Do methodological differences in experiments with stream shredders imply variability in outputs? A microcosm approach

Abstract Experiments are useful scientific tools for testing hypotheses by manipulating variables of interest while controlling for other factors that can bias or confuse the results and their interpretation. However, to ensure accuracy and reproducibility, experiments must have transparent and repeatable methodologies. We experimentally tested the effect of different methodological approaches in microcosm experiments on the consumption and survival of shredders. We found that the shredder species, the presence or absence of the case in the shredders, and the use or non-use of air-pumps in the microcosms did not affect the shredder performance (i.e., consumption and survival). Furthermore, the type of water (stream or bottled) did not affect shredder performance. On the other hand, the amount of light had a negative effect on shredder performance, with constant light (i.e., 24 hours) reducing shredder consumption and survival. Our results highlight the importance of transparent and repeatable methodologies in experiments. Different methodological approaches in microcosm experiments can influence the results and their interpretation. This finding is especially worrying when we measure gains and losses in ecosystem functions by recreating natural conditions in the laboratory, where factors that are not of interest may affect or interact with the results. In addition, our findings offer valuable insights that can help researchers design experiments with shredders from neotropical streams.