Zooplankton as indicators in lakes: a scientific-based plea for including zooplankton in the ecological quality assessment of lakes according to the European Water Framework Directive (WFD)

Abstract

With the implementation of the EU Water Framework Directive (WFD), the member states have to classify the ecological status of surface waters following standardised procedures. It was a matter of some surprise to lake ecologists that zooplankton were not included as a biological quality element (BQE) despite their being considered to be an important and integrated component of the pelagic food web. To the best of our knowledge, the decision of omitting zooplankton is not wise, and it has resulted in the withdrawal of zooplankton from many so-far-solid monitoring programmes. Using examples from particularly Danish, Estonian, and the UK lakes, we show that zooplankton (sampled from the water and the sediment) have a strong indicator value, which cannot be covered by sampling fish and phytoplankton without a very comprehensive and costly effort. When selecting the right metrics, zooplankton are cost-efficient indicators of the trophic state and ecological quality of lakes. Moreover, they are important indicators of the success/ failure of measures taken to bring the lakes to at least good ecological status. Therefore, we strongly recommend the EU to include zooplankton as a central BQE in the WFD assessments, and undertake similar regional calibration exercises to obtain relevant and robust metrics also for zooplankton as is being done at present in the cases of fish, phytoplankton, macrophytes and benthic invertebrates.

Ecological status assessment of European lakes: a comparison of metrics for phytoplankton, macrophytes, benthic invertebrates and fish

“…The application of the betterperforming metrics presented here may be part of the way forward to improve the quality and comparability of national assessment systems across Europe. We also encourage further work that seeks to develop ecological indicators that are currently not part of WFD requirements, such as zooplankton (Caroni & Irvine, 2010;Jeppesen et al, 2011), and that the four existing BQEs are further evaluated from an integrated ecosystem perspective (Moss, 2008). Sector authorities, the public and politicians are more likely to accept the use of biological indicators as a basis for decisions on costly management measures to reduce human impacts on lakes, if the links between these indicators and ecosystem services can be convincingly demonstrated.…”

Evaluation of vertical and horizontal changes in community structure of zooplankton in a deep dam lake

“…Moreover, a major portion of the zooplanktonic community appears to consist of very common species. The freshwater zooplankton occupy an important and strategic position within the trophic web of a lake ecosystem and are sensitive to anthropogenic impacts (Jeppesen et al, 2011). Understanding the relationship between the zooplankton community and its spatial and temporal distribution is important for the comprehension of trophic interactions within a reservoir.…”

“…Zooplankton species are commonly utilized as bioindicators for environmental changes since they respond quickly to environmental pollution as a whole community (Whitman et al, 2004;Altindag et al, 2009;Kaya et al, 2010;Sellami et al, 2010). Zooplankton as indicators of ecological circumstances have importance due to their position in the food web; they reflect the top-down regulators (fish), bottom-up factors (phytoplankton), and benthic status, and thus they supply information about the relative importance of top-down and bottom-up control and their effects on water transparency (Zhao et al, 2008;Jeppesen et al, 2011).…”

Sustainable Management of Eutrophic Lakes and Reservoirs

“…A number of these measurements can be used to classify the trophic state of lakes or reservoirs [50]. The trophic state can range between oligotrophic where the ecosystem is nutrient deficient, to mesotrophic where there is an intermediate amount of nutrients and productivity, to eutrophic where nutrients are in excess.…”