Sediment–water interaction in phosphorus cycling as affected by trophic states in a Chinese shallow lake (Lake Donghu)

Abstract

Lake sediment substantially accumulates nutrients, while little is known regarding the conditions under which it tends to be a sink or source of phosphorus. It is postulated that the above functions were largely dependent on trophic state. To test this hypothesis, composition, abundance, and size-spectrum of phytoplankton were studied in a Chinese shallow lake (Lake Donghu), together with concentrations and sorption behaviors of phosphorus in water column and sediment. Relationships among these variables were also examined by structural equation model. In the basins with the lowest phosphorus concentration, sediment was a phosphorus source as judged by equilibrium phosphorus concentration, directly affecting the abundance of phytoplankton with smaller size. Contrastingly, in the basins with the highest phosphorus concentration, sediment tended to uptake phosphorus, companied by the lowest ratio of nitrogen to phosphorus, diversity, and evenness of phytoplankton with the smaller size one dominating. Oscillatoria sp. was directly affected by ammonia and phosphorus. Moreover, with a balanced exchange of phosphorus between sediment and water column, phytoplankton increased markedly with the highest diversity and evenness in the basins having intermediate phosphorus concentration. Overall, trophic state modulated sediment functions to supply nutrient and was in turn greatly affected by the sediment in shallow lakes.

Seasonal characteristics of phosphorus sorption by sediments from plain lakes with different trophic statuses

“…Lake sediment substantially accumulates nutrients, and can be seen as a general porous medium storing a variety of nutrients. Trophic status modulates sediment functions to supply nutrients, and in turn, is greatly affected by the sediment in shallow lakes [ 8 ]. As one of the main factors that influence the P concentration in lakes, P sorption of the sediment has different characteristics because of the different conditions in the lake [ 9 , 10 ], which can cause the change of the trophic status.…”

Threats to the Lower Section of the River after Fish Mortality in the Ecological Environment of the Oder River

“…Substantiated by examinations conducted upon the western basin of Lake Erie, nourished by the extrinsic phosphorus loading from the primary tributary, the Maumee River, it becomes apparent that under anoxic circumstances, the flux of phosphorus exhibits augmentation concomitant with a temperature rise. Specifically, in the scenario of four days of oxygen depletion at a temperature of 30 • C, bottom sediment deposits contribute approximately 415 metric tons of dissolved phosphorus-an approximation corresponding to the vernal phosphorus loading from the Maumee River [61].…”

“…In contradistinction to nitrogen, phosphorus solely exists within the aqueous and solid phases, excluding the gaseous phase. The interplay of phosphorus migration between bottom sediments and water is emblematic of an equilibrium process [61]. This dynamic equilibrium governs the buffering effect exerted by sediment deposits upon variations in bioavailable phosphorus fractions within the water.…”

What maintains seasonal nitrogen limitation in hyper-eutrophic Lake Dianchi? Insights from stoichiometric three-dimensional numerical modeling

“…Benthic TPO4 flux acts distinctively from N because their mechanisms are different. Benthic fluxes of both TPO4 and NH4 + are mainly controlled by the oxygen concentration at the surface sediment; hypolimnetic hypoxia would significantly enhance TPO4 release and impairs nitrification, which is a main consumption pathway for NH4 + (Chen et al 2018, Chen et al 2016, Malecki et al 2004). However, hypolimnetic hypoxia would simultaneously enhance denitrification, which depletes NO3and indirectly reduces benthic N flux (Nowlin et al 2005).…”