Student Research Projects

An Investigation of Factors Influencing Nutrient Excretion in Betta splendens

Student Lisa Murray '14
Faculty Mentor(s)
Department Biology
Course BIO 489: Research in the Natural Sciences


Previous research on nutrient cycling by fish has examined factors such as mass, temperature, and diet, which have important effects on nutrient excretion. However, no previous study has examined the effect of sex on nutrient excretion, even though sex can have large impacts on fish size and reproductive investment. This study was undertaken to determine whether the sex of a fish impacts the excretion of nitrogen and phosphorus in Betta splendens. This study also considered the effects of feeding (fed vs. unfed) and mass on excretion rates. It was hypothesized that because of their larger size, males would excrete more nutrients than females.

We conducted direct nutrient excretion measures by examining changes in N and P concentrations over a 4 hour period. We did not measure any detectable change in phosphorus concentrations during the excretion experiments, even in the fed fish treatment. Ammonia nitrogen excretion was significantly higher in the fed fish treatment, and the unfed treatment showed no detectable change in ammonia nitrogen over time. There was no significant effect of mass or fish sex on ammonia excretion in B. splendens. The relative inactivity of this species may impact the patterns of excretion that we observed.