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Dipnet (DN) sampling is routinely employed for macroinvertebrate bioassessments in wetlands, but it has been demonstrated that some taxa are more effectively collected with activity traps (AT). The Minnesota Pollution Control Agency (MPCA) used both DN and AT methods to evaluate the biological condition of depressional wetlands in the Mixed Wood Plains (MWP) and Temperate Prairies (TP) ecoregions. Two indices of biotic integrity (IBIs) were developed for each ecoregion using: 1) DN data alone and 2) composite samples consisting of both DN and AT data. ATs collected more active taxa such as diving beetles and swimming Hemiptera. DNs collected more taxa and collected more skating taxa and those associated with sediment or vegetation. A comparison of the effectiveness of the IBIs to evaluate biological condition indicated that the composite data had a slightly better relationship with anthropogenic disturbance and was marginally more precise. A comparison of sampling and processing costs revealed that sampling using composite samples was 130 % greater and processing was 50 % greater compared to DN-only samples. Based on the cost and limited benefit of adding AT samples, a DN-only sampling protocol is recommended to assess biological condition in depressional wetlands. [ABSTRACT FROM AUTHOR]

Macroinvertebrates are increasingly used as indicators of wetland integrity and productivity. However, accurate interpretation of biological information depends on effective sampling methods, which are also preferably cost-effective. We compared sampling yield, precision, and cost-effectiveness of two traditional wetland sampling methods (dipnet, stove pipe corer) to a dipnet combined with a dropframe in wetlands in the Platte River Valley, USA. The dropframe method was designed to be more quantitative than standard dipnet techniques and to maximize capture of mobile taxa. We compared measures of macroinvertebrate community structure (e.g., abundance, richness, diversity) and function (functional structure, habitat associations), as well as processing time for each sampling technique in vegetated and non-vegetated habitats. Vegetated habitats harbored higher richness, diversity, abundance, and biomass of most invertebrates. The dipnet consistently yielded the lowest values in vegetated and non-vegetated habitats, suggesting that sampling with a dipnet alone can greatly underestimate macroinvertebrate populations and diversity. The corer and the dropframe yielded similar results, but the dropframe produced significantly higher richness values. While the dropframe appeared to be a good choice for sampling in these wetlands, sample processing times for this method were more than two times longer than the other methods. Results provide a basis for informed decisions regarding quantitative sampling of wetland macroinvertebrates. [ABSTRACT FROM AUTHOR]

Aquatic invertebrates are excellent indicators of ecosystem quality; however, choosing a sampling method can be difficult. Each method and associated protocol has advantages and disadvantages, and finding the approach that minimizes biases yet fulfills management objectives is crucial. To test the effects of both sampling methods and sample handling—i.e., to composite samples or leave them as replicates—we collected aquatic invertebrates from the Niobrara River at Agate Fossil Beds National Monument, Nebraska, using three methods and two sample handling protocols. We compared aquatic invertebrate assemblages collected with a Hester-Dendy multi-plate sampler, Hess sampler, and a D-frame dipnet. We calculated six common bioassessment metrics from composite (combined) and replicate (separate) samples. Hess samples contained the highest taxonomic richness (capturing 77% of all taxa observed) and dipnet samples the least (47%). Hester-Dendy samples had the greatest proportion of Ephemeroptera, and Ephemeroptera, Plecoptera, and Trichoptera (EPT). Dipnet samples had the lowest evenness values. In terms of sample handling, composite samples had inflated richness, diversity, and evenness compared with replicate samples, but bioassessment metrics calculated from proportions or averages (i.e., Hilsenhoff's Biotic Index and the proportion of EPT taxa) did not differ between them. The proportion of invertebrate groups from composite samples were not statistically different among sampling methods, but several groups differed between replicate samples collected by different methods. Ultimately, we recommend collecting replicate samples with a Hess sampler when the goal of the study is to detect ecosystem change, among locations or differences in variables of interest. [ABSTRACT FROM AUTHOR]