Estimating vertebrate, benthic macroinvertebrate, and diatom taxa richness in raftable Pacific Northwest rivers for bioassessment purposes

Abstract

The number of sites sampled must be considered when determining the effort necessary for adequately assessing taxa richness in an ecosystem for bioassessment purposes; however, there have been few studies concerning the number of sites necessary for bioassessment of large rivers. We evaluated the effect of sample size (i.e., number of sites) necessary to collect vertebrate (fish and aquatic amphibians), macroinvertebrate, and diatom taxa from seven large rivers in Oregon and Washington, USA during the summers of 2006-2008. We used Monte Carlo simulation to determine the number of sites needed to collect 90-95% of the taxa 75-95% of the time from 20 randomly located sites on each river. The river wetted widths varied from 27.8 to 126.0 m, mean substrate size varied from 1 to 10 cm, and mainstem distances sampled varied from 87 to 254 km. We sampled vertebrates at each site (i.e., 50 times the mean wetted channel width) by nearshore-raft electrofishing. We sampled benthic macroinvertebrates nearshore through the use of a 500-μm mesh kick net at 11 systematic stations. From each site composite sample, we identified a target of 500 macroinvertebrate individuals to the lowest possible taxon, usually genus. We sampled benthic diatoms nearshore at the same 11 stations from a 12-cm(2) area. At each station, we sucked diatoms from soft substrate into a 60-ml syringe or brushed them off a rock and rinsed them with river water into the same jar. We counted a minimum of 600 valves at 1,000× magnification for each site. We collected 120-211 diatom taxa, 98-128 macroinvertebrate taxa, and 14-33 vertebrate species per river. To collect 90-95% of the taxa 75-95% of the time that were collected at 20 sites, it was necessary to sample 11-16 randomly distributed sites for vertebrates, 13-17 sites for macroinvertebrates, and 16-18 sites for diatoms. We conclude that 12-16 randomly distributed sites are needed for cost-efficient sampling of vertebrate richness in the main stems of our study rivers, but 20 sites markedly underestimates the species richness of benthic macroinvertebrates and diatoms in those rivers.

Benthic diatom and macroinvertebrate assemblages, a key for evaluation of river health and pollution in the Shahrood River, Iran

“…One approach for assessing river pollution is to use bio-indicators such as benthic diatom and macroinvertebrate communities (Hirst et al 2002;Hering et al 2006;Hughes et al 2012;Namin et al 2013a, b;O'Driscoll et al 2014;Tan et al 2014a). The use of biotic communities for monitoring aquatic environments, especially water quality, has several widely known advantages over physicochemical monitoring (Hering et al 2006;Sharifinia et al 2012a;Findik 2013;Tan et al 2014b).…”

Assessment of the ecological health of heavily utilized, large lowland rivers: example of the lower Yellow River, China

“…Reference species richness was based on detailed surveys and the wide experience of experts, so it represents a level that is not likely to be observed in conventional river health surveys. The importance of sampling effort in large rivers has been investigated and reviewed in many studies (e.g., Bady et al 2005;Flotemersch et al 2006;Hughes et al 2011). Sampling effort is a significant issue, particularly for fish, because practicalities mean that only a small proportion of the total river area is sampled and only a limited time is available for sampling.…”

“…For each indicator group, the score was weighted by data quality in terms of relative sampling effort (Table 5). Many studies have shown that abundance and diversity continue to increase up to a given sampled area (e.g., Colwell and Coddington 1994;Connor et al 2000;Gotelli and Colwell 2001;van Gemerden et al 2005;Hughes et al 2011). In a comprehensive river health survey, a first step would be to establish the relationship between the value of the chosen index score and the level of sampling effort in order to determine the level of sampling effort at which the index value stabilizes.…”

Effects of fixed-count size on macroinvertebrate richness, site separation, and bioassessment of Chinese monsoonal streams

“…Such studies have been conducted for estimating effects on taxa richness (e.g., Cao et al, 2002a;Hughes et al, 2012;Ligeiro et al, 2013) and site and group separation (e.g., Cao et al, 2002a;Ligeiro et al, 2013). In addition, they have been used for evaluating the variability of multimetric indices (MMIs) (e.g., Doberstein et al, 2000;Dolph et al, 2010;Li et al, 2001) and the performance of observed-to-expected (O/E) indices (i.e., RIV-PACS: River Invertebrate Prediction and Classification System) (e.g., Ostermiller and Hawkins, 2004).…”