Distribution of macroinvertebrates in relation to the quantity and quality of organic matter in streams in the western Czech Republic

Data on benthic macroinvertebrates from the western Czech Republic were used to test the hypothesis that benthic macroinvertebrates are either ‘low-cost’ or ‘high-cost’ life forms. A wide head and long legs were regarded as ‘high-cost’ features, whereas a simple tube-like body without appendages as ‘low-cost’. A second hypothesis was that the quantity and nutritional value of benthic and suspended organic matter ingested was correlated to the forms present. The suspended organic matter deposits on the bottom, so total organic carbon concentration (TOC) was used to represent food availability. Because the nutritional value depends on the quantity of algae, the chlorophyll-a concentration to TOC ratio (Chl-a : TOC) was used to represent food quality. The results confirmed both hypotheses, showing that the high-cost life forms prefer high food quality (Chl-a : TOC) and low food quantity (TOC), whereas the low-cost life forms prefer the opposite. The findings help to better understand the distribution patterns of rare and endangered species.