine fishes at the southern tip of South America

Floristic Similarities between the Lichen Flora of Both Sides of the Drake Passage: A Biogeographical Approach.

This paper analyses the lichen flora of Navarino Island (Tierra del Fuego, Cape Horn Region, Chile), identifying species shared with the South Shetland Islands (Antarctic Peninsula). In this common flora, species are grouped by their biogeographic origin (Antarctic-subantarctic endemic, austral, bipolar, and cosmopolitan), their habitat on Navarino Island (coastal, forest, and alpine), their morphotype (crustaceous, foliaceous, fruticulose, and cladonioid), and the substrate from which they were collected (epiphytic, terricolous and humicolous, and saxicolous). A total of 124 species have been recognised as common on both sides of the Drake Passage, predominantly bipolar, crustaceous, and saxicolous species, and with an alpine distribution on Navarino Island. The most interesting fact is that more than 30% of the flora is shared between the southern tip of South America and the western Antarctic Peninsula, which is an indication of the existence of a meridian flow of propagules capable of crossing the Antarctic polar front.

Decapods of the Southern Tip of South America and the Marine Protected Area Namuncurá–Burdwood Bank: A Nearshore–Offshore Comparison

The Marine Protected Area (MPA) Namuncurá−Burdwood Bank was created in 2013 to protect the benthic community. After five years of multidisciplinary research, it was reorganized, and a second, contiguous MPA Namuncurá−Burdwood Bank II was created. The objectives of this study were to evaluate the decapod assemblages in both the previous and current management zones and to compare them with the neighboring areas of southern South America. The decapod fauna was studied integratively by comparing captured species onboard scientific expeditions with online records. Our study showed that the original design of the MPAN−BB had the lowest decapod species richness. However, the constitution of a larger protected area, including the slope, increased the species richness, with unique records of Campylonotus arntzianus and Lithodes couesi. The MPA could be considered ecologically representative as it shares various species with the nearby areas (the Beagle Channel and the Atlantic). Furthermore, we theorize it could act as a “hub” for decapod species as marine currents provide the Burdwood Bank with new individuals from the west and disperse them northward to the Patagonian Shelf and eastward to the Scotia Arc. This result shows the great value of protecting this area, ensuring the conservation of the decapod fauna of southern South America.

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.

Shrub encroachment occurs near previously invaded areas in Patagonia (southern South America)

AbstractDuring the last century shrub encroachment has occurred in many arid and semiarid areas of the world. Patagonia is a large xeric territory located in the southern tip of South America, which has been grazed by sheep for more than a century. In many areas overgrazing led to vegetation change (shrub encroachment), which in turn reduced sheep carrying capacity and caused ranch abandonment. However, these changes in physiognomy did not occur everywhere, and even some authors did not find evidence that shrub encroachment is currently occurring. Our objectives were to determine if encroachment really happened in NE Patagonia and, in the case of confirming shrub encroachment, to evaluate if the increase in shrub density was spatially homogeneous. We used object‐based image analysis to evaluate shrub density and cover in aerial photographs taken in 1970 and 2018. In both dates, shrub density showed a clear contrast between two kinds of areas showing higher and lower density than was expected by chance. Shrub density and cover more than doubled between 1970 and 2018. This increase was concentrated in those areas with moderate or high densities of shrubs in 1970. Our results confirm the occurrence of shrub encroachment in NE Patagonia and demonstrate that it is currently concentrated near previously invaded areas. These findings have implications when defining protocols for monitoring shrub encroachment since monitors should focus on both areas that already have shrubs and areas that lack them.

Genomic insights into isolation of the threatened Florida crested caracara (Caracara plancus).

We conducted a population genomic study of the crested caracara (Caracara plancus) using samples (n = 290) collected from individuals in Florida, Texas, and Arizona, United States. Crested caracaras are non-migratory raptors ranging from the southern tip of South America to the southern United States, including a federally protected relict population in Florida long thought to have been isolated since the last ice age. Our objectives were to evaluate genetic diversity and population structure of Florida's apparently isolated population and to evaluate taxonomic relationships of crested caracaras at the northern edge of their range. Using DNA purified from blood samples, we conducted double-digest restriction site associated DNA sequencing and sequenced the mitochondrial ND2 gene. Analyses of population structure using over 9,000 SNPs suggest that two major clusters are best supported, one cluster including only Florida individuals and the other cluster including Arizona and Texas individuals. Both SNPs and mitochondrial haplotypes reveal the Florida population to be highly differentiated genetically from Arizona and Texas populations, whereas, Arizona and Texas populations are moderately differentiated from each other. The Florida population's mitochondrial haplotypes form a separate monophyletic group, while Arizona and Texas populations share mitochondrial haplotypes. Results of this study provide substantial genetic evidence that Florida's crested caracaras have experienced long-term isolation from caracaras in Arizona and Texas and thus, represent a distinct evolutionary lineage possibly warranting distinction as an Evolutionarily Significant Unit (ESU) or subspecies. This study will inform conservation strategies focused on long-term survival of Florida's distinct, panmictic population.

Stratospheric ozone, UV radiation, and climate interactions

This assessment provides a comprehensive update of the effects of changes in stratospheric ozone and other factors (aerosols, surface reflectivity, solar activity, and climate) on the intensity of ultraviolet (UV) radiation at the Earth’s surface. The assessment is performed in the context of the Montreal Protocol on Substances that Deplete the Ozone Layer and its Amendments and Adjustments. Changes in UV radiation at low- and mid-latitudes (0–60°) during the last 25 years have generally been small (e.g., typically less than 4% per decade, increasing at some sites and decreasing at others) and were mostly driven by changes in cloud cover and atmospheric aerosol content, caused partly by climate change and partly by measures to control tropospheric pollution. Without the Montreal Protocol, erythemal (sunburning) UV irradiance at northern and southern latitudes of less than 50° would have increased by 10–20% between 1996 and 2020. For southern latitudes exceeding 50°, the UV Index (UVI) would have surged by between 25% (year-round at the southern tip of South America) and more than 100% (South Pole in spring). Variability of erythemal irradiance in Antarctica was very large during the last four years. In spring 2019, erythemal UV radiation was at the minimum of the historical (1991–2018) range at the South Pole, while near record-high values were observed in spring 2020, which were up to 80% above the historical mean. In the Arctic, some of the highest erythemal irradiances on record were measured in March and April 2020. For example in March 2020, the monthly average UVI over a site in the Canadian Arctic was up to 70% higher than the historical (2005–2019) average, often exceeding this mean by three standard deviations. Under the presumption that all countries will adhere to the Montreal Protocol in the future and that atmospheric aerosol concentrations remain constant, erythemal irradiance at mid-latitudes (30–60°) is projected to decrease between 2015 and 2090 by 2–5% in the north and by 4–6% in the south due to recovering ozone. Changes projected for the tropics are ≤ 3%. However, in industrial regions that are currently affected by air pollution, UV radiation will increase as measures to reduce air pollutants will gradually restore UV radiation intensities to those of a cleaner atmosphere. Since most substances controlled by the Montreal Protocol are also greenhouse gases, the phase-out of these substances may have avoided warming by 0.5–1.0 °C over mid-latitude regions of the continents, and by more than 1.0 °C in the Arctic; however, the uncertainty of these calculations is large. We also assess the effects of changes in stratospheric ozone on climate, focusing on the poleward shift of climate zones, and discuss the role of the small Antarctic ozone hole in 2019 on the devastating “Black Summer” fires in Australia. Additional topics include the assessment of advances in measuring and modeling of UV radiation; methods for determining personal UV exposure; the effect of solar radiation management (stratospheric aerosol injections) on UV radiation relevant for plants; and possible revisions to the vitamin D action spectrum, which describes the wavelength dependence of the synthesis of previtamin D3 in human skin upon exposure to UV radiation.Graphical abstract

Chondrichthyans from the southern tip of South America with emphasis on the marine protected area Namuncurá-Burdwood Bank: exploring egg nursery grounds

Chondrichthyans from the southern tip of South America with emphasis on the marine protected area Namuncurá-Burdwood Bank: exploring egg nursery grounds

The Antarctic Peninsula: Argentina and Chile in the era of global change

ABSTRACT While Argentine-Chilean relations have long been swayed between cooperation and confrontation since their independence in the 19th century and a long-standing presence in Antarctica, the stretch between Tierra del Fuego to the Antarctic Peninsula stands as the closest lane (i.e. about 1,000 km) to any other continent. Despite their territorial dispute over islands on the fractured southern tip of South America and territorial claims on the Antarctic, their common diplomatic ground successfully defuses any potential geopolitical instability. Along with Chile and Argentina, British claims overlap in the Antarctic Peninsula, which establishes unique geopolitical conditions in the whole of Antarctica. In this context, scientific missions and growing tourist activities could transform the region into the Antarctic gateway. From potential mineral resources exploitation to the United States-China global competition, the South Atlantic area could become a strategic bridgehead in light of the brewing geopolitical shift during the 21st century. Considering that climate change and geostrategic conditions evolve somewhat quickly to transform the Western Antarctic area, this article aims to assess and comprehend how these external drivers may affect the two South American countries. Given the fact that Antarctica is part of their respective national narrative, how do Argentina and Chile intend to maintain their presence and protect their interest in these shifting conditions? What are the vectors for partnering with the world’s great powers, such as China? Ultimately, could this space become a choke point through the 21st century?

The impact of local and climate change drivers on the formation, dynamics, and potential recurrence of a massive fish-killing microalgal bloom in Patagonian fjord

Harmful algal blooms (HABs) in southern Chile are a serious threat to public health, tourism, artisanal fisheries, and aquaculture in this region. Ichthyotoxic HAB species have recently become a major annual threat to the Chilean salmon farming industry, due to their severe economic impacts. In early austral autumn 2021, an intense bloom of the raphidophyte Heterosigma akashiwo was detected in Comau Fjord, Chilean Patagonia, resulting in a high mortality of farmed salmon (nearly 6000 tons of biomass) within 15 days. H. akashiwo cells were first detected at the head of the fjord on March 16, 2021 (up to 478 cells mL−1). On March 31, the cell density at the surface had reached a maximum of 2 × 105 cells mL−1, with intense brown spots visible on the water surface. Strong and persistent high-pressure anomalies over the southern tip of South America, consistent with the positive phase of the Southern Annular Mode (SAM), resulted in extremely dry conditions, high solar radiation, and strong southerly winds. A coupling of these features with the high water retention times inside the fjord can explain the spatial-temporal dynamics of this bloom event. Other factors, such as the internal local physical uplift process (favored by the north-to-south orientation of the fjord), salt-fingering events, and the uplift of subantarctic deep-water renewal, likely resulted in the injection of nutrients into the euphotic layer, which in turn could have promoted cell growth and thus high microalgal cell densities, such as reached by the bloom.

Mercury and stable isotopes portray colony-specific foraging grounds in southern rockhopper penguins over the Patagonian Shelf.

Mercury pollution is a serious global environmental issue and the characterization of its distribution and its driving forces should be urgently included in research agendas. We report unusually high mercury (Hg) concentrations (>5μg/g) along with stable isotopes values in feathers of southern rockhopper penguins (Eudyptes chrysocome) from colonies in the Southwest Atlantic Ocean. We found a highly heterogenous prevalence of Hg throughout the study area and over a three-fold higher mean Hg concentration in southernmost colonies. Variation in Hg concentrations among colonies is primarily explained by site, rather than by trophic position. We provide further support to the existence of a Hg hotspot in the food web of the Patagonian Shelf and spatially restrict it to the southern tip of South America. Our findings highlight the need for regional and colony-based seabird conservation management when high local variability and plasticity in foraging habits is evident.

UNDERSTANDING THE THERMAL COAL MOVEMENTS FROM COLOMBIA TO CHILE THROUGH THE PANAMA CANAL USING LOGIT MODELS- LOOKING AHEAD

This study attempted to specify logit models for bulkers transporting mostly thermal coal from the East Coast of Colombia to Chile through the Panama Canal compared to the alternative route. The preliminary proposed predictors for the logit models included voyage cost variables and Canal's attributes. For the route choice of coal from the East Coast of Colombia to Chile, voyage cost factors such as Panama Canal cost, distance difference between Panama versus alternative route, post arrival of vessel to the next port and the maximum transit draft were important factors in this choice, as well as Panama Canal attributes such as vessel arrivals at the Panama Canal and the Panamax Plus requirement to transit the neopanamax locks. The route choice involved the Panama Canal and Cape Horn/Magellan Strait in the Southern tip of South America. This study analyzed coal traffic between October 1, 2016, and September 30, 2020, and briefly discussed the future of coal movements through Panama, given Chile's long term plans to generate electricity using renewanable energy sources and hydrogen. This paper is a contribution to the discrete choice literature and attempted to provide insights into route choice factors involving the Panama Canal, proposing new preliminary explanatory variables to better understand route choices that may apply in future Panama Canal studies. The study will be a contribution to the universal maritime coal transportation literature, and it is a continuation on research related to the Panama canal, particularly on route choices using AIS information.

A first look at the genetic diversity of Enteroctopus megalocyathus (Cephalopoda: Enteroctopodidae) captured by the king crab fishery in the south of Chile

AbstractThe octopus fishery in the southern tip of South America is based on Enteroctopus megalocyathus. It is fished on both the Atlantic and Pacific coasts, but no study has yet investigated the genetic variability of this octopus, which is frequently collected as bycatch. The genetic identity and diversity of E. megalocyathus from specimens caught by the king crab fishery along the Beagle Channel in southern Chile was investigated using sequences of three mitochondrial (16S rRNA, COI and COIII) and one nuclear (rhodopsin) markers. Homologous sequences from other Enteroctopodidae were included to determine the genetic variability of E. megalocyathus. In addition to E. megalocyathus, genetic data allowed us to identify Muusoctopus eureka, a species also collected by the king crab fishery. Enteroctopus megalocyathus was found to be genetically similar to E. zealandicus; the genetic distances between these two species were low, 0% (16S rRNA), 0.2% (COI) and 0.6% (COIII), which was also confirmed by the phylogenetic topologies, as both species are in the same clade. Enteroctopus megalocyathus has low levels of genetic diversity, as shown by haplotype and nucleotide diversity values for the mitochondrial markers (Hd = 0.06–0.32; π = 0.0001–0.003), and null diversity for the nuclear marker. All the haplotypic networks resolved with the mtDNA markers showed shared haplotypes among E. megalocyathus, E. magnificus and E. zealandicus. The low genetic diversity of E. megalocyathus can be attributed to both the geological history of South America and the life history of the species, rather than to the king crab fishery.

Locations for the best lidar view of mid-level and high clouds

Abstract. Mid-level altocumulus clouds (Ac) and high cirrus clouds (Ci) can be considered natural laboratories for studying cloud glaciation in the atmosphere. While their altitude makes them difficult to access with in situ instruments, they can be conveniently observed from the ground with active remote-sensing instruments such as lidar and radar. However, active remote sensing of Ac and Ci at visible wavelengths with lidar requires a clear line of sight between the instrument and the target cloud. It is therefore advisable to carefully assess potential locations for deploying ground-based lidar instruments in field experiments or for long-term observations that are focused on mid- or high-level clouds. Here, observations of clouds with two spaceborne lidars are used to assess where ground-based lidar measurements of mid- and high-level clouds are least affected by the light-attenuating effect of low-level clouds. It is found that cirrus can be best observed in the tropics, the Tibetan Plateau, the western part of North America, the Atacama region, the southern tip of South America, Greenland, Antarctica, and parts of western Europe. For the observation of altocumulus, a ground-based lidar is best placed at Greenland, Antarctica, the western flank of the Andes and Rocky Mountains, the Amazon, central Asia, Siberia, western Australia, or the southern half of Africa.

Crossing the Great Divide of Software Engineering

The Great Divide, the continental divide of the Americas, is a water divide extending from the Bering Sea to the southern tip of South America, the Strait of Magellan. The Great Divide separates the watersheds that drain into the Pacific Ocean from those river systems that drain into the Atlantic and Arctic Oceans. While there are many other examples of geological and geographical divides, the Great Divide stands out by its magnitude and higher peaks compared to other divides and its spanning multiple countries and continents. The divide does not necessarily define any different characteristics on either of its sides; it is simply a water passage dividing the Americas into two. To hiking enthusiasts, hiking the Great Divide is defined by its magnitude, typically easily taking up to five months. Due to its clear visualization power, the Great Divide has been a source of inspiration for metaphors in movies, albums, books, and topics when describing any conundrum with two sides.

Gametogenic cycle of the marine gastropod Trophon geversianus in a harsh Patagonian intertidal environment

ABSTRACT The edible marine gastropod Trophon geversianus shows a large geographic distribution along the southern tip of South America, inhabiting both rocky intertidal and shallow subtidal zones, with distinct behavioural responses to environmental stressful conditions (desiccation, temperature amplitude and high irradiation). Nevertheless, its reproductive biology has been poorly reported to date. We studied the gametogenic cycle of an intertidal rocky shore population from northern Patagonia (Argentina), in order to investigate the relation between gonadal changes and seasonal environmental variables. Mature individuals were taken monthly during an annual reproductive season and processed by standard histology procedures (haematoxylin and eosin). Adults of T. geversianus registered different gonadal maturation stages along the year, showing a marked seasonal variation without a resting period. The highest gamete evacuation season in both sexes was registered when the environmental stress was minimum (winter), while a greater number of individuals with gonads in proliferation and growth were predominant during maximum environmental stress (summer). The reproduction pattern presented an extended period of evacuation and a short phase of non-evacuation, associated to drastic seasonal environmental changes in the intertidal zone of Atlantic Patagonia. This information is useful to protect the resource and assure the sustainability of intertidal populations.