Do macrophytes, diatoms and non-diatom benthic algae give redundant information? Results from a case study in Poland

Abstract

a b s t r a c tWe analyzed species composition and abundance of macrophytes, diatoms and non-diatom benthic algae, water chemistry and habitat structure of 24 river sites in Poland, in order to better understand which parameters structure macrophyte and benthic algae communities. Community patterns for macrophytes and diatoms are most closely related, while macrophytes and non-diatom benthic algae have the weakest relationship. Environmental parameters best explaining community patterns are channel substrate parameters for non-diatom benthic algae, and a combination of channel substrate and river bank characteristics for submerged macrophytes, emergent macrophytes and diatoms. Among the organism groups investigated, the diatom community pattern is best correlated to the environmental data similarity matrix. We hypothesize that the results can be explained by the shorter generation time of diatoms compared to macrophytes, and by a higher dispersal rate of diatoms compared to macrophytes and non-diatom benthic algae. This has several practical consequences for bioindication: (1) Diatoms are usually the organism group most closely following environmental parameters, for both increasing and decreasing impact. (2) Since the biotic indices developed for the Water Framework Directive are meant to primarily indicate ecological changes, not water chemistry, the nature of diatoms to closely reflect water chemistry is not necessarily advantageous. (3) The applicability of macrophyte and probably also non-diatom benthic algae indices is more locally restricted, while diatom indices are applicable to greater areas. (4) In ecosystems which are subject to changing environmental conditions, differences in biotic indices between macrophytes, diatoms and non-diatom benthic algae are to be expected. These differences could provide information relating to ecosystem stability. (5) In stable ecosystems, analyzing one of the three organism groups "diatoms", "non-diatom benthic algae" and "macrophytes" will be sufficient to characterize the quality element "macrophytes and phytobenthos", as required by the Water Framework Directive. However, in ecosystems subject to increasing pressure, macrophytes likely will have a tendency to indicate "too good", while in ecosystems subject to decreasing pressure, diatoms will have a tendency to indicate "too good".

Interactions between pH and nutrients on benthic algae in streams and consequences for ecological status assessment and species richness patterns

“…The search for an explanation of observed patterns in diversity-productivity relationships in meta-analysis (Whittaker, 2010;Cardinale et al, 2011) might therefore be complicated by the fact that some studies deal exclusively with diatoms, whilst others pool diatoms and non-diatom benthic algae richness. Our results are consistent with the results of Schneider et al (2012), who described differences in stream diatom and non-diatom benthic algae community patterns, and suggest that benthic primary producers in streams are not the homogenous group they often are treated as. Moreover, whilst diatom and non-diatom indices both are suitable for status assessment, their assemblage patterns follow different ecological principles.…”

“…Though most use diatoms as proxies for the complete phytobenthos assemblage, the validity of this approach has been questioned (Schneider et al, 2012). Indices based on speciescomposition of non-diatom benthic algae have been developed for trophic status (periphyton index of trophic status PIT, Schneider & Lindstrøm, 2011) and acid conditions (acidification index periphyton AIP, Schneider & Lindstrøm, 2009) for rivers in Norway.…”

Assessment of ecological status in UK lakes using benthic diatoms

“…Indices derived from macrophytes might not be a direct indication of water-column nutrient concentrations because most macrophytes derive most of their nutrients from the sediments, whereas their epiphytes rely on nutrients in the littoral water column and are considered the primary scavengers of nutrients from the water column (Wetzel 2001). The shorter generation time for diatoms means they provide an indication of increasing or decreasing water quality over time scales of weeks, whereas macrophytes, with longer generation times and lower rates of dispersal, are slower to respond (Schneider et al 2012). Schneider et al (2012) suggested that differences in assessments between biotic indices based on diatoms and those based on macrophytes are expected in ecosystems subjected to environmental change, and they postulated that differences between indices inform us of ecosystem stability.…”

“…The shorter generation time for diatoms means they provide an indication of increasing or decreasing water quality over time scales of weeks, whereas macrophytes, with longer generation times and lower rates of dispersal, are slower to respond (Schneider et al 2012). Schneider et al (2012) suggested that differences in assessments between biotic indices based on diatoms and those based on macrophytes are expected in ecosystems subjected to environmental change, and they postulated that differences between indices inform us of ecosystem stability. In some lakes, we recorded either no difference (Wastwater, (Table 5).…”

Bryophytes and macro-algal growths as a part of macrophyte monitoring in rivers used for ecological assessment

“…According to the WFD, macrophytes and phytobenthos comprise one biological quality element. The applicability of different plant groups can be more or less restricted due to the spatial scale and their behaviour is influenced by the stability or changes of river environmental conditions (Schneider et al, 2012).…”