St. Croix Watershed Research Station, Science Museum of Minnesota, 16910 152nd Street North, Marine on St. Croix, Minnesota, 55047, USA.
Department of Biology, University of St. Thomas, 2115 Summit Avenue, St. Paul, Minnesota, 55105, USA.
Ecol Appl. 2016 Dec;26(8):2660-2674. doi: 10.1002/eap.1382. Epub 2016 Sep 12.
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. We examine the modern and historical stability of 11 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 yr 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 yr 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.
浅水湖泊中从清水大型植物占优势到浊水浮游植物占优势的生态转变通常被认为是快速的短期转变。北美草原洼地地区浅水湖泊的沉积物记录中的硅藻残留物提供了新的证据，表明这些湖泊的长期生态稳定性是由大的体制转变的遗留物所定义的。我们检查了 11 个浅水湖泊的现代和历史稳定性。目前，四个湖泊处于清水状态，三个湖泊始终处于浊水状态，四个湖泊的状态每年都在发生变化（过渡状态）。过去 150-200 年的湖泊沉积物记录表明：（1）硅藻组合特征是清水或浊水湖泊的特征；（2）在景观发生重大变化之前，所有湖泊都处于稳定的清水状态的体制中；（3）目前被归类为浊水或过渡状态的湖泊在过去 150-200 年内经历了一次强烈的体制转变，此后一直处于浊水占主导地位的体制中；（4）鱼类引入对湖泊食物网的自上而下的影响似乎是强烈体制转变的主要驱动因素，而不是增加的养分供应。根据我们的发现，我们展示了一种可以被湖泊管理者用来识别那些具有接近清水-浊水体制转变阈值的生态历史的湖泊的方法；通过生物操纵，这些湖泊可能更容易恢复到清水状态。不幸的是，许多这些湖泊现在是管理景观的一部分，可能需要继续干预。
