Effect of <i>Pomacea canaliculata</i> grazing on three submerged macrophytes and the related physicochemical factors

Abstract

外来种福寿螺（Pomacea canaliculata）相较我国本土螺类其牧食量更大且繁殖速度更快，对栖息地水生植物的现存量和实施水生植被恢复的生态治理工程的成功性可能构成威胁，目前对福寿螺影响浅水湖泊沉水植物的重建缺乏足够的研究.本文通过设置不同沉水植物种类组合系统，研究福寿螺对3种常用于浅水富营养化湖泊治理的沉水植物密刺苦草（Vallisneria denseserrulata）、轮叶黑藻（Hydrilla verticillata）、穗花狐尾藻（Myriophyllum spicatum）的牧食偏好以及不同植物配置系统理化因子的响应变化，结果表明福寿螺对沉水植物植株附着偏好为密刺苦草>轮叶黑藻>穗花狐尾藻，而牧食破坏强度为轮叶黑藻>穗花狐尾藻>密刺苦草，轮叶黑藻最容易受到福寿螺牧食影响而快速消亡，穗花狐尾藻叶片也会被全部牧食仅剩下茎，而苦草存活受到的影响较小.福寿螺会导致轮叶黑藻+密刺苦草组合系统中总氮、氨氮、总磷、正磷酸盐浓度显著升高，而密刺苦草+穗花狐尾藻组合中总磷、正磷酸盐浓度显著升高，但是在轮叶黑藻+穗花狐尾藻组合中仅总氮浓度显著升高.研究表明福寿螺能够影响沉水植物间的竞争关系，但是3种沉水植物均不能阻止福寿螺的牧食；福寿螺牧食会显著降低沉水植物生物量，最终会影响草型清水态系统的稳定性.;Compared with native snails in China, Pomacea canaliculata snails exert a higher grazing pressure on plants and have faster growth and reproduction rates, which may negatively affect aquatic plants' standing stock and ecological reestablishment. However, few studies have examined the potential effects of the presence of P. canaliculata on submerged macrophyte reestablishment. In this study, we assessed the preference of P. canaliculata for three submerged plants, namely Vallisneria denseserrulata, Hydrilla verticillata, and Myriophyllum spicatum—which have been largely planted for recovering Chinese eutrophic shallow lakes. The results indicated that the attachment preference of P. canaliculata for submerged macrophytes was in the following order: V. denseserrulata>H. verticillata>M. spicatum. Moreover, P. canaliculata grazing negatively affected plant survival in the following order of magnitude: H. verticillata>M. spicatum>V. denseserrulata. H. verticillata was the most vulnerable to snail grazing and died out rapidly. M. spicatum leaves had been completely consumed by the end of the experiment. V. denseserrulata was the least influenced by P. canaliculata. Compared with the controls, the concentrations of total nitrogen (TN), ammonia nitrogen (NH₃-N), total phosphorus (TP), and soluble reactive phosphate (SRP) were higher with the H. verticillata + V. denseserrulata treatment; TP and SRP concentrations were higher with the V. denseserrulata + M. spicatum treatment; and TN concentrations were higher with the V. denseserrulata + M. spicatum treatment. These results suggest that the grazing preference of P. canaliculata alters the competitive advantage of submerged macrophyte. However, none of the submerged macrophytes prevented P. canaliculata grazing, resulting in decreases in the production of the submerged macrophytes and in the likelihood of clear-water state establishment.