Ecological stoichiometry of carbon, nitrogen, and phosphorus of periphyton in different habitats of Caohai Wetland, Guizhou Province

Abstract

为深入了解湿地周丛生物碳（C）、氮（N）、磷（P）生态化学计量的变化规律及其影响因素，对贵州草海湿地4种不同生境（湖滨带、人工湿地、农田沟渠、污水处理厂）中周丛生物两个生长阶段（生长期和衰老期）的C、N、P生态化学计量学进行了研究.结果表明：水体营养指数依次为污水处理厂（51.55±4.50）>农田沟渠（50.41±4.50）>人工湿地（47.20±6.72）>湖滨带（41.86±6.91），湿地下游水域水质较上游明显改善.总体来看，在不同生境间，周丛生物C、N、P含量随着水体营养浓度的升高而增加，但周丛生物化学计量比呈下降的趋势.同一生境中，生长期周丛生物的C、N、P含量和C：N都小于衰老期周丛生物，N：P和C：P则相反.周丛生物生长期N、P元素为弱稳态型（H_N=2.358，H_P=2.576），衰老期为稳态型（H_N=10.99，H_P=5.78），整体来看两个生长阶段周丛生物的N：P呈稳态型（H_N：P=4.504）.根据周丛生物最佳生长速率计量比得出湖滨带处于P限制状态，而人工湿地、污水处理厂和农田沟渠则不受养分限制.相关性分析表明水体营养水平显著影响周丛生物的N、P元素含量及化学计量比，尤其是水体TP和TN浓度.非线性曲面拟合分析表明，周丛生物N：P和C：N分别受水体TP和TN浓度的主要影响，而水体TN和TP浓度对周丛生物C：P的影响同等重要.该研究表明，基于水体TP、TN浓度和周丛生物化学计量比的三维模型可用来评估水体营养水平和周丛生物化学计量之间的关系.;To understand the changes and influencing factors of the periphyton ecological stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) in the wetland, we analyzed the ecological stoichiometry of C, N, and P in two growth stages (periphyton growth period and periphyton decline period) in four different habitats (lakeside zone, artificial wetland, farmland ditch, and sewage treatment plant) of Caohai Wetland in Guizhou Province. The results show that the trophic level index was in the order of sewage treatment plant (51.55±4.50)> farmland ditches (50.41±4.50)> constructed wetland (47.20±6.72)> lakeside zone (41.86±6.91), and the water quality from upstream to downstream show a trend of gradual improvement. Interestingly, the contents of C, N, and P in periphyton increased with increasing water nutrient concentration, while the periphyton stoichiometric ratio shows a decreasing trend. The contents of C, N, P and C：N of periphyton in the growing period were lower than those in the decline period in the same habitat but the contents of N：P and C：P were opposite. The elements of N and P in the growth period of the periphyton are weakly stable (H_N=2.358, H_P=2.576), and the aging stage is the steady-state type (H_N=10.99, H_P=5.78). On the whole, the N：P of periphyton in the two growth stages is in steady-state (H_N：P=4.504). According to the measurement ratio of the optimal growth rate of the periphyton, the lakeside zone is in the P-restricted state, while the constructed wetlands, sewage treatment plants, and farmland ditches are not subject to nutrient restrictions. Correlation analysis shows that the content of N, P, and the stoichiometric ratio of periphyton are significantly affected by the level of water nutrition, especially total phosphorus (TP) and total nitrogen (TN) concentrations. Non-linear surface fitting analysis shows that N：P of periphyton is mainly affected by the changes of TP concentration, while C：N is mainly affected by TN concentration, and TN and TP concentrations are equally important to C：P. This study shows that the three-dimensional model based on the TP and TN concentrations of water, and the stoichiometric ratio of periphyton can be used to evaluate the relationship between the trophic level of the water and the stoichiometry of periphyton.