Stefan Woelfl - Academia.edu (original) (raw)
Papers by Stefan Woelfl
European Journal of Protistology, 2022
Brazilian Journal of Biology, 2021
The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet ... more The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet radiation and/or fish predation. However there is no information on this topic in Chilean North Patagonian lakes up to date. Therefore, this study deals with a first characterization of plankton crustacean daily vertical migration in two temperate, oligotrophic lakes (Villarrica and Panguipulli lakes, 39°S) in Southern Chile. Zooplankton were collected at different depths intervals (0-10m, 10-20 m, 20-30m, 30-40m) at early morning, middle day, evening and night in the studied site. The results revealed that zooplankton species (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus, and Tropocyclops prasinus) are abundant in surface zones at night, early morning and evening, whereas at middle day the zooplankton abundances are high at deep zones. The results agree with observations for Argentinean and North American lakes where these daily migration patterns in cr...
Science of The Total Environment, 2021
Salmon aquaculture is an important economic activity globally where local freshwater supplies per... more Salmon aquaculture is an important economic activity globally where local freshwater supplies permit land-based salmon aquaculture facilities to cultivate early life stage salmon. Nitrogen, phosphorus and organic matter in aquaculture effluents contribute to the eutrophication of adjacent and downstream rivers and lakes. This study quantifies the enrichment of nutrients in land-based salmon aquaculture facility effluents compared to receiving waters. We measured nutrient concentrations and dissolved organic matter (DOM) quantity and quality via fluorescence spectroscopy in streams and effluent waters associated with 27 facilities in Chile. We found that facilities added on average 0.9 (s.d. = 2.0) mg-C L-1, 542 (s.d. = 637) μg-total N L-1, and 104 (s.d. = 104) μg-total P L-1 to effluents compared to stream waters. DOM in stream water was enriched in humic-like fluorescence, while aquaculture effluents were enriched in protein-like DOM fluorophores. Principal component and correlation analysis revealed that tryptophan-like fluorescence was a good predictor of total N and P in effluents, but the strength of significant linear relationships varied among individual facilities (r2: 0.2 to 0.9). Agreement between laboratory fluorescence and a portable fluorometer indicates the utility of in-situ sensors for monitoring of both tryptophan-like fluorescence and covarying nutrients in effluents. Thus, continuous in-situ sensors are likely to improve industry management and allow more robust estimates of aquaculture-derived nutrients delivered to receiving waters.
Environmental Research, 2022
In this study, the occurrence and diffusive air-water exchange of POPs in Panguipulli Lake (39º42... more In this study, the occurrence and diffusive air-water exchange of POPs in Panguipulli Lake (39º42'S-72º13'W), an oligotrophic lake located in northern Patagonia (Chile), were determined. Air and water samples were collected between March and August 2017 (autumn-winter) and analyzed for concentrations of OCPs (α-HCH, β-HCH, γ-HCH and HCB) and PCBs (PCB-28,-52,-101,-118,-153,-158,-180) using gas chromatography coupled with an electron capture detector. The direction of air-water exchange direction was evaluated using a fugacity approach (ƒw ƒa-1), and net diffusive exchange fluxes (FAW, ng m-2 d-1) were also estimated. Total ∑4OCP levels in air ranged from 0.31 to 37 pg m-3, with a maximum for β-HCH, while Σ7PCB levels ranged from 3.05 to 43 pg m-3. The most abundant congener was PCB-153, accounting for 60% of the total PCBs in air. Surface water ∑4OCPs measured in this study ranged from 1.01 to 3.9 pg L-1, with γ-HCH predominating, while surface water Σ7PCB levels ranged from 0.32 to 24 pg L-1, with PCB-101, PCB-118, and PCB-153 presenting the highest levels. Diffusive air-water exchanges of HCB, α-HCH, γ-HCH and PCBs in the form of volatilization from the lake to air predominated; in contrast, for β-HCH net deposition dominated during the sampling period. Estimates suggested faster microbial degradation in the dissolved phase compared to atmospheric degradation for all analyzed POPs. Overall, these results could indicate that the oligotrophic lakes of northern Patagonia act as a secondary source of atmospheric POPs, mainly PCBs and some OCPs. This study is a first attempt to understand the occurrence of POPs in air and water, as well as their dynamics in oligotrophic lakes in the southern hemisphere.
Science of The Total Environment, 2020
Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds of environmental conce... more Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds of environmental concern. This study aims to investigate the influence of local sources of anthropogenic PAHs and their air-water exchange fluxes in an oligotrophic North-Patagonian lake in Chile. The monitoring was carried out in Panguipulli Lake during a six-month period during the autumn and winter seasons (March to August 2017) using a high-volume air sampler and a pump system for water samples. We detected and quantified fifteen PAHs in the gas phase (mean ∑15PAHs = 11.6 ng m-3) and dissolved water phase (mean ∑15PAHs = 961.8 pg L-1). Methylphenanthrenes and pyrene dominated the concentrations of PAHs in the studied phases. To determine sources of PAHs we used the PAH ratios of Light Molecular Weight/Heavy Molecular Weight (∑LMW/∑HMW) and Phenanthrene/Anthracene (Phe/Ant). The PAH ratio results revealed a pyrogenic source. We estimated the air-water diffusive exchange fluxes and fugacity ratios for the studied compounds. In general, air-water diffusive exchanges of PAHs showed a net volatilization for the less hydrophobic (log KOW < 4) and lighter PAHs (MW ≤ 170 g mol-1), and a net deposition trend for the more hydrophobic (log KOW 4-7) and higher molecular weight PAHs (MW ≥ 178 g mol-1). We found a significant correlation between log water/air fugacity ratios and log KOW of PAHs. Therefore, it is suggested that this oligotrophic lake acts as a sink by accumulating hydrophobic and mid-high molecular weight PAHs derived mainly from pyrogenic sources. This study is the first attempt to understand the sources and behavior of PAHs in oligotrophic lakes in the Southern Chile where information is scarce regarding the occurrence of PAHs.
Science Advances, 2019
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of w... more River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosyste...
Animal Biology, 2019
With their ultraoligotrophic status, the Chilean North Patagonian lakes have mixotrophic ciliates... more With their ultraoligotrophic status, the Chilean North Patagonian lakes have mixotrophic ciliates in their pelagic environments as producers, whereas the primary consumers are crustaceans that are low in abundance and species numbers. The aim of the present study was to determine the potential grazer role of mixotrophic ciliates on crustacean zooplankton collected in a lake without mixotrophic ciliates. Three experiments were conducted; one had a control with mixotrophic ciliates and an experimental treatment including the copepod Boeckella gracilipes obtained from Caburgua lake, whereas the second and third experiments had a control without zooplankton, and three treatments with the addition of Daphnia pulex and Mesocyclops araucanus, and a third treatment with equal amounts of both species. The results revealed grazing effects on the mixotrophic ciliates in the experimental treatments. This finding supports the evidence from the field and experiments suggesting that, in the transi...
Hydrological Processes, 2016
Land cover changes have a great impact on nitrogen (N) and phosphorous (P) fluxes catchments. In ... more Land cover changes have a great impact on nitrogen (N) and phosphorous (P) fluxes catchments. In this study we wanted to compare different land covers: deciduous (D), evergreen (E) (both native forests) and exotic Eucalyptus globulus plantation (EP), affected precipitation and stream discharge on N and P species concentrations and fluxes, under a low deposition climate in south central Chile. For this we collected bulk precipitation, throughfall and stream water samples after 41 rainfall events in E and EP, during the period June 2009 – March 2011 and 31 rainfall events in D, during the period October 2009 – March 2011. The highest canopy enrichment of N and P species for throughfall was observed in deciduous forest, while E. globulus showed the minimum enrichment. Total nitrogen (Total-N) discharge in EP was about 8.6 times higher than that of E and D catchments. Total-N annual retention was positive only in E and D catchments. However, EP catchment showed a net loss (-4.79 kg N ha-1 yr-1). The biggest difference was observed in nitrate stream concentrations, which showed low values for E (3.4 ± 1.3 µg L-1), while EP and D showed higher nitrate concentrations (84.9 ± 16.7 and 134.7 ± 36.7 µg L-1, for EP and D respectively). Total phosphorous (Total-P) discharge flux was low in EP (0.4 kg P ha-1 yr-1), and negligible in E and D forests (<0.1 kg P ha-1 yr-1). Total-P annual retention was near to 1.0 kg N ha-1 yr-1 (on E and D), while a net loss (-1.5 kg N ha-1 yr-1) was observed for EP. We attribute the observed differences in nutrient throughfall enrichment due to high multi-stratified canopies in the native forests. Both deciduous and evergreen native forest covered catchments showed the highest retention of total-N and total-P, in contrast to Eucalyptus covered plantation.
International Review of Hydrobiology, 2015
Blooms of cyanobacteria have negative effects on aquatic organisms and even on human health, sinc... more Blooms of cyanobacteria have negative effects on aquatic organisms and even on human health, since many species can synthesize dangerous toxins. Studies on cyanobacteria and their potential toxicity have been very scarce in Chile and have been limited to lakes of the central zone. Recently, North-Patagonian lakes, although characterized by their low nutrient concentration and low productivity, revealed also the presence of blooms of cyanobacteria, mainly constituted by Microcystis and Dolichospermum species (former Anabaena sp.). To identify potential toxicological risk associated to these blooms, six North Patagonian lakes (Lakes Caburgua, Villarrica, Calafquen, Panguipulli, Ranco, and Puyehue) were sampled during the summer period and screened for the presence of cyanobacteria and different toxins. Our results revealed for the first time the presence of microcystins in all studied lakes, whereas other toxins such as cylindrospermopsin, saxitoxin, and anatoxin were negative for all sites. By applying a genomic approach, Cylindrospermopsis raciborskii was found in one lake (Lake Ranco) constituting the first report of this cyanobacterium in a Chilean lake. This study highlights the effectiveness of molecular methods as a first approach to describe cyanobacteria and their potential cyanotoxins in Chilean North-Patagonian lakes.
Response of the catchment to the eruption of Copahue 2.5 km river lake ice field crater caldera o... more Response of the catchment to the eruption of Copahue 2.5 km river lake ice field crater caldera outline lava flow (holocene) ash fall, Aug 20th. basement rock
Science of The Total Environment, 2015
Chile is the second largest producer of salmonids worldwide. The first step in the production of ... more Chile is the second largest producer of salmonids worldwide. The first step in the production of salmonids takes place in land-based aquacultures. However, the effects of the discharge from these aquacultures on stream dissolved organic matter (DOM) content, molecular composition and degradability are unknown. The aim of this study was thus to investigate the inputs of anthropogenic DOM from land-based aquaculture to the predominantly pristine river systems of North Patagonia. We hypothesized, that i) DOM exported from land-based aquaculture mainly consists of protein-like fluorescence (tyrosine and tryptophan) released from fish feces and food remains, and that ii) this DOM is highly degradable and therefore rapidly turned-over within the receiving streams. In the North Patagonian region we conducted a screening of ten land-based aquacultures and an intensive sampling campaign for one aquaculture. This was combined with longitudinal transects and a degradation experiment in order to couple the composition of DOM exported from land-based aquacultures to its degradability in streams. We measured dissolved organic carbon (DOC) concentration by high-temperature catalytic oxidation and DOM composition by fluorescence spectroscopy and parallel factor analysis. In the effluent of the ten screened aquacultures and in the repeated sampling of one aquaculture, we consistently found an increase of DOC concentrations and a dominance of protein-like fluorescence. The protein-like fluorescence rapidly disappeared downstream of the aquacultures, and in the degradation experiment. 21% of the DOC export from the repeatedly sampled aquaculture resulted from food addition and 76% from fish production. We conclude that large amounts of degradable DOM are exported from land-based aquacultures. This probably has strong effects on the ecological structure and function of North Patagonian streams, and similarly affected streams worldwide.
Standard methods for sampling, fixation and quantification of organisms in highly acid environmen... more Standard methods for sampling, fixation and quantification of organisms in highly acid environments with pH values at or below 3 are presented. Some important problems are discussed, together with recommendations on how to handle the material. Examples of specific problems are included, especially the effects of fixatives on the cell dimensions of species of Chlamydomonas, Oxytricha and Actinophrys, and on cell numbers of Actinophrys. Mixed populations of heterotrophic protists should be preserved with Lugol's solution, because other fixatives do not permit the recognition of heliozoans. * Author for correspondence tozoa, and then uses this and other information to provide an overview. Methods Effects of fixation on cell dimensions In order to quantify the effects of different fixatives on the linear dimensions and cell volume, one alga (Chlamydomonas sp.) and two protozoa (ciliate and heliozoan) from extremely acid environments were selected. Chlamydomonas was isolated from a water sample of the highly acidic Rio Agrio, Argentina (pH: 1.15-1.3, acidity: 1500 mmol l −1 , 288 mg l −1 Fe, 74 mg l −1 Al, 13 000 mg l −1 sulphate, F. Pedrozo, pers. comm.). It was both cultured for several months in the original water and preserved with 1% HgCl 2 , 2% formaldehyde, 1% glutaraldehyde and 2% acidic Lugol's solution. The control measurements were done immediately, whereas the preserved cells were measured after 2 days. A 5-ml aliquot of the preserved sample was allowed to settle in an Utermöhl chamber. Measurements were carried out using a computer-based image analysing system (Kontron 400, Zeiss) and a inverted microscope (Leitz Fluovert) at ×800 magnification.
Limnologica - Ecology and Management of Inland Waters, 2014
ABSTRACT Dissolved organic matter (DOM) in freshwater ecosystems has its origin in a multitude of... more ABSTRACT Dissolved organic matter (DOM) in freshwater ecosystems has its origin in a multitude of terrestrial and aquatic sources which determine amount, composition and thereby its functions. Spectroscopic methods are used to characterize chromophoric DOM. Among these methods, absorbance and fluorescence spectroscopy can provide indications of sources, behavior, and biogeochemical cycling of DOM. Since DOM is defined as the part of the organic matter pool which passes filters from 0.22 to 0.7 μm, sample filtration is required before spectroscopic measurements can be done. However, the use of different filter types might be influencing the results of DOM composition measurements. In order to assess the effect of different filters, we used three filter types with nominal pore sizes of 0.7, 0.45 or 0.22 μm, measured difference spectra, calculated spectroscopic indexes (S275-295, S350-400, Sr, SUVA254, E2:E3, fluorescence index, β: α, humification index) and fluorescence components (parallel factor analysis, PARAFAC), obtained via spectroscopic measurements from water with different characteristics (e.g. river water, wetland, sewage effluent). Our results show that the filter types had significant but small effects on the chromophoric DOM composition and that meta-analyses of DOM composition based on studies with different pore size can be done, when keeping potential minor filtration effects in mind. This is important for further meta-analysis which might inter-compare data sets on spectroscopic characterization of DOM
European Journal of Protistology, 2022
Brazilian Journal of Biology, 2021
The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet ... more The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet radiation and/or fish predation. However there is no information on this topic in Chilean North Patagonian lakes up to date. Therefore, this study deals with a first characterization of plankton crustacean daily vertical migration in two temperate, oligotrophic lakes (Villarrica and Panguipulli lakes, 39°S) in Southern Chile. Zooplankton were collected at different depths intervals (0-10m, 10-20 m, 20-30m, 30-40m) at early morning, middle day, evening and night in the studied site. The results revealed that zooplankton species (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus, and Tropocyclops prasinus) are abundant in surface zones at night, early morning and evening, whereas at middle day the zooplankton abundances are high at deep zones. The results agree with observations for Argentinean and North American lakes where these daily migration patterns in cr...
Science of The Total Environment, 2021
Salmon aquaculture is an important economic activity globally where local freshwater supplies per... more Salmon aquaculture is an important economic activity globally where local freshwater supplies permit land-based salmon aquaculture facilities to cultivate early life stage salmon. Nitrogen, phosphorus and organic matter in aquaculture effluents contribute to the eutrophication of adjacent and downstream rivers and lakes. This study quantifies the enrichment of nutrients in land-based salmon aquaculture facility effluents compared to receiving waters. We measured nutrient concentrations and dissolved organic matter (DOM) quantity and quality via fluorescence spectroscopy in streams and effluent waters associated with 27 facilities in Chile. We found that facilities added on average 0.9 (s.d. = 2.0) mg-C L-1, 542 (s.d. = 637) μg-total N L-1, and 104 (s.d. = 104) μg-total P L-1 to effluents compared to stream waters. DOM in stream water was enriched in humic-like fluorescence, while aquaculture effluents were enriched in protein-like DOM fluorophores. Principal component and correlation analysis revealed that tryptophan-like fluorescence was a good predictor of total N and P in effluents, but the strength of significant linear relationships varied among individual facilities (r2: 0.2 to 0.9). Agreement between laboratory fluorescence and a portable fluorometer indicates the utility of in-situ sensors for monitoring of both tryptophan-like fluorescence and covarying nutrients in effluents. Thus, continuous in-situ sensors are likely to improve industry management and allow more robust estimates of aquaculture-derived nutrients delivered to receiving waters.
Environmental Research, 2022
In this study, the occurrence and diffusive air-water exchange of POPs in Panguipulli Lake (39º42... more In this study, the occurrence and diffusive air-water exchange of POPs in Panguipulli Lake (39º42'S-72º13'W), an oligotrophic lake located in northern Patagonia (Chile), were determined. Air and water samples were collected between March and August 2017 (autumn-winter) and analyzed for concentrations of OCPs (α-HCH, β-HCH, γ-HCH and HCB) and PCBs (PCB-28,-52,-101,-118,-153,-158,-180) using gas chromatography coupled with an electron capture detector. The direction of air-water exchange direction was evaluated using a fugacity approach (ƒw ƒa-1), and net diffusive exchange fluxes (FAW, ng m-2 d-1) were also estimated. Total ∑4OCP levels in air ranged from 0.31 to 37 pg m-3, with a maximum for β-HCH, while Σ7PCB levels ranged from 3.05 to 43 pg m-3. The most abundant congener was PCB-153, accounting for 60% of the total PCBs in air. Surface water ∑4OCPs measured in this study ranged from 1.01 to 3.9 pg L-1, with γ-HCH predominating, while surface water Σ7PCB levels ranged from 0.32 to 24 pg L-1, with PCB-101, PCB-118, and PCB-153 presenting the highest levels. Diffusive air-water exchanges of HCB, α-HCH, γ-HCH and PCBs in the form of volatilization from the lake to air predominated; in contrast, for β-HCH net deposition dominated during the sampling period. Estimates suggested faster microbial degradation in the dissolved phase compared to atmospheric degradation for all analyzed POPs. Overall, these results could indicate that the oligotrophic lakes of northern Patagonia act as a secondary source of atmospheric POPs, mainly PCBs and some OCPs. This study is a first attempt to understand the occurrence of POPs in air and water, as well as their dynamics in oligotrophic lakes in the southern hemisphere.
Science of The Total Environment, 2020
Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds of environmental conce... more Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds of environmental concern. This study aims to investigate the influence of local sources of anthropogenic PAHs and their air-water exchange fluxes in an oligotrophic North-Patagonian lake in Chile. The monitoring was carried out in Panguipulli Lake during a six-month period during the autumn and winter seasons (March to August 2017) using a high-volume air sampler and a pump system for water samples. We detected and quantified fifteen PAHs in the gas phase (mean ∑15PAHs = 11.6 ng m-3) and dissolved water phase (mean ∑15PAHs = 961.8 pg L-1). Methylphenanthrenes and pyrene dominated the concentrations of PAHs in the studied phases. To determine sources of PAHs we used the PAH ratios of Light Molecular Weight/Heavy Molecular Weight (∑LMW/∑HMW) and Phenanthrene/Anthracene (Phe/Ant). The PAH ratio results revealed a pyrogenic source. We estimated the air-water diffusive exchange fluxes and fugacity ratios for the studied compounds. In general, air-water diffusive exchanges of PAHs showed a net volatilization for the less hydrophobic (log KOW < 4) and lighter PAHs (MW ≤ 170 g mol-1), and a net deposition trend for the more hydrophobic (log KOW 4-7) and higher molecular weight PAHs (MW ≥ 178 g mol-1). We found a significant correlation between log water/air fugacity ratios and log KOW of PAHs. Therefore, it is suggested that this oligotrophic lake acts as a sink by accumulating hydrophobic and mid-high molecular weight PAHs derived mainly from pyrogenic sources. This study is the first attempt to understand the sources and behavior of PAHs in oligotrophic lakes in the Southern Chile where information is scarce regarding the occurrence of PAHs.
Science Advances, 2019
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of w... more River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosyste...
Animal Biology, 2019
With their ultraoligotrophic status, the Chilean North Patagonian lakes have mixotrophic ciliates... more With their ultraoligotrophic status, the Chilean North Patagonian lakes have mixotrophic ciliates in their pelagic environments as producers, whereas the primary consumers are crustaceans that are low in abundance and species numbers. The aim of the present study was to determine the potential grazer role of mixotrophic ciliates on crustacean zooplankton collected in a lake without mixotrophic ciliates. Three experiments were conducted; one had a control with mixotrophic ciliates and an experimental treatment including the copepod Boeckella gracilipes obtained from Caburgua lake, whereas the second and third experiments had a control without zooplankton, and three treatments with the addition of Daphnia pulex and Mesocyclops araucanus, and a third treatment with equal amounts of both species. The results revealed grazing effects on the mixotrophic ciliates in the experimental treatments. This finding supports the evidence from the field and experiments suggesting that, in the transi...
Hydrological Processes, 2016
Land cover changes have a great impact on nitrogen (N) and phosphorous (P) fluxes catchments. In ... more Land cover changes have a great impact on nitrogen (N) and phosphorous (P) fluxes catchments. In this study we wanted to compare different land covers: deciduous (D), evergreen (E) (both native forests) and exotic Eucalyptus globulus plantation (EP), affected precipitation and stream discharge on N and P species concentrations and fluxes, under a low deposition climate in south central Chile. For this we collected bulk precipitation, throughfall and stream water samples after 41 rainfall events in E and EP, during the period June 2009 – March 2011 and 31 rainfall events in D, during the period October 2009 – March 2011. The highest canopy enrichment of N and P species for throughfall was observed in deciduous forest, while E. globulus showed the minimum enrichment. Total nitrogen (Total-N) discharge in EP was about 8.6 times higher than that of E and D catchments. Total-N annual retention was positive only in E and D catchments. However, EP catchment showed a net loss (-4.79 kg N ha-1 yr-1). The biggest difference was observed in nitrate stream concentrations, which showed low values for E (3.4 ± 1.3 µg L-1), while EP and D showed higher nitrate concentrations (84.9 ± 16.7 and 134.7 ± 36.7 µg L-1, for EP and D respectively). Total phosphorous (Total-P) discharge flux was low in EP (0.4 kg P ha-1 yr-1), and negligible in E and D forests (<0.1 kg P ha-1 yr-1). Total-P annual retention was near to 1.0 kg N ha-1 yr-1 (on E and D), while a net loss (-1.5 kg N ha-1 yr-1) was observed for EP. We attribute the observed differences in nutrient throughfall enrichment due to high multi-stratified canopies in the native forests. Both deciduous and evergreen native forest covered catchments showed the highest retention of total-N and total-P, in contrast to Eucalyptus covered plantation.
International Review of Hydrobiology, 2015
Blooms of cyanobacteria have negative effects on aquatic organisms and even on human health, sinc... more Blooms of cyanobacteria have negative effects on aquatic organisms and even on human health, since many species can synthesize dangerous toxins. Studies on cyanobacteria and their potential toxicity have been very scarce in Chile and have been limited to lakes of the central zone. Recently, North-Patagonian lakes, although characterized by their low nutrient concentration and low productivity, revealed also the presence of blooms of cyanobacteria, mainly constituted by Microcystis and Dolichospermum species (former Anabaena sp.). To identify potential toxicological risk associated to these blooms, six North Patagonian lakes (Lakes Caburgua, Villarrica, Calafquen, Panguipulli, Ranco, and Puyehue) were sampled during the summer period and screened for the presence of cyanobacteria and different toxins. Our results revealed for the first time the presence of microcystins in all studied lakes, whereas other toxins such as cylindrospermopsin, saxitoxin, and anatoxin were negative for all sites. By applying a genomic approach, Cylindrospermopsis raciborskii was found in one lake (Lake Ranco) constituting the first report of this cyanobacterium in a Chilean lake. This study highlights the effectiveness of molecular methods as a first approach to describe cyanobacteria and their potential cyanotoxins in Chilean North-Patagonian lakes.
Response of the catchment to the eruption of Copahue 2.5 km river lake ice field crater caldera o... more Response of the catchment to the eruption of Copahue 2.5 km river lake ice field crater caldera outline lava flow (holocene) ash fall, Aug 20th. basement rock
Science of The Total Environment, 2015
Chile is the second largest producer of salmonids worldwide. The first step in the production of ... more Chile is the second largest producer of salmonids worldwide. The first step in the production of salmonids takes place in land-based aquacultures. However, the effects of the discharge from these aquacultures on stream dissolved organic matter (DOM) content, molecular composition and degradability are unknown. The aim of this study was thus to investigate the inputs of anthropogenic DOM from land-based aquaculture to the predominantly pristine river systems of North Patagonia. We hypothesized, that i) DOM exported from land-based aquaculture mainly consists of protein-like fluorescence (tyrosine and tryptophan) released from fish feces and food remains, and that ii) this DOM is highly degradable and therefore rapidly turned-over within the receiving streams. In the North Patagonian region we conducted a screening of ten land-based aquacultures and an intensive sampling campaign for one aquaculture. This was combined with longitudinal transects and a degradation experiment in order to couple the composition of DOM exported from land-based aquacultures to its degradability in streams. We measured dissolved organic carbon (DOC) concentration by high-temperature catalytic oxidation and DOM composition by fluorescence spectroscopy and parallel factor analysis. In the effluent of the ten screened aquacultures and in the repeated sampling of one aquaculture, we consistently found an increase of DOC concentrations and a dominance of protein-like fluorescence. The protein-like fluorescence rapidly disappeared downstream of the aquacultures, and in the degradation experiment. 21% of the DOC export from the repeatedly sampled aquaculture resulted from food addition and 76% from fish production. We conclude that large amounts of degradable DOM are exported from land-based aquacultures. This probably has strong effects on the ecological structure and function of North Patagonian streams, and similarly affected streams worldwide.
Standard methods for sampling, fixation and quantification of organisms in highly acid environmen... more Standard methods for sampling, fixation and quantification of organisms in highly acid environments with pH values at or below 3 are presented. Some important problems are discussed, together with recommendations on how to handle the material. Examples of specific problems are included, especially the effects of fixatives on the cell dimensions of species of Chlamydomonas, Oxytricha and Actinophrys, and on cell numbers of Actinophrys. Mixed populations of heterotrophic protists should be preserved with Lugol's solution, because other fixatives do not permit the recognition of heliozoans. * Author for correspondence tozoa, and then uses this and other information to provide an overview. Methods Effects of fixation on cell dimensions In order to quantify the effects of different fixatives on the linear dimensions and cell volume, one alga (Chlamydomonas sp.) and two protozoa (ciliate and heliozoan) from extremely acid environments were selected. Chlamydomonas was isolated from a water sample of the highly acidic Rio Agrio, Argentina (pH: 1.15-1.3, acidity: 1500 mmol l −1 , 288 mg l −1 Fe, 74 mg l −1 Al, 13 000 mg l −1 sulphate, F. Pedrozo, pers. comm.). It was both cultured for several months in the original water and preserved with 1% HgCl 2 , 2% formaldehyde, 1% glutaraldehyde and 2% acidic Lugol's solution. The control measurements were done immediately, whereas the preserved cells were measured after 2 days. A 5-ml aliquot of the preserved sample was allowed to settle in an Utermöhl chamber. Measurements were carried out using a computer-based image analysing system (Kontron 400, Zeiss) and a inverted microscope (Leitz Fluovert) at ×800 magnification.
Limnologica - Ecology and Management of Inland Waters, 2014
ABSTRACT Dissolved organic matter (DOM) in freshwater ecosystems has its origin in a multitude of... more ABSTRACT Dissolved organic matter (DOM) in freshwater ecosystems has its origin in a multitude of terrestrial and aquatic sources which determine amount, composition and thereby its functions. Spectroscopic methods are used to characterize chromophoric DOM. Among these methods, absorbance and fluorescence spectroscopy can provide indications of sources, behavior, and biogeochemical cycling of DOM. Since DOM is defined as the part of the organic matter pool which passes filters from 0.22 to 0.7 μm, sample filtration is required before spectroscopic measurements can be done. However, the use of different filter types might be influencing the results of DOM composition measurements. In order to assess the effect of different filters, we used three filter types with nominal pore sizes of 0.7, 0.45 or 0.22 μm, measured difference spectra, calculated spectroscopic indexes (S275-295, S350-400, Sr, SUVA254, E2:E3, fluorescence index, β: α, humification index) and fluorescence components (parallel factor analysis, PARAFAC), obtained via spectroscopic measurements from water with different characteristics (e.g. river water, wetland, sewage effluent). Our results show that the filter types had significant but small effects on the chromophoric DOM composition and that meta-analyses of DOM composition based on studies with different pore size can be done, when keeping potential minor filtration effects in mind. This is important for further meta-analysis which might inter-compare data sets on spectroscopic characterization of DOM