两种沉水植物及其叶面附着细菌对钙磷添加的响应研究

Response of Two Submerged Plants and Their Leaf Epiphytic Bacterial Community to the Addition of Calcium and Phosphorus

沉水植物光合作用形成的微环境有利于水体中钙和磷形成CaCO_(3)-P共沉淀,但不同的沉水植物种类诱导CaCO_(3)-P共沉淀的能力不同。本研究以菹草和伊乐藻为研究对象,设置钙离子添加质量浓度(0和100 mg/L)和无机磷添加质量浓度(0、0.2和2 mg/L)2个变量,通过测定培养液pH,总磷(TP)、溶解性活性磷(SRP)、叶绿素含量(Chl-a)和碱性磷酸酶活性(TAPA),植株干重全磷、灰分总磷和钙磷的含量及叶面附着细菌的群落特征,探讨植物及其叶面附着细菌对水体钙磷添加的响应。研究结果表明:(1)钙离子添加降低了水体TP和SRP,水体TAPA与pH负相关,菹草体系中,Chl-a与水体pH负相关,而伊乐藻体系中,Chl-a与pH正相关,添加100 mg/L钙离子浓度处理后,菹草上覆水中TAPA与SRP、TP负相关,而伊乐藻上覆水Chl-a与TP、SRP的正向关联被干扰;(2)菹草与伊乐藻的灰分总磷和钙磷的含量随磷浓度升高而增加,添加100 mg/L钙离子浓度处理后,菹草的灰分总磷和钙磷的含量升高,而伊乐藻的灰分总磷和钙磷含量降低,菹草的灰分钙磷含量大于伊乐藻;(3)菹草和伊乐藻叶面附着细菌中,变形菌门(Proteobacteria)与蓝藻门(Cyanobacteria)的相对丰度均位于前两名,两者之和占相对丰度的71%~84%,无钙离子添加处理中,添加2 mg/L磷处理中,菹草和伊乐藻叶面附着变形菌门丰度降低,蓝藻门丰度升高,添加100 mg/L钙离子后,随磷浓度升高,菹草变形菌门丰度升高,蓝藻门丰度降低,而伊乐藻变形菌门丰度变化不大,但蓝藻门丰度升高。总之,由于钙磷共沉淀能力的差异,2种植物的钙磷含量、植物叶面的形态结构和细菌群落组成表现出明显的种间差异。

The microenvironment produced by photosynthesis in submerged plants is conducive to co-precipitation of calcite(CaCO_(3))and phosphate(PO_(4)^(3-)).However,the extent of CaCO_(3)-PO_(4) coprecipitation varied among different submerged species.In this study,Potamogeton crispus and Elodea canadensis were selected for research,and we investigated the response of submerged plants and their leaf epiphytic bacteria to additions of Ca^(2+)and PO_(4)^(3-)to the water.The experiments were carried out in buckets(38 cm,30 cm)from December 22,2020 to January 8,2021.Six Ca2+and PO_(4)^(3-)treatments(0 mg/L PO_(4)^(3-),0 mg/L Ca;0.2 mg/L PO_(4)^(3-),0 mg/L Ca;2.0 mg/L PO_(4)^(3-),0 mg/L Ca;0 mg/L PO_(4)^(3-),100 mg/L Ca;0.2 mg/L PO_(4)^(3-),100 mg/L Ca;2.0 mg/L PO_(4)^(3-),100 mg/L Ca)were set for each plant species,and a control group with no plants.Each treatment was run in triplicate,and water from each treatment was sampled every three days,beginning on Day 2,and the plants were collected at the end of the experiment.Solution pH,total phosphorus(TP),soluble reactive phosphorus(SRP),chlorophyll(Chl-a)and total alkaline phosphatase activity(TAPA)were measured and plants were analyzed for total phosphorus(dry weight),TP and calcium phosphate(Ca-PO_(4))and the leaf epiphytic bacteria community was characterized.Results show that(1)the addition of Ca^(2+)decreased the concentration of TP and SRP in water,and the concentration of TAPA had a negative correlation with pH.The content of Chl-a in P.crispus culture treatments was negatively correlated with pH,while Chl-a was positively correlated with pH in E.canadensis culture treatment.After adding Ca^(2+)concentration of 100 mg/L,TAPA in overlying water of P.crispus treatments had a negative correlation with SRP and TP,while the correlation between TP and SRP in overlying water of E.canadensis and Chl-a was positive.(2)Total phosphorus in dry weight,total phosphorus in ash and calciumphosphate in ash of P.crispus and E.canadensis increased with the increase of phosphorus concentration.In 100 mg/L Ca^(2+)adding treatments,total phosphorus in ash and Ca-P contents of P.crispus increased,while those of E.canadensis decreased.Ca-P concentration of P.crispus was higher than that of E.canadensis.(3)The relative abundance of Proteobacteria and Cyanobacteria were both the richest in the microbial communities attached to the leaves of P.crispus and E.canadensis,accounting for 71%-84% of the total abundance.In the treatment of 2.0 mg/L P+0 mg/L Ca,the abundance of Proteobacteria on both species reduced,while that of Cyanophyta increased.After adding Ca^(2+)concentration of 100 mg/L,the abundance of Proteobacteria on the leaves of P.crispus increased with the increase of phosphorus concentration,but the abundance of Cyanophyta decreased.For E.canadensis,the abundance of Proteobacteria changed little,while the abundance of Cyanophyta increased with the increase of phosphorus concentration.In conclusion,the Ca-P contents,the morphological structure of the leaves and the composition of leaf epiphytic bacteria showed significant interspecific differences due to the difference in co-precipitation capacity of calcium and phosphate.