Phytoplankton abundance and contributions to suspended particulate matter in the Ohio, Upper Mississippi and Missouri Rivers

Abstract

Main channel habitats of the Ohio, Missouri, and Upper Mississippi Rivers were surveyed during the summers of 2004, 2005 and 2006 using a probability-based sampling design to characterize inter-annual and inter-river variation in suspended chlorophyll a (CHLa) and related variables. Large (fivefold) differences in CHLa were observed with highest concentrations in the Upper Mississippi (32.3 ± 1.8 lg L -1 ), intermediate values in the Missouri (19.7 ± 1.1 lg L -1 ) and lowest concentrations in the Ohio (6.8 ± 0.5 lg L -1 ). Inter-annual variation was small in comparison to inter-river differences suggesting that basin-specific factors exert greater control over river-wide CHLa than regional-scale processes influencing climate and discharge. The rivers were characterized by variable but generally low light conditions as indicated by depth-averaged underwater irradiance \4 E m -2 day -1 and high ratios of channel depth to euphotic depth ([3). Despite poor light conditions, regression analyses revealed that TP was the best single predictor of CHLa (R 2 = 0.40), though models incorporating both light and TP performed better (R 2 = 0.60). Light and nutrient conditions varied widely within rivers and were inversely related, suggesting that riverine phytoplankton may experience shifts in resource limitation during transport. Inferred grazing and sedimentation losses were large yet CHLa concentrations did not decline downriver indicating that growth and loss processes were closely coupled. The contribution by algae to suspended particulate organic matter in these rivers (mean = 41%) was similar to that of lakes (39%) but lower relative to reservoirs (61%).

Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin

“…However, most samples from January and June 2015 and February 2016 do not carry a plankton signature (Table S1). This concurs with previous studies that determined the composition of POM in the Mississippi basin downstream of our study area that is predominantly derived from autochthonous plankton [Bukaveckas et al, 2011;Kendall et al, 2001;Yang et al, 2016] but demonstrates that allochthonous POM sources are important in large rivers under certain conditions. Added macronutrients (fertilizer) in this basin may stimulate photosynthesis beyond what would naturally occur, adding modern POC to the suspended load and producing a POC composition which is not distinct from other UMR watersheds, despite its significantly more aged DOC.…”

Longitudinal Plankton Dynamics in the Rivers Rhine and Elbe

“…A possible explanation for this surprisingly strong phytoplankton growth is the extremely low discharge during the sampling campaign with mean water travel times of 10 days, demonstrating the importance of water residence time for phytoplankton dynamics. The spatio‐temporal development of hydraulic conditions has a strong impact on the longitudinal phytoplankton development, and lower water levels also ameliorate the light climate in the water column, whereas high discharge conditions with deeper and often more turbid water may inhibit phytoplankton growth by light limitation (Reynolds, ; Bukaveckas et al ., ). During our surveys in the Rhine, light penetration near the river bottom was mostly above 1% of surface light irradiance, while compensation depth in the Elbe was mostly equal to water depth.…”

Darkness at the break of noon: Phytoplankton production in the Lower Mississippi River

“…To test the effects of artificial light vs. natural sunlight, we compared production measurements made in the photosynthetron and the field. Third, nutrient concentrations, useful in modeling phytoplankton production in some systems (Soetaert et al 1994;Bukaveckas et al 2011), were not considered here, because phytoplankton production is seldom nutrient-limited in the LMR main channel (C. Ochs unpubl. ).…”

“…This value is intermediate between ratios reported for three major tributaries of the LMR: the Upper Mississippi (C : Chl a 5 22), the Ohio River (26), and the Missouri River (70; Bukaveckas et al 2011). We evaluated our assumption of a C : Chl a ratio of 50 by a simulation analysis in which we calculated doubling times (dt) of Table 2.…”