INVESTIGADORES
QUEIMALIÑOS claudia Patricia
congresos y reuniones científicas
Título:
Effect of field environmental variables on bacterivory by mixotrophic flagellates in oligotrophic shallow lakes
Autor/es:
GEREA, M; QUEIMALIÑOS, C; UNREIN, F
Lugar:
Torino
Reunión:
Congreso; 33rd SIL Congress; 2016
Resumen:
Mixotrophy usually dominates bacterivory in oligotrophic aquatic environments. Mixotrophic organisms could be differentiated along a spectrum of nutritional strategies according to the contribution of bacterivory to their growth. The bacterivory rate of different mixotrophs could be affected differentially by the environmental conditions, like temperature, nutrient concentrations or bacterial abundance. We analyzed the bacterivory rates of different mixotrophic flagellates (MF) under different natural field conditions along an annual period. A total of eight grazing experiments were performed in two oligotrophic shallow lakes of North Patagonia (Argentina), where the phytoplanktonic community is dominated by MF. Short-term grazing experiments were run in triplicate using fluorescently labeled bacteria (FLB). Bacterivory rates were estimated for each MF taxa. The CSGR (cell-specific grazing rate) varied from 0.21 to 6.74 bact. flag.-1 h-1. Pseudopedinella spp. were the most bacterivorous MF in both lakes and their CSGR (avg. 3.6 bact.flag-1h-1) were significantly related to the bacterial abundance, a functional response typical of heterotrophic organisms. Chrysochromulina parva, Ochromonas ovalis, Dinobryon divergens and Cryptomonas erosa, showed similar CSGR (between 0.52 and 2.79 bact. flag.-1 h-1). O. ovalis and C. erosa showed a negative relationship between CSGR with water temperature and total dissolved phosphorus concentration. The lowest CSGR was estimated for Plagioselmis lacustris (avg. 0.62 bact.flag-1h-1), which showed a negative relationship with the total dissolved nitrogen concentration. The negative relations found between CSGR and nutrient concentrations support the premise that phagotrophy could be related with the acquisition of limiting nutrients. The specific ingestion rate, in percentage of the cell carbon ingested per day (%C d-1) decreased with the predator size, thus, smaller flagellates tended to ingest a higher % of C related to its size than larger ones. Interestingly, Pseudopedinella spp. were always situated above the regression line of this relationship, while P. lacustris was always situated below. Our results suggest that along the spectrum of nutritional strategies of the MF found in this oligotrophic condition, Pseudopedinella spp. should be considered as the most heterotrophic flagellates, and on the other side of the gradient, P. lacustris should be placed as one of the most autotrophic species.