Microbial pelagic metabolism and CDOM characterization in a phytoplankton-dominated vs. a macrophyte-dominated shallow lake

TORREMORELL A.; PÉREZ G.; LAGOMARSINO L.; HUBER P; QUELMARIÑOS C; BUSTINGORRY, J.; FERMANI P.; LLAMES M.E.; UNREIN F.

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2015 vol. 752 p. 203 - 221

0018-8158

Dominant primary producer in macrophyte or phytoplankton dominated shallow lakes might imply differences in dissolved organic carbon (DOC) composition. We com pared chromophoric dissolved organic matter (CDOM), plankton respiration (R), and bacterial (BP) and primary production (PP), in two contrasting shallow lakes. We hypothesized that DOC from the macrophyte dominated lake would be qualit atively inferior, so that it can support a lower yield than DOC from the phytoplankton dominated one. Macrophyte dominated lake had more humic and aromatic CDOM, though molecular weight was similar in both lakes. A clear synchronism between lakes was observed in mean depth and sever al CDOM absorption coefficients,suggesting an external driver of the variat ion in DOC concentration and CDOM quality. The positive BP-PP and BP- Chl-a correlations in the macrophyte-dominated lake point out to a dependence of bacteria on phytoplankton for a supply of labile DOC . In turn, BP in the phyto plankton -dominated lake was balanced with grazing by HF (heterotrophic flagellates). The significantly higher HB:DO C and HF:DOC carbon ratios in the phyto plankton -domin ated lake also suggest that better DOC qual ity would mean relatively more efficient C transf er to higher trophic levels . According to PP:B P and PP:R ratios both lakes should be considered autotrophic, although the macroph yte-dom inated lake would be compara tively more heterotrophic.