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Processing Methods

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Samples collected can either provide qualitative or semi-quantitative data. For the LIRB, qualitative multihabitat (QMH) sampling along with semi-quantitative targeted-habitat sampling of one habitat type were conducted. This habitat type was one that supports the faunistically richest community of benthic invertebrates, known as richest-targeted habitat (RTH).

Qualititative Multihabitat Sampling (QMH)
The objective of QMH sampling is to obtain as complete a list of invertebrate taxa present in a sampling reach as is possible in the time available. The primary sampling gear used to collect QMH samples in wadeable streams is a D-frame kick net with a 210-um mesh net. This net is used to collect samples by kicking, dipping, or sweeping. QMH sampling includes as many habitat types as possible, including those sampled by semi-quantitative methods. Equal sampling effort is applied to each habitat type within the time available.

Visual collections along with D-frame net collections are also conducted to collect highly-motile invertebrates. This may mean manually collecting large rocks, twigs, clay, or coarse organic debris and removing any organisms.

For nonwadeable streams, QMH sampling methods depend on the depth of the water, current velocity, and bed material. For the LIRB, the D-frame kick net was often used while the Petite Ponar, a grab sampler, was also used to collect invertebrates.

Semi-Quantitative Targeted-Habitat Sampling
The objective of semi-quantitative targeted sampling is to obtain representative samples of benthic invertebrate communities. Semi-qualititative sampling methods characterize the structure of invertebrate communities in terms of the relative abundance of each taxon rather than the absolute density. Information gathered is used to interpret how the community is functioning, compare sites, and to relate community structure to characteristics affecting water quality.

In LIRB studies, the RTH was sampled using a slack sampler with a dolphin bucket. The mesh size used was 425-um. The sampler is held perpendicular to the direction of flow and pressed tightly against the stream bottom. Benthic invertebrates are collected from an area approximately 0.25 m² immediately upstream of the sampler.