Mangueira Lagoon Research Articles

Diagnostic locus for identification of silverside hybrids (odontesthes humensis and odontesthes bonariensis) in a natural population

Hybridization is a natural phenomenon that occurs more often in fish than in other vertebrates. The use of nuclear and mitochondrial molecular markers provides valuable results in the detection of these events. The aim of this study was to investigate the occurrence of interspecific hybrids in natural populations of silverside. The samples of Odontesthes humensis, Odontesthes bonariensis, and individuals that were morphologically different from pure species were collected in the Mangueira lagoon, located in southern Brazil. Result: Six tetranucleotide microsatellite loci were synthesized and tested. The UFPEL_OH3 locus proved to be diagnostic for the detection of silverside hybrids, and it was possible to distinguish between pure and hybrid species. The mitochondrial marker gene cytb synthesized from conserved Odontesthes sequences in the GenBank genetic database showed no differences in the genetic sequence of the samples, needing further studies to confirm the hypothesis.

Determination of aliphatic hydrocarbons in surface sediments of Mangueira Lagoon (RS—Brazil)

Determination of aliphatic hydrocarbons in surface sediments of Mangueira Lagoon (RS—Brazil)

Organic carbon accumulation in oligotrophic coastal lakes in southern Brazil during the last century

We report organic carbon (OC) accumulation rates in three freshwater ecosystems in southern Brazil, along the largest shallow coastal lagoon ecosystem in the world, the Patos-Mirim-Mangueira. After European colonisation in the seventeenth century, regional wetlands started being replaced by agricultural fields (mostly rice). We used excess 210Pb to develop chronologies for lagoon sediment cores and quantify bulk sediment and OC accumulation rates. In the past 120 years, OC accumulation rates in Mirim and Mangueira Lagoons, which are influenced by rice paddies, averaged 14.9 ± 8.5 and 6.4 ± 3.7 g C m−2 year−1, respectively. Greater accumulation rates were estimated for macrophyte-dominated Nicola Lake (69.9 ± 38.5 g C m−2 year−1) located within the protected Taim Wetland with no direct influence of rice plantations. Starting in the early twentieth century, the construction of dams and drainage canals altered regional hydrology. Despite these anthropogenic changes, only a mild increase in OC accumulation was observed in Mirim Lagoon (15% only in site MIR2) after 1970. Mangueira Lagoon experienced the lowest OC burial rates despite increasing sedimentation rate and OC burial after the mid-1970s. This is probably because these large lakes (> 500 km2) have great nutrient-dilution potential, and their well-mixed water columns prevent nutrients from accumulating in the sediments over time.

Determination of Cr, Cu, Ni, Pb and Zn in the sediments of Mangueira Lagoon/RS/Brazil

The Mangueira Lagoon is 123 km long and 7.6 km wide at its widest point, with an average depth of 2.5 m. By the fact that this lagoon is one of the youngest geological formations on Earth (only 4.5 thousand years), little is known about the geology of its sediments. This work describes the concentration of the toxic metals Cr, Cu, Ni, Pb and Zn in surface sediments samples of Mangueira Lagoon. The sediment samples were collected and underwent pseudo-acid digestion (aqua regia / perchloric acid). The extracts obtained were analyzed by atomic absorption spectroscopy in flame. Cu and Zn were detected at all points during the test. Zn is a major element, ranging from 2.5 mg kg-1 ± 0.3% to 4.1 mg kg-1 ± 2.4%, followed by Cu with values between 2.0 mg kg-1 ± 8.5% to 2.5 mg kg-1 ± 4.2%. Considering the parameters established by the CCME (Canadian Environmental Quality Guidelines), TEL (Threshold Effect Level) and PEL (Probable Effect Level), the concentrations of toxic metals found in the surface sediment were low and showed low environmental impacts. These results constitute a contribution to a better understanding of the processes that occur in the region, serving as a basis for future work.

Determination of trace metals in water from Mangueira Lagoon – RS, Brazil

Abstract Determination of trace metals was carried out in Mangueira Lagoon, in the southern zone of Rio Grande do Sul. Samples were collected at five points to evaluate the concentrations of the following trace metals: copper, zinc, lead, chromium, nickel and iron. Metals were determined by digestion with concentrated nitric acid and pre-concentrated in Chelex 100 resin analyzed by atomic absorption spectrophotometry. In parallel, the physical-chemical parameters pH, chlorides, alkalinity, hardness and organic matter in the water were determined. Potassium and sodium metals were analyzed by atomic emission spectrometry. The analyzes of pH and conductance were analyzed in the field while the others were done in the laboratory of the research group of environmental contaminants (GPCA). Through the results of physical-chemical parameters of the water, the Mangueira Lagoon exhibits a low degree of contamination, but in the future may compromise the biota of the lagoon. Regarding the focus of this work, of Cu, Cr, Fe, Ni, Pb, and Zn (heavy metals), only lead and iron obtained the values above that are established in CONAMA 357/2005.

RENDIMENTO CORPORAL E COMPOSIÇÃO QUÍMICA DO FILÉ DA VIOLA (Loricariichthys anus)

Loricariichthys anus (Viola) is currently the largest fish species of economic value of Mangueira Lagoon and, because of that, the aim of this work was to analyze its body yield and the chemical composition of its fillet. Forty animals caught in Mangueira Lagoon were divided into two groups of 20 animals each. The weight presented a variation of 128 to 190g in group A and of 234 to 293g in group B. Biometric evaluation was performed in Ichthyology Laboratory of UFPEL, where the animals were evaluated regarding length and weight, which were used for body yield calculation. Carcass yield, head yield, visceral yield, skin yield, clean trunk yield and fillet yield were evaluated. Chemical analysis was performed in dried fillet to obtain the values of protein, lipids, ash and moisture, and in natural matter to assess the fatty acid content. The weight of animals affects carcass yield. The viola fillet is lean, with high protein content and higher amount of unsaturated fatty acids compared to saturated.KEYWORDS: Body yield; carcass; chemical composition; fish fillet; Loricariichthys anus (Viola).

Ownership of fishing areas and use of fishing resources by artisanal fishermen in a pond in southern Brazil

The Mangueira Lagoon located in southern Brazil, has its northern portion included in the Taim Ecological Station, a federal conservation unit. The fishing practice is among the activities at this region. It has its own characteristics due to environmental conditions and specific physiography of the area. A field protocol based on geographic information was used to characterize the occupation process and the use of fishing resources. Socio-economic information was collected through interviews of the fishermen and also based on fishing data. After compiling the data a statistical descriptive analyses was completed. The average catch per fisherman in the region is 4,766.5 kg per year. The Loricariichthys anus showed the highest catch volume, ensuring the economic viability of the local activity. The constant increase of the activity may be compromising the reproductive cycle of the local ichthyological fauna, thus compromising the fishery sustainability.

English

The aim of this study was to determine elemental constituent of microalgal biomass Spirulina platensis LEB-18 grown on the shores of Mangueira Lagoon, South of Brazil. The spread of inoculum was performed in standard Zarrouk medium. When the microalgae concentration reached 0.50 g L-1, the biomass was separated by filtration and dried in a tray dryer at 50°C for 5 h. The harvested biomass was then ground in a ball mill, sieved to achieve a particle size of 88 µm (~ 300 mg) in triplicate, digested with concentrated HNO3 and diluted with up to 5% HNO3 for subsequent quantification. Mineral content was determined by inductively coupled plasma optical emission spectrometry with axial view and other nutrients by standard methods. Among the macro minerals, in μg g-1 ± standard deviation, calcium (15.108±529), sodium (14.6552±485) and potassium (14.036±109) were found in the largest amount. The micro mineral present in greater quantity, in μg g-1 ± standard deviation, was the iron (956±9) and nutrients present in the following order: protein (58.5%), ash (12.0%), carbohydrate (7.5%), lipid (7.0%) and crude fiber (0.95%). Results were compared with the values of minerals for human consumption recommended by the Food and Drug Administration and also with the Recommended Daily Intake (RDI) of minerals by Brazilian Legislation. The findings proved promising for the use of S. platensis strain LEB-18 as an alternative source of essential minerals and other nutrients for the human body. Key words: Cyanobacterium, chemical element, nutritional importance, optical emission spectrometry.

Fluxos de nutrientes associados às descargas de água subterrânea para a Lagoa Mangueira (Rio Grande do Sul, Brasil)

This study assesses the importance of groundwater discharge to dissolved nutrient levels in Mangueira Lagoon. A transect of an irrigation canal in the margin of Lagoon demonstrated a strong geochemical gradient due to high groundwater inputs in this area. Using 222Rn as a quantitative groundwater tracer, we observed that the flux of dissolved inorganic nitrogen (DIN), silicate and phosphate (1178 and 1977; 26190 and 35652; 167 and 188 mol d-1 for winter and summer, respectively) can continually supply/sustain primary production. The irrigation canals act as an artificial underground tributary and represent a new source of nutrients to coastal lagoons.

Estrutura populacional de capivaras na Estação Ecológica do Taim, Brasil, RS

Uma população de capivaras (Hydrochoerus hydrochaeris) foi monitorada na região limítrofe entre a Estação Ecológica do Taim e áreas de cultivo de arroz no extremo sul do Rio Grande do Sul, Brasil. O objetivo foi caracterizar a estrutura populacional, a densidade e os períodos reprodutivos da capivara na Estação Ecológica do Taim, RS, e em seu entorno. De agosto de 2003 a agosto de 2005, foram realizados 25 censos de contagem direta, em um transecto de 4.000 metros de comprimento, às margens da Lagoa Mangueira. Foi obtida a abundância de animais segundo seu sexo e classe etária. A abundância foi de 608,6±27,9 indivíduos e a densidade média foi de 5,1±0,2ind. ha-1. Houve variação no número de animais do primeiro para o segundo ano de amostragem, sendo significativamente maior no último. Foram identificados, em média, 22,0±0,8 grupos na área, constituídos predominantemente de fêmeas adultas (47,5%), seguidas de juvenis (24,8%), filhotes (17%) e machos adultos (7,7%). A abundância de animais variou segundo a distribuição espacial, sendo maior no interior da Estação Ecológica do Taim (9,5ind. ha-1). Houve flutuações sazonais no recrutamento da população, tendo suas maiores densidades de filhotes no outono.

Evidences of continental groundwater inputs to the shelf zone in Albardão, RS, Brazil

The southern coastal region of Brazil is highly productive and many of its oceanographic processes are still poorly understood due to a great number of forces, such as the continental input from the Plata River and Patos Lagoon, several distinct oceanic water masses, and a complex contribution from groundwater. The shelf near Albardão is highly rich in dissolved nutrients, particularly in the coastal zone. The narrow sandy barrier that separates the ocean from Mangueira Lagoon has led us to wonder about the possibility of groundwater, and if it might play a role in the productivity of the surrounding area. In order to test this hypothesis, nutrient data from Mirim and Mangueira Lagoons and from Albardão were collected during a rainy period. The present work shows the need to include groundwater transport from Mangueira Lagoon to the coastal zone as one of the main sources for the productivity in that region. However, for such phenomenon to be quantified and better understood, it becomes necessary to use natural isotopes as tracers of the underground input.

Major Ion Chemistry in a Freshwater Coastal Lagoon from Southern Brazil (Mangueira Lagoon): Influence of Groundwater Inputs

This paper characterizes major ion distributions and investigates whether groundwater exerts a major control on the chemical functioning of Mangueira Lagoon, a large (90 km long), shallow (∼4–5 m deep), and fresh coastal lagoon in southern Brazil. Water volumes equivalent to ∼80% of the total annual input are used in the summer for irrigating nearby rice plantations, the most important regional economic activity. While Na+ and Cl− are the major ions in local groundwater, Na+ and HCO3− are the most enriched ions in lagoon water. The ion concentrations measured in Mangueira Lagoon were homogeneous, except for a few samples affected by rainwater and groundwater inputs. A shore-normal transect starting at the pump house of a rice irrigation canal indicated strong groundwater input at this canal. In spite of the small volume contribution (∼2% of precipitation), groundwater discharge accounts for 50–70% of major ion inputs into the lagoon, with ∼70% of the groundwater inputs being anthropogenically derived (e.g., from the rice irrigation canals). This may have serious implications for the management of the coastal water resources from Mangueira Lagoon and other similar areas as groundwater associated with agricultural systems may be contaminated by fertilizers and pesticides. The results imply that groundwater should not be neglected in dissolved species’ budgets even when its volume contribution is small.

Tracing anthropogenically driven groundwater discharge into a coastal lagoon from southern Brazil

Summary We investigated the distribution of naturally occurring geochemical tracers ( 222 Rn, 223 Ra, 224 Ra, 226 Ra, CH 4 , δ 18 O, and δ 2 H) in the water column and adjacent groundwater of Mangueira Lagoon as proxies of groundwater discharge. Mangueira Lagoon is a large (90 km long), shallow (∼4–5 m deep), fresh, and non-tidal coastal lagoon in southern Brazil surrounded by extensively irrigated rice plantations and numerous irrigation canals. We hypothesized that the annual, intense irrigation for rice agriculture creates extreme conditions that seasonally change groundwater discharge patterns in the adjacent lagoon. We further supposed that dredging of irrigation canals alters groundwater fluxes. While the activities of 222 Rn in shallow groundwater were 2–3 orders of magnitude higher than in surface water, CH 4 and radium isotopes were only ∼1 order of magnitude higher. Therefore, 222 Rn appears to be the preferred groundwater tracer in this system. Radon concentrations and conductivities were dramatically higher near the pump house of rice irrigation canals, consistent with a groundwater source. Modeling of radon inventories accounting for total inputs (groundwater advection, diffusion from sediments, and decay of 226 Ra) and losses (atmospheric evasion, horizontal mixing and decay) indicated that groundwater advection rates in the irrigation canals (∼25 cm/d) are over 2 orders of magnitude higher than along the shoreline (∼0.1 cm/d). Nearly 75% of the total area of the canals is found in the southern half of the lagoon, where groundwater inputs seem to be higher as also indicated by methane and stable isotope trends. In spite of the relatively small area of the canals, we estimate that they contribute nearly 70% of the total (∼57,000 m 3 /d) groundwater input into the entire Mangueira Lagoon. We suggest that the dredging of these canals cut through aquitards which previously restricted upward advection from the underlying permeable strata. The irrigation channels may therefore represent an important but previously overlooked source of nutrients and other dissolved chemicals derived from agricultural practices into the lagoon.

Isolation and Characterization of a New Arthrospira Strain

A filamentous microorganism, morphologically similar to the cyanobacterium Arthrospira, was isolated from Mangueira Lagoon in Brazil, from which Arthrospira has not previously been isolated. Random amplified polymorphic DNA (RAPD) comparison with the standard Arthrospira platensis strains LEB 52 and Paracas indicated that the organism isolated was an Arthrospira isolate, which we denominated strain LEB 18. The RAPD analysis showed conserved sequences which indicated that the three strains belonged to the same genus, and were all Arthrospira species, but there were sufficient differences between them suggesting that they were separate strains. The strain LEB 18 was cultivated in undiluted Zarrouk medium and in 60% and 20% (v/v) Zarrouk medium diluted with sterilized Mangueira Lagoon water (MLW) using illuminance rates of 32.5, 45.5 and 58.5 micromol m(-2) s(-1) according to a complete 32 factorial design with a triplicate central point. The strains LEB 52 and Paracas were cultived in the conditions central point. Our new isolate produced the highest specific growth rate (Umax = 0.22 d(-1)) in 60% Zarrouk medium diluted with MLW and illuminated with 58.5 micromol m(-2) s(-1) and the highest protein content (86.0% w/w).

Repeated batch cultivation of the microalga Spirulina platensis

The cultivation of photosynthetic microorganisms such as the microalga Spirulina platensis can provide an alternative source of food. The water in Mangueira Lagoon (Rio Grande do Sul state, southern Brazil) has several required nutrients for the growth of Spirulina and could be added to culture medium to reduce the cost of producing S. platensis. Although little studied, repeated batch cultivation is a very useful technique because it has a better cost–benefit ratio than other cultivation methods. In a series of runs, we studied the influence of cell concentration, renewal rate and strain on the specific growth rate and biomass productivity of S. platensis during repeated batch cultivation, the runs taking place in 2-l Erlenmeyer flasks for 2160 h at 30 °C and a light intensity of 2500 lux under a 12 h photoperiod. The three factors studied had a significant (P < 0.05) effect on the results (specific growth rate and productivity). Using Zarrouk’s medium, the highest specific growth rate (μX) was 0.111 day−1 while the biomass productivity (PX) was 0.0423 g l−1 day−1, while Mangueira Lagoon water supplemented with 10% Zarrouk’s medium gave μX = 0.113 day−1 and a productivity PX = 0.0467 g l−1 day−1. These values were two to three times higher than the results obtained in batch cultivation, indicating that the repeated batch cultivation of S. platensis is attractive and convenient.

Simultaneous Cultivation of Spirulina platensis and the Toxigenic Cyanobacteria Microcystis aeruginosa

Mangueira Lagoon, located in the extreme south of Brazil, has water with physicochemical characteristics such as alkaline pH and carbonate levels propitious for the growth of the cyanobacterium Spirulina platensis. Previously published studies have shown that Mangueira Lagoon water supplemented with small quantities of carbon and nitrogen is suitable for S. platensis cultivation and can significantly reduce production costs. We studied mixed cultures of Spirulina platensis and the toxic cyanobacterium Microcystis aeruginosa using a 2(3) factorial design in which the three factors were the initial biomass concentration of S. platensis and M. aeruginosa and the type of culture medium (100% Zarrouk's medium or 80% Mangueira Lagoon water plus 20% Zarrouk's medium). The highest S. platensis maximum specific growth rate (mu(max)) occurred in the culture with the highest M. aeruginosa biomass concentration and when undiluted culture medium was used (micro(max) = 0.283 d(-1)). The highest M. aeruginosa specific death rate (k) was obtained in the presence of S. platensis (k = 0.555 d(-1)) and was independent of the initial M. aeruginosa biomass concentration and culture medium, demonstrating that S. platensis cultures are not susceptible to contamination by M. aeruginosa. The culture medium had no significant influence (p > 0.05) on S. platensis micro(max) values, indicating that production costs could be reduced by using a medium consisting of 80% Mangueira Lagoon water plus 20% Zarrouk's medium.

Alimentação do peixe-rei (Odontesthes bonariensis, Atherinopsidae) nas lagoas Mirim e Mangueira, Rio Grande do Sul, Brasil

Foi estudada a alimentação natural do peixe-rei (Odontesthes bonariensis Cuvier &amp; Valenciennes, 1835) nas lagoas Mirim e Mangueira, Estado do Rio Grande do Sul, Brasil. O conteúdo estomacal de 60 indivíduos de peixe-rei (Odontesthes bonariensis) provenientes dessas lagoas mostraram que esta espécie tem amplo espectro alimentar. Uma grande variedade de alimentos é consumida, sem afetar o crescimento, pois os peixes dos dois ambientes apresentaram condição corporal semelhante. Na lagoa Mangueira, crustáceos (Isopoda) representaram 65% da dieta dos peixes e na lagoa Mirim, moluscos (Bivalvia e Gastropoda) perfizeram 70% dos conteúdos de estômago identificados.

Improving Spirulina platensis biomass yield using a fed-batch process

Increasing interest is being shown in the cyanobacterium Spirulina platensis because of its nutritional properties when used as food supplement and possible therapeutic effects. One of the most important areas being studied is the development of alternative nutrient sources which can be used to decrease the production costs of commercially produced S. platensis and obtain high productivity. Water from Mangueira Lagoon (Rio Grande do Sul State, Brazil) has high levels of carbonates and a high pH and has the potential to be used as a culture medium for S. platensis, although some nutrient supplementation may be required. We tested the effect of unsupplemented Mangueira Lagoon water (MLW) or MLW supplemented with 1.125 or 2.250 mg/l of urea and/or 21 or 42 mg/l of sodium bicarbonate on the growth of S. platensis in fed-batch culture using a 3 2 factorial design and found that there the addition of 1.125 mg/l of urea resulted in a 2.67 fold increase times in the final biomass concentration of S. platensis.

Spirulina platensis growth in open raceway ponds using fresh water supplemented with carbon, nitrogen and metal ions.

To investigate the feasibility of using fresh water from Mangueira Lagoon (Rio Grande do Sul, Brazil) for biomass production in open raceway ponds (0.7 m long, 0.18 m wide, 0.075 m deep) we studied the influence of nutrient addition (carbon as sodium bicarbonate, nitrogen as urea, phosphate, sulfate, ferric iron, magnesium and potassium) on the growth rate of the cyanobacteria Spirulina platensis using a 22 factorial design. In unsupplemented lagoon water production of S platensis was 0.78 +/- 0.01 g/l (dry weight basis) while the addition of 2.88 g/l of sodium bicarbonate (without added urea, phosphate, sulfate or metal ions) resulted in 0.82 +/- 0.01 g/l after 400 hours of culture. The further addition of phosphate and metal ions resulted in growth for up to 750 h and a final S. platensis biomass of 1.23 +/- 0.04 to 1.34 +/- 0.03 g/l.

Modelling of Spirulina platensis growth in fresh water using response surface methodology

The influence of nutrient addition on the growth rate of Spirulina platensis in the Mangueira Lagoon water was studied in order to investigate the feasibility of using this water for biomass production. The addition of urea and sodium bicarbonate was studied through surface response methodology, over concentration ranges from 0.0 to 0.01170 M, and 0.0–19.70 gl−1 respectively. The growth of Spirulina platensis in Mangueira Lagoon water with no addition of nutrients was carried out and compared with the biomass growth after nutrient addition. The results indicated that the optimal level of nutrients was 0.00585 M urea and without the addition of sodium bicarbonate. The biomass concentration was 1.4 gl−1 in 780 h of cultivation and the doubling time (t d) was 3.85 days. In 300 h, the biomass concentration in the medium without nutrient addition was 0.9 gl−1, with a doubling time of 3.80 days.