Carbon flux in the microbial epipelagic food chain in a meso-oligotrophic coastal ecosystem: Ubatuba-SP

• Autor(a) principal: Lima, Hevelim Serrão de
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/21/21134/tde-30032020-110037/
• topic: bactéria heterotrófica; biomassa de carbono; Brazilian coast; Carbon biomass; Costa Brasileira; Grazing; Heterotrophic bacteria; oligotrófico; oligotrophic; pastejo; picoplâncton; picoplankton

In meso-oligotrophic regions the food web is longer, and the primary Carbon biomass production comes from the photosynthesis of pico-autotrophic organisms. Heterotrophic bacteria also represent an important role in these food chain, where most of the energy flows within the steps of the microbial loop before it reaches higher trophic levels. This study investigated the main origin of organic carbon accumulated by the second trophic level. Mortality and growth rates were estimated using in situ microcosm incubations. Synechococcus and heterotrophic bacteria represented more than 40% of the microbial community. Dilution technique applied in three experiments conducted in Ubatuba. It was quantified grazing and growth rate of heterotrophic bacteria, pico- and nanoplankton. Heterotrophic bacteria grazing was 53.85 µgC.L-1 per day, 2.53 µgC.L-1 per day and 3.00 µgC.L-1. The autotrophic biomass of carbon grazed 2.26 µgC.L-1 per day for Synechococcus and 35.97 µgC.L-1 for picoeukaryotes in the second experiment. Synechococcus grazed biomass was 1.14 µgC.L-1 per day and Picoeukaryotes grazed biomass was 50.46 µgC.L-1. The results of the experiments showed the flux of Carbon from both heterotrophic and autotrophic bacteria to grazers of the second trophic level was not as important as the flux of Carbon from picoeukarytes to grazers.