Spatial variability of chromophoric dissolved organic matter in a large floodplain river: control factors and relations with phytoplankton during a low water period

GISELA MAYORA; MELINA DEVERCELLI; DIEGO FRAU

ECOHYDROLOGY

JOHN WILEY & SONS INC

Lugar: New York; Año: 2016

1936-0584

Chromophoric dissolved organic matter (CDOM) affects ecological processes in freshwater environments. Few studies assessedits spatial variability and relations with phytoplankton in floodplain rivers. Therefore, these topics were examined in ahydrological connectivity gradient in the Middle Paraná system. Absorption coefficients at 250 and 365 nm were measured toestimate CDOM concentration and molecular weight (MW), to find their explanatory limnological variables (RedundancyAnalysis, RDA), and to assess their contribution to the explanation of phytoplankton structure (Canonical CorrespondenceAnalysis, CCA). Conductivity and turbidity explained CDOM significantly. Increased conductivity from the main channel tofloodplain lakes was associated with increased CDOM concentration. The lake indirectly connected to the river showed thehighest turbidity associated with high-MW-CDOM, while the isolated lake showed the highest conductivity associated with low-MW-CDOM. Phytoplankton structure was significantly explained by conductivity, turbidity, and high-MW-CDOM (CCA).Environments directly connected to the river (with the lowest conductivity) were associated with diatoms. Phytoflagellates wereassociated with turbidity and high-MW-CDOM in the lake indirectly connected to the river, whereas Cyanobacteria wereassociated with conductivity and low-MW-CDOM in the isolated lake. The combined effect of physical factors and CDOMexplained the highest fraction of species variation (partial CCA). As a conclusion: (1) CDOM increases as hydrologicalconnectivity with the river decreases; (2) lake sediment resuspension is linked to an increase of high-MW-CDOM; (3) lakeisolation from the river corresponds to an increase in low-MW-CDOM; and (4) CDOM explains phytoplankton structuresignificantly and should be considered as an important variable in studies of microalgal assembly.