Data from: The legacy of large regime shifts in shallow lakes

Ecological shifts in shallow lakes from clear-water macrophyte-dominated to turbid-water phytoplankton-dominated are generally thought of as rapid short-term transitions. Diatom remains in sediment records from shallow lakes in the Prairie Pothole Region of North America provide new evidence that the long-term ecological stability of these lakes is defined by the legacy of large regime shifts. Here we examine the modern and historical stability of eleven shallow lakes. Currently, four of the lakes are in a clear-water state, three are consistently turbid-water, and four have been observed to change state from year to year (transitional). Lake sediment records spanning the past 150-200 years suggest that: 1) the diatom assemblage is characteristic of either clear or turbid lakes; 2) prior to significant landscape alteration, all of the lakes existed in a regime of a stable clear-water state; 3) lakes that are currently classified as turbid or transitional have experienced one strong regime shift over the past 150-200 years, and have since remained in a regime where turbid-water predominates; and 4) top-down impacts to the lake food web from fish introductions appear to be the dominant driver of strong regime shifts, and not increased nutrient availability. Based on our findings we demonstrate a method that could be used by lake managers to identify lakes that have an ecological history close to the clear-turbid regime threshold; such lakes might more easily be returned to a clear-water state through biomanipulation. The unfortunate reality is that many of these lakes are now part of a managed landscape and will likely require continued intervention.

浅水湖泊从清水大型水生植物（macrophyte）主导稳态向浊水浮游植物（phytoplankton）主导稳态的生态转型，以往普遍认为属于短期快速的生态过程。北美草原坑洼地区（Prairie Pothole Region）浅水湖泊沉积物记录中的硅藻残体（diatom remains），为这类湖泊的长期生态稳定性由大型稳态转换的遗留效应所决定提供了全新证据。本研究针对11个浅水湖泊的现代与历史生态稳定性展开探究。当前，其中4个湖泊处于清水稳态，3个始终维持浊水状态，另有4个湖泊的生态状态逐年波动（过渡态）。对过去150至200年的湖泊沉积物记录分析结果显示：1）硅藻群落特征可明确区分清水或浊水湖泊类型；2）在景观发生显著人为改造之前，所有湖泊均稳定处于清水主导的稳态；3）当前归类为浊水或过渡态的湖泊，在过去150至200年间均经历过一次剧烈的稳态转换，此后长期以浊水状态占优；4）鱼类引种对湖泊食物网产生的下行调控效应，是驱动这类剧烈稳态转换的主导因素，而非营养盐负荷的升高。基于本研究发现，我们提出了一套可被湖泊管理者用于识别生态历史接近清水-浊水稳态转换阈值的湖泊的方法；此类湖泊可通过生物操纵（biomanipulation）手段更高效地恢复至清水稳态。遗憾的是，这类湖泊如今大多已纳入人工管理的景观体系，后续或需持续的人工干预方能维持其生态状态。