RESUMEN El impacto del cambio climático en los sistemas hidrológicos de una región pueden identificarse a través de la caracterización estadística de parámetros hidrometeorológicos como la lluvia, la temperatura, la húmedad y la evaporación. Para entender la influencia del cambio climático este estudio evalúa las tendencias estadísticas en los días lluviosos, en los días no lluviosos y en la tasa de evaporación en la cuenca del Río Limbang, en Sarawak, Malasia, al norte de la isla de Borneo. Para la investigación se utlizó la pluviosidad anual y la información mensual de evaporación en un período de 46 años (1970-2015) para tres estaciones pluviométricas: Limbang DID, Ukong y Long Napir. El modelo de regresión lineal y las técnicas de estimación de inclinación de Mann Kendall y Sen se aplicaron para detectar las tendencias estadísticas en días lluviosos y de evaporación. Para todas las estaciones se encontró un incremento en la tendencia anual de días lluviosos. Los días no lluviosos mostraron una baja estadística significativa en las estaciones de Limbang DID y de Ukong. Los índices mensuales de evaporación mostraron mostraron un incremento generalizado, mientras que la mayor tendencia de incremento se observó en los meses de septiembre (2.55 mm/año) para la estación Limbang DID, y para Ukong en los meses de diciembre (2.61 mm/año). La evaporación medida en la estación de Ukong también muestra una baja no significativa para junio y septiembre. Una comparación de la evaporación y del control de variables meteorológicas como la pluviosidad, la temperatura y la húmedad relativa indica una influencia relacionada en varias intensidades. Las características locales de precipitación, de viento y de fluctuación de temperatura atmosférica sobre la región juega un rol importante en el incremento de la evaporación. El análisis identificó una tendencia de incremento estadística significativa en los días lluviosos y de evaporación en la cuenca del Río Limbang. Los resultados del presente estudio pueden usarse como información de planeación determinante para micro y macroproyectos hidroeléctrios en la cuenca del río.

ABSTRACT Impact of climate change over the hydrological system in a region can be identified through statistical characterization of hydrometeorological parameters such as rainfall, temperature, humidity and evaporation. In order to understand the influence of climate change, statistical trend characteristics of rainy days, non-rainy days and evaporation rate in the Limbang River Basin (LRB) in Sarawak, Malaysia, Northern Borneo was assessed in the present research. Annual rainfall and monthly evaporation data, over a period of 46 years, (1970 - 2015) corresponding to three rain gauging stations, the Limbang DID, Ukong and Long Napir were used in the research. Linear regression model, Mann Kendall and Sen's slope estimator techniques were applied to detect the statistical trends in rainy days and evaporation. A statistically significant increasing trend in annual rainy days was found at all the stations. Non-rainy days showed a statistically significant decreasing trend at Limbang DID and Ukong. Monthly evaporation rates showed an overall increasing trend and the greatest increasing trend in evaporation was observed in September (2.55 mm/year) for the Limbang DID and in December (2.61 mm/year) for Ukong. Evaporation measured at the Ukong station also showed a non-significant decrease during June and September. A comparison of the evaporation controlling meteorological variables such as rainfall, temperature and relative humidity indicates inter-influence at various strengths. Along with local precipitation characteristics, wind and fluctuation of atmospheric temperature over the region plays a vital role in increased rate of evaporation from the region. Overall, the analysis identified a statistically significant increasing trend in rainy days and evaporation in the LRB. The results of the present research can be used as critical planning data for micro and macro hydroelectric projects in the river basin.

Resumo Neste trabalho estudamos a influência da construção da barragem de Sobradinho na vazão diária do rio São Francisco, Brasil, analisando correlações de longo alcance em séries temporais de magnitude e sinal obtidas a partir da anomalia das vazões utilizando o método Detrended Fluctuation Analysis. A série de magnitude está relacionada com as propriedades não lineares da série original enquanto que a série de sinal está relacionada as propriedades lineares. Foram analisados os dados de vazão registrados durante o período 1929-2009, divididos nos períodos anterior a construção (1929 a 1972) e após a construção da barragem de Sobradinho (1980 a 2009) em pequenas escalas (menos de 365 dias) e em grandes escalas (mais de 365 dias). Após a construção da barragem de Sobradinho os expoentes-DFA para a série de magnitude aumentaram tanto em pequenas escalas (0,895 para 1,013) quanto para grandes escalas (0,371 para 0,619) indicando que a memória associada a componentes não lineares se tornou mais forte. Para a série de sinais, os expoentes-DFA aumentaram em pequenas escalas (0,596 para 0,692) indicando maior persistência na direção dos incrementos da vazão e diminuíram em grandes escalas (0,381 para 0,259) indicando maior anti-persistência (incrementos positivos são mais propensos a serem suscedidos por incrementos negativos e vice versa). Estes resultados trazem novas evidências quanto as alterações hidrológicas no rio São Francisco causadas pela atividade humana.

Abstract In this work we study the influence of the Sobradinho dam construction on daily streamflow of São Francisco River, Brasil, by analyzing long-range correlations in magnitude and sign time series obtained from streamflow anomalies, using the Detrended Fluctuation Analysis (DFA) method. The magnitude series relates to the nonlinear properties of the original time series, while the sign series relates to the linear properties. The streamflow data recorded during the period 1929-2009, were divided in the periods pre-construction (1929 to 1972) and post-construction (1980 to 2009) of Sobradinho dam and analyzed for small scales (less than 1 year) and for large scales (more than 1 year). In post-construction of Sobradinho dam, DFA-exponents of magnitude series increased at small scales (0.895 to 1.013) and at large scales (0.371 to 0.619) indicating that the memory associated with nonlinear components becames stronger. For sign series, the DFA-exponent increased at small scales (0.596 to 0.692) indicating stronger persistence of flow increments direction, and decreased at large scales (0.381 to 0.259) indicating stronger anti-persistence (positive increments are more likely to be followed by negative increments and vice versa). These results provide new evidence on the hydrological changes in the São Francisco River caused by human activities.

Recently, the agricultural zones of Carabobo present problems with the water available for crops influenced by the fluctuation between Precipitation and Potential Evapotranspiration. It is for this reason that the need arises to analyze the climatic types according to the degree of humidity. The Climatic Hydrological Balance methodology was used for 25 rainfall stations in Carabobo, Venezuela, for a period of common registration (1969 - 1999). The results show that four regions were found where humidity behaves differently, the greatest excesses are to the south of the state and it was found that the climatological stations located north of Carabobo have a greater annual deficit. The most relevant agricultural areas are represented by a water index of (-2.16 to -18.96); which determines a dry sub-humid climate with annual rainfall ranging between 921 mm and 1063 mm. This study generated vital information in those agricultural areas that require additional irrigation or controls with structural drainage works that prevent certain crops sensitive to excess water from being damaged.

In the north of the province of Santa Fe, especially in the forest wedge, Lower Submeridionals and Occidental Domo, there are more than three million head of cattle, where one of the main determinants of production is the irregular quality of groundwater For the watering of the hacienda. The fluctuation between dry and wet hydrological scenarios has a direct impact on production, where not only the free water table, which is the only available water, varies, but also the chemical quality of the water. In collaboration with the INA, the Government of Santa Fe and UNL Research Centers, INTA has developed research and transfer demonstration units in the fields of producers and experimental units of the Institution, designing and proposing different technologies that are consensual with the Producers in the management of rainwater supplemented with the underground. 3 water systems were implemented with different ways of using rainwater with groundwater, systematizing terrain to guarantee access and recharge of the free aquifer, with pumping mechanisms using renewable energy and with suction systems that do it in the part Surface of the aquifer, where all converge to a central mixing tank, to ensure that all animals take water with the same chemical quality, whatever the place of grazing. Since 2011 the variables of interest are monitored, where the premise is to have controlled the salinity of the water in the central mixing tank and that its variations throughout the year are gradual, since this maximizes livestock production. This is visualized in each of the three systems and, fundamentally in the central mixing tank, where the quantity, quality and opportunity during the year clearly show very positive results in the place studied.

En el norte de la provincia de Santa Fe, especialmente en la Cuña Boscosa, Bajos Submeridionales y Domo Occidental, se encuentran más de tres millones de cabezas de ganado vacuno, donde uno de los principales condicionantes en la producción es la irregular calidad del agua subterránea para el abrevado de la hacienda. La fluctuación entre escenarios hidrológicos secos y húmedos repercute directamente en la producción, donde no solo varía el nivel freático del acuífero libre, único aprovechable, sino fundamentalmente la calidad química del agua. El INTA, articulando con el INA, con el Gobierno de Santa Fe y con Centros de Estudio de la UNL, ha concretado unidades demostrativas de investigación y transferencia en campos de productores y unidades experimentales de la Institución, diseñando y proponiendo distintas tecnologías consensuadas con los productores en lo que hace al manejo del agua de lluvia complementada con la subterránea. 3 Sistemas de Aguadas se concretaron con diferentes maneras de aprovechar el agua de lluvia con el agua subterránea, sistematizando terrenos para garantizar el acceso y recarga del acuífero libre, con mecanismos de bombeo mediante energía renovable y con sistemas de succión que lo hacen en la parte superficial del acuífero, donde todos convergen a un tanque central de mezcla, para garantizar así que todos los animales tomen agua con la misma calidad química, cualquiera sea el lugar de pastaje. Desde el año 2011 se monitorean las variables de interés, donde la premisa es tener controlada la salinidad del agua en el tanque central de mezcla y que sus variaciones a través del año sean graduales, ya que esto maximiza la producción ganadera. Esto se visualiza en cada uno de los 3 sistemas y, fundamentalmente en el tanque central de mezcla, donde la cantidad, calidad y oportunidad durante el año evidencian claramente resultados muy positivos en el lugar estudiado.

A contribuição da recarga para sistemas regionais de fluxo de água subterrânea é uma informação essencial requerida para estabelecer o gerenciamento sustentável de recursos hídricos. O objetivo deste trabalho foi determinar o escoamento de água subterrânea na Bacia do Ribeirão da Onça usando um modelo de balanço hídrico da zona saturada do subsolo. A bacia está localizada em uma área de afloramento do Sistema Aquífero Guarani (SAG). O método do balanço hídrico envolveu a determinação de valores de recarga direta, variação do armazenamento de água subterrânea e escoamento de base. A recarga direta foi determinada pelo método de flutuação da superfície livre (WTF, em inglês). O escoamento de base foi calculado pelo método de separação da hidrógrafa, que foi gerada por um modelo chuva-vazão, com suporte de medições quinzenais de vazão na seção de controle. Amostras indeformadas de solo foram coletadas em profundidades correspondentes à zona de flutuação do nível freático, para determinação do rendimento específico do solo (porosidade drenável). Os balanços hídricos na zona saturada foram calculados para os anos hidrológicos de fevereiro de 2004 a janeiro de 2007. A recarga direta variou de 14,0% a 38,0% e o escoamento subterrâneo de água variou de 0,4% a 2,4% da respectiva precipitação durante o mesmo período.

The contribution of recharge to regional groundwater flow systems is essential information required to establish sustainable water resources management. The objective of this work was to determine the groundwater outflow in the Ribeirão da Onça Basin using a water balance model of the saturated soil zone. The basin is located in the outcrop region of the Guarani Aquifer System (GAS). The water balance method involved the determination of direct recharge values, groundwater storage variation and base flow. The direct recharge was determined by the water table fluctuation method (WTF). The base flow was calculated by the hydrograph separation method, which was generated by a rain-flow model supported by biweekly streamflow measurements in the control section. Undisturbed soil samples were collected at depths corresponding to the variation zone of the groundwater level to determine the specific yield of the soil (drainable porosity). Water balances were performed in the saturated zone for the hydrological years from February 2004 to January 2007. The direct recharge ranged from 14.0% to 38.0%, and groundwater outflow from 0.4% to 2.4% of the respective rainfall during the same period.

En este estudio se implementó el modelaje de distribución de especies para establecer el rango de distribución potencial de Podocnemis lewyana, explorar los componentes del clima que pueden influenciar dicha distribución y evaluar posibles fluctuaciones de su distribución bajo escenarios de clima futuro. Los modelos obtenidos predicen una distribución continua de sur a norte por todo el río Magdalena, desde los municipios de Rivera y Palermo en el departamento de Huila, hasta los departamentos de Atlántico y Magdalena en el norte. La temperatura fue el elemento del clima que más influyó en la distribución de P. lewyana; esta especie tiende a estar presente en climas cálidos y con poca variabilidad en la temperatura. El modelo de distribución transferido a los escenarios de clima futuro predicen un aumento en el rango geográfico de P. lewyana. Sin embargo, teniendo en cuenta las preferencias de hábitat de esta especie y su fuerte asociación con los cuerpos de agua, este resultado debe tomarse con cautela, dado que el modelo solo tuvo en cuenta variables climáticas terrestres. Dadas las características de historia de vida de esta especie (presencia de determinación sexual dependiente de la temperatura, alta temperatura pivotal y un rango de transición de temperatura muy estrecho), y el efecto negativo de los cambios en los regímenes hidrológicos en la mortalidad embrionaria, la expansión del área potencial de P. lewyana en el futuro no significa que esta especie no vaya a verse afectada por el cambio climático global.

We implemented a species distribution modelling approach to establish the potential distribution of Podocnemis lewyana, to explore the climatic factors that may influence the species' distribution and to evaluate possible changes in distribution under future climate scenarios. The distribution models predicted a continuous distribution from south to north along the Magdalena River, from Rivera and Palermo in the department of Huila to the departments of Atlántico and Magdalena in the north. Temperature was the variable most influential in the distribution of P. lewyana; this species tends to be present in warm regions with low temperature variability. The distribution model predicted an increase in the geographic range of P. lewyana under climate change scenarios. However, taking into account the habitat preferences of this species and its strong association with water, this result should be treated with caution since the model considered only terrestrial climatic variables. Given the life history characteristics of this species (temperature-dependent sex determination, high pivotal temperature and a very narrow transition range) and the negative effect of changes in hydrological regimes on embryo survival, expansion of the potential distribution of P. lewyana in the future does not mean that the species will not be affected by global climate change.

The current distribution and conservation status of six native freshwater fishes of the Baja California peninsula (Entosphenus tridentatus, Oncorhynchus mykiss nelsoni, Fundulus lima, Cyprinodon macularius, Gasterosteus aculeatus and Gobiesox juniperoserrai), included in the Norma Oficial Mexicana-059-2010, were assessed on the basis of information generated during the study period of 2000-2014. Except for E. tridentatus in the Santo Domingo river drainage and G. juniperoserrai in the Las Pocitas-San Hilario drainage, most of the species were recorded in the hydrological basins sampled. Oncorhynchus mykiss nelsoni showed a significant population fluctuation in the San Rafael river in relation to the dynamics of the base flow and the forest fire events. Fundulus lima presented the probable extirpation from four drainages (San Javier, Bebelamas, San Luis, and Las Pocitas-San Hilario) that is contrasting with the finding of a new population in the Santa Cruz stream. Cyprinodon macularius in the most important remnant population in Baja California (cerro Prieto geothermal ponds) showed interannual fluctuations related with the level of flooding and availability of marginal habitats. Gasterosteus aculeatus showed a progressive population reduction in the southernmost distributional locality (mouth of El Rosario river), as well as the extirpation in the lower Santo Domingo river basin and its recent presence in the mouth of the Cantamar river. Gobiesox juniperoserrai, known only from the type locality is determined as extirpated.

Se determinó el estatus actual de conservación de 6 peces dulceacuícolas nativos de la península de Baja California (Entosphenus tridentatus, Oncorhynchus mykiss nelsoni, Fundulus lima, Cyprinodon macularius, Gasterosteus aculeatus y Gobiesox juniperoserrai), incluidos en la Norma Oficial Mexicana 059-2010, a partir de la información obtenida durante el periodo 2000-2014. Con excepción de E. tridentatus en la cuenca del río Santo Domingo y de G. juniperoserrai en la cuenca de Las Pocitas-San Hilario, la mayoría de las especies fueron registradas en las cuencas hidrológicas muestreadas. Oncorhynchus mykiss nelsoni registró una marcada fluctuación poblacional en el río San Rafael, en estrecha relación con la dinámica del flujo hidrológico y los eventos de incendio forestal. Fundulus lima presentó su probable extirpación en 4 cuencas: San Javier, Bebelamas, San Luis y Las Pocitas-San Hilario, lo cual contrasta con el hallazgo de una nueva población en el arroyo Santa Cruz. Cyprinodon macularius en su población remanente más importante en Baja California -lagunas de la planta geotérmica cerro Prieto- denotó fluctuaciones interanuales relacionadas directamente con el nivel de inundación de las lagunas y la disponibilidad de hábitat. Gasterosteus aculeatus exhibió un descenso poblacional progresivo en la localidad más austral de su distribución (río El Rosario), además de la extirpación de la población de la bocana del río Santo Domingo y el redescubrimiento de una nueva población en la bocana del río Cantamar. Gobiesox juniperoserrai, especie conocida sólo de la localidad tipo, es determinada como extirpada.

Se realizó un reconocimiento taxonómico y estimación de la densidad en el ensamblaje de rotíferos en el lago Largo, del sistema de lagos Yahuarcaca, en la ribera colombiana del río Amazonas, a partir de muestreos en las fases hidrológicas de aguas bajas, ascenso y descenso. Se identificaron 68 especies, 28 de ellas son nuevos registros para ambientes colombianos. Se encontró aumento en la riqueza en las épocas de ascenso y descenso, siendo mayor en la zona litoral respecto de la limnética, y la tendencia a mayor similitud taxonómica entre ambas zonas en el periodo de aguas bajas, debido al mínimo desarrollo de macrófitas en esta fase y la consecuente menor heterogeneidad espacial. Se observó el predominio de rotíferos con trofi adaptados para moler y triturar partículas (maleado y maleorramado) en las épocas de aguas bajas (Brachionus ahlstromi) y descenso (Filina saltator) y en la época de ascenso de Polyarthra vulgaris, con trofi adaptado para perforar y succionar fluidos de algas y otros organismos (virgado) y apéndices que favorecen la rápida natación. En general, se establecieron posibles relaciones entre la riqueza y la densidad de rotíferos con cambios en características como el desarrollo de vegetación acuática en el litoral, profundidad del lago, nivel de conectividad con los otros lagos del sistema Yahuarcaca, influencia de aguas blancas del Amazonas y negras de origen local, potenciales recursos nutricionales y depredadores, y posible efecto de arrastre por la corriente.

We conducted a taxonomic recognition and density estimation of the assemblage of rotifers in Lake Largo, in the floodplain system of Yahuarcaca, connected with the Amazon River, in Colombia. Two samplings were made for each hydrological phase (low water, filling and draining phases); 68 species were identified, 28 of them are new records for Colombian environments. We found an increased in species richness in the filling and draining phases, being higher in the littoral than in limnetic region, and a tendency to a higher taxonomic similarity between the two areas during low water periods, due to the reduced macrophyte development in that period and consequent reduced spatial heterogeneity. We observed the predominance of rotifers with trophi adapted for grinding and crushing particles (malleate and malleorramate) in low water phase (Brachionus ahlstromi) and draining phase (Filina saltator) and Polyarthra vulgaris, with a trophi adapted to pierce and suck out the fluids of algae and other organisms (virgate), and appendices that support the rapid swimming, at the filling phase. In general, we established possible relations between rotifers richness and density with changes in characteristics as the development of aquatic vegetation in the littoral zone, lake depth, level of connectivity with other lakes of Yahuarcaca system, level of influence of white waters from the Amazon river, and black waters from local origin, potentials nutritional resources and predators, and drag effect by the current.

Spatial distribution of the energy and flows of the hydrologic cycle in the form of evapotranspiration, runoff and infiltration within a region is a function of the climate (precipitation, temperature and evaporation) and landscape (relief, soil, land cover) of the area, and constitutes the hydrological cycle. The general model evaluating each of these sections and flows is the water balance. Methods for calculating the water balance in a region are based on either mass transference or energy transference. The aim of the present work was to calculate the spatially distributed regional water balance in a poorly gauged basin by each of three methods, and to evaluate these methods by comparing the results. Spatial modelling of the hydrometeorological variables used the ArcView 3.2 geographic information system; hydrological modelling made using HEC system version 3.1.0. The first approach was based on analysis of the information recorded at the available meteorological stations, point estimation of the monthly water balance according to the Thornthwaite and Mather method, and the use of Thiessen polygons. The second approach was based on the calculation and distribution of the parameters for the Thornthwaite and Mather method. The third approach used the FAO-Penman equation. The models were applied to the Lake Cuitzeo basin. The result obtained by the third method indicated a mean annual volume of runoff of 229.05 hm³. This volume is only 8.5 hm³ less than that estimated as necessary for maintaining a depth of 1 m throughout the Lake Cuitzeo water body. This difference represents a possible fluctuation of 2 cm in the mean level of the surface of the lake. The HEC model represents an alternative for modelling the basin since it requires relatively few inputs, of which the main ones (temperature, precipitation, potential evapotranspiration, evapotranspiration) are obtainable or deducible by means of one or other of the approaches presented here.

La distribución espacial de la energía y los flujos de ciclo hidrológico en forma de vapor (evapotranspiración), escurrimiento e infiltración en una región, son una función de las características climáticas (precipitación, temperatura y evaporación) y del paisaje (relieve, suelo y cobertura) de un área y constituyen el llamado ciclo hidrológico. El modelo general de evaluación de cada uno de los compartimentos y flujos es el balance hídrico. Los métodos desarrollados para calcular el balance hídrico de una región toman como base el enfoque de transferencia de masa o el de transferencia de energía. Este trabajo se planteó como objetivo calcular, comparar y evaluar tres aproximaciones en la estimación del balance hídrico regional espacialmente distribuido en cuencas sin datos de aforos. El modelamiento espacial de las variables hidrometeorológicas se efectuó en el sistema de información geográfica ArcView 3.2, y el modelamiento de los del escurrimiento se realizó con el sistema HEC versión 3.1.0. La primera aproximación está basada en el análisis de la información registrada en las estaciones meteorológicas disponibles, estimación puntual del balance hídrico mensual conforme al método de Thornthwaite y Mather y de polígonos de Thiessen; la segunda, en el cálculo y distribución de los parámetros para la aplicación del Método de Thornthwaite y Mather; finalmente la tercera aproximación se basó en el uso de la ecuación de FAO - Penman. Se escogió a la cuenca del lago de Cuitzeo como área de aplicación de los modelos. Destaca que mediante el resultado de la 3ª aproximación el volumen anual promedio de escurrimientos corresponde a 229.05 hm³. Dicho volumen es apenas 8.5 hm³ inferior al estimado como necesario para mantener 1 m de profundidad en la extensión del cuerpo de agua del lago de Cuitzeo. Esta diferencia representa en esa misma extensión una eventual fluctuación de 3 cm en el nivel medio del espejo del lago. El modelo HEC representa una alternativa para el modelamiento de la cuenca ya que demanda relativamente de pocos insumos, los principales (T, PP, PET, ET) obtenibles o espacializables mediante alguna de las aproximaciones presentadas aquí.

This paper provides an integrated approach to the analysis of the geological, hydrological and hydrogeological characteristics of the Cape Flats: a coastal plain sand formed within the mountains of the Cape Town metropolitan area. The study is mainly based on evaluation of available data, on surface water and groundwater, rainfall and selected springs, to describe the Cape Flats aquifer. Qualitative analysis has shown that both surface water and groundwater of the investigated area are of good quality; whereas sources of contamination indicated are restricted to certain parts of the area. Interpretation of hydrogeological data and aquifer parameters revealed that the Cape Flats aquifer has good storage characteristics to support its development for water supply, although the generally unconfined conditions render it highly susceptible to pollution from the surface. From the analysis of long-term climate data in Cape Town, it is evident that fluctuation exists in the pattern of rainfall; this rainfall pattern has implications for recharge and water management issues in the city. Therefore, a conceptual hydrogeological model was developed to elucidate groundwater flow and recharge mechanisms in the Cape Flats.

The spatio-temporal variation of the distribution and composition of the phytoplankton community was studied through a Principal Component Analysis (PCA) and a Cluster Analysis (CA). Based on the seasonal behavior of the most important hydrological factors and on the CA, it was established that the Carretas-Pereyra lagoon system varies throughout the year presenting eurihaline and polyhaline habitats during the dry season and mesohaline and polyhaline ones during the wet season. It was also established that in Chantuto-Panzacola the polihaline and eurihaline habitats of the dry season become polyhaline during the wet season while the mesohaline habitat remains unchanged throughout the whole year. The structure of the phytoplankton community is dependent by the key environmental characteristics of the seasonal habitats established in both systems, situation that generates a succession of the species. The PCA analysis showed that during the dry season there is a dominance of marine species (diatoms and dinoflagellates) distributed along the eurihaline habitat, but during the rainy season the community is made up by both, freshwater species (diatoms of the genera Navicula and cyanophytes) distributed along the mesohaline habitat and brackish species which are found throughout the polihaline habitat. Finally, a phytoplankton succession was established for both systems (Carretas-Pereyra and Chantuto-Panzacola): Dominance of Diatoms (dry season) -Dinoflagellates (dry-wet season) -Cyanophytes (wet season).

Se estudió la comunidad fitoplanctónica de los sistemas lagunares Carretas-Pereyra y Chantuto-Panzacola del estado de Chiapas, realizando una caracterización espacial y en dos épocas del año de su distribución, composición y abundancia relativa, asociándola a las variaciones de las condiciones físico-químicas mediante el empleo del Análisis de Componentes Principales (ACP) y el Análisis de Conglomerados (AC). Con base en el comportamiento hidrológico estacional y en el AC se observó que el sistema Carretas-Pereyra varía a lo largo del año presentando habitats polihalinos a euhalinos en la época de secas y mesohalinos a polihalinos durante lluvias. También se evidenció que en Chantuto-Panzacola el habitat mesohalino permanece como tal durante ambas épocas mientras que los habitats polihalino y euhalino presentes en secas adquieren características polihalinas en lluvias. La estructura de la comunidad fitoplanctónica está condicionada por las características ambientales de los habitats establecidos en ambos sistemas, lo que origina una sucesión estacional en las especies que la componen. El ACP demostró que durante la época de secas se observa la dominancia de grupos de estirpe marina (diatomeas y dinoflagelados principalmente) distribuidos a lo largo del habitat euhalino, mientras que durante lluvias la comunidad está integrada tanto por especies de agua dulce (diatomeas del género Navicula y cianofitas principalmente) distribuidas en el habitat mesohalino, como por especies con afinidades salobres que se encuentran en el habitat polihalino. Finalmente, puede establecerse que la sucesión en los sistemas Carretas-Pereyra y Chantuto-Panzacola sigue el siguiente orden: Dominancia de diatomeas (secas) -dinoflagelados (secas-lluvias) -cianofitas (lluvias).

Foram analisadas as flutuações temporais de algumas variáveis limnológicas, nas regiões limnética e litorânea de uma lagoa de inundação (lagoa dos Patos) da planície de inundação do alto rio Paraná (22(0) 43'12"S e 53(0) 17'37"W) em relação a fatores climatológicos e hidrológicos. Temperatura da água, profundidade da zona eufótica, material em suspensão, condutividade elétrica, alcalinidade total, pH, oxigênio dissolvido, dióxido de carbono, nitrogênio total, nitrogênio total Kjedahl, fósforo total, fósforo dissolvido, fósforo solúvel reativo e clorofila-a foram medidas, mensalmente, de março de 1993 a fevereiro de 1994. Os resultados obtidos evidenciaram a importância do regime hidrológico sobre a dinâmica das variáveis limnológicas. Durante eventos de inundação, observou-se a diluição dos nutrientes da lagoa, especialmente das frações de fosfato, seguida de uma fertilização do ambiente por nutrientes da região marginal inundada. Nos períodos de baixa conectividade, eventos autóctones como ressuspensão do sedimento causada por chuva e ventos regem os eventos limnológicos na lagoa.

Temporal variations of some limnological variables in limnetic and littoral regions of Patos lagoon, a "várzea" lake on the floodplain of the Upper Paraná River (22(0) 43'12"S e 53(0) 17'37"W), were studied in relation to hydrological and climatological factors. Measurements of water temperature, euphotic zone, suspended material, electrical conductivity, total alkalinity, pH, dissolved oxygen, carbon dioxide, total nitrogen, total Kjeldahl nitrogen, total phosphorus, dissolved phosphorus, reactive soluble phosphorus and chlorophyll a were taken monthly between March 1993 and February 1994. Results lend evidence to the importance of the hydrological regime on the dynamic of limnological variables in floodplain lakes. A dilution of nutrients in the lagoon, especially phosphates, occurred during floods. This was followed by fertilization of the environment by nutrients from the inundated marginal regions. During low connectivity periods, autochthonous, events such as ressuspension of sediment, brought on by wind and rain, governed limnological events in the lagoon.

Ecological studies including occurrence, relative abundance and spatial distribution of 15 species of Brachyura, as well as the fluctuation in the annual cycle are carried out in mangrove (27º 34' 14" and 27º 35' 31" L.S.; 48º 30' 07"and 48º 31' 33" L. W.), during the year 1986. The hydrological parameters temperature, salinity and pH of surface and intersticial waters were also studied. Chasmagnathus granulata was the most abundant specie, followed by Uça uruguayensis, Aratus pisonii and Callinectes danae. The number of males was higher than females. In the spring a larger rate of Catches occurred. The species Eurytium limosum, Cardisoma guanhumi that had the state of São Paulo as their austral boundaru and Uça maracoani the state of Paraná, have now their boundaries of distribution expanded is for as the City of Florianópolis, in the state of Santa Catarina.