克氏原螯虾对3种不同生长型沉水植物清水态系统的影响

鉴于克氏原螯虾（Procambarus clarkii）是目前全球入侵最广、对淡水生态系统最具破坏性的物种之一，探究其对沉水植物清水态系统的影响，有助于防范克氏原螯虾入侵给浅水湖泊带来的生态风险。通过受控实验，研究了克氏原螯虾对直立型沉水植物轮叶黑藻（Hydrilla verticillata）、冠层型沉水植物穗花狐尾藻（Myriophyllum spicatum）和莲座型沉水植物密刺苦草（Vallisneria denseserrulata）的影响以及不同植物培养系统对理化因子的响应变化。结果显示，直立型轮叶黑藻相对生物减少量（60.5%）大于冠层型穗花狐尾藻（45.7%）和莲座型密刺苦草（39.0%）；克氏原螯虾进入后导致3种生长型沉水植物清水态系统的总悬浮物浓度、叶绿素a和营养盐均极显著增高（P<0.01）。研究表明，水生态系统中的克氏原螯虾会直接降低沉水植物生物量，并扰动底泥增加水体的悬浮物、叶绿素a和营养盐浓度，导致水体由清水态向浊水态转变，也会通过直接牧食或扰动破坏，降低沉水植物生物量，最终影响草型清水态系统的稳定性。

Effect of Procambarus clarkii on Clearwater Lakes with Submerged Macrophytes

Procambarus clarkii, native to the southern United States and north-eastern Mexico, is the most widely distributed invasive species globally and the most devastating to freshwater ecosystems. In this study, we investigated the effects of red swamp crayfish (P. clarkii) on the water of clear shallow lakes planted with three submerged macrophytes: Hydrilla verticillate, Myriophyllum spicatum, and Vallisneria denseserrulata. Our aim was to better understand the ecological risks posed by P. clarkii. From October 7 to November 1 of 2020, controlled experiments were conducted in large bucket mesocosms to simulate clearwater systems with macrophytes. Each plant species was tested separately, with and without crayfish, giving a total of 6 groups (3 treatment groups with crayfish and 3 control groups without crayfish). Water samples were collected each week to determine the physicochemical properties of the water and the wet biomass of the submerged macrophytes was measured at the beginning and end of the test. The macrophyte biomass in all treatment groups decreased significantly (P<0.05) compared to control groups, but the effects on H. verticillata and V. denseserrulata were larger than the effect on M. spicatum, with respective decreases in biomass of 60.5%, 45.7%, 39.0%. P. clarkii grazing and defecation disturbed the sediments and significantly increased total suspended solids, nutrients and chlorophyll a, transforming the water from a clearwater state to a turbid state. To summarize, invasive P. clarkii pose a significant risk to the stability of grass-type clearwater lakes.