Three hundred ways to assess Europe's surface waters: An almost complete overview of biological methods to implement the Water Framework Directive

According to the Water Framework Directive (WFD), the status of European surface waters is assessed using aquatic organism groups. Here we present an overview of 297 assessment methods, based on a questionnaire survey addressing authorities in all countries implementing the WFD. Twenty-eight countries reported on methods applied to rivers (30%), coastal waters (26%), lakes (25%) and transitional waters (19%). More than half of the methods are...