Microbial pelagic metabolism and CDOM characterization in a phytoplanktondominated versus a macrophyte-dominated shallow lake

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

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2015

0018-8158

Dominant primary producer in macrophyte-or phytoplankton-dominated shallow lakesmight imply differences in dissolved organic carbon(DOC) composition. We compared chromophoricdissolved organic matter (CDOM), plankton respiration(R), and bacterial (BP) and primary production(PP), in two contrasting shallow lakes. We hypothesizedthat DOC from the macrophyte-dominatedlake would be qualitatively inferior, so that it cansupport a lower yield than DOC from the phytoplankton-dominated one. Macrophyte-dominated lakehad more humic and aromatic CDOM, thoughmolecular weight was similar in both lakes. A clearsynchronism between lakes was observed in meandepth and several CDOM absorption coefficients,suggesting an external driver of the variation in DOCconcentration and CDOM quality. The positive BPPPand BP-Chl-a correlations in the macrophytedominatedlake point out to a dependence of bacteriaon phytoplankton for a supply of labile DOC. In turn,BP in the phytoplankton-dominated lake was balancedwith grazing by HF (heterotrophic flagellates).The significantly higher HB:DOC and HF:DOCcarbon ratios in the phytoplankton-dominated lakealso suggest that better DOC quality would meanrelatively more efficient C transfer to higher trophiclevels. According to PP:BP and PP:R ratios bothlakes should be considered autotrophic, although themacrophyte-dominated lake would be comparativelymore heterotrophic.