美国Apopka湖的富营养化及其生态恢复

Eutrophication and Restoration of Lake Apopka,USA

本文系统地回顾了美国佛罗里达州大型浅水湖--Apopka湖富营养化和生态恢复的过程.流域水文状况的改变,围湖种植和向湖排放农业污水是Apopka湖从"草清型"转变为"藻浊型"湖泊的根本原因.50多年来,尽管内源控制的手段几经改变,但是,控制外源营养输入一直是Apopka湖整治的主要措施之一.Apopka湖富营养化的研究主要包括Apopka湖原始状态分析,浮游植物区系,生长限制因子,初级生产力,沉积物的理化特征和再悬浮,碳、氮、磷蕴藏量和释放率,富营养化的古湖沼学证据,外源磷负荷和恢复指标等.目前,Apopka湖生态恢复主要采取降低外源磷输入,通过人工湿地清除湖中悬浮物和颗粒磷,捕鱼除磷和生物操纵,种植水生植物和提高水位变动幅度等措施.最后介绍了围绕Apopka湖的富营养化及其恢复的学术争论.最后,还讨论了该湖研究和整治一些可能的存在问题和建议.

This paper provides a literature review on eutrophication and restoration of Lake Apopka, a large, shallow and subtropical lake in Florida, USA. Prior to 1947, Lake Apopka was a clear-water, submerged macrophyte-dominated system with a famous recreation fishery. Hydrologic alteration of the drainage basin and large-scale agricultural development of floodplain has resulted in catastrophic changes in Lake Apopka ecosystem. These changes include excessive phosphorus loading to the lake, massive die-off of the submerged macrophytes and virtual disappearance of the large-mouth bass population. Nowadays, Lake Apopka is a hypereutro-phic system dominated by picophytoplankton and rough fish gizzard shad. Approximately 90% of the lake bottom is covered by a layer of 50 cm thick, unconsolidated, flocculent organic materials largely originated from water column production. Measures of Lake Apopka restoration include (1) reduction of external phosphorus loading, (2) removal of phosphorus and other suspended solids from the lake by filtration through the marsh flow-way and by mass removal of gizzard shad, (3) improvement of food-web structure by removing gizzard shad, (4) restoration of habitat through shoreline plantation and (5) increases in water level fluctuation. Major research covers a variety of topics including analysis of past water quality conditions, estimates of external and internal phosphorus loading, setting water quality goal, sediment characterization, resuspension, nutrient inventory and fluxes, paleolimno-logical evidences for eutrophication, primary productivity, phytoplankton community structure, and limiting nutrients. Recent debates on eutrophication mechanisms and restoration strategies are also presented.