Spatiotemporal Variations in Seston C:N:P Stoichiometry in a Large Eutrophic Floodplain Lake (Lake Taihu): Do the Sources of Seston Explain Stoichiometric Flexibility?

Abstract

Although sources of seston are much more complicated in lakes compared to oceans, the influences of different sources on the spatiotemporal variations in seston stoichiometry are still underexplored, especially in large eutrophic floodplain lakes. Here, we investigated seston stoichiometric ratios across a typical large eutrophic floodplain lake (Lake Taihu, East China) over one year. In addition, we used the n-alkane proxies to examine the influence of the seston source on seston stoichiometry variation. Throughout the study, the average value of the C:N:P ratio of 143:19:1 across Lake Taihu was close to the canonical lake's ratios (166:20:1). Similar to other eutrophic lakes, seston C:N ratios varied the least across all environments, but C:P and N:P ratios varied widely and showed a strong decreasing trend in ratios of N:P and C:P from growing season to senescence season. This seasonal change was mainly associated with the decreasing contribution from algal-derived materials in seston pools because the non-algal dominated seston exhibited significantly lower ratios than algal-dominated seston. Furthermore, the spatial heterogeneity of stoichiometric ratios was also related to the seston source. During the senescence season, the terrestrial-dominated seston from agricultural watershed exhibited the lowest ratios in estuary sites compared with other areas. Statistically, the predictive power of environmental variables on stoichiometric ratios was strongly improved by adding n-alkanes proxies. Apart from source indicators, particulate phosphorus (PP) contents also partly explained the spatiotemporal variations in stoichiometric ratios. This study, thus, highlights the utility of multiple-combined n-alkane proxies in addition to simple C:N ratios to get more robust source information, which is essential for interpreting the spatiotemporal variations in seston stoichiometric ratios among eutrophic floodplain lakes and other freshwater ecosystems.

A Kinetics Model for Predicting Microcystis Growth Based on the Synergistic Effect of Nitrogen and Phosphorus on the Growth of Microcystis densa (Cyanobacteria)

“…These results suggested that the concentration of approximately 8 mg l -1 was the maximum threshold of M. densa for N demand. This concentration was significantly higher than the N concentration in most lakes and reservoirs [35,36], which suggested that M. densa could grow rapidly in most waters and N concentrations in natural waters would not restrict the growth of M. densa.…”

The shift from macrophytic to algal particulate organic matter favours dissimilatory nitrate reduction to ammonium over denitrification in a eutrophic lake

“…The decreased denitrification during algal blooms may be just the redistribution of the N removal amount over the whole year. Secondly, in the growing season (from late spring to early autumn), the POM derived from algal sources was dominant in all areas of northern Lake Taihu, and in the senescence season (from late autumn to early spring), the spatial differences of POM sources between the littoral area and the centre area of the lake are significant due to the influence of terrestrial inputs or macrophytes (Cai et al., 2020). Nitrate ammonifiers at the centre area of the lake may be adapted to use algal detritus but nitrate ammonifiers in littoral area may not be, which is likely to lead to the different response of DNRA on POM sources (Salk et al., 2017).…”

History and Trends in Ecological Stoichiometry Research from 1992 to 2019: A Scientometric Analysis

“…Ecosystem feedback between biological factors (such as consumer stoichiometry) and environmental factors (such as resource stoichiometry) in biological systems is under homeostatic regulation, and has effects through a reciprocal influence of the supply and demand balance of elements between organisms, and between the organism and the environment. From studies on marine life, for example plankton (phytoplankton and zooplankton) [44][45][46], aquatic hyphomycetes [47,48], algae [49,50] and daphnia [51], our understanding of consumer stoichiometry, consumer population stability and community organization structure has greatly increased. However, large variations have been observed in the nutrient content of autotrophic organisms in different life periods, leading to large variations in stoichiometric ratios (such as C:N:P).…”