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Remote sensing coupled with the measurement of physical, chemical and biological variables is an important tool in water resource management. The aim of this study, therefore, was to evaluate the dynamics of the physical, chemical and biological variables of the waters of an intermittent river and an artificial surface reservoir using multivariate analysis and in response to land use and occupation in the hydrographic basin. The study was carried out in the hydrographic basin of the River Cruxati in four study areas (three river areas and one artificial reservoir), with images obtained from the OLI sensor of the Landsat-8 satellite. The limnological variables measured were pH, electrical conductivity, dissolved oxygen, turbidity, nutrients (total nitrogen and total phosphorus) and chlorophyll a. The limnological variables were analysed using Principal Component Analysis - PCA, Tukey's test and Cluster Analysis. Eutrophication of the areas under study was calculated using the Trophic State Index. The PCA allowed three components to be selected that indicated the quality of the surface water, river and artificial reservoir, explaining 88.57% of the total variance. The limnological variables responsible for the grouping were electrical conductivity, dissolved oxygen and turbidity. Land use and occupation has influenced water quality in the stretches of river. Anthropisation has had an influence on the levels of dissolved oxygen, and the presence of agricultural areas has caused an increase in turbidity. However, the most conserved landscape (artificial reservoir) had the highest degree of eutrophication due to the difference in water dynamics between the lentic and lotic environments. RESUMO O sensoriamento remoto atrelado a mensuração de variáveis físicas, químicas e biológicas são importantes ferramentas para a gestão de recursos hídricos. Portanto, objetivou-se avaliar a dinâmica das variáveis físicas, químicas e biológicas das águas de rio intermitente e de reservatório superficial artificial por meio da análise multivariada e em resposta ao uso e ocupação dos solos de sua bacia hidrográfica. O estudo foi realizado na bacia hidrográfica do rio Cruxati em quatro áreas de estudo (três áreas de rio e um reservatório artificial) e as imagens foram obtidas do sensor OLI do satélite Landsat-8. As variáveis limnológicas mensuradas foram: pH, condutividade elétrica, oxigênio dissolvido, turbidez, nutrientes (nitrogênio total e fósforo total) e clorofila a. As variáveis limnológicas foram analisadas através da Análise de Componentes Principais - ACP, teste de Tukey e Análise de Agrupamento. A eutrofização das áreas estudadas foi calculada através do Índice do Estado Trófico. A ACP permitiu a seleção de três componentes indicadoras da qualidade das águas superficiais, rio e reservatório artificial, explicando 88,57% da variância total. As variáveis limnológicas responsáveis pelo agrupamento foram: condutividade elétrica; oxigênio dissolvido e a turbidez. O uso e ocupação do solo influenciou na qualidade da água dos trechos de rio. A antropização teve influência sobre o teor de oxigênio dissolvido e a presença de áreas agriculturáveis causou o aumento da turbidez. Porém, a paisagem mais conservada (reservatório artificial) foi a que apresentou maior grau de eutrofização devido a diferença na dinâmica hidrológica entre ambientes lênticos e lóticos.

Mangroves have a relevant ecosystem function due to their efficiency in blue carbon sequestration. Autotrophic carbon conservation in mangroves remains controversial. In this sense, autotrophic nutrient assimilation by crabs can highlight their ecosystem function. This study aims to identify the relationship between quality sources and food partitioning in two leaf-eating crabs, Ucides cordatus and Goniopsis cruentata. Quantification of the litterfall biomass, analysis of the soil, the C/N ratio and stable isotopes (δ13C and δ15N) were used to evaluate food sources and crab tissues in two mangrove forests. The litterfall and soil C contents and C/N ratios of the Pacoti River (PR) were higher than those of the Jaguaribe River. The higher C/N ratios of the litterfall of the PR led to higher nitrogen ingestion from complementary food sources (soil and omnivorous invertebrates). The nutritional requirements and food partitioning behavior of both species emphasize the ecosystem functions of leaf-eating crabs concerning the assimilation and conservation of autotrophic carbon and nitrogen in mangroves.