Fabricio Damián Cid

Modelling spatial and temporal variations in the water quality of an artificial water reservoir in the semiarid Midwest of Argentina

Temporal and spatial patterns of water quality of an important artificial water reservoir located in the semiarid Midwest of Argentina were investigated using chemometric techniques. Surface water samples were collected at 38 points of the water reservoir during eleven sampling campaigns between October 1998 and June 2000, covering the warm wet season and the cold dry season, and analyzed for dissolved oxygen (DO), conductivity, pH, ammonium, nitrate, nitrite, total dissolved solids (TDS), alkalinity, hardness, bicarbonate, chloride, sulfate, calcium, magnesium, fluoride, sodium, potassium, iron, aluminum, silica, phosphate, sulfide, arsenic, chromium, lead, cadmium, chemical oxygen demand (COD), biochemical oxygen demand (BOD), viable aerobic bacteria (VAB) and total coliform bacteria (TC). Concentrations of lead, ammonium, nitrite and coliforms were higher than the maximum allowable limits for drinking water in a large proportion of the water samples. To obtain a general representation of the spatial and temporal trends of the water quality parameters at the reservoir, the three-dimensional dataset (sampling sites×parameters×sampling campaigns) has been analyzed by matrix augmentation principal component analysis (MA-PCA) and N-way principal component analysis (N-PCA) using Tucker3 and PARAFAC (Parallel Factor Analysis) models. MA-PCA produced a component accounting for the general behavior of parameters associated with organic pollution. The Tucker3 models were not appropriate for modelling the water quality dataset. The two-factor PARAFAC model provided the best picture to understand the spatial and temporal variation of the water quality parameters of the reservoir. The first PARAFAC factor contains useful information regarding the relation of organic pollution with seasonality, whereas the second factor also encloses information concerning lead pollution. The most polluted areas in the reservoir and the polluting sources were identified by plotting PARAFAC loadings as a function of the UTM (Universal Transverse Mercator) coordinates.

Contamination of heavy metals in birds from Embalse La Florida (San Luis, Argentina).

Embalse La Florida is an artificial lake located in midwestern Argentinas San Luis province. It provides drinking water to approximately 70% of the provinces human population and approximately 20% of the province is irrigated with water from the reservoir. The presence of heavy metals in Embalse La Floridas water has previously been reported. Nevertheless, no information about the levels of these contaminants in birds is available for this region. The aim of this study, therefore, is to (1) establish baseline data on lead (Pb) and cadmium (Cd) levels in birds from Embalse La Florida, (2) assess metal accumulation patterns between organs and bird species, and (3) evaluate the potential risk that these heavy metals pose for the local avifauna. We measured Pb and Cd in bone, pectoralis muscle, liver, gonad, and brain of three bird species representative of the Embalse La Florida ecosystem: Podiceps major (Great Grebe), Phalacrocorax brasilianus (Neotropic Cormorant), both of which are piscivorous, and Pitangus sulphuratus (Great Kiskadee), which is omnivorous. We also measured both heavy metals in Great Grebe eggs. Pb and Cd were detected in all of the tissues we assayed, and Pb concentrations were significantly higher than those for Cd in all tissues. The patterns of Pb and Cd accumulation differed between tissues, however. In general, gonads had the highest concentrations of Pb while Cd tended to accumulate in the liver. An interspecific analysis revealed that the omnivorous species had higher levels of both metals in bone, liver, and brain compared to both piscivorous species. There were no differences in Pb and Cd concentrations between males and females. The highest liver level of Pb (4.69 ppm wet weight) detected in Great Kiskadee, was comparable to those associated with toxic effects in birds, and Pb concentrations found in the liver of two females and two males (2.07 to 2.32 ppm wet weight) were also similar to those that could be physiologically detrimental in other species. In all birds assayed, Cd levels in liver tissue were lower than those typically shown to be harmful. Our results indicate that Great Kiskadees are highly polluted by Pb and their exposure to this contaminant exceeds the level reported to trigger adverse effects. This is the first study to assay heavy metals in birds from midwest Argentina and provides a starting point for studies examining the impact that these metals have on both wildlife and humans in the region.

Effect of fasting on the structure and function of the gastrointestinal tract of house sparrows (Passer domesticus).

Starvation is a condition that often affects animals in nature. The gastrointestinal tract is the organ system displaying the most rapid and dramatic changes in response to nutrient deprivation. To date, little is known about starvation phases and effects on the organ morphology and digestive function in small passerine birds. In this study, we determined the phases of starvation and examined the effect of final stage of starvation in the organ morphology and, intestinal histology and enzymatic function in the small intestine. Our results show the three phases of the classical model of fasting in a shorter period of time. The mass of heart, pancreas, stomach, small intestine and liver of long-term fasted birds was reduced between 20 and 47%. The mass decrease in small intestine was correlated with reduction in small intestinal histology: perimeter, mucosal thickness, villus height and width. In contrast, the enzyme activity of sucrase-isomaltase and aminopeptidase-N in enterocytes, all expressed per μg of protein, was higher in long-term fasted birds than fed animals. This suggest that, while autophagy of digestive organs is induced by starvation, consistent with phenotypic plasticity, the activity of sucrase-isomaltase and aminopeptidase-N remains high, probably as an anticipatory strategy to optimize digestion at re-feeding time.

Spatial and temporal patterns of richness and abundance in the anuran assemblage of an artificial water reservoir from the semiarid central region of Argentina

This constitutes the first study of anuran fauna composition of an artificial permanent water reservoir, in a semiarid ecosystem of San Luis. Species richness, relative abundance, spatial distribution and pattern of summer activity were estimated in the anuran community of the Embalse La Florida, an artificial water reservoir in the semiarid central region of the sierras of San Luis, Argentina. This reservoir represents one of the few sources of water available for reproduction and early development of amphibian species in the zone. We identified anurans using call surveys during two summers at fifteen sites, belonging to four zones around the shorelines of the reservoir. Eight amphibian species ( Rhinella arenarum , Melanophryniscus stelzneri , Leptodactylus bufonius , Leptodactylus mystacinus , Odontophrynus americanus , Odontophrynus occidentalis , Pleurodema tucumanum and Hypsiboas cordobae ) were recorded at the shores of the embalse. The highest species richness (seven) was detected in the preserve located on the north shore. Species richness analyzed by month or survey was not correlated with weather variables. The highest relative abundance of anurans was detected at the highly modified campsites area, which may provide stable food and refugia. Relative abundance of all anuran species was positively correlated with precipitation. This permanent water reservoir may act as an important site of amphibian fauna concentration, which is important to monitor and preserve.

Effect of fasting in the digestive system: histological study of the small intestine in house sparrows.

In birds and mammals the metabolic response to fasting has been studied and can be characterized by three consecutive phases reflecting metabolic and physiological adjustments. An effective way to minimize energy expenditure during food scarcity is to decrease the mass of the organs. As the digestive system is metabolically expensive to maintain, the small intestine and the liver are the most affected organs. We evaluated the effects of phase III starvation on the mass of the different organs and histological parameters on house sparrows, a small non-migrant bird. In a short period of time (34 h) we observed a larger reduction in the digestive organ mass when compared to the mass of the body and non-alimentary tissues. Furthermore, the intestinal mass was proportionally more reduced than its length and nominal surface area. A reduction on the intestinal mucosal layer also resulted in a shortening of villus (length and thickness) and crypt depth. Moreover, the morphology of the enterocytes changed from cylindrical to cubical, suggesting that the surface exposed to the lumen was conserved. This may indicate an adaptive response to the moment of refeeding. The nominal surface area/body mass remained constant in both groups and several histological parameters were reduced, suggesting that starving induces the atrophy of the small intestine. However, the goblet cells were conserved after fasting indicating a protective tendency.

Differential transcriptional responses underlie dietary induction of intestinal carbohydrase activities in house sparrow nestlings

Many species show diet-induced flexibility of activity of intestinal enzymes; however, molecular and genetic mechanisms responsible for such modulation are less known, particularly in altricial birds. The goal of our study was to test whether a diet-induced increase in activity of intestinal maltase and sucrase in house sparrow nestlings is matched with an increase in maltase-glucoamylase (MG) and sucrase-isomaltase (SI) complex mRNAs respectively. Both enzyme activities were significantly higher in mid-intestine of nestlings fed a medium-starch (MS) diet compared to those fed a starch-free (SF) diet. In contrast to the similar pattern of dietary induction for both enzyme activities, diet MS elevated significantly only the level of MG mRNA, but not SI mRNA. The coordinated increase in activity of maltase and in MG mRNA is consistent with the hypothesis that dietary induction of this enzyme is under transcriptional control. In contrast, the lack of such coordination for changes in activity of sucrase and SI mRNA suggests that upregulation of this enzyme may be achieved by post-translational factor(s). We conclude that genetic mechanisms responsible for diet-induced flexibility of digestive enzymes in birds may differ from that observed in mammals.

DIFFERENCES IN BIRD ASSEMBLAGES BETWEEN NATIVE NATURAL HABITATS AND SMALL-SCALE TREE PLANTATIONS IN THE SEMIARID MIDWEST OF ARGENTINA

ABSTRACT We studied the effects on structure of bird assemblages after replacement of native natural habitats by small-scale tree plantations used for recreational purposes. The richness and diversity were similar among habitats; however, the total bird abundance was greater in the tree plantations compared to the natural habitats. Also, we found that small-bodied birds that forage in the foliage had higher abundance in the natural habitats, while larger-bodied species that live in open spaces and forage on the ground occurred in higher abundance in the tree plantations. The comparative evaluation of the seasonal effect on avian assemblages of the contrasting habitats showed that natural habitats had a greater annual fluctuation of abundance values, while the tree plantations were more constant. Our study demonstrates that small-scale tree plantations for recreational purposes exert strong effects on bird assemblages, because they increase the abundance of the generalist and common bird species in the region.

House sparrow biomarkers as lead pollution bioindicators. Evaluation of dose and exposition length on hematological and oxidative stress parameters

House sparrows (Passer domesticus) have been proposed as a key ecological indicator of urban pollution. Remarkably, we lack knowledge about the physiological effects of lead on this bird species. Therefore, this study was aimed to evaluate the effect of Pb on several physiological parameters in house sparrows exposed to environmental Pb concentrations. In a first experiment, birds were exposed to Pb sub-lethal doses (from 1.3 to 14.0 µg of Pb/g animal/day) during 5 days, which resulted in a dose response increase of blood Pb levels and decrease of blood ALAD activity. However, at the higher doses tested (> 7 μg of Pb/g animal/day) the blood ALAD activity inhibition (~82%) remained constant. Hematocrit and hemoglobin were significantly reduced only at the highest-doses, and the stress indicator, heterophils to lymphocyte (H/L) ratio, did not show apparent changes. In a second experiment, house sparrows were exposed to Pb in drinking water (12.3 ppm) during either 15 or 30 days. Pb concentration used in this study was enough to produce blood lead levels equivalents to those found recently in house sparrows inhabiting urban areas, reduced blood ALAD activity and inversion of the H/L ratio. Decreasing blood ALAD activities were correlated with increasing blood Pb levels. In addition, Pb exposure produced modification in the levels of hepatic antioxidant enzymes, increased GST activity and decreased CAT activity, without lipid peroxidation. In conclusion, our results suggest that blood ALAD activity is a reliable and sensitive biomarker for environmental Pb exposure in house sparrows, additionally chronic exposure produce physiological stress (H/L inversion) and small changes in antioxidant enzyme activity. Finally, this specie could be considered a bioindicator for monitoring the urban Pb contamination.