Date of Award

Spring 4-18-2024

Document Type

Honors Thesis



First Advisor

Jeff Wesner

Second Advisor

Vojsava Gjoni

Third Advisor

Andrea Liebl


Metabolic scaling, macroinvertebrates, fish, temperature, predation

Subject Categories

Biology | Population Biology


The common assumption in regard to metabolic rate scaling with body size is the 3/4 law, which predicts a scaling exponent of 0.75 between log metabolic rate and log body size. Supporting evidence exists for this theory on a large, general scale. However, factors such as temperature, predation, and environment can cause the scaling exponent to deviate from 0.75. This paper takes a closer look at the effects of temperature and predation on metabolic rates via oxygen consumption in freshwater macroinvertebrate populations. To do this, 24 tanks were filled with water to allow natural populations of macroinvertebrates (predominantly Chironomidae) to colonize. The tanks were randomly heated, heated with a fish living in the tank, unheated with a fish, or neither. Benthic macroinvertebrates were sampled and sorted into individual vials. The decrease in dissolved oxygen content was then measured over 30 minutes. The results suggest a metabolic scaling more in the ranges of 0.4 and 0.5 across treatments, substantially lower than the 0.75 predicted by theory. An interaction between temperature and predation was also observed. Increased temperatures caused the scaling exponent to increase in the absence of fish but decrease in the presence of fish. These findings indicate not only a strong deviation from 0.75, but also provide insight on how environmental changes will shape ecosystem dynamics in the future.



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