Turbidity and dissolved organic matter as significant predictors of spatio‐temporal dynamics of phosphorus in a large river‐floodplain system

Abstract

Phosphorus (P) inputs are increasing in river-floodplain systems, but the factors which influence the dynamics of this nutrient are not clear. To assess P dynamics in this kind of river, the main channel of the Middle Paraná River, 3 anabranches, 9 secondary channels, and 20 lakes (7 permanently connected and 13 temporarily connected to the fluvial system) were sampled. Multiple linear regressions were applied to explain spatio-temporal patterns of P through commonly measured limnological variables.Particulate P increased during the sediment peak (evaluated through turbidity). Soluble reactive P (SRP) was positively associated with dissolved organic matter (DOM, mainly the chromophoric fraction), which increased during high waters in the fluvial system but was highly variable in each kind of aquatic environment. In temporarily connected lakes, vegetated zones dominated by emergent macrophytes displayed the highest SRP and chromophoric DOM concentrations. The flood and sediment peak positively affected P load in the river due to the increase in dissolved and particulate fractions, respectively. In addition, particle-bound alkaline phosphatase activity was positively associated with SRP concentration and load. These results suggest that the sediment peak incorporates particulate P in the system while the floodplain is a P source during floods through exportation of the dissolved fraction. Dissolved P could be largely exported associated with DOM, which stimulates phosphatase biosynthesis by decreasing P bioavailability. The effect of aquatic macrophytes on P dynamics seems to be influenced by DOM exudation. According to these considerations, DOM should be taken into account to analyse P dynamics in river-floodplain systems. KEYWORDS aquatic macrophytes, chromophoric dissolved organic matter, hydrosedimentological regime, Middle Paraná River system, particle-bound alkaline phosphatase activity, spatio-temporal patterns of phosphorus

Presence of Leptospira spp. in a Mosaic of Wetlands Used for Livestock Raising under Differing Hydroclimatic Conditions

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Relationships between algal primary productivity and environmental variables in tropical floodplain wetlands

“…Additionally, our field results identified a positive correlation between turbidity and phosphorus, suggesting the positive turbidity-productivity relationship may be driven by availability of nutrients. In river-floodplain systems, turbidity can be associated with TP concentration (Mayora et al 2018). While nutrients may be the underlying driver of productivity, turbidity may provide a surrogate measure for algal productivity and can easily be monitored by remote sensing, as long as it is within the range of ground observations.…”

Nutrient Concentrations in Macrophytes from Lotic and Lentic Environments of the Middle Parana River, Argentina

“…These authors found that the abundance of Phalaris arundinacea, Scirpus lacustris, Carex riparia, and Eleocharis palustris increases when there is a decrease in the amount of nutrients in the water. Mayora, Schneider and Rossi [11] reported that soluble reactive phosphorus was positively correlated with dissolved organic matter, which increased during high waters in the Middle Parana River system. Studies carried out in the Middle Parana River floodplain have demonstrated that aquatic plants have shown fast growth, high productivity, and a wide response to floods and pollutant exposition [3], [12], [13].…”