Benthic algae as bioindicators of agricultural pollution in the streams and rivers of southern Québec (Canada)

Abstract

The objective of this study was to evaluate the effect of agricultural pollution on periphyton in streams and rivers of southern Québec. We sampled benthic algae incubated from mid-July to mid-August on artificial substrates at 29 sites and analysed the variations in community structure and total community biomass. Diatom community structure as well as total benthic algae community were analysed. Water samples were taken to provide background chemical information, and land use data were also obtained. Preliminary tests showed that colonisation of the artificial substrates (unglazed ceramic tiles) resulted in biomass levels (Chlorophyll a and ash-free dry weight) and species composition that were not statistically different from those on natural rock substrates. The canonical correspondence analyses showed that pH, conductivity and suspended solids were the most significant environmental variables accounting for variations among sites and diatom community structure. No additional resolving power was obtained by including cyanobacteria, green algae and flagellates. This total community analysis substantially increased variance and sample processing time while reducing the relationship with environmental variables. These results indicate that an analysis based exclusively on diatoms provided the optimal approach. Traditional nutrient measurements (phosphorus and nitrogen) did not explain a significant part of the variance in the species composition among sites. The ordination analyses clearly separated agriculturally-impacted streams from reference sites, but no significant grouping was observed related to the intensity and type of agriculture, indicating the greater importance of local farming practices. The use of periphyton as a bioindicator provides an integrated measurement of water quality as experienced by the aquatic biota, and therefore offers a useful addition to physico-chemical water quality monitoring strategies.

The influence of land use on water quality and diatom community structures in urban and agriculturally stressed rivers

“…Taylor et al (2007b) also noted that A. minutissima is generally found in clean, freshwaters that are well oxygenated. The findings of this study are in agreement with the findings of Lavoie et al (2004), who found A. minutissima to be prevalent at reference/natural sites. In a study on organic and agricultural pollution, this species was found only in the uppermost river sites where conditions were oligotrophic .…”

Benthic soft-bodied algae as bioindicators of stream water quality

“…Some of these studies (e.g., Lavoie et al, 2004;Kelly et al, 2008;Potapova and Carlisle, 2011) contribute to the impression that soft-bodied algae did not improve stressor responsiveness of diatoms alone, but they were based on taxonomy methods that allowed mainly genus-level or coarser identifications of soft-bodied algae which may account for the conclusions. In contrast, studies designed to explore the full potential of soft-bodied algae demonstrated that they enhance bioassessment power along the following lines of consideration: (1) multimetric indices based on entire algal communities, created in southern Californian streams, showed better responsiveness to anthropogenic stress over indices based either on diatoms or soft-bodied algae assemblages alone (Fetscher et al, 2014); (2) the best performing softbodied algal index exhibited greater discriminatory power than its diatom counterpart near the higher end of the range of anthropogenic disturbance (Fetscher et al, 2014); (3) differences in diatom and soft-bodied algal biotic indices were detected in ecosystems which are subject to changing environmental conditions; these differences could provide indications related to ecosystem stability (Schneider et al, 2012); (4) diatom and soft-bodied algal communities respond to nutrient supply and pH differently, with diatom taxon richness generally increasing with nutrient availability in contrast to decreasing soft-bodied algae richness (Schneider et al, 2013); (5) diatoms in conjunction with soft-bodied algae provide a more robust assessment of nutrient conditions, inferring nitrogen (N) limitation in 20% more sites than monitoring with either algal group alone (Stancheva et al, 2013b).…”

“…However, surprisingly little has been published addressing the performance of diatoms compared to soft-bodied algae as bioindicators (Lavoie et al, 2004;Kelly, 2006, Kelly et al, 2008, Schneider et al, 2012Stancheva et al, 2013b) or on the relative strength of indices derived from a single assemblage vs. combined assemblages (Potapova and Carlisle, 2011;Fetscher et al, 2014). Some of these studies (e.g., Lavoie et al, 2004;Kelly et al, 2008;Potapova and Carlisle, 2011) contribute to the impression that soft-bodied algae did not improve stressor responsiveness of diatoms alone, but they were based on taxonomy methods that allowed mainly genus-level or coarser identifications of soft-bodied algae which may account for the conclusions.…”

Terrestrial diatoms as tracers in catchment hydrology: a review

“…Terrestrial diatom species distribution and abundance are largely controlled by soil pH and land use. 12,[30][31][32][33] Collection of terrestrial diatoms living on plants or rocks (phytobenthic diatoms) can be removed with a toothbrush and mixed with water in a glass bottle. …”