Trophic parameters and method validation in Lake Riñihue (North Patagonia: Chile) from 1978 through 1997 (original) (raw)

Oligotrophic patterns in southern Chilean lakes: The relevance of nutrients and mixing depth

2002

Southern Chilean monomictic, temperate lakes are generally oligotrophic with high water transparency, low productivity and some apparent resistance to disturbances such as phosphorus additions. This paper attempts to explain low chlorophyll-a values using descriptive and experimental approaches. Three different scales are used, (a) a micro scale both in space and time, with experimental manipulations of N, P and total light in 24 enclosures in lake Llanquihue, (b) a longer time scale analysing 18 months of data in several sites within lake Llanquihue grouped as salmon farming sites, town bays and control sites, and (c) a broader time scale (9 years) by monitoring lakes Puyehue, Rupanco and Llanquihue, all in the Araucanian lake region and Yelcho lake in the north Patagonian region. In the Llanquihue in-lake sampling, total phosphorus values varied between 1 and 12 µg L -1 between sites, showing marginal site effects, P = 0.09 (salmon sites had greater values), however, chlorophyll a...

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.

The Trophic State of Patagonian Argentinean Lakes and its Relationship with Depth Distribution in Sediment Phosphorus

International Journal of Environmental Research

The parameters used to determine the trophic state of a water body are: total phosphorus (TP), transparency (Secchi disk depth) and chlorophyll a. However, these parameters show strong seasonal fluctuations which may hinder the estimation of trophic state. Some authors have proposed that sediments be used as an additional tool to evaluate the trophic state of a water body. The aim of this study was to determine the depth distribution of sediment TP in relation with the lake trophic state. Nine sediment corers from water bodies located in Patagonian Region (Argentina) were studied. The nutrient concentrations in pore water and in sediments were analyzed. The results obtained showed that there is a relationship between the depth distribution of sediment TP and the trophic state for all studied environments. Two exceptions were noted to this general pattern (Lakes Caviahue and Lácar). Our findings indicate that both pore water and sediments could be considered as the best parameters to estimate the tropic state of a water body compared to the water column.

Changes in Planktivory and Herbivory Regimes in a Shallow South American Lake (Lake Blanca Chica, Argentina) Over the Last 250 Years

Water

Shallow lakes are vulnerable ecosystems impacted by human activities and climate change. The Cladocera occupy a central role in food webs and are an excellent paleoecological indicator of food web structure and trophic status. We conducted a paleolimnological study in Lake Blanca Chica (Argentina) to detect changes on the planktivory and herbivory regimes over the last 250 years. Generalized additive models were fitted to the time series of fish predation indicators (ephippial abundance and size, mucrone size, fish scales, and the planktivory index) and pheophorbide a concentration. The cladoceran assemblage changed from littoral-benthic to pelagic species dominance and zooplankton switched from large-bodied (Daphnia) to small-bodied grazers (Bosmina) ca. 1900 due to increased predation. The shift in planktivory regime (ca. 1920–1930), indicated by fish scales and the planktivory index, as well as herbivory (ca. 1920–1950), was triggered by eutrophication. Changes in planktivory aff...

Application of the Lake Biotic Index (LBI) in the ecological characterization of a North Patagonian lake in Chile

Heliyon

Increased pollution and degradation of water resources and their associated ecosystems has stimulated the development of tools and methodologies to characterize, estimate, predict, and reverse the environmental impact of anthropic effects on water bodies. The Secondary Water Quality Standards (NSCA) adopted in Chile have incorporated the use of bioindicators complementary to physicochemical analyses, in order to determine the ecological condition of lotic and lentic environments. Our research used the "Lake Biotic Index" (LBI) to establish the ecological condition of Lake Rupanco using benthic macroinvertebrates. The results indicated an Oligo-Eubiotic condition for this lake given the high concentration of oxygen and low organic matter content in sediments, in addition to low biogenic potential and good taxa preservation in both the autumn and spring surveys. Features of the ecological condition obtained through the application of the LBI (benthic subsystem) conform to the results of physicochemical and microalgae analyses undertaken previously in Lake Rupanco (pelagic subsystem). Based on these results, we support application of the LBI index as a complementary tool for the integrated management of lentic ecosystems.

Summer phytoplankton composition and nitrogen limitation of the deep, naturally-acidic (pH∼2.2) Lake Caviahue, Patagonia, Argentina

Limnologica - Ecology and Management of Inland Waters, 2007

During the warm seasons of 1998-2004, the naturally-acidic (pH$2.2) Lake Caviahue was sampled for conductivity, temperature, oxygen, light, nutrients, and phytoplankton (density, biomass and chlorophyll a) with a view to studying the summer phytoplankton population changes with relation to environmental factors, as well as the significance of nitrogen limitation on the phytoplankton yield. Lake Caviahue is characterized by its low transparency, CO 2 , and N concentration; significant P values; a distinctive vertical distribution of phytoplankton biomass with high values along the water column; and sometimes maximum meta-hypolimnion values. Biodiversity is very low as a result of extreme environmental conditions, Chlorophyceae being the prevailing algae group. Two types of bioassays were carried out to assess nitrogen limitation. For the first bioassay, a solution of ammonium-nitrogen chloride and/or wastewater (rich in ammonium and phosphorus) was used, while one of the lake's sediments was the source of nutrients for the second bioassay. Contrary to the case of acidic mining lakes, N-ammonium proved to be a significant supportive capacity limiting factor as to phytoplankton yield. The present paper provides for the first time information on phytoplankton nitrogen limitation in a naturally-acidic lake.

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.

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 Concentrations and Trophic State of Small Patagonian Andean lakes

Journal of Freshwater Ecology, 2006

We analyzed nutrient, chlorophyll, and ionic concentrations in 17 lakes along a strip of land located in the rainy Andes Mountains and the ecotone with the dry Patagonian steppe, from 36 to 44° S latitude. Most of the sampled lakes had the ionic composition of Andean lakes and showed ultraoligotrophic conditions, while a few with the ionic composition of the Patagonian Plateau lakes showed higher nutrient concentrations. Chlorophyll was correlated to P and N concentrations, but chlorophyll /TP ratio was lower than reported in previous worldwide surveys. A lithology dominated by igneous rock together with the remoteness and pristine character of the basins contribute to the oligotrophic status of the lakes. Two other factors appear to be important in maintaining the oligotrophic condition. Andisols, allophanic soils developed over volcanic ash deposits in the rainy areas, have large P retention capability and therefore decrease the load of P to the lakes. Natural dense Nothofagus spp. forests, with a geographical distribution coincident with that of the andisols, are efficient mechanisms for nitrogen retention through nitrogen resorption from senescent leaves.