THE POTENTIAL OF ZOOPLANKTON COMMUNITIES FOR ECOLOGICAL ASSESSMENT OF LAKES: REDUNDANT CONCEPT OR POLITICAL OVERSIGHT?

Zooplankton communities are an important component of the pelagic food web, but they are absent from the list of biotic elements to be considered for the assessment of ecological status in Annex V of the Water Framework Directive (2000/60/EC). We report here on an assessment of zooplankton populations across 32 lakes that represent a gradient of alkalinity and anthropogenic impact, primarily owing to nutrients and/or acidity. Acidic and oligotrophic lakes were typified by a high relative abundance of cladocerans, but with some key taxa groups absent from the most acidified lakes. Zooplankton total abundance increased across the trophic gradient. This interplay between acidity and productivity provides the potential to assess effects of anthropogenic pressure on zooplankton communities. Incorporation of ecological function, as opposed to structure, can additionally be evaluated through community attributes, particularly fecundity and size distribution. The assessment of the zooplankton can be cost-effective and related to reference conditions. Reasons for this omission from the requirements of monitoring under the Water Framework Directive are unclear, but this should not preclude the use of zooplankton communities if they can provide a valuable component for ecological assessment.