Carbon,nitrogen,phosphorus stoichiometry and burial estimation of macrophyte-to algae-dominated stage of Yilong lake
Understanding the stoichiometry of carbon(C),nitrogen(N)and phosphorus(P)in lake sediments is of great significance in enhancing the stoichiometric studies of terrestrial water ecosystems and revealing the response trajectory of biogenic elements between macrophyte-and algae-dominated lake ecosystems.Based on 20 sediment cores covering the whole lake,the total organic carbon(TOC),total nitrogen(TN)and total phosphorus(TP)in the sediments of shallow eutrophic Yilong lake were measured,and the influence of macrophyte-and algae-dominated lake on the carbon,nitrogen and phosphorus stoichiometry was discussed.The results showed that the stoichiometric characteristics of C,N and P in lake sediments presented spatial and temporal heterogeneity.The contents of TOC,TN and TP in the algae-dominated stage of Yilong lake were(4.83±1.47)％,(0.42±0.09)％and(0.04±0.01)％,respectively,which were significantly higher than those in the macrophyte-dominated stage((3.87±0.98)％,(0.31±0.08)％and(0.03±0.02)％,respectively).The C∶N∶P value of 347∶26∶1 for the algae-dominated lake stage was significantly lower than that of the macrophyte-dominated lake stage(519∶35∶1).This reflected the effect of aquatic plant community succession during the macrophyte-to algae-dominated stage transformation,and the impact of altered water environments on the ecological stoichiometry of low homeostasis organisms.Among different elements,due to the composition of organic matter sources,the function and activity of chemical elements,the C and N elements in sediments of Yilong lake were mainly enriched in the estuary and littoral zone,while the P element was enriched in the deep-water area,resulting in a low coupling between the P element and the C and N elements.In the surface 0～15 cm layer,the burial amounts of TOC,TN and TP in the sediments of Yilong lake were 1829 t/km2,160 t/km2 and 16 t/km2,respectively.The average burial rate in the top 0～5 cm(algae-dominated stage)was elevated by 30％-36％compared to the bottom 10～15 cm(macrophyte-dominated stage),but burial in the bottom 10-15 cm layer was 1.5 times higher than in the top 0-5 cm layer,as affected by water content.Comparison with other eutrophic lakes revealed that temperature greatly influenced the effective burial of organic matter in lakes and played a key role in regulating the source and sink functions of C,N and P in lake sediments.The high water temperature of Yilong lake made it easier for sediment nutrients to be released into the lake water,which aggravated the difficulty of lake ecological restoration.The ecological stoichiometry and burial characteristics of lake revealed in this study can provide an important scientific basis for deepening the understanding of C,N and P cycles in plateau lakes and evaluating nutrient burial.
Yilong lakeeutrophicationmacrophyte-and algae-dominated lakeecological stoichiometrystorage of carbon,nitrogen and phosphorus
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