Uncertainty in ecological status assessments of lakes and rivers using diatoms

Abstract

The EU's Water Framework Directive requires all surface water bodies to be classified according to their ecological status. As biological communities show both spatial and temporal heterogeneity, expressions of ecological status will, inevitably, have an element of uncertainty associated with them. A consequence of this environmental heterogeneity is that there is a risk that status inferred from one or more samples is different to the true status of that water body. In order to quantify the scale of temporal uncertainty associated with benthic diatoms, replicate samples were collected from sites across the ecological status gradient in lakes and rivers in the UK. Variability (expressed as standard deviation of temporal replicate samples from a single site) could be described using a polynomial function and this was then used to calculate the risk of placing a water body in the wrong ecological status class. This risk varied depending on the distance from the class boundaries and the number of replicates. Based on these data, we recommend that ecological status is determined from a number of samples collected from a site over a period of time.

Quality assurance of diatom counts in Europe: towards harmonized datasets

“…However, this is only possible if datasets can be merged easily. Even though diatom indices have been proven to be quite robust for the assessment of ecological status (Kelly et al, 2009 ;Kahlert et al, 2012 ;Almeida et al, 2014 ), diatom taxa lists can often not be compared directly. The reason for this is the lack of harmonization of diatom identification and counting techniques among regions or countries, which leads to inconsistent diatom datasets if not a form of taxa harmonization is used before analysis (Vyverman et al, 2007 ;Stevenson et al, 2010 ;Kelly et al, 2014 ).…”

Overview and application of the National Aquatic Ecological Monitoring Program (NAEMP) in Korea

“…Various biological metrics, including individual and aggregated indices of algae, macrophytes, macroinvertebrates, and fish, have been proposed for various spatial extents, mostly in North America and Europe (Osborne and Sua´rez-Seoane, 2002;Hering et al, 2006;Pont et al, 2006;Johnson et al, 2007;Ode et al, 2008;Stoddard et al, 2008). Although uncertainties remain in applying these metrics in ecological regions and spatial scales that differ from those for which the metrics were developed and verified (Kelly et al, 2009;No˜ges et al, 2009), assessments of ecological status using biological indices and habitat condition have become drivers of water management and restoration practices.…”

Distribution of benthic diatoms in Korean rivers and streams in relation to environmental variables

“…The sensitivity of diatom physiology to habitat conditions manifests as a great ecological variability in biomass and species composition (Stevenson et al, 1996). This variability, which can lead to uncertainties in ecological status assessment (Kelly et al, 2009), is due to complex interactions among ecological variables that can affect diatom physiology and community composition (Stevenson, 1997). Despite these uncertainties, studies of diatom distribution provide an effective tool for assessing the ecological integrity of various lotic ecosystems (Kelly and Whitton, 1995;Whitton and Rott, 1996;Kelly, 2002).…”