INVESTIGADORES
RODRIGUEZ patricia laura
congresos y reuniones científicas
Título:
Phytoplankton production in a vegetated floodplain wetland: A field experiment simulating alternative stable states
Autor/es:
PIZARRO, H.; RODRÍGUEZ, PATRICIA; DE TEZANOS PINTO, P.; VERA, M. S.; CHAPARRO, G.; O´FARRELL, I.
Lugar:
Joao Pessoa, Paraíba, Brasil
Reunión:
Congreso; Congresso Brasileiro de Plàncton & IV Plankton Symposium; 2007
Institución organizadora:
Sociedade Brasileira de Plâncton
Resumen:
The phytoplankton production response to different free floating plant coverage was experimentally explored in a nitrogen deficient floodplain wetland. Two different alternative states naturally occurring in these ecosystems were simulated: phytoplankton (T1-constant high light) and free floating plants (T2-constant low light) dominant states. Field enclosure experiments were performed in late summer for one month, with a 10 day sampling frequency. Fishes were added to control zooplankton grazing in all enclosures and meshes were placed to mimic the plants effect in T2. Each treatment was run by triplicate. Light, temperature, oxygen and pH were measured in the depth profile at 10 cm intervals and the extinction coefficient calculated. Phytoplankton samples for production (14C assimilation technique) and quantitative analysis, nutrients and chlorophyll a were obtained from integrated samples. Repeated measures ANOVA indicate significant differences in production both between treatments and in time. Under T2, production remained low and similar throughout the study, whilst in the T1 production increased with time. These differences are mainly explained by the strong light reduction at T2 which favours anoxia, sustain low phytoplankton biomass and low chlorophyll a (as result of forward stepwise multiple regression) thus establishing a self stabilizing state with low fluctuations. Conversely, waters at T1 remained oxygenic and the higher mean irradiance allowed the maintenance of high phytoplankton biomass, even under nutrient deficient resources. Moreover, final phytoplankton assemblage in T1 evolved while in T2 final assemblages were similar in all enclosures.