Caracterização da estruturação espacial dos povoamentos da epifauna do litoral rochoso do distrito de Mercúfi. província de Cabo Delgado (Norte de Moçambique), com uso de Sistema de Informação Geográfica: distribuição, abundância, diversidade e conservação

Dissertação de mest. em Estudos Marinhos e Costeiros, Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2002

Síntese enzimática de ésteres de açúcar: surfactantes e polímeros como novos materiais ambientalmente seguros

Sugar esters are substances which possess surfactant, antifungical and bactericidal actions and can be obtained through two renewable sources of raw materials: sugars and vegetable oils. Their excellent biodegradability, allied to lhe fact that they are non toxic, insipid, inodorous, biocompatible, no-ionic, digestible and because they can resist to adverse conditions of temperature, pH and salinity, explain lhe crescent use of these substances in several sections of lhe industry. The objective of this thesis was to synthesize and characterize surfactants and polymers containing sugar branched in their structures, through enzymatic transesterification of vinyl esters and sugars, using alkaline protease from Bacillus subtilis as catalyst, in organic medium (DMF).Three types of sugars were used: L-arabinose, D-glucose and sucrose and two types of vinyl esters: vinyl laurate and vinyl adipate. Aiming to reach high conversions from substrates to products for a possible future large scale industrial production, a serie of variables was optimized, through Design of Experiments (DOE), using Response Surface Methodology (RSM).The investigated variables were: (1) enzyme concentration; (2) molar reason of substrates; (3) water/solvent rale; (4) temperature and (5) time. We obtained six distinct sugar esters: 5-0-lauroyl L-arabinose, 6-0-lauroyl D-glucose, 1'-O-lauroyl sucrose, 5-0-vinyladipoyl L-arabinose, 6-0-vinyladipoyl D-glucose and 1 '-O-vinyladipoyl sucrose, being lhe last three polymerizable. The progress of lhe reaction was monitored by HPLC analysis, through lhe decrease of sugar concentration in comparison to lhe blank. Qualitative analysis by TLC confirmed lhe formation of lhe products. In lhe purification step, two methodologies were adopted: (1) chromatographic column and (2) extraction with hot acetone. The acylation position and lhe chemical structure were determined by 13C-RMN. The polymerization of lhe three vinyl sugar esters was possible, through chemical catalysis, using H2O2 and K2S2O8 as initiators, at 60°C, for 24 hours. IR spectra of lhe monomers and respective polymers were compared revealing lhe disappearance of lhe vinyl group in lhe polymer spectra. The molar weights of lhe polymers were determined by GPC and presented lhe following results: poly (5-0-vinyladipoyl L-arabinose): Mw = 7.2 X 104; PD = 2.48; poly (6-0-vinyladipoyl D-glucose): Mw = 2.7 X 103; PD = 1.75 and poly (1'-O-vinyladipoyl sucrose): Mw = 4.2 X 104; PD = 6.57. The six sugar esters were submitted to superficial tension tests for determination of the critical micelle concentrations (CMC), which varied from 122 to 167 ppm. Finally, a study of applicability of these sugar esters, as lubricants for completion fluids of petroleum wells was' accomplished through comparative analysis of lhe efficiency of these sugar esters, in relation to three commercial lubricants. The products synthesized in this thesis presented equivalent or superior action to lhe tested commercial products

Utilização agrícola de composto de resíduo sólido urbano.

O porquê do uso agronõmico do composto de lixo. Critérios de aplicação e de manejo do composto. Efeitos sobre as propriedades do solo. Capacidade de troca catiônica (CTC). rEAÇÃO DO SOLO. Nutrientes. Relação C/N. Nitrogênio. Fósforo. Potássio, cálcio, magnésio e sódio. Enxofre e micronutrientes. Salinidade e sociedade. Elementos inorgânicos potencialmente tóxicos. Efeitos sobre as plantas.

Caracterização e avaliação agronômica de novos isolados de rizóbio obtidos de nódulos de genótipos silvestes de feijoeiro-comum.

Este trabalho teve como objetivos avaliar a capacidade de utilização de fontes de C, tolerância à salinidade e temperatura, caracterizar genotipicamente e determinar a eficiência agronômica de novos isolados de rizóbio em condições de campo.

Estudo paramétrico da recuperação de petróleo pesado por aquecimento eletromagnético resistivo

Electrical resistive heating (ERH) is a thermal method used to improve oil recovery. It can increase oil rate and oil recovery due to temperature increase caused by electrical current passage through oil zone. ERH has some advantage compared with well-known thermal methods such as continuous steam flood, presenting low-water production. This method can be applied to reservoirs with different characteristics and initial reservoir conditions. Commercial software was used to test several cases using a semi-synthetic homogeneous reservoir with some characteristics as found in northeast Brazilian basins. It was realized a sensitivity analysis of some reservoir parameters, such as: oil zone, aquifer presence, gas cap presence and oil saturation on oil recovery and energy consumption. Then it was tested several cases studying the electrical variables considered more important in the process, such as: voltage, electrical configurations and electrodes positions. Energy optimization by electrodes voltage levels changes and electrical settings modify the intensity and the electrical current distribution in oil zone and, consequently, their influences in reservoir temperature reached at some regions. Results show which reservoir parameters were significant in order to improve oil recovery and energy requirement in for each reservoir. Most significant parameters on oil recovery and electrical energy delivered were oil thickness, presence of aquifer, presence of gas cap, voltage, electrical configuration and electrodes positions. Factors such as: connate water, water salinity and relative permeability to water at irreducible oil saturation had low influence on oil recovery but had some influence in energy requirements. It was possible to optimize energy consumption and oil recovery by electrical variables. Energy requirements can decrease by changing electrodes voltages during the process. This application can be extended to heavy oil reservoirs of high depth, such as offshore fields, where nowadays it is not applicable any conventional thermal process such as steam flooding

Contribuição da catodoluminescência para o entendimento da diagênese da formação Jandaíra: áreas do campo de petróleo da fazenda Belém e Lajedo do Rosário

The general objective of this study was to contribute to the understanding of the chemical evolution of fluids that percolate through carbonate rocks of the Jandaíra Formation. The oxidation and reduction conditions in which grains, source and cement were formed was investigated using the cathodoluminescence technique (CL). The study area is located in the west part of the Potiguar Basin (Fazenda Belém field) and Rosário Ledge (Felipe Guerra municipality, State of Rio Grande do Norte, Brazil). The analysis of thin sections of carbonate rocks under CL revealed that grains (allochemical or not) and diagenetic products (micritization, dolomitization, neomorphism and cementation) exhibit since absence of luminescence the various luminescence colors (yellow, orange, red, brown, and blue) in a variety of intensities. As pure calcite shows dark blue luminescence, the occurrence of different luminescence colors in calcite crystals suggest one or more punctual crystal defects such as free electron, free space and impurity. The dyeing of thin sections with alizarin and potassium ferrocyanide revealed the absence of ferrous carbonate in the different lithotypes of Jandaíra Formation. Therefore, the different colors and intensities of CL observed in these rocks are probably caused by the presence of ion activators such as Mn2+ and is not an activator/inhibitor combination. In the same way, the absence of luminescence is very probably caused by the absence of activator ions and not due to the low concentration of inhibitor ions such as Fe2+. The incorporation of Mn2+ in the different members of the Jandaíra Formation must have been controlled by the redox state of the depositional environment and diagenesis. Therefore, it is possible that the luminescent members have been formed (e.g.,ooids) or have been modified (gastropod neomorphism) under reduction conditions in the depositional environments, in subsurface during the burial, or, in the case of Rosario Ledge samples , during the post-burial return to surface conditions. As regards the sudden changes from low to moderate and to strong luminescence, these features should indicate the precipitation of a fluid with chemical fluctuations, which formed the frequent zonations in the block cement of the Rosario Ledge samples. This study suggests that the different intensities and colors of CL should be correlated with the Mn2+ and Fe2+ contents, and stable isotopes of samples to determine the salinity, temperature, pH e Eh conditions during deposition

Aplicação de sistemas microemulsionados ácidos em acidificação de poços

Stimulation operations have with main objective restore or improve the productivity or injectivity rate in wells. Acidizing is one of the most important operations of well stimulation, consist in inject acid solutions in the formation under fracture formation pressure. Acidizing have like main purpose remove near wellbore damage, caused by drilling or workover operations, can be use in sandstones and in carbonate formations. A critical step in acidizing operation is the control of acid-formation reaction. The high kinetic rate of this reaction, promotes the consumed of the acid in region near well, causing that the acid treatment not achive the desired distance. In this way, the damage zone can not be bypassed. The main objective of this work was obtain stable systems resistant to the different conditions found in field application, evaluate the kinetic of calcite dissolution in microemulsion systems and simulate the injection of this systems by performing experiments in plugs. The systems were obtained from two non ionic surfactants, Unitol L90 and Renex 110, with sec-butanol and n-butanol like cosurfactants. The oily component of the microemlsion was xilene and kerosene. The acqueous component was a solution of HCl 15-26,1%. The results shown that the microemulsion systems obtained were stable to temperature until 100ºC, high calcium concentrations, salinity until 35000 ppm and HCl concentrations until 25%. The time for calcite dissolution in microemulsion media was 14 times slower than in aqueous HCl 15%. The simulation in plugs showed that microemulsion systems promote a distributed flux and promoted longer channels. The permeability enhancement was between 177 - 890%. The results showed that the microemulsion systems obtained have potential to be applied in matrix acidizing

Estudo comparativo de dois tipos de cultivo: monocultivo (camarões) versus cultivo integrado (algas/camarões)

The integrated culture of seaweed and aquatic animals is an ancient practice in Asian countries. The expansion of this practice to western countries is consequence of the recognition of this system as a sustainable alternative that allows economical diversification and mitigation of environmental impacts generated by effluents of aquaculture. This study evaluated the growth of the seaweed Gracilaria caudata and of the shrimp Litopenaeus vannamei in monoculture (shrimps) and integrated culture (shrimps and algae) systems, and accessed the effect of the seaweed in the water quality. There were two treatments in the experiment: monoculture (shrimps) and integrated culture (shrimps/ algae). The organisms were cultured in 6 aquaria (10L) filled with seawater (35.0±0.0 PSU and 28.1±0.4°C) for 28 days. The nutrients of water (PO43-, NH4+, NO2-, NO3- and DIN), the biomass and the relative growth rate (RGR, % day-1) of seaweed and shrimps were measured weekly. The parameters pH, temperature, salinity and dissolved oxygen were measured daily. The concentration of NH4+ in integrated culture (62.8±25.2µM) was lower (Mann-Whitney p<0.001) than in monoculture (85.6±24.3µM). The mean of PO4- in monoculture (10.4±4.6µM) was markedly higher (Mann-Whitney; p=0.024) than that in integrated culture (8.7±4.1µM). The level of dissolved oxygen in integrated culture (6.0±0.6mg/L) was higher (t-Student; P=0.014) than that in shrimp monoculture (5.8±0.6mg/L). The mean values of the parameters pH, NO2-, NO3- and DIN were 7.5±0.2, 10.1±12.2µM, 24.5±3.2µM and 120.17±30.76µM in monoculture, and 7.5±0.2, 10.5±13.2µM, 27.4±3.5µM and 100.76±49.59µM in integrated culture. There were not differences in these parameters between treatments. The biomass and RGR of seaweed reached 15.0±1.9g and 7.4±2.8% day-1 at the end of the experiment. The performance of shrimp was favorable in monoculture (1.5±0.8g; 5.7±1.6% dia-1) and in integrated culture (1.5±0.7g; 5.2±1.2% dia-1), and the rate of survival was 100% in both treatments. The tolerance and favorable performance of Gracilaria caudata suggest that this seaweed might be integrated into shrimp (Litopenaeus vannamei) culture systems

Influência da profundidade e dos parâmetros ambientais sobre o desenvolvimento de Gracilaria birdiae (Rhodophyta, Gracilariales) em viveiro de camarão

This study evaluates the influence of depth and environmental parameters on the development of Gracilaria birdiae Plastino & Oliveira (Gracilariaceae Rhodophyta) in an organic shrimp pound (Litopenaeus vannamei) under euthrophical conditions. PVC structures (module) witch four ropes laden with 150 g of macroalgae each, were kept during 35 days at three different depths (surface, 10 and 20 cm depth). Wet biomass weighing and environmental parameters (temperature, salinity, turbidity, pH, transparence, precipitation, evaporation, insolation, accumulated solar radiation, nitrite, nitrate, ammonium and orthophosphate) were measured weekly. At all three proposed depths, the macroalgae displayed a higher biomass at the end of experiment than at the initial inoculations. The module kept at a 10 cm depth presented the greatest average biomass (186,3), followed by that kept at 20 cm (180,4 g) and the surface module (169,9 g). Biomass variations showed algae to suffer the direct effects of depths. Biomass loss was associated with the factors that influence light penetration, such as sediment deposits above the thallus, rate of evaporation and precipitation. The smallest loses occurred in the algae kept on surface (0,16%), followed by the algae kept at 20 cm (0,20%) and 10 cm (0,22%). The specific growth rate (SGR) of G. birdiae showed no significant difference between the three depths nor the sample periods. Nevertheless, the modules kept at 10 and 20 cm depths presented similar growth evolution, both growing 0,38%·per day-1, while the module kept on surface had an average SGR of 0,36%·day-1. The models related to growth rate demonstrated temperature, salinity, pH, orthophosphate, ammonium, precipitation and turbidity as the principal environmental parameters influencing the development of G. birdiae

Análise do comportamento e crescimento do camarão branco Litopenaeus vannamei (Boone, 1931) em diferentes substratos inconsolidados

The aim of this study was to test the sediment preference of L. vannamei shrimp. It was observed shrimp visit frequency, swimming and burying behaviour at different sediment compositions for 24h. Juvenile (0.93 ± 0.29g) and sub-adult shrimps (10.0 ± 1.18g) were obtained from the aquaculture station at Universidade Federal Rural do Semi-Árido UFERSA, and held in a plastic tank (water volume 500 L) supplied with aerated water and kept at constant temperature, pH, and salinity. Shrimp was fed by commercial shrimp dry food. The experimental substrates were composed by A: medium sand + thick sand + very thick sand + gravel; B: very fine sand + fine sand; and C: silt + clay. Thus, six different substrate combinations were tested: A, B, C, A+B, A+C, B+C. To test preference, it was used a cylindrical tank (40 l) divided into six differently substrate compartments. A single shrimp was introduced each tank and the frequency at which this shrimp visited each compartment was recorded over a 24h study period. It was tested 54 shrimp (18 sub-adult males, 18 subadult females and 18 juveniles). For each trial, sediment and water were changed to avoid pheromones and residues influence. Shrimp were weighted and sub-adults were divided by sex: males present petasma and females present thelycum. Data were collected on the experimental day at 19:30; 20:30; 00:30; 1:30; 05:30; 06:30; 13:30 and 14:30 h. At each time point, shrimp were observed for 20-min periods, in which we noted down which compartment the shrimp was occupying at 2-min intervals. Thus, for each period we had eleven observations (88 observations per day). For observations at night, it was used dim red light that did not affect shrimp behaviour. At each 20-min period, it was observed visit frequency in each substrate, if shrimp was burred or not or if it was swimming. There was not significant difference between light and dark burry activity for females. Swimming activity was significantly higher at night, mainly at 00:30 and 01:30 h. All L. vannamei shrimp showed preference for sediment B. This animal presents cyclic activity, spends the day light period buried and swims at night

Estrutura e dinâmica do fitoplânctone bacterioplâncton em cultivos de camarão no Rio Grande do Norte-Brasil: impacto sobre o ambiente natural

This work aimed to study the structure and dynamic of Phytoplankton and Bacterioplankton in a complete cycle of shrimp cultivation (Litopenaeus vannamei) and determine the environmental factors responsible for the structural changes of these communities. The study was realized in a saltwater shrimp farm (Macaíba, RN), between September/2005 and February/2006, and in a freshwater shrimp farm (Ceará Mirim, RN), between May/2007 and September 2007. The samplings were collected weekly in saltwater farm and every fifteen days in freshwater farm. Total phosphorus, chlorophyll a and environmental parameters (pH, dissolved oxygen, salinity, temperature, depth and water transparency) were measured. Qualitative and quantitative analysis of the phytoplankton and bacterioplankton were carried out. The Shannon-Wiener ecologic indexes of diversity and the Pielou equitability indexes were calculated to the phytoplankton. Bacterial density was determined by epifluorescence microscopy. The data were statistically analyzed by Pearson correlation and t-Test. Chlorophycea were predominat in salt water and in the captation/drainage point (24 to 99%). Diatoms had higher wealth. The species Choricystis minor had the highest occurrence (100%) and dominance (90-100%), thus showing its adaptation to the high temperatures, salinity and low water transparency conditions. Filamentous Cyanobacteria like Oscillatoria sp., Pseudoanabaena sp. and Phormidium sp. had constant levels. The negative correlation between chlorophycea and water transparency, and the positive correlation between chlorophyll a and salinity, showed that the phytoplankton was well adapted to the low transparency and to the high salinity. The bacterioplankton was negatively correlated with the total phosphorus and salinity. In freshwater, Cyanobacteria were predominant (>80%), presenting some producers of toxins species like Microcystis sp., Aphanizomenon sp., Cylindrospermopsis raciborskii e Anabaena circinalis. Cyanobacterial density and total phosphorus and chlorophyll a concentrations exceeded the maximum value allowed by legislation. The means of total phosphorus varied from 264 to 627 Wg.L-1 and the means of chlorophyll a oscillated between 22 and 182 Wg.L-1. The phytoplankton species were selected by low availability of the light, high pH, temperature and high availability of total phosphorus. The bacterioplankton showed high densities (5,13 x 107 to 8,50 x107 Bac.mL-1). The studied environments (ponds and rivers) presented a high level of trophic state based on the high concentrations of chlorophyll a and total phosphorus and cyanobacteria dominance. The composition of species in the ponds and rivers was similar, as well as high concentrations of total phosphorus and chlorophyll a, highlighting the pollution caused by the discharges of the farms in natural environment

Análise da estrutura e transporte do zooplâncton no estuário do Rio Caravelas (Bahia-Brasil) através do uso do zooscan

Spatial-temporal dynamics of zooplankton in the Caravelas river estuary (Bahia, Brazil). The survey was conducted in order to describe the zooplankton community of the estuary Caravelas (Bahia, Brazil), to quantify and relate the patterns of horizontal and vertical transport with the type of tide (neap and spring) and tidal phase (flood and ebb). Zooplankton samples were collected with the aid of a suction pump (300L), filtered in plankton nets (300μm) and fixed in saline formalin 4%. Samples were collected at a fixed point (A1), near the mouth of the estuary, with samples taken at neap tides and spring tides during the dry and rainy seasons. Samples were collected for 13 hours, at intervals of 1 hour in 3 depths: surface, middle and bottom. Simultaneous collection of biological, we measured the current velocity, temperature and salinity of the water through CTD. In the laboratory, samples were selected for analysis in estereomicroscope, with 25 groups identified, with Copepoda getting the highest number of species. The 168 samples obtained from temporal samples were subsampled and processed on equipment ZooScan, with the aid of software ZooProcess at the end were generated 458.997 vingnettes. 8 taxa were identified automatically, with 16 classified as a semi-automatic. The group Copepoda, despite the limited taxonomic refinement ZooScan, obtained 2 genera and 1 species identified automatically. Among the seasons dry and wet groups Brachyura (zoea), Chaetognatha, and the Calanoid copepods (others), Temora spp., Oithona spp. and Euterpina acutifrons were those who had higher frequency of occurrence, appearing in more than 70% of the samples. Copepoda group showed the largest percentage of relative abundance in both seasons. There was no seasonal variation of total zooplankton, with an average density of 7826±4219 org.m-3 in the dry season, and 7959±3675 org.m-3 in the rainy season, neither between the types and phases of the tides, but seasonal differences were significant recorded for the main zooplankton groups. Vertical stratification was seen for the major zooplankton groups (Brachyura, Chaetognatha, Calanoida (other), Oithona spp, Temora spp. e Euterpina acutifrons). The scale of this stratification varied with the type (square or tide) and tidal phase (flood or ebb). The instantaneous transport was more influenced by current velocity, with higher values observed in spring tides to the total zooplankton, however, there was a variation of this pattern depending on the zooplankton group. According to the data import and export of total zooplankton, the outflow of organisms of the estuary was higher than the input. The results suggest that the estuary of Caravelas may influence the dynamics of organic matter to the adjacent coast, with possible consequences in National Marine Park of Abrolhos

Influência dos fatores abióticos sobre a variação espaço-temporal de paralonchurus brasiliensis (Steindachner, 1875) (pisces, sciaenidae) componente da fauna acompanhante da pesca de camarões no litoral Norte de São Paulo

Knowledge of the environmental factors influence on the spatial-temporal variation of fishes is important to fisheries management and conservation. Thus, the aim of this work was to analyze the influence of the abiotical factors on the spatial-temporal distribution of Paralonchurus brasiliensis (Pisces, Sciaenidae) caught by-catch with the shrimp fishing of Ubatuba and Caraguatatuba regions, north coast of São Paulo State. The fishes were captured every month from January to December 2002. Samples were collected by otter trawl at 5, 10, 15, 20, 25, 30 and 35m depths. The temperatures (surface and bottom), salinities (surface and bottom), sediment features and organic matters were verified for each depth. During all period of the study 12.642 specimens of P. brasiliensis were captured at Ubatuba and 17.166 at Caraguatatuba, which totalized the biomass of 267 for the first and 339kg for the other region. The females outnumbered males in fish population. The greatest values of biomass and number of individuals were registered at the summer and autumn seasons, while the lowest values were observed at the winter and spring seasons. The greatest abundances were found from 15 to 25m depth. In this study, it was verified that P. brasiliensis is a coastal waters associate species. The spatialtemporal distribution of P. brasiliensis is affected by intrusion of SACW and depth for the coastal region and by depth and sediment in sheltered areas such as Caraguatatuba

Avaliação da ecotoxicidade de percolados em áreas de disposição de resíduos na região metropolitana de Natal/RN

Leachates are effluent produced by decomposition of solid waste, they have complex composition and can be highly toxic. Therefore such percolated liquid should be collected and treated properly to avoid environmental contamination of soil and of water bodies. The objective of this study was to evaluate the toxicity through ecotoxicological tests with Ceriodaphnia dubia (Cladocera - Crustacea) of percolated liquids generated in two different systems of municipal solid waste (MSW) disposal in the city of Natal/ RN: A Sanitary Landfill in the Metropolitan Region of Natal/ RN, and in a dump off area. Furthermore, it was evaluated the possible contamination of the underground water of the dump off area. Two monthly samples were taken at four points between the months of May/2009 and January/2010. The Point "A" corresponds to the end of the pond leachate treatment in ASRMN; The Point "B" corresponds to a containment pond at the dump. The Point "C" is an area near one of the cells of the dump off area where the leachate outcrops; The Point "D" stands for an underground water well at the area. The last point, called "E" was sampled only once and corresponds to the slurry produced by temporary accumulation of solid waste in the open area of the dump. The ecotoxicological tests, acute and chronic, followed the ABNT 13373/2005 rules, with some modifications. The samples were characterized by measuring the pH number, the dissolved oxygen (DO), the salinity, BOD5, COD, Cd, Cu, Pb, Cr, Fe, Mg, Ni, and Zn. At Point A, the average number of EC50-48h ranged between 1.0% and 2.77% (v/v), showing a high toxicity of the leachate to C.dubia in all months. To this point, positive correlations were found between the EC50- 48 with precipitation. Negative correlations were found between the EC50- 48h with salinity. At point B there was no response of the acute exposure of organisms to the test samples. At point C the EC50-48h ranged from 17.68% to 35.36% in just two months of the five ones analyzed, not correlated meaning. Point D, the EC50-48h level ranged between 12.31% and 71.27%, showed a negative correlation with, only, precipitation. Although it was observed toxicity of underground water in the Landfill Area, there was no evidence of water contamination by leachate, however, due to the toxic character of this water, additional tests should be conducted to confirm the quality of water that is used for human supply. At point E there was no acute toxicity. These results support the dangers of inappropriate disposal of MSW to water bodies due to the high toxicity of the leachate produced highlighting the necessity of places of safe confinement and a treatment system more effective to it

Abundância e distribuição sazonal de espécies autóctones de camarões peneídeos no canal de abastecimento do sistema primar de aquicultura orgânica (Laguna de Guaraíras, Tibau do Sul, Rio Grande do Norte, Brasil)

Guaraíras lagoon, located in Tibau do Sul in the eastern littoral of Rio Grande do Norte (Brazil), presents a permanent connection to the sea, which guarantees the occurrence of a rich biodiversity, which includes the autochthonous shrimp species Litopenaeus schmitti, Farfantepenaeus subtilis and Farfantepenaeus brasiliensis. In spite of being subject to a strong human intervention in the last decade, mainly related to the installation of shrimp (Litopenaeus vannamei) farms, the lagoon is still scarcely studied. The present study aims at characterizing the populations of the three autochthonous penaeid shrimp species inhabiting Guaraíras, taking into consideration their abundance and seasonal distribution in the inflow channel of Primar System of Organic Aquaculture (Tibau do Sul, Rio Grande do Norte, Brazil). Twelve monthly samples were carried out from May 2005 to April 2006 with the aid of a circular cast net in the inflow channel, which is daily supplied with water from Guaraíras. Sampling months were grouped in trimesters according to the total pluviosity, thus comprising four trimesters. Water salinity was monitored twice a week and temperature values registered on a daily basis at noon, during the study period. The daily pluviosity data from the municipality of Tibau do Sul were supplied by Empresa de Pesquisa Agropecuária do Rio Grande do Norte (EMPARN). Collected shrimp were identified, weighted, measured and sexed. L. schmitti specimens (0.2 g to 17.8 g) were distributed in 1.3 g weight classes intervals. From the eighth sampling month (December 2005) onwards, males were classified into three categories, in accordance with the development of their petasm: (a) rudimentary petasm, (b) partially formed petasm, and (c) completely formed petasm. Among the ecological variables, rainfall showed the greatest dispersion (s.d.=187.74Rainfall and abundance of L. schmitti were negatively correlated (r = -0.85) whereas its abundance and water salinity were positively correlated (r = 0.63). Among 1,144 collected individuals, 1,127 were L. schmitti, 13 were F. subtilis and 4 were F. brasiliensis, which corresponded to 98.51%, 1.14% and 0.35% of the total of collected individuals. L. schmitti occurred in 100 % of all samples. Differently, the presence of F. subtilis and F. brasiliensis was restricted to 33% and 17% of the collected samples, respectively. The present study confirmed the occurrence of L. schmitti, F. brasiliensis and F. subtilis in Guaraíras. However, this lagoon seems to be primarily inhabited by juvenile Litopenaeus schmitti. The population of L. schmitti analysed showed a seasonal pattern of distribution. In general, in the months of high salinity and absence of rain, the number of individuals was higher than in the wet months. Further studies on the reproductive biology and ecology of L. schmitti, F. brasiliensis and F. subtilis may elucidate questions referring to the abundance, period, and phase of occurrence of these shrimp genera in Guaraíras. Finally, the risks associated to the establishment of L. vannamei in the lagoon provide a novel outlet for studies in this biotope