Concentrations and controls of dissolved organic matter in a constricted-channel region of the Ohio River

摘要: A 12-month study was conducted to measure the concentrations ofdissolved organic matter (DOC, TDN, TDP) in four sites within a119 km long reach of Ohio River, near Louisville, KY. In thisstudy we test whether specific geomorphological and biologicalfactors influenced variations dissolved matter.Concentrations DOC river averaged ≈1200μmol/L, varied by nearly two orders magnitudeseasonally (mean during base flow ≈620 μmol/L).Peak periods for at all were April–May. Thesite nearest a navigation dam (deeper, lower current velocities)had significantly TDN greater C:Nratios than upstream sites. The largest tributary entering thisreach (Kentucky River) had no significant effect on levels DOMin main river, despite having greaterconcentrations most monthsof year. Concentrations DOC, TDP notsignificantly different littoral pelagic habitats allsites studied, suggesting little floodplain influence DOM inthis constricted-channel section River. C:N ratios ofDOM among seasons; C:Nexceeded or equaled Redfield summer fall (6 10),but below (1.8 3.0) winter spring.Regression models suggest that total phytoplankton densities andflow conditions are important factors regulating this very large river.