The invertebrate fauna of a forest stream and its association with fine particulate matter

The invertebrate fauna colonising wooden blocks placed in a beech forest stream was studied over a period of 1 year. At least 31 species were taken during the course of the study, with 3 species of Chironomidae predominating numerically. Most species were associated principally with fine particulate matter (FPM) deposited on the upper surfaces of blocks, although a stonefly, Spaniocerca zelandica, was most abundant on the barer surfaces. Of the Chironomidae, Paucispinig‐era approximata and Polypedilum canum had clearly defined life history patterns with emergence from February to April and October to January, respectively. Psectrocladius sp. had a poorly defined life history. Gut contents of 16 insect species showed that 4 were predominantly predatory, and the remainder were detritivores. The latter could be categorised as shredders (large particle detritivores) or collector‐browsers which mainly ingested particles in the dominant (<50 μm) size range. Oxygen consumption by fine stream sediments was similar at different times of year which suggests that the food quality of detritus may tie relatively constant at all times.