Nutrient Concentrations and Trophic State of Small Patagonian Andean lakes (original) (raw)
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Chemical composition and the nitrogen-regulated trophic state of Patagonian lakes
Limnologica - Ecology and Management of Inland Waters, 2007
Chemical composition and nutrient concentrations of 39 relatively poorly known Patagonian lakes (38-501S and from 701 to 681W) are described and analysed using principal component analysis (PCA). The general relationships between nutrients (total phosphorus, bioavailable phosphorus and dissolved inorganic nitrogen) and plankton biomass are examined.
Journal of Limnology, 2008
Eighteen small shallow lakes located in the Northern Patagonian Lake District, in southern South America, were sampled in 2001 and analysed for the main chemical variables (pH, conductivity, alkalinity, major ions and nutrients). The study lakes span a wide geographical and altitudinal range and belong partly to the Pacific and partly to the Atlantic watershed. The main aim of this study was to investigate the relationships between water chemistry and physical/geographical properties of these lakes. Secondly, the nitrogen content of the lakes was considered in detail, and results compared to those obtained in previous studies carried out in other remote areas of the globe (the Central Southern Alps in Italy, the Sierra da Estrela region in Portugal, the Svalbard Islands in the Arctic, the Khumbu-Himal region in Nepal, and the Terra Nova Bay area in Antarctica). In the Alps, lakes are characterised by markedly high nitrogen concentrations, manly as nitrate, due to the high inputs of nitrogen compounds from downwind sources like the Po Plain in Northern Italy. Conversely, lakes at remote locations such as the Andes, Antarctica and Himalaya are characterised by a low nitrogen content, mainly as organic nitrogen. This status is related to the limited atmospheric inputs of nitrogen affecting these regions.
Hydrobiologia, 2001
Fernando Pedrozo1, Liam Kelly2, Mónica Diaz1, Pedro Temporetti1, Gustavo Baffico1, Robert Kringel5, Kurt Friese6, Margarete Mages3, Walter Geller3 & Stefan Woelfl4 1CONICET-Universidad Nacional del Comahue, Quintral 1250, (8400) Bariloche, Argentina Fax: +2944-422111. ...
Nitrogen and phosphorus dynamics and retention in ecotones of Lake Titicaca, Bolivia/Peru
Hydrobiologia, 1993
We are studying present conditions and consequences of material movement from land to water in the Lake Titicaca basin, and how fluxes are affected by human activities. The principal objective of this research is to describe and explain the variability in the Andean Altiplano of (a) water, nutrient and sediment fluxes from land and (b) composition, nutrient limitation and other important features of nearshore lake communities, and compare the effects of different agricultural practices (especially traditional and modern) on these factors. We are focusing on a comparison of the impacts of two forms of agriculture in this region: ancient raised fields currently under rehabilitation, and flat pastures and fields, which are more common. Results of the first year of study indicate there is substantial variability in nitrogen and phosphorus dynamics in relation to ecotone complexity (simple vs. intermediate vs. complex), Raised field sites have the beneficial effect of reducing high available nutrient concentrations (nitrate and soluble reactive phosphorus) and sediment load (measured as turbidity) as the water passes through them enroute to the lake. Aquatic vegetation (algae and macrophytes) reflect well ambient total nitrogen and phosphorus concentrations. Experimental nutrient limitation bioassays indicate that nitrogen is the most important limiting nutrient, though there is important spatial variability within the landscape, and phosphorus as well as nitrogen can be limiting.
Limnology and trophic status of glacial lakes in the tropical Andes (Cajas National Park, Ecuador)
Freshwater Biology, 2016
1. The tropical Andes has a high density of glacial lakes that are situated in the high-altitude p aramo (3500-4500 m). Ecological information about such lakes is scant despite the fact that these lakes are an important source of water for drinking, irrigation and electricity generation and feed several major tributaries of the Amazon. In this study, we provide data on a survey of 31 lakes in Cajas National Park (Ecuador). Two of the lakes were monitored monthly during one year. In situ nutrient addition experiments were carried out in three of the lakes. 2. Seasonal monitoring in two lakes revealed a thermal stratification of the water column between October and June, with a small temperature difference between epi-and hypolimnion (2-3°C). Oxygen depletion of the hypolimnion towards the end of the stratification period indicated that no complete mixing of the water column occurred during stratification. There was no evidence of depletion of nutrients in the epilimnion or accumulation in the hypolimnion during stratification. There were also no clear seasonal changes in chlorophyll-a (Chl-a) concentration nor in phytoplankton community composition in the two lakes. 3. Inputs of dissolved organic carbon (DOC) from the vegetated catchment resulted in high DOC concentrations (median 2.9 mg L À1) compared to temperate mountain lakes. Water transparency was relatively low, with a median extinction coefficient for photosynthetic active radiation of 0.50 m À1 and for UV-B radiation of 10.13 m À1. Although the thermocline was deep and water transparency was low, estimates of the critical depth for photosynthesis were deeper than the mean water depth in all lakes, suggesting that phytoplankton was not light limited. 4. The phytoplankton community was dominated by chlorophytes (e.g. Oocystis), diatoms (small Cyclotella spp.) or small colonial cyanobacteria (Aphanocapsa, Merismopedia). The zooplankton community was either dominated by large cladocerans and cyclopoid copepods, or by the calanoid copepod Boeckella occidentalis. 5. Total concentrations of phosphorus (P) and nitrogen (N) were comparable to those in temperate mountain lakes (4-35 lg P L À1 and 162-758 lg N L À1) while Chl-a concentrations were in the lower range (<1 lg L À1). A large part of the total nutrient pool consists of dissolved organic N and P that appeared to have a low bioavailability to phytoplankton. The median seston N:P ratio of 44, a positive correlation between Chl-a and total P concentration, as well as nutrient addition assays carried out in three lakes all pointed to P limitation of phytoplankton.
Nutrient Export and Periphyton Biomass in a Stream-Lake Basin from the Patagonian Andean Region
2020
We characterized how land use influenced dissolved nutrients and periphytic algal biomass in an Andean basin from Northwest Patagonia. Nutrient export, especially dissolved inorganic nitrogen increased with human population density. However, no correlation between nutrient concentration and algal biomass was found, which could instead be limited by light availability. Our results suggest that local N-limited ecosystems are liable to eutrophication by increased demographic pressure and that alternative wastewater treatment strategies are necessary for sustainable growth.
Volcanic nutrient inputs and trophic state of Lake Caviahue, Patagonia, Argentina
Journal of Volcanology and Geothermal Research, 2008
The strategies for eutrophication control, remediation, and policy management are often defined for neutral to alkaline freshwater systems, as they are most suitable for human use. The influence of nutrients on eutrophication in a naturally-acidic lake is poorly known. The main purpose of the present work is to evaluate the significance of volcanic nutrients in the control of the trophic state of the acidic Lake Caviahue, located at North Patagonia, Argentina. Acidic water systems were most studied on artificial acidified lakes, such as mining lakes in Germany or pit lakes in the United States. Lake Caviahue received a very high P load (42-192 ton P/yr) and low N load (14 ton N/yr), mainly as ammonium with quite low N:P ratios (b 1.0). The magmatic activity of the Copahue volcano represents the main natural contribution of nutrients and acidity to the Lake Caviahue. The lake is oligotrophic in terms of CHLa. Neither the transparency nor the nutrient, dissolved or particulate, contents are to date representative of the trophic state of the lake. High P loads do not imply the eutrophication of the lake. We suggest that nitrogen and not phosphorus represents the key control nutrient in volcanically acidified lakes as TON was better related to CHLa observed (0.13-0.36 mg/m 3 ) in the lake. The pH increased around one unit (pH 2.0-3.0) during the last five years suggesting that the lake has not yet returned to a stable state.
Lake Caviahue: an extreme environment as a potential sentinel for nutrient deposition in Patagonia
Hydrobiologia, 2017
The objective of this study was to determine if extreme acidic Lake Caviahue could be used as a sentinel of atmospheric deposition hypothesizing that the physiological state of algae will be the indicator parameter. The lake was sampled from 2000 to 2015 in order to determine chlorophyll concentration, algae abundance and phytoplankton in vivo fluorescence as a way to evaluate the physiological state of algae. Development and physiological state of phytoplankton in different seasons was related to concentration and dynamics of nutrients in the lake. Laboratory experiments of Keratococcus rhaphidiodes to nitrogen (N) enrichment confirmed that an increase in nutrient content enabled a better physiological state of algae (e.g. higher chlorophyll per cell). Therefore, under the projected scenarios of climate change, the increase of available N through the increase in deposition and the increase of dissolved inorganic carbon, as consequence of higher atmospheric CO 2 , will compensate the natural nutrient constraints observed in the phytoplankton of the lake. The effect that the atmospheric CO 2 has on the DIC, and this on algal development, as well as the influence that N has on algal growth, make Lake Caviahue an interesting sentinel of nutrient deposition at regional level.
Nutrient cycling in Patagonian ecosystems
Ecología …, 1998
The knowledge on nutrient cycling in Patagonian ecosystems of Argentina is scarce. However, studies not directly focused on nutrient cycling provide relevant information about the mechanisms of nutrient conservation in the climatically different ecosystems of the region. Here, we identified indicators of litter decomposition and soil N mineralization rates of some representative species of the dominant plant functional groups along the wide precipitation gradient of Patagonia. Senescent leaves and litter of forest trees have higher C concentration and C/N ratio and lower N concentration than steppe shrubs. Within the tree life form, evergreen species have higher C/N ratio than deciduous species. Differences in N concentration between green and senescent leaves suggest a higher N use efficiency in forest trees than in steppe shrubs. Within the steppe, grasses have higher nutrient use efficiency than shrubs due to their higher C and much lower N, P and K content in senescent leaves and litter. Thus, we hypothesize the occurrence of (i) a gradient from nutrientconserving ecosystems in wetter sites (Andean-Patagonian forest) to relatively nutrient-rich (low nutrient use efficient) ecosystems in drier sites (Patagonian steppe), and (ii) differences in nutrient conservation mechanisms among different functional groups: in the Andean-Patagonian forests N conservation and N use efficiency is greater in evergreens than in deciduous woody species and in conifers than in broad-leaf species, whereas in the Patagonian steppe, grasses have higher nutrient resorption than shrubs. Likely as a consequence of these differences in litter quality, potential N mineralization is greater in deciduous than in evergreen Patagonian forests. Within the steppe, N inineralization seems to depend on grass and shrub cover, which in turn is regulated by disturbance, largely grazing. Since nutrient conservation in vegetation, specially N, is associated to the rates of litter decomposition and soil N mineralization, the confirmation of these patterns would allow to predict ecosystem resilience and resistance to nutrient losses, and contribute to understand and predict the response of the different Patagonian species or functional groups to interannual climatic variability and natural or anthropogenic disturbances. There is a special need for further research on P cycling, nutrient allocation in vegetation, and field measurements of litter decomposition and N mineralization.