A novel quantification method for stream-inhabiting, non-diatom benthic algae, and its application in bioassessment

Abstract

Non-diatom benthic algae from 104 streams in southern California were studied. We present a novel method for quantification of non-diatom algae that seeks to improve upon two important aspects of existing methods: separate processing of macroalgae and microalgae to avoid sample blending and consequent loss of macroalgal integrity, and for better viewing, counting a well-mixed microalgal subsample on a standard microscope slide instead of using a counting chamber. Our method provided high-quality taxonomic and quantitative data with low uncertainty. A total of 260 algal taxa were recorded, 180 of which were identified to species level. The median total algal biovolume per site was 22.7 mm 3 cm -2 (range: \0.001-836.9 mm 3 cm -2 ), the median species number was 11 (range: 2-43). Total algal biovolume and species number correlated with canopy cover (negative) and water temperature (positive), but not with measured water chemistry constituents. The proportion of heterocystous cyanobacteria and Zygnemataceae were strongly negatively correlated with nitrate concentrations and TN. The proportion of red algae was negatively correlated with TP. Species optima calculations combined with indicator species analysis identified [40 algal species as potential indicators of nutrient conditions. Proposed here is a practical tool for non-diatom algal quantification that enhances its application to stream bioassessment.

Benthic soft-bodied algae as bioindicators of stream water quality

“…Several soft-bodied algal metrics passed the screening process for IBI development, including two indicator guilds with contrasting responses to local stressors, each based on a subset of taxa with similar function in the ecosystem. The guild metric with negative response to increasing levels of generalized stressor combined a proportion of Zygnemataceae, heterocystous cyanobacteria and red algae, in agreement with previous observations that each group is sensitive to particular nutrient or other water chemistry constituents (Stancheva et al, 2012a). The opposite metric consists of proportions of Cladophora glomerata L., Rhizoclonium hieroglyphicum (C. Agardh) Kütz., Ulva flexuosa Wulfen, and Stigeoclonium spp., which have been evaluated as the strongest indicators of high levels of TN, TP, DOC, Cu and non-reference conditions (Tables 1 and 2, Figure 1), except for Stigeoclonium which did not fulfill statistical criteria because of its rare distribution in the study area.…”

“…According to Biggs (1987) and Biggs and Kilroy (2000), thorough sample blending minimizes subsampling error without damaging thalli. In contrast, we argue that this sample processing may lower the resolution of taxonomic analysis, especially in regards to macroalgal component characterized by high diversity of vegetative and reproductive morphology, which need to be observed during the identification process (review by Stancheva et al, 2012a). Simultaneous analysis of diatoms and soft-bodied algae provides valuable quantitative information for biovolume proportions among taxonomic groups, which is important in determination of potential shift in dominant algal groups.…”

“…A novel quantification method for stream soft-bodied algae collected by multihabitat quantitative sampling for the SWAMP program in California was developed in an attempt to increase taxonomic resolution of the data and to produce precise biovolume information (Stancheva et al, 2012a. Sample blending is avoided by gentle removal of macroalgae, which preserves their integrity.…”

“…Potapova and Carlisle (2011) attributed the poor performance of soft-bodied algal metrics to the taxonomic method which precludes from species level identification and recommended development of new methods that better characterize the softbodied algal communities. Fetscher et al (2014) constructed the first IBIs based on soft-bodied algae alone derived from more than 451 stream samples collected predominantly in southern California (SWAMP, modified field method by Fetscher et al, 2009, and novel taxonomic method by Stancheva et al, 2012a). Soft-bodied algal metrics were taxonomic -algal phyla, indicator species and indicator guilds, and were expressed in two ways: proportion of total biovolume (relative biovolume), and proportion of total species number (relative species richness).…”

“…In addition, algal-nutrient interactions are discussed in the light of their bioindicator potential. Examples are included from our research experience incorporating soft-bodied algae in stream bioassessment in California as part of the Surface Water Ambient Monitoring Program of the California State Water Resources Control Board (SWAMP, http://www.waterboards.ca.gov/water_ issues/programs/swamp/) (Stancheva et al, 2012a(Stancheva et al, ,b, 2013a(Stancheva et al, ,b, 2014Fetscher et al, 2013Fetscher et al, -2015Wehr et al, 2013).…”