Variation of density, species composition and dominance of Rotifers at a shallow tropical reservoir (Broa reservoir, SP, Brazil) in a short scale time

Abstract

Rotifers are the predominant group of zooplankton found in the majority of reservoirs, constituting more than 60% of the total zooplankton present. Being opportunistic organisms, they easily adapt to changes in environmental conditions, and it is therefore difficult to establish a constant level of composition and occurrence of a species in specific areas at specific times. In order to establish how changes in composition and predominance of a species occurs within a dynamic system, the daily variation in the total density of rotifers and that of the dominant species were studied at short intervals during a period of 20 days at Lobo (Broa) reservoir. Filinia pejleri and Keratella americana were the predominant species, making up 64.3% of the total rotifers. However, during the first five days of the study, there was a predominance of two genera, Conochilus (C. coenobasis and C. unicornis) and Keratella (K. americana and K. cochlearis), with the genus Conochilus being substituted by the genus Filinia from the seventh day onwards, which, together with the genus Keratella, was predominant until the end of the study period. The increase in density of Filinia pejleri and Keratella americana was found to be associated with increased wind speed. The resulting turbulence could cause changes in the behavior and metabolism of the organisms, increasing the rate of reproduction, which in turn could be attributed to the greater availability of food through the suspension of material from the lake bed.

Efeito das variáveis abióticas e do fitoplâncton sobre a comunidade zooplanctônica em um reservatório do Nordeste brasileiro

“…O grupo dos Copepoda foi o mais atingidos pela depleção do oxigênio. Em contraposição, os Rotifera, apresentaram-se negativamente correlacionados com este fator por serem oportunistas (RODRÍGUEZ & MATSUMURA-TUNDISI, 2000). A manutenção deste grupo depende mais especialmente da temperatura e do recurso algal ou particulado (DEVETTER, 1998).…”

Water level influences on body condition of Geophagus brasiliensis (Perciformes: Cichlidae) in a Brazilian oligotrophic reservoir

“…Overall, Lajes Reservoir can be classified as oligotrophic, due to low nutrient (mainly nitrogen) and chlorophyll α concentrations (Table 1) while Lobo Reservoir is known as a typically mesotrophic environment (Rodríguez & Matsumura-Tundisi, 2001). The trophic state plus the wide oscillations in water level limit space (shelters) and food availability, being probably the determinant factors for the low K values.…”

Diversidad Y Abundancia De Comunidades Zooplanctonicas Litorales Del Humedal Pantanos De Villa, Lima, Peru

“…En adición, el amplio espectro de partículas alimenticias explotadas por los rotíferos, el cual tiene la habilidad de consumir bacterias, algas y detritus de diferentes tamaños, permite diferentes dietas para muchas especies simultáneamente presentes en los cuerpos de agua (Arora & Mehra 2003). La zona litoral ha sido señalada como la que presenta una mayor diversidad de rotíferos en comparación a la zona limnética (Rodriguez & Matsumura-Tundisi 2000). Se encontró en el presente estudio una dominancia numérica de los rotíferos a pesar de emplear una malla de 75 um, el cual podría subestimar la cantidad de pequeños organismos.…”