Northern Patagonian Lakes Research Articles

Machine learning modeling of lake chlorophyll content in a data scarce region (Northern Patagonia, Chile): insights for environmental monitoring

Among South America, Chile is highly susceptible to climate change impacts on water resources and ecosystems. Chilean lakes and rivers have been impacted by anthropogenic activities leading to chemical pollution and eutrophication. Concerns for conservation and management of water resources has led to the current development of secondary norms for environmental quality of Northern Patagonian lakes. In this context, we analyze historical limnological databases (1979-2022) for these lakes utilizing Random Forest (RF) models. After filtering, we retained data for 11 lakes including key variables of: dissolved oxygen, electric conductivity, transparency, temperature, pH, total nitrogen, total phosphorus and chlorophyll-a. This dataset yielded robust results, accurately predicting chlorophyll-a content. Furthermore, we added lake geomorphological parameters, enhancing the performance of the model. Our study demonstrates the need to improve long-term monitoring programs, optimizing environmental data recording and decreasing costs. We conclude that the studied lakes generally maintain their oligotrophic characteristics, however further analysis suggests that these lakes are more sensitive to nitrogen loading than phosphorus. Our results highlight the need to implement adaptative management plans at the watershed level to regulate anthropogenic nitrogen contamination (from agriculture, pisciculture and urbanization). The features selected by RF, coupled with the assessment of historical trophic state variation, allow the establishment of permissible concentration thresholds for major nutrients and other sentinel parameters, informing the development of regulations such as the secondary norms for environmental quality. Lastly, the enhanced performance of RF modeling when including geographical parameters unveils the need to standardize and integrate geographical data in monitoring practices.

Роль бактерій як основи пелагічних харчових ланцюгів в ультраоліготрофних північних патагонських озерах: міні-огляд

The northern Patagonian lakes are located in the South American Andes between 38—41° of Argentina and Chile. In their original stage, these lakes were described as ultraoligotrophic due the presence of perennial native forest that avoided the nutrients inputs from surrounding basin. The first studies described low phytoplankton abundances, but in recent studies, the presence of mixotrophic ciliates has been reported that may be a basis on trophic webs under the ultraoligotrophic status. They can graze on heterotrophic bacteria and nannoflagellates and can also do photosynthesis. Under the ultraoligotrophic status, the bacteria would have the basis on pelagial food webs because these would be grazed by zooplankton and mixotrophic ciliates. Nevertheless, when the lakes have a transition from oligotrophy to mesotrophy, although the bacterial biomass increases, they would not have an exclusive role because of a complex interaction between phytoplankton and grazer zooplankton.

First fecundity observations on female copepods from three northern Patagonian lakes (Pellaifa, Calafquén, Panguipulli; Chile)

Abstract The crustacean zooplankton in Chilean Patagonian lakes is characterized by a marked dominance of calanoid copepods when under an oligotrophic status. The aim of the present study was to analyse the number of eggs and the relation of that feature with the total length of females of calanoid and cyclopoid copepods reported in three northern Chilean Patagonian lakes. The calanoid copepods found were Boeckella gracilipes in Lake Pellaifa and Tumeodiaptomus diabolicus in the lakes Panguipulli and Calafquén, whereas the cyclopoid Mesocyclops araucanus was found in the lakes Pellaifa and Calafquén. For calanoid copepods, high egg numbers were found and thus also a high value for the ratio of egg number per female length in Lake Panguipulli, whereas for M. araucanus a high value was found in Lake Pellaifa. These differences would presumably be associated with community structure, specifically predator-prey relationships and possibly other interactions, as, e.g., potential interspecific competition.

Observations on crustacean zooplankton in two connected north Patagonian lakes (Calafquén-Pellaifa, 39°S, Chile)

Abstract The northern Patagonian lakes (38-41°S), are characterized by their location in catchment basins that have been markedly altered through human intervention. In those basins, the original native, perennial forest has been replaced by towns, villages and agricultural zones. The present study was done in two interconnected north Patagonian lakes (the lakes Calafquén and Pellaifa), where the species composition of the crustacean zooplankton community was compared, using a biodiversity index and size-structure null models. The results denoted the presence of marked differences between both sites, Calafquén lake being inhabited by less species and in general showing lower abundances of individuals in comparison to Pellaifa lake. The results of size-structure null models revealed the absence of interspecific competition for both sites. The obtained results would agree with similar observations for other northern Patagonian lakes in Argentina and Chile.

An update on the global stressors and constraints affecting Daphnia populations in large Chilean Patagonian lakes (39-51°S)

The zooplankton communities in Chilean Patagonian lakes (39-51°S) are characterized by the low presence of daphniid cladocerans, i.e., under conditions of the usual native oligotrophy and, thus, low mineral concentrations. Nevertheless, from some northern Patagonian lakes (39-41°S) a marked abundance of daphniids has been reported. According to the literature, as well as evidence from field observations, the main causes of such marked changes in the local zooplankton assemblages would be changes in phytoplankton quantity and quality, providing increased energetic resources for the zooplankton communities. Such energetic resources might decrease the stress effects of low calcium concentrations, as calcium constitutes an essential nutrient for caparace formation in Daphniidae; in addition, energetic expenses needed to perform vertical migrations due to fish predation and exposure to natural ultraviolet radiation can better be provided for. This is a markedly different situation compared to North Patagonian lakes, where daphniid abundance and number of species are related only to phytoplankton quantity and quality in term of phosphorus/nitrogen molar ratio.

Culture of native species of zooplanktonic crustaceans: Tumeodiaptomus diabolicus (Brehm, 1935) from northern Patagonian lakes (Chile)

The inland waters of Chile hold endemic species of crustaceans, and these habitats are threatened at present due to pollution as a result of human activities. Until now, the environmental studies performed have not considered native species for evaluating environmental risks. The aim of the present study was to do a first culture experiment with the freshwater copepod Tumeodiaoptomus diabolicus that inhabits central and northern Chilean Patagonian lakes. The copepods were cultured under two dietary regimes, i.e., a diet of microalgae and an artificial diet. The experiment was conducted over 12 days, and the maximum growth was obtained with the artificial diet. The present results would agree with similar results obtained for pseudodiaptomid copepods, that are massively used for aquaculture activities. In accordance with the obtained results and published data in the literature, T. diabolicus culture could be relatively easily done, and would thus qualify as an assay for investigating environmental conditions.

Use of null models to explain crustacean zooplankton assemblages in North Patagonian lakes with presence or absence of mixotrophic ciliates (38°S, Chile)

Zooplankton assemblages in Northern Patagonian lakes are characterized by a low species richness and a marked dominance of calanoid copepods. The aim of the present study was to do a null model analysis to explain the composition of the zooplankton assemblages in two North Patagonian lakes. The first aspect to which null model analysis was applied was species co-occurrence, and there the model indicates that the species associations found are not random. The second aspect was niche sharing, and that analysis denotes that the species do not share niches. The third aspect tested was size overlap, and the model there denotes that the species have no size overlap. The results obtained indicate that the sites are relatively homogeneous, which would explain the random effect in species co-ocurrence, whereas the absence of niche sharing is due to the presence of different energetic resources at both sites investigated, which would separate the niche of each species from those of other faunistic elements. Finally, the third application of the null model analysis demonstrates that there is no competition among the species reported upon herein.

Subaqueous landslides at the distal basin of Lago Nahuel Huapi (Argentina): Towards a tsunami hazard evaluation in Northern Patagonian lakes

The May 22nd, 1960 Valdivia earthquake, Chile (Mw 9.5) triggered a series of subaqueous mass-wasting processes (debris flows and slides) in Lago Nahuel Huapi (Argentina), generating a tsunami-like wave that hit the coasts of San Carlos de Bariloche. Aiming to provide a first preliminary insight into tsunami hazards for the lakeshore communities, in this paper we identify and characterize the subaqueous landslides at the populated distal basin of the lake. Swath bathymetric and seismic profiling surveys were carried out and high-resolution digital elevation models were derived from these data to perform a landslide inventory map. A series of morphometrical parameters (including the landslide area, the volume of displaced materials and the run-out distance, among others) were estimated upon selected events. The results indicated that landslide activity at the distal basin of Lago Nahuel Huapi has been concentrated in the vicinity of Bariloche (massive landslide triggered by the 1960 earthquake) and within steep delta fronts where the slope failures typically initiate at shallow waters (9–11m depth). The sliding mass frequently travels basinward along a great distance (≥1000m). At the delta fronts, the volume of material removed by landslides can reach ~40×104m3, leaving scar areas of up to 13m thick. The periodic occurrence of rotational–translational mass movements initiating at the upper edge of the delta fronts, with vertical displacements of the mobilized materials reaching ~200m, probably represents a potential tsunami hazard for the nearby populated coasts.

Respuesta de diatomeas a eventos de incendios en las cuencas de dos lagos de Patagonia Norte, Chile: Análisis del registro sedimentario

Response of diatom to fire events in watersheds of two Northern Patagonian lakes, Chile: Analysis of the sedimentary record Forest fires can generate changes in aquatic ecosystems, mainly due to increased nutrients by increased erosion and runoff. However, contradictory results were observed in the biological response of these ecosystems, depending on the environmental conditions in each region. The aim of this study was to asses, using a paleolimnological study, the response of diatoms communities in Thompson and Frio lakes located in the Region of Aysen (Northern Patagonian) to wildfires as a consequence of colonization of the area. The results indicated that the Thompson Lake presented significant changes in the composition of diatom assemblages due to fire and a post-fire recovery period. However, the Frio Lake showed no significant changes in response to the fire period, neither in diatom species composition nor in community parameters such as the absolute abundance, richness, diversity, dominance and the ratio between planktonic/benthonic diatoms. Such differences between lakes could be attributed, in order of importance, to the trophic status existing before the occurrence of fires, the watershed slope and the lake volume.

Use of null models to explain crustacean zooplankton assemblages in waterbodies of Alerce Andino National Park (41°S, Chile)

The zooplankton assemblages in deep, mostly oligotrophic northern Patagonian lakes are characterized by low species numbers and a marked dominance of calanoid copepods. In the present study, data collected in field work on six water bodies located in Alerce Andino National Park (41°S) were analysed using the Jaccard Index of community similarity and a co-occurrence of null models, and such with the aim of determining potential regulating factors for the observed crustacean assemblages, using a presence-absence matrix. A significant correlation between species number and surface area was found. The null model used species co-occurrence, and the basis of this model is that the species associations observed are random. The results revealed the absence of regulating factors and indicate that the sites are relatively homogeneous, with low species numbers and similar plankton assemblages at all studied sites. This finding is in accordance with similar descriptions for zooplankton assemblages in other Chilean Patagonian lakes.

Use of Null Models to Explain Crustacean Zooplankton Assemblages in Northern Patagonian Lakes (Chile) with and Without Mixotrophic Ciliates

AbstractThe zooplankton assemblages in deep, mostly oligotrophic northern Patagonian lakes are characterized by a low species number and a marked dominance of calanoid copepods, as well as often by the presence of large mixotrophic ciliates (Stentor). In the present study, data collected in field work on four northern Patagonian lakes were analysed using co-occurrence of null models, with the aim to determine potential regulating factors for the observed crustacean and mixotrophic ciliate assemblages, using a presence-absence matrix. The null model uses species co-occurrence, and the basis of this model is that the species associations observed are random. The results revealed the absence of regulating factors and indicate that the sites are relatively homogeneous, with low species numbers, and similar plankton assemblages at all study sites. This finding coincides with similar descriptions for zooplankton assemblages in other Chilean Patagonian lakes.

Aquaculture, non‐native salmonid invasions and associated declines of native fishes in Northern Patagonian lakes

Summary1. Even though intensive aquaculture production of salmonids in lakes occurs in many locations around the world published studies on the survival and reproductive success of escaped cultured salmonids in freshwater ecosystems are not common. A recent expansion of aquaculture in Chile has led it to become the world’s second largest producer of cultured salmonids.2. We document the recent history of escaped and self‐sustaining salmonid populations over a wide spatial scale and a long temporal scale in Chilean Patagonian lakes. Our hypotheses are that salmonid density in lakes will be higher where there is intensive aquaculture, due to greater numbers of potential escapees. Secondly, if non‐native salmonids have adverse impacts on native fishes, increases in the abundance of non‐native species should be associated with decreases in relative abundance of native species. Finally, if the first two hypotheses are correct we anticipate that diets of salmonids may show evidence of predation on native fishes, diet overlap with native species, and evidence of the influence of feed from aquaculture operations in the diets of salmonids and native fishes.3. We sampled six lakes with gill nets from 1992 to 2001. Our results show that the relative abundance of free‐living salmonids is closely related to the level of fish farming production. Salmonids are the top predators and in lakes with fish farming the main prey item is native fishes. The relative abundance of native fishes has decreased, most likely due to predation by salmonids.4. Our study contributes to the understanding of the effects of non‐native salmonids in oligotrophic lakes, and it provides a starting point to judge the establishment of new fish farming sites in lakes around the world.

Presumptive environmental effects on body shape of Aplochiton zebra (Pisces, Galaxiidae) in northern Patagonian lakes

The family Galaxiidae exhibits a marked tendency toward morphological variation, particularly in characteristics related to feeding and caudal propulsion. The body shape of Aplochiton zebra from six Andean water bodies was examined and related to diet and to environmental characteristics such as transparency and predation risk. Although adults and larger juveniles showed no inter-lake dependence in their morphology, smaller juveniles (SL < 40 mm) did show differences in eye diameter and dorsal fin length. Aplochiton zebra juveniles from Lake Puelo, where transparency showed the minimum value, have the largest eyes; those from Lake Futalaufquen with high transparency values have the smallest eyes. No clear relationship to predation risk was established. In Futalaufquen, Puelo and Rivadavia lakes the relationship between the principal components for morphology and for diet indicates, at least in part, that variation in body shape – and particularly traits related to swimming ability – could be related to diet.

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.

Cold-temperate lakes of South America: do they fit northern hemisphere models?

Comparative studies on cold-temperate lakes on a worldwide basis have often neglected this lake category in the southern hemisphere. This study describes and analyzes the main limnological characteristics of 54 Argentine Patagonian lakes located between 38° and 55° S latitude. By principal components analysis of summer data, three basic types of Patagonian lakes were identified: Andean, ecotone and plateau. These groups were distributed across a gradient defined mainly by trophic and edaphic characteristics, and secondarily by lake morphometry and climatic factors. Most lakes deeper than 50m showed summer stratification, with a mean thermocline depth of 38 m. Thermocline depth showed a direct correlation with latitude. The best single predictors of thermocline depth were fetch and lake area. Thermocline depth was not only deeper than predicted by northern hemisphere models, but also deeper than in other southern hemisphere lakes of similar surface area located in Chile and New Zealand. Surface water temperatures were correlated with latitude. Only northern Patagonian lakes showed significant differences in surface water temperatures on both sides of the Andes. The best single predictors of chlorophyll were Secchi disk depth and mean depth. Models from the literature overestimated chlorophyll concentrations for Argentine Patagonian lakes, particularly under eutrophic conditions. We suggest that cold-temperate lakes in Argentina differ in their thermal regime from northern hemisphere lakes at equivalent latitudes, owing to the marked oceanic influence on the southern hemisphere land mass, together with the strong and persistent westerly winds. These features coupled with lower nutrient contents make the use of global models inadequate for Argentine cold-temperate lakes.

The Fishes of the Pacific Slope of South America and the Bearing of Their Distribution on the History of the Development of the Topography of Peru, Ecuador and Western Colombia

Next article FreeGeographical Distribution IIThe Fishes of the Pacific Slope of South America and the Bearing of Their Distribution on the History of the Development of the Topography of Peru, Ecuador and Western ColombiaCarl H. EigenmannCarl H. Eigenmann Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 57, Number 650May - Jun., 1923 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/279914 Views: 40Total views on this site Citations: 5Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:Fernando C. P. Dagosta, Mário C. C. de Pinna A history of the biogeography of Amazonian fishes, Neotropical Ichthyology 16, no.33 (Oct 2018).https://doi.org/10.1590/1982-0224-20180023Fernando C. P. Dagosta, Mário de Pinna Biogeography of Amazonian fishes: deconstructing river basins as biogeographic units, Neotropical Ichthyology 15, no.33 (Sep 2017).https://doi.org/10.1590/1982-0224-20170034R. M. McDowall Galaxias and Gondwana, (Jun 2010): 169–203.https://doi.org/10.1007/978-90-481-9271-7_8IVÁN ARISMENDI, DORIS SOTO, BROOKE PENALUNA, CARLOS JARA, CARLOS LEAL, JORGE LEÓN-MUÑOZ Aquaculture, non-native salmonid invasions and associated declines of native fishes in Northern Patagonian lakes, Freshwater Biology 54, no.55 (May 2009): 1135–1147.https://doi.org/10.1111/j.1365-2427.2008.02157.xR. M. McDOWALL The galaxiid fishes of South America, Zoological Journal of the Linnean Society 50, no.11 (Jun 2008): 33–73.https://doi.org/10.1111/j.1096-3642.1971.tb00751.x