Northern Patagonian Coast Research Articles

Spatial distribution of lower intertidal decapods on the northern Patagonian coast (Pelluhuín beach, Puerto Montt, 41°29′S, Chile)

Abstract The decapod fauna of Chile’s intertidal shores in inner seas south of 40°S has relatively low diversity because of the presence of low-salinity waters due to river inputs and glacial smelts; nevertheless it is possible that the same decapods species are found as on the northern and central Chilean coast. The aim of the present study was to determine the spatial distribution patterns of lower intertidal decapods on Pelluhuín beach, a small beach south of Puerto Montt, northern Patagonia. Data were obtained by counting individuals from random quadrants in intertidal zones; to the obtained data the variance/mean ratio was applied to determine if the specimens have a random, aggregate or uniform distribution, which are associated with Poisson, negative binomial or positive binomial distributions respectively. Among four of the species observed, a uniform distribution (positive binomial) was reported, and one had an aggregated pattern (negative binomial). The sites correspond to rocky shores in semi-urban zones, and in a protected zone. Our results on the interpretative probabilistic models of aggregated distribution patterns agree with previously reported observations of decapods on the rocky shores of Northern and Central Chile, specifically in interpretative probabilistic models.

Explaining the diversification of lithic projectile points from the northern Patagonian coast (Argentina) during the Holocene using phylogenetic and comparative methods

Using phylogenetic and comparative methods, this paper explores how the interrelations between size and shape defined the evolutionary trajectories of lithic projectile point of the northern coast of Patagonia (Argentina) during Middle and Late Holocene. The results indicate the existence of an allometric relationship between shape and weight of the points that led their diversification process, at least in part. Also, variations in weight appear to have affected the likelihood of generating new morphological variants, suggesting the existence of restrictions on design that acted in different ways along the temporary span studied in this paper.

Hydrochemical, Isotopic, and Geophysical Studies Applied to the Evaluation of Groundwater Salinization Processes in Quaternary Beach Ridges in a Semiarid Coastal Area of Northern Patagonia, Argentina

Quaternary sea level fluctuations have led to the development of beach ridges on many South Atlantic coasts. The objective of this paper was to asses from lithological, hydrochemical, isotopic, and geophysical studies the salinization processes affecting groundwater stored in Pleistocene and Holocene beach ridges of the northern Patagonian coast. A hydrogeomorphological characterization of the area was performed using digital elevation models, the interpretation of satellite images, and field studies. Vertical electrical soundings were performed on transects running perpendicular to beach ridges in order to define variations in the freshwater-saltwater interface position. The salinity, chemistry, and stable isotopes of the groundwater were analyzed. The results demonstrated that the groundwater salinization of Pleistocene ridges responds to processes associated with the geological-geomorphological evolution of the area. The cementation of these surface sediments limits rainwater infiltration, which consequently prevents the development of freshwater lenses. This suggests that saline water is the result of ancient marine ingressions. Freshwater lenses develop in Holocene beach ridges; however, slight water salinization is detectable in the most populated areas as a result of intensive exploitation. The data provided are useful for freshwater resource prospection along the arid coast of Patagonia, where beach ridge deposits abound and populations experience serious drinking water supply problems.

DOMOIC acid, Pseudo-nitzschia spp and potential vectors at the base of the pelagic food web over the northern Patagonian coast, Southwestern Atlantic

Plankton composition and density, and domoic acid (DA) content in microplankton and mesozooplankton were assessed over the northern Patagonian coastal shelf in late austral summer 2013. Maximum values of DA in these two plankton fractions as well as maximum densities of both Pseudo-nitzschia spp. (mainly the toxigenic P. australis) and DA potential vectors were only detected on the southern coast of San Matías Gulf and the eastern coast of Valdés Peninsula. In this zone, waters were characterized by low temperature, high nitrate, and intermediate values of silicic acid and phosphate. Based on the high association between the DA values recorded and the values of either micro- and mesozooplankton grazer density or biomass, we inferred that DA transfer from Pseudo-nitzschia spp. occurred largely through the small copepods Euterpina acutifrons and Oithona nana, Calanidae nauplii and Calanidae copepodites, Noctiluca scintillans, and euphausiid developmental stages. Small copepods, Calanidae nauplii and copepodites, and cladocerans were proposed as novel DA vectors although this suggestion requires experimental confirmation. This study provides the first lines of evidence of the co-occurrence of Pseudo-nitzschia spp. blooms with DA production and accumulation in mesozooplanktonic grazers at the base of the food web and of the environmental and oceanographic conditions that seem to favor these processes over the northern Patagonian shelf coasts.

New genetic diversity for endangered bottlenose dolphin subspecies along the Argentine coast

Abstract This study analyzed mtDNA sequences of two bottlenose dolphin subspecies found along the northern Patagonian coast, Argentina: the endangered Tursiops truncatus gephyreus and the data deficient Tursiops truncatus truncatus. Three haplotypes were recovered from nine samples. The most frequent haplotype represented the coastal morph, also two haplotypes showing falcate dorsal fin, a characteristic describing the oceanic morph. This finding suggests that both morphs may exist in sympatry in Argentina. Furthermore, sampling was extended beyond the species’ previously known range, including individuals as far as seven hundred kilometers to the south. Therefore, new genetic data, despite being preliminary, hint at an unexpectedly higher genetic diversity of matrilines than previously anticipated.

Presence of Cyrtograpsus angulatus Dana, 1851 (Decapoda, Brachyura) on the Chilean northern Patagonian coast

The marine fauna of decapod Crustacea, in all its diversity, can be negatively affected as a result of environmental changes, both on a local or a global scale. The present study aims to report the existence ofCyrtograpsus angulatusDana, 1851, on the northern Patagonian coast, while concurrently describing some other decapod species associated with the various habitats.C. angulatuswas originally described from the Chilean coast north of 36°43′S, and the present study revealed its presence down to 44°S. In the estuaries investigated,C. angulatusis the exclusive decapod species, whereas in coastal zones it can coexist with other species of marine decapods. Nevertheless, according to the null model of the co-occurrence of species, the species associations tested did not show any structured pattern. Some ecological and biogeographical patterns in relation to this species and its biocoenoses are discussed.

GENETICS AND DEMOGRAPHY OF KELP GULLS IN PATAGONIA

The Kelp Gull (Larus dominicanus), a common seabird in coastal Patagonia, has recently increased in overall abundance and distribution, creating some concerns for the protection and conservation of other native, threatened species. We combined genetic and demographic data of four large Kelp Gull colonies distributed along 1800 km of the northern Patagonian coast of Argentina to further understand patterns of population growth and migration of the species. DNA analysis of variable intron sequences of two separate genes (myelin proteolipid protein, β-fibrinogen) revealed similar intra-colony levels of DNA sequence diversity. Pairwise FST comparisons revealed significant differentiation of the northernmost colony, Islote La Pastosa, from the two southern colonies, Punta Tombo and Isla Vernaci Sudoeste (p < 0.05). Indirect estimates of gene flow suggest significant mixing among colonies (Nm > 6). Demographic estimates revealed that Islote La Pastosa showed an increase in the number of breeding individuals over time (λ = 1.075), representing an area of potential population expansion. This is consistent with previous studies that have suggested that the demographic connectivity among Kelp Gull colonies in Patagonia may follow a source-sink dynamics, where growth rates of growing colonies are fuelled by the immigration of individuals from nearby colonies. The observed pattern also reflects the overall expansion of the species in the Patagonian region. This study suggests that proper management strategies for the Kelp Gull should take into account the genetic and demographic dynamics of this species.

The evolution of projectile points and technical systems: A case from Northern Patagonian coast (Argentina)

In this paper we present the results of the phylogenetic analysis of projectile points dating from the Middle-Late and final Late Holocene recovered from different sites along the coast of San Matías Gulf (Río Negro province, Argentina). In order to study the evolution of weapon systems we have used maximum parsimony phylogenetic reconstruction and tree based comparative methods. This allowed us to explore different evolutionary models addressing the technical systems used in the area.The results suggest the existence of a robust phylogenetic signal that gradually evolved into at least two technical systems. One of the most important results however, was the evidence of a certain morphological continuity. In turn this suggests that, rather than a direct replacement, there was an adaptation of propellant-type weapons towards the bow and arrow.We concluded that this pattern of metric and morphological continuity might be related to transitional forms between the different technical systems, with design types used in both systems. There would have been a degree of experimentation so as to produce performance effective projectile points, this would have occurred in a framework of trial and error in a context of low risk.

Taphonomic evaluation of penguin (Spheniscidae) remains at a shell-midden on the northern coast of Patagonia (San Matías Gulf, Río Negro, Argentina)

Archaeological deposits in continental Patagonia that allow an adequate discussion of the exploitation of seabirds, particularly the Spheniscidae, are scarce. In many cases, characteristics of bone assemblages seem to indicate the natural incorporation of penguin bones into archaeological contexts. This suggests it is not always possible to support the argument that the presence of penguin remains indicates, a priori, consumption by humans. The Bajada de los Pescadores (BP2) site, San Matías Gulf (Río Negro, Patagonia, Argentina), provides a case study that allows the origin of these deposits and their contents to be evaluated in terms of the exploitation of penguins and other marine resources by hunter-gatherers during the Late Holocene. This paper discusses the origin of the archaeological deposit, its context, and the agents involved in its formation. The analysis used criteria formulated previously in the framework of actualistic taphonomic observations, with the aim of assessing the integrity of this sample, and evaluating its contribution towards clarifying the role of penguins in the subsistence of people on the northern Patagonian coast.

Paravortex panopea n. sp. (Platyhelminthes: Rhabdocoela) on clams from the northern Patagonian coast, Argentina: pathogeny and specificity

Abstract During a histopathological survey of the geoduck, Panopea abbreviata (Hiatellidae), and the razor clam, Ensis macha (Pharidae), in northern Patagonian gulfs (Argentina), turbellarian worms were found in the intestine lumen. In this work, we described a new species of Paravortex (Platyhelminthes, Graffillidae). We collected the hosts by scuba diving and dissected alive for studying the turbellarians. In this new species, the pharynx continues in a short esophagus and the latter in a saccular intestine. Gravid specimens have from 2 to 8 twin embryos in the parenchyma. A short penis papilla arises from the seminal vesicle and the gonopore presents a strong sphincter. This species resembled P. nicolli Szidat, 1965, which was described paraziting Mytilus edulis platensis in Buenos Aires, Argentina. The new species can be differentiated from P. nicolli mainly by the presence of a penis papilla and a sphincter between genital atrium and gonopore. This turbellarian species was significantly more prevalent in geoducks (28 %, n = 210) than in razor clams (6 %, n = 480) (KW, p < 0.0001). For both host species, no evidence of direct physical damage caused by turbellarians was observed.

Helminths of the kelp gull, Larus dominicanus, from the northern Patagonian coast

The helminth community of Larus dominicanus (Charadriiformes) is reported from Península Valdés, on the Patagonian coast, Argentina. From March 2000 to April 2004, 29 kelp gulls were collected and dissected. All the birds were parasitized by at least 2 of 18 parasite species: 2 cestodes (1 Tetrabothriidae, 1 Dilepididae), 10 trematodes (2 Echinostomatidae, 3 Microphallidae, 2 Gymnophallidae, 1 Philophthalmidae, 1 Dicrocoeliidae, 1 Diplostomatidae), 4 nematodes (2 Acuariidae, 1 Capillaridae, 1 Anisakidae), and 2 acanthocephalans (Polymorphidae). The mean intensity was 3,204 parasites per host, and all helminths parasitized the gastrointestinal tract or associated glands. The helminth community of L. dominicanus on the Peninsula Valdés coast seems to be richer than those reported by previous authors in other localities in Argentina. This could be due to a greater diversity in prey items available. Nine species are recorded for the first time from the kelp gull and seven species are recorded for the first time from Argentina.

The reproductive cycle of the red octopus Enteroctopus megalocyathus in fishing areas of Northern Patagonian coast

The reproductive cycle of Enteroctopus megalocyathus was studied based on monthly diving surveys carried out between July 2004 and June 2007 over fishing areas at San José and Nuevo gulfs (Northern Patagonian coast, Argentine). Spermatophore production and storage and ovary-weight increase followed the trend in sea bottom temperatures, and reached maximum values at the beginning of summer. Mature males were found from mid winter onwards, while a low proportion of females showed spermatangia attached to the distal oviducts from mid spring to mid summer when they attained advanced maturity stages. A low frequency of spawning activity was observed during summer and winter months. There were no significant seasonal differences in the sex ratio. Total body weight (BW) and dorsal mantle length (ML) at 50% maturity were estimated at 1072 g and 135.4 mm for males and at 1613 g and 158.5 mm for females. Potential fecundity ranged from 1429 to 6427 oocytes and the number of fully developed spermatophores storage ranged from 1 to 13. Both, potential fecundity and number of spermatophores were significantly correlated with BW and ML. Although mating and breeding can occur in fishing areas, our results suggest that they are most likely to take place in sites deeper than the fishing grounds. This pattern is discussed considering the temperature-regulated aspects of cephalopods reproduction and the local oceanographic processes occurring in the gulfs.

A survey of larval digeneans in the commonest intertidal snails from Northern Patagonian coast, Argentina

AbstractOver a two-years period, a survey was carried out in order to increase the knowledge of digeneans parasitising the commonest intertidal gastropods on the Patagonian coast, Southwestern Atlantic Ocean. A total of 4,725 gastropods were examined. Six species of digenean parasitising four snail species were found; four of them were registered for first time: Maritrema sp. 1 (Microphallidae) in Crepidula dilatata (Calyptraeidae), Parorchis sp. (Philophtalmidae) and sporocyst of Renicolidae in Trophon geversianus (Muricidae), and Diphterostomum sp. (Zoogonidae) in Buccinanops globulosus (Nassariidae). Two other species were found in Siphonaria lessoni (Siphonariidae): Maritrema sp. 2 and Hemiuridae. One snail species, Tegula patagonica (Trochidae) was not parasitised. These gastropods act as first intermediate host, and C. dilatata, S. lessoni and B. globulosus also frequently host metacercariae within the sporocyst. Overall prevalences varied from 0.16% of Diphterostomum in the intertidal population of B. globulosus to 33.45% of Maritrema sp. 1 in C. dilatata.

Primeros registros de arte rupestre en el litoral de Patagonia Septentrional chilena

The presence of rock art in the northern Patagonian coast is reported for the first time. The findings correspond to caves on the Vilcun hill (42o49`S-72o50`O), Santa barbara, close to the modern city of Chaiten and are both paintings and engravings. No surface archaeological materials were found.

Do native grazers from Patagonia, Argentina, consume the invasive kelp Undaria pinnatifida?

The invasive kelp Undaria pinnatifida (Phaeophyceae, Laminariales) was first reported in Golfo Nuevo in 1992 and since then it has spread widely over more than 170 km, all along the northern Patagonian coast, Argentina. Field observations in the region have indicated the potential role of invertebrate grazers, like the sea urchins Arbacia dufresnii and Pseudechinus magellanicus and the gastropod Tegula patagonica, in controlling algal density. Laboratory experiments were conducted to ascertain whether, and if so, to what extent these grazers actually feed on the algae. The studied sea urchins fed on the alga, whereas the snail scraped off biofouling adhered to its surface. Higher densities of grazers were observed on the kelp during summer and might be attributed to increasing in metabolism with increasing temperature, and degradation of blades and sporophylls, which possibly increase their palatability.

The Weights of Chipped Stone Points: A Clue to Their Functions

The Weights of Chipped Stone Points: A Clue to Their Functions