Laura de Cabo - Academia.edu (original) (raw)

Papers by Laura de Cabo

Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima we... more Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima were evaluated. The experiment was carried out in a greenhouse and plants were grown as mono-plant cultures and mixed-plant cultures. Three different media were used: tap water and the chemically defined media Lemna and Hutner 1/10. Duration of the experiment was 7 days. Initial and final dry weights and DIN and SRP concentrations were determined. Relative growth rates (RGR) and nutrient uptake rates were calculated. L. gibba´s RGR values increased significantly in Hutner 1/10 medium when types of cultures were analyzed separately. RGR values decreased in Lemna and Hutner 1/10 media in mixed-plant cultures. S. minima did not show significant differences in its RGR values. In mono-plant cultures N and P uptake rates in Lemna medium were significantly larger for L. gibba. In Hutner 1/10 medium P uptake rate was greater for S. minima and N uptake rate was larger for L. gibba. The presence of S. minima negatively affected L. gibba´s growth.

Limnetica

The basin area of the Durazno Stream covers approx. 360 km 2 of a plain with a gentle slope, main... more The basin area of the Durazno Stream covers approx. 360 km 2 of a plain with a gentle slope, mainly devoted to cattle farming and agriculture. This study examines the variability of chemical composition of surface water of the stream in relation to stream discharge, estimated from a hydrological deterministic model from rainfall data. Fifteen samplings were carried out, four in high flow condition and the rest in baseline flow. In each sampling, the main physico-chemical variables were determined. Since discharge data from this stream were not available, it was estimated in situ through an instantaneous unitary hydrograph model. Both estimations of stream discharge were similar. The main forms of dissolved inorganic nitrogen were ammonium and nitrate. The four significant components of PCA that explained 84.4 % of total variance were: mineral component, particulate matter content, ammonium and dissolved phosphorus levels, and nitrates' level. The decreased concentrations of major ions and conductivity during high flow condition suggest solutes' dilution by the massive inflow of water originated by rainfalls. The highest concentrations and loads of suspended solids (SS) (86 mg/l and 22638 kg/day) and particulate organic carbon (POC) (3.1 mg/l and 832 kg/day) were observed in the sample obtained during the rising limb of the hydrograph following a drought period, suggesting that basin erosive processes are more important during the first hours of the storm. Three of the samplings that were carried out in high flow conditions showed low mineral and nutrient content that revealed better water quality. In contrast, the sampling with the greatest total runoff (14.1 mm) showed high concentrations of ammonium (1205 µg/l) and dissolved phosphorus (561 µg/l), suggesting that a long stagnant period on soils with low permeability, could favor reduction processes of nitrate to ammonium and mobilization of dissolved phosphorus to overlying water. The nutrients' loads increased in high flow conditions most likely due to runoff from the riverbank soils. The rise of nutrients, SS, POC and total organic carbon (TOC), loads in the same or in higher proportion than the stream discharge, alerts on the risk of contamination of surface water in an agricultural basin.

Hydrobiologia, 1999

Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water... more Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4+ concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4+ depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4+ and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4+ did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3- contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.

The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at ide... more The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at identifying the dynamics of water quality in an area with low or ''background'' concentrations of pollutants within the Reconquista River system in order to better define levels of pollution in the main system. In

Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima we... more Nutrient uptake and competitive ability of the aquatic species Lemna gibba and Salvinia minima were evaluated. The experiment was carried out in a greenhouse and plants were grown as mono-plant cultures and mixed-plant cultures. Three different media were used: tap water and the chemically defined media Lemna and Hutner 1/10. Duration of the experiment was 7 days. Initial and final dry weights and DIN and SRP concentrations were determined. Relative growth rates (RGR) and nutrient uptake rates were calculated. L. gibba´s RGR values increased significantly in Hutner 1/10 medium when types of cultures were analyzed separately. RGR values decreased in Lemna and Hutner 1/10 media in mixed-plant cultures. S. minima did not show significant differences in its RGR values. In mono-plant cultures N and P uptake rates in Lemna medium were significantly larger for L. gibba. In Hutner 1/10 medium P uptake rate was greater for S. minima and N uptake rate was larger for L. gibba. The presence of S. minima negatively affected L. gibba´s growth.

Limnetica

The basin area of the Durazno Stream covers approx. 360 km 2 of a plain with a gentle slope, main... more The basin area of the Durazno Stream covers approx. 360 km 2 of a plain with a gentle slope, mainly devoted to cattle farming and agriculture. This study examines the variability of chemical composition of surface water of the stream in relation to stream discharge, estimated from a hydrological deterministic model from rainfall data. Fifteen samplings were carried out, four in high flow condition and the rest in baseline flow. In each sampling, the main physico-chemical variables were determined. Since discharge data from this stream were not available, it was estimated in situ through an instantaneous unitary hydrograph model. Both estimations of stream discharge were similar. The main forms of dissolved inorganic nitrogen were ammonium and nitrate. The four significant components of PCA that explained 84.4 % of total variance were: mineral component, particulate matter content, ammonium and dissolved phosphorus levels, and nitrates' level. The decreased concentrations of major ions and conductivity during high flow condition suggest solutes' dilution by the massive inflow of water originated by rainfalls. The highest concentrations and loads of suspended solids (SS) (86 mg/l and 22638 kg/day) and particulate organic carbon (POC) (3.1 mg/l and 832 kg/day) were observed in the sample obtained during the rising limb of the hydrograph following a drought period, suggesting that basin erosive processes are more important during the first hours of the storm. Three of the samplings that were carried out in high flow conditions showed low mineral and nutrient content that revealed better water quality. In contrast, the sampling with the greatest total runoff (14.1 mm) showed high concentrations of ammonium (1205 µg/l) and dissolved phosphorus (561 µg/l), suggesting that a long stagnant period on soils with low permeability, could favor reduction processes of nitrate to ammonium and mobilization of dissolved phosphorus to overlying water. The nutrients' loads increased in high flow conditions most likely due to runoff from the riverbank soils. The rise of nutrients, SS, POC and total organic carbon (TOC), loads in the same or in higher proportion than the stream discharge, alerts on the risk of contamination of surface water in an agricultural basin.

Hydrobiologia, 1999

Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water... more Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4+ concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4+ depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4+ and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4+ did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3- contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.

The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at ide... more The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at identifying the dynamics of water quality in an area with low or ''background'' concentrations of pollutants within the Reconquista River system in order to better define levels of pollution in the main system. In