Picocyanobacteria photosynthetic efficiency under Daphnia grazing pressure

CRISTIANA CALLIERI,; E BALSEIRO,; ROBERTO BERTONI,; BEATRIZ ESTELA MODENUTTI O BEATRIZ MODENUTTI O B. MODENUTTI

JOURNAL OF PLANKTON RESEARCH

Oxford University Press

Lugar: Oxford; Año: 2004 vol. 12 p. 1471 - 1477

0142-7873

Daphnia hyalina was used to assess the impact of zooplankton on the photosynthetic activity of picocyanobacteria. A phosphorus-limited laboratory system was designed, composed of 3-
m filtered lake water with natural assemblages to which non-axenic Synechococcus sp. was added. Different treatments with and without Daphnia were arranged; aliquots from these were sampled during 3-day incubations to measure changes in picocyanobacterial net primary production (NPP), excreted organic carbon (EOC), dissolved organic carbon (DOC) and photosynthetic parameters (photosynthesis– irradiance response curves). Bacterial number, biovolume and production were measured in both the treatment and control to evaluate possible bacterial interferences. A significant increase of picocyanobacterial photosynthesis and efficiency (2- and 3-fold increase of Pmax and respectively) was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production. was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production. lake water with natural assemblages to which non-axenic Synechococcus sp. was added. Different treatments with and without Daphnia were arranged; aliquots from these were sampled during 3-day incubations to measure changes in picocyanobacterial net primary production (NPP), excreted organic carbon (EOC), dissolved organic carbon (DOC) and photosynthetic parameters (photosynthesis– irradiance response curves). Bacterial number, biovolume and production were measured in both the treatment and control to evaluate possible bacterial interferences. A significant increase of picocyanobacterial photosynthesis and efficiency (2- and 3-fold increase of Pmax and respectively) was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production. was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production.
m filtered lake water with natural assemblages to which non-axenic Synechococcus sp. was added. Different treatments with and without Daphnia were arranged; aliquots from these were sampled during 3-day incubations to measure changes in picocyanobacterial net primary production (NPP), excreted organic carbon (EOC), dissolved organic carbon (DOC) and photosynthetic parameters (photosynthesis– irradiance response curves). Bacterial number, biovolume and production were measured in both the treatment and control to evaluate possible bacterial interferences. A significant increase of picocyanobacterial photosynthesis and efficiency (2- and 3-fold increase of Pmax and respectively) was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production. was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production. max and respectively) was observed in bottles supplemented with Daphnia, whereas cell-specific bacterial production did not. At the same time, the EOC:NPP ratio was 2.3 times lower with the grazer. This result clearly shows the impact of P recycling mediated by a grazer on picocyanobacterial growth and production.