Answer and Explanation:
Macroinvertebrate communities show spatial and temporal variability. Many taxons have more affinity for one specific type of habitat.
There are two principal sampling techniques. Qualitative and cuantitave. Qualitative techniques provide data about the river richness and the relationship between the different taxonomic group's abundance. They allow the obtention of the most representative and abundant taxons, estimates their densities, biomass, and calculates the diversity indexes for each sampling site by period. Nets are needed to sample.
Every possible microhabitat must be sampled. The use of the different sampling elements depends on the substrate.
- Hard-substrated sites, such as rocks or wood and organic matter, are sampled using a Surber net.
- The net is placed counter-current.
- The substrate must be moved and removed up to 10-15 cm deep, checking that animals and the thin sediment lie on the net.
- Samplings must be done from downstream to the upstream direction, taking replicates per substrate.
- Invertebrates must be washed on a strainer.
- Finally, place each of the samples in a plastic bottle, fixate the material with formaldehyde 4% and take it to the lab for its taxonomic identification.
