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Estudo da dinâmica microbiana do rio Guadiana : impacte da construção da barragem do Alqueva
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Abstract(s)
Foi levada a cabo urna campanha de amostragem que decorreu entre Abril e Outubro,
cobrindo o período de Primavera-Verão de 1999; com uma frequência de amostragem de 2 colheitas por mês em 3 estações situadas na zona de alto estuário de rio; com o objectivo de responder as seguintes questões: De que forma a produção primária afecta e bacterioplâncton? Qual a relação entre a produção primaria e a produção bacteriana? Como se reflecte na densidade e biomassa bacterianas do rio Guadiana? E ainda de que forma é controlada a comunidade bacteriana do rio? Ao longo de toda a campanha de amostragem o rio manteve-se sempre muito turvo, dificultando as recolhas e inutilizando algumas amostragens. Esta condição anormal das aguas do rio deve-se ã construção da barragem do Alqueva. 0 que nos permitiu estudar o impacte que a construção de barragens pode ter a nível da dinâmica das comunidades microbianas, as quais representam a base da cadeia alimentar em qualquer sistema. Ao longo de todo o período de amostragem a abundância bacteriana (AB) registou uma média de 3.6xl06 BT.ml`1 i0.84, a abundância de nanoflagelados heterotróficos (I-INF) uma média de Léxlüs HNF.ml" iU.?l e a abundância de nanoflagelados autotroficos (ANF) uma média de 5.9xl03 ANF.nrI" i2.48. Os valores de HNF situam-se dentro do intervalo de valores observados em sistemas semelhantes, mas a abundância bacteriana e de ANF situaram-se abaixo do registado em anos anteriores para a
mesma zona. Por outro lado a produção bacteriana (PB) foi superior ao “normal” atingindo uma média de 23.96 ugC.l".h`1 ¬_'-36.91 e a biomassa bacteriana OSB) registou uma média de 50.5? pgC.l`1 il 1.37 ao longo de todo o período de amostragem. Nem a BB nem a AB parecem explicar verdadeiramente a PB observada. A produção primaria (PP), embora baixa encontra-se dentro dos valores registados em anos anteriores para a mesma zona do rio.
A sampling campaign was carried out, between April and October, covering the spring-summer period of 1999, with a sampling frequency of twice a month, in 3 sampling sites, in the high estuary zone of the river Guadiana; with the aim of answering the following questions: How does primary production affect bacterioplankton? What is the relationship between primary production and bacterial production? How does it reflect on bacterial abundance and biomass of the river? And how is the bacterial community of the river controlled? Throughout the sampling campaign the river always remained very turbid, making it difficult to collect samples and rendering some samples tmusable. This abnonnal condition of river waters was due to the construction of the Alqueva dam. This allowed us to study the impact of dam construction on microbial community dynamics, which represents the base of the food web in any system. Throughout the sampling period, bacterial abundance (AB) showed an average of 3.6x106 BT.ml`1 10.84, the abundance of heterotrophic nanoflagellates (I-INF) averaged l.6xl03 HNF.ml`1 d:0.7l and the abundance of autotrophic nanoflagellates (ANF) averaged 5.9xl03 ANF.ml'l i2.48. The values of HNF were in the range of observed values in similar systems, but bacterial and ANF abundance were below the values obtained in previous years for the same acne. On the other hand bacterial production (PB) vvas higher tlran normal, reaching an average of 23.96 ugC.l`1.h'1 :I:36.9l and bacterial biomass (BB) attained an average of 50.57 |.rgC.l'1 ill.87, throughout the sampling period. Neither BB nor AB seemed to truly explain observed PB. The low values of primary production (PP) were in the range of previous years in the same river zone.
A sampling campaign was carried out, between April and October, covering the spring-summer period of 1999, with a sampling frequency of twice a month, in 3 sampling sites, in the high estuary zone of the river Guadiana; with the aim of answering the following questions: How does primary production affect bacterioplankton? What is the relationship between primary production and bacterial production? How does it reflect on bacterial abundance and biomass of the river? And how is the bacterial community of the river controlled? Throughout the sampling campaign the river always remained very turbid, making it difficult to collect samples and rendering some samples tmusable. This abnonnal condition of river waters was due to the construction of the Alqueva dam. This allowed us to study the impact of dam construction on microbial community dynamics, which represents the base of the food web in any system. Throughout the sampling period, bacterial abundance (AB) showed an average of 3.6x106 BT.ml`1 10.84, the abundance of heterotrophic nanoflagellates (I-INF) averaged l.6xl03 HNF.ml`1 d:0.7l and the abundance of autotrophic nanoflagellates (ANF) averaged 5.9xl03 ANF.ml'l i2.48. The values of HNF were in the range of observed values in similar systems, but bacterial and ANF abundance were below the values obtained in previous years for the same acne. On the other hand bacterial production (PB) vvas higher tlran normal, reaching an average of 23.96 ugC.l`1.h'1 :I:36.9l and bacterial biomass (BB) attained an average of 50.57 |.rgC.l'1 ill.87, throughout the sampling period. Neither BB nor AB seemed to truly explain observed PB. The low values of primary production (PP) were in the range of previous years in the same river zone.