Does the type of streambed matter?
Hard bottom (stony or gravelly) streambeds can be expected to support quite different communities to soft bottom (sandy, muddy or weedy) streams that are more common in slower flowing reaches. Below are some generalisations about invertebrate communities of hard and soft bottom streams:
- hard bottom streams tend to support higher numbers of taxa,
- hard bottom streams tend to support more grazing leptophlebiid mayflies and Latia limpets,
- hard bottom streams also tend to support more stoneflies, caddisflies, dobsonflies, and non-swimming elmid and hydraenid beetles,
- soft bottom streams tend to be slower flowing and may be weedy, and these conditions support more shrimps, amphipods, ostracods, damselflies, Ferrissia limpets, and Gyraulus snails,
- soft bottom habitats suit the burrowing oligochaete worms, mussels, and Chironomus midges.