Mosaics of vegetation, riparian forests, and wetlands have an important quantitative and qualitative role on the hydrological cycle. Riparian forests protect the water quality of rivers, lakes and reservoirs. Wetlands control floods, sedimentation and regulate the water quality by enhancing processes such as denitrification, phosphorus and heavy metal retention. Both ecosystems of transition are fundamental. The removal of wetlands and forests (riparian and mosaics of vegetation) affects environmental services of these ecosystems, causing loss of economic assets of the capital natural and accelerating degradation of rivers, lakes, reservoirs and the watersheds. Protection of these ecosystems of transition is thus fundamental for the development of agriculture. The loss of services affects society, human health, increasing costs of recovery and deteriorating human-ecological relationships. Resumo: Florestas ripárias, mosaicos de vegetação e áreas alagadas têm papel fundamental na proteção dos recursos hídricos mantendo a qualidade da água em excelentes condições para abastecimento e recarregado aquíferos repondo, portanto, volumes substanciais de águas para o componente subterrâneo. A remoção de florestas ripárias e áreas alagadas têm um efeito extremamente negativo degradando a qualidade das águas superficiais e subterrâneas, acelerando a sedimentação de lagoas, represas e rios, e diminuindo o estoque de água nas nascentes e aquíferos. Todos os serviços ambientais dos ecossistemas aquáticos ficam comprometidos com o desmatamento e remoção de áreas naturalmente alagadas, portanto a preservação destas áreas é essencial para regular tanto o ciclo hidrológicos como os ciclos biogeoquímicos. A remoção destas áreas torna insustentável a agricultura em curto prazo. Palavras-chave: bacias hidrográficas, florestas ripárias, áreas alagadas, ciclo hidrológico, biogeoquímica da água, qualidade da água, quantidade da água.
The diel mixing patterns of two small floodplain lakes, Lago Jacaretinga in the Amazon drainage, and Lago Cristalino in the Rio Negro system, were investigated during both the high-water and low-water states of the Amazon River hydrograph. Measurements included temperature, oxygen, ammonia, phosphate, and chlorophyll. In both lakes thermal stratification developed during the day and was eroded at night. During the low-water period when the lakes were shallow, nocturnal circulation extended to the lake bottom, whereas when the lakes were deeper (greater than about 5 m), circulation did not reach the bottom and an anoxic hypolimnion developed. During the low-water period, percent of oxygen concentrations were relatively high but always less than saturation. Low oxygen concentrations were observed during the high-water period. At all times nocturnal mixing supplied a significant amount of oxygen to the lake ecosystems. Nighttime upward mixing of recycled nitrogen and phosphorus also appeared to be important nutrient sources for algal productivity.
Studies were made on the seasonal variation and qualitative composition of the Appendicularia population from a limited area of the South Atlantic 25º09.5'S to 24º04.0'S latitude and 47º48.4'W to 46º00.4'W longitude at the São Paulo State coast off Cananéia and off Santos. The pattern of the seasonal variation was irregular for the most important species (O. longicauda). Some qualitative differences regarding the species composition are discussed.
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