Inland Waters ( IF 3.1 ) Pub Date : 2020-06-01 , DOI: 10.1080/20442041.2020.1752081 Martin Søndergaard 1, 2 , Liselotte S. Johansson 1 , Eti E. Levi 1 , Torben L. Lauridsen 1, 2 , Erik Jeppesen 1, 2, 3
In the EU Water Framework Directive, lakes are classified into different types primarily on the basis of morphological and chemical characteristics. Lake type definition is not trivial because the different lake types may require different nutrient loading reduction targets to achieve the goal of at least “good” ecological status. Using data from 770 Danish lakes, we illustrate some of the problems associated with classification. In Denmark, 16 potentially different lake types are defined using an alkalinity boundary of 0.2 meq/L, a colour boundary of 60 mg/L Pt, a salinity boundary of 0.5‰, and a water mean depth boundary of 3 m. However, all classification variables showed considerable seasonal and interannual variation. Most lakes with a mean depth <3 m were polymictic, but stratification depended on lake size, complicating simple classification according to depth. Conditional inference tree analyses defined relatively clearly delineated groups of macrophytes, phytoplankton, and fish based on species presence, thereby confirming the relevance of using lake type classification. Alkalinity and salinity were the 2 most important factors and defined alkalinity split points at 0.07 and 0.76 meq/L and salinity split points between 0.5‰ and 4‰. However, with a few exceptions, the individual taxa occurred over a broad range of lake characteristics. Lake classification may be necessary for management reasons, but the absence of well-defined boundaries among lake types and a large natural variability in morphological and chemical characteristics urge cautious decisions when defining targets for external nutrient loading reduction for the various lake categories.
中文翻译:
湖泊类型及其定义:以丹麦为例
在欧盟水框架指令中,主要根据形态和化学特征将湖泊分为不同类型。湖泊类型的定义并非无关紧要,因为不同的湖泊类型可能需要不同的养分减少指标,以实现至少“良好”生态状态的目标。使用来自770个丹麦湖泊的数据,我们说明了与分类相关的一些问题。在丹麦,使用0.2 meq / L的碱度边界,60 mg / L Pt的色度边界,0.5‰的盐度边界和3 m的水平均深度边界定义了16种潜在的不同湖泊类型。但是,所有分类变量均显示出相当大的季节性和年际变化。大多数平均深度<3 m的湖泊都是多峰的,但是分层取决于湖泊的大小,根据深度使简单分类变得复杂。条件推断树分析根据物种的存在定义了相对清晰地划分的大型植物,浮游植物和鱼类的组,从而确认了使用湖泊类型分类的相关性。碱度和盐度是两个最重要的因素,其碱度分界点分别为0.07和0.76 meq / L,盐分分界点在0.5‰至4‰之间。但是,除少数例外,单个分类群的分布范围广泛。由于管理原因,可能需要对湖泊进行分类,但是在为各种湖泊类别确定减少外部养分负荷的目标时,缺乏湖泊类型之间界限分明的界限以及形态和化学特征的较大自然变异性,因此必须谨慎决策。