Assessment of benthic algal biomonitoring protocols to evaluate effects of shoreline development on the nearshore zone of Precambrian Shield lakes in Ontario

Author： Thomas Kathryn E.

Publisher： Taylor & Francis Ltd

ISSN： 1040-2381

Source： Lake and Reservoir Management, Vol.27, Iss.4, 2011-12, pp. : 398-413

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Abstract

We assessed the ability of benthic algal biomonitoring protocols to detect effects of differences in shoreline development in the littoral zone of oligo- to mesotrophic Precambrian Shield lakes in south-central Ontario. The study sites (n = 28 in Aug 2006, n = 29 in Aug 2007) spanned a broad gradient of shoreline development (e.g., intact forest, cottages, marinas) but a modest gradient of nutrient concentration (3–22 μg/L total phosphorus). Each site was sampled for water chemistry (nutrients, ions, metals, pH) and 5 levels of benthic algal bioassessment, which differed in the amount of time, resources and expertise required. Level 1 involved visual descriptions of algal cover; Level 2 involved biomass measurements (chlorophyll a, ash-free dry mass); Level 3 involved enumeration of algae to a coarse taxonomic level (i.e., the major algal classes); Level 4 involved quantification of photosynthetic pigments by high-performance liquid chromatography; and Level 5 involved high taxonomic resolution enumeration of diatom communities. Multi- and univariate numerical analyses (e.g., PCA, ANOSIM, ANOVA) were used to assess relationships between measurements of shoreline development, water chemistry, and benthic algal metrics. Results identified that Level 5 was the most sensitive to track differences in the shoreline development among sites. For lakes on the Precambrian Shield, we suggest that benthic algal biomonitoring programs focus on Level 5, despite the higher requirements of time, technical skill, and training. We further recommend that the other levels of bioassessment be explored further in other regions where broader gradients of shoreline development and lake trophic status exist. [Supplemental materials are available for this article. Go to the publisher's online edition of Lake and Reservoir Management to view the supplemental file.]