Strength and uncertainty of phytoplankton metrics for assessing eutrophication impacts in lakes

Abstract

Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. AbstractPhytoplankton constitute a diverse array of short-lived organisms which derive their nutrients from the water column of lakes. These features make this community the most direct and earliest indicator of the impacts of changing nutrient conditions on lake ecosystems. It also makes them particularly suitable for measuring the success of restoration measures following reductions in nutrient loads. This paper integrates a large volume of work on a number of measures, or metrics, developed for using phytoplankton to assess the ecological status of European lakes, as required for the Water Framework Directive (WFD). It assesses the indicator strength of these metrics, specifically in relation to representing the impacts of eutrophication. It also examines how these measures vary naturally at different locations within a lake, as well as between lakes, and how much variability is associated with different replicate samples, different months within a year and between years. On the basis of this analysis, three of the strongest metrics (chlorophyll-a, Phytoplankton Trophic Index (PTI) & cyanobacterial biovolume) are recommended for use as robust measures for assessing the ecological quality of lakes in relation to nutrient enrichment pressures and a minimum recommended sampling frequency is provided for these three metrics.

The role of phytoplankton diversity metrics in shallow lake and river quality assessment

“…As compared with biomass and sensitivity/tolerance metrics that are considered robust measures of the actual state of waters, diversity metrics have higher uncertainties (Carvalho et al, 2013). On the other hand, when longer time periods are evaluated, changes in diversity (mostly changes in plane number of species) provide important information about the mechanisms that drive the systems into positive or negative directions.…”

“…Diversity metrics are capable of describing system properties such as complexity, stability, and functioning of ecosystems (Hacker and Gaines, 1997); therefore, they became parts of several multimetric indices used for biological quality assessment (Hering et al, 2006;Stoddard et al, 2008;Carvalho et al, 2013). Applicability of diversity-based approaches needs a clear relationship between stressors and diversity metrics as response variables (European Commission, 2010).…”

“…Based on quantitative and qualitative characteristics of phytoplankton several types of metrics have been elaborated and used in Europe: e.g. biomass, sensitivity/tolerance, composition and bloom metrics (Carvalho et al, 2013). Among the various water quality problems, eutrophication is indisputably a phenomenon that is closely related to phytoplankton issues.…”

“…Instead of that, we investigated the changes of diversity along phytoplankton productivity, which is the most robust phytoplankton metric used for quality assessment (Carvalho et al, 2013).…”

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

“…Carvalho et al, 2012;Phillips et al, 2012;Dudley et al, 2012;Mjelde et al, 2012;Argillier et al, 2012;Clarke, 2012) or are published elsewhere (e.g. Kolada et al, 2011;Böhmer et al, 2011;Pilotto et al, 2011;Miler et al, 2012;Emmrich et al, 2011Emmrich et al, , 2012a.…”