INVESTIGATIONS AND MANIPULATIONS OF TROPHIC LEVELS
IN A POND ENVIRONMENT

Dan Currie, Mario DeFranco, Laura Fong, Rashi Grewal, Andrew Herman, Jane Hur, Rachel Kolesnikov-Lindsey, Linda Karas, Lea Pope, Max Wiedmann

Advisor: Michael Roche
Assistant: Matt Singer

ABSTRACT

Over the course of a four week investigation in Drew University’s Long Pond in the Zuck Arboretum, the dynamics of trophic levels were explored through controlled manipulation. Leading concerns dealt with aspects of the “top-down” and “bottom-up” predation theories, testing the validity of each. Exclusion chambers (plastic bags) grouped around a floatation device (PVC framework) provided control of variables, and a simplified experimental setting in a natural habitat. Inquiries dealing with the effect of increased nitrates and phosphates on trophic levels helped investigate the “bottom-up” forces through chemical testing, while manipulation of bullhead catfish as consumer organisms provided a study of the alternative “top-down” forces. Several population counts failed to garner conclusive evidence towards the initial design yet opened doors into alternative investigations. One experiment demonstrated the ability of the pond and nutrient-enriched chambers to sustain Daphnia populations. A study designed to test the food preferences of small versus larger catfish revealed an unexplained absence of plankton. Another experiment tested the effectiveness of rye versus white bread for baiting catfish. This final study showed a significant difference in ability of the rye bread to attract bullhead catfish (p = 0.097, d = 0.1).

Team 9