Los Alerces Research Articles

Trace Elements in Plankton, Benthic Organisms, and Forage Fish of Lake Moreno, Northern Patagonia, Argentina

The Northern Patagonian Andean range shared by Chile and Argentina has numerous glacial oligotrophic lakes protected in a series of National Parks. Recent baseline surveys indicated that concentrations in muscle and liver tissues from various fish species from across Nahuel Huapi and Los Alerces National Parks in Argentina were comparable or higher than similar fish species from other parts of the world. As a result, Lake Moreno, in Nahuel Huapi National Park, was chosen to investigate multiple element sinks, trends, and transfer in a representative Patagonia aquatic food web. The metals and metalloids Ag, As, Ba, Br, Cs, Co, Cr, Fe, Hg, K, Na, Rb, Se, and Zn were analyzed in three size plankton fractions, submerged macrophytes, biofilm, insect larvae, amphipods, decapods, gastropods (snails), annelids (earthworms), and forage fish. Except for nanoplankton (10–53 μm; small-celled algae, rotifers) and microplankton (53–200 μm; larger algae, ciliates, zooplankton nauplii), which share elemental compositional similarities, each taxon category had its own distinctive compositional pattern, revealed by principal component analysis. Nano- and microplankton tend to be relatively elevated in some metals, including As, Co, Cr, Fe, Hg, Zn, and Rb, followed by biofilm. Shredder-scrapper Trichoptera (caddisflies) have higher concentration of most of the studied elements than other insect larvae taxa, especially carnivorous Odonata (Anisoptera, dragonflies), which were associated with lower elemental contents. Those trends point to an overall tendency for biodiminishing element concentrations with trophic level in the benthos of Lake Moreno.

Dietary Overlap Between Huemul and Livestock in Los Alerces National Park, Argentina

ABSTRACT We evaluated the potential for interspecific competition for forage between huemul (Hippocamelus bisulcus) and livestock in Los Alerces National Park, Argentina. We studied winter diets based on microhistological analysis of fecal samples. Huemul selected herbs and shrubs, sheep showed preference for herbs and grasses, and cattle selected grasses. As predicted for small‐bodied species, huemul had a narrower dietary niche than did larger bodied cattle. Competition for forage would be more likely between huemul and sheep than between huemul and cattle. Our results might be helpful to managers in areas where domestic and wild ungulates live in sympatry in order to reduce competition, especially in wintering areas where food is scarce.

Selenium and Mercury in Native and Introduced Fish Species of Patagonian Lakes, Argentina

A survey of mercury (Hg) and selenium (Se) contents was performed in fish collected from lakes located in two National Parks of the northern patagonian Andean range. Two native species, catfish (Diplomystes viedmensis) and creole perch (Percichthys trucha), and three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), were caught from lakes Nahuel Huapi, Moreno, Traful, Espejo Chico, and Guillelmo belonging to Nahuel Huapi National Park and from lakes Futalaufquen and Rivadavia, Los Alerces National Park. In lake Moreno, fish diet items were analyzed and rainbow trout grown in a farm. Hg and Se were measured in muscle and liver tissues by instrumental neutron activation analysis. The average concentrations in muscle of Hg for all species, ages, and lakes are between 0.4 to 1.0 microg g(-1) dry weight (DW) with a few fish, mainly native, exceeding the United States Environmental Protection Agency health advisory for freshwater fish limited consumption, and from 0.8 to 1.5 microg g(-1) DW for Se. Average concentrations in liver of Hg in all species range from 0.4 to 0.9 microg g(-1) DW. Brown trout, the top predator in these lakes, showed the lowest average Hg burden in both tissues. Se concentrations in the liver of brown and rainbow trout, up to 279 microg g(-1) DW, are higher than those expected for nearly pristine lakes, exceeding 20 microg g(-1) DW, the threshold concentration associated with Se toxicity. These species show lower Hg contents in muscle, suggesting a possible detoxification of Hg by a Se-rich diet. Creole perch and velvet catfish livers have lower Se concentrations, with a narrower span of values (2.3 to 8.5 microg g(-1) and 3.3 to 5.5 microg g(-1) DW respectively).

Trace Elements as Fingerprint of Lake of Provenance and of Species of Some Native and Exotic Fish of Northern Patagonian Lakes

A survey of trace element contents in fish muscle and liver was performed in different lakes of two northern Patagonian national parks: Nahuel Huapi and Los Alerces national parks. The aim of the work was to obtain the first set of reference data on elements that are not liable to be disturbed by human activities and to identify compositional patterns related to the species and site of collection. The species studied are native creole perch and velvet catfish and exotic brown trout, rainbow trout, and brook trout. The elements analyzed are Br, Cs, Fe, Rb, Se, Na, and Zn. Trace elements in muscle of brown trout, rainbow trout, and creole perch showed statistical patterns that allow one to identify the national park of origin, as well as which of the lakes (Traful, Espejo Chico, or the Nahuel Huapi-Moreno system) of the Nahuel Huapi National Park from which they come. Contents in the liver provide similar but less clear patterns than contents in muscle; however, in some particular cases, they provide additional information. Trace element contents in muscle are also good indicators of the species collected within a lake.

The Spatial Configuration of Vegetation as an Indicator of Landscape Degradation Due to Livestock Enterprises in Argentina

1. The spatial configuration characteristics of vegetation were studied in order to develop ecological indicators of landscape degradation produced by livestock-related activities in Argentine subantarctic forest. This study was carried out in the Los Alerces National Park (LANP). 2. Two indices were devised. One, the 'D' index, was designed to express the variations in the vegetation types as related to the area occupied by each, the area-perimeter ratio, and the configuration regularity. The D index enabled determination of the degradation stage of different vegetation types, and the past and recent impact of livestock in a given area, providing some significant effects at landscape level could be detected. 3. The second index, the 'V' index, summarizes field information such as cover of annual species, cover of exotic species, cover of Rumex acetosella, total biomass and clonal biomass. This index was designed to evaluate the aptitude of the D index to monitor landscape degradation. 4. The identification and distribution of areas at risk, at a regional scale, facilitates the detection of those rural settlements that pose an imminent or potential hazard to the conservation of forest resources and require urgent changes in livestock management.

A survey of the Southern River otter Lutra provocax in Lanin, Puelo and Los Alerces National Parks, Argentina, and evaluation of its conservation status

A survey of the huillin or southern river otter Lutra provocax distribution was made in Lanin, Puelo and Los Alerces National Parks. Signs of otters were found at only 4 of 175 sites visited and all of these were in the south of Lanin. According to local people the species occurred in all three National Parks until 25–40 years ago. The main reason for the loss of huillines seems to be intensive hunting in the past. The geography and structure of the hydrological basins may help explain the lack of recolonisation by huillines from remnant populations. Signs of mink Mustela vison were found in both Puelo and Los Alerces and, while mink could not have been responsible for the decline of the otter, they may hinder re-establishment of otter populations. Human disturbance and tourism are not thought to have a significant impact on huillin distribution although remote refuges should be maintained, and our results show the importance of good coastal vegetation cover for permanent populations of the species. It is clear that the only important and permanent population of huillines in Argentina, between 39°S and 43°S, occurs at Nahuel Huapi National Park, which was surveyed in 1982–1983. This population is now of critical importance for the conservation of the species, which should retain its ‘endangered’ status in Argentina. Measures to implement huillin conservation are proposed.

The National Parks and Reserves of Argentina

The idea of national parks in Argentina started in 1903 with the gift of 7,500 hectares to the Argentine nation by Francisco P. Moreno, one of the earliest Argentine naturalists. But even this area, since greatly enlarged, did not receive legislative guarantee until 1934, after the late Dr. Hugo Salomon had repeatedly insisted that the integrity of national parks and reserves could only be assured by legal enactment. Fourteen areas, including three still only projected, are set aside as national parks or other forms of nature reserves in Argentina. Of the six northerly reserves all but Iguazú and Finca El Rey belong to the Chaco formation. All the southern reserves lie in the Cordillera of the Andes, except for Laguna Blanca in the Precordillera and the national monument Los Bosques Petri-ficados in the Patagonian plateau. Los Alerces, Nahuel Huapi, Lanin and Iguazú conform more or less to the requirements of national parks laid down by the Convention on Nature Protection and Wild Life Preservation in the Western Hemisphere 1940; this the Argentine Government has signed.