EXPERIENTIAL LEARNING APPLICATIONS FOR AN AQUAPONICS SYSTEM: INTER-DISCIPLINARY GEOLOGY-BIOLOGY RESEARCH AND TEACHING

Aquaponics is the symbiotic cultivation of plants and fish in a closed-loop, re-circulating system. Water is pumped from a fish tank into an elevated gravel bed where Nitrosomonas and Nitrobacterbacteria break down the toxic ammonia to nitrite and then to nitrate, a key nutrient for plant development. A variety of crops can be grown in the gravel bed utilizing the available nitrogen and further cleaning the water. ‘Clean’ water is then drained under gravity from the gravel bed back into the fish tank below and the cycle continues. In order to facilitate inter-disciplinary research and experiential learning at St. Lawrence University, we have constructed a 250 gal aquaponics (AP) system that is currently utilized by both geology and biology faculty as an instructional tool. Microbially-produced sedimentary structures (e.g., stromatolites) are readily preserved and well studied in carbonate marine environments. However, equivalent structures in siliciclastic sedimentary environments are less studied but just as important as both physical processes and biological activity are required to produce many sedimentary surface structures. Geology students can utilize an AP system to investigate topics such as sedimentary structures formed from bacterial mats, bacterial breakdown of rocks, and biomineralization during fossil formation. We currently have sandstone and sand samples as well as glass substrates colonized by a variety of bacteria and have been monitoring progress using time-lapse photography and SEM work. In natural systems, elements such as nitrogen occur in many different forms (e.g., nitrate, nitrite) that are largely controlled by denitrifying bacteria. This microbial biogeochemical cycling strongly influences the chemistry of natural ecosystems. Within biology courses, an AP system can be used to demonstrate microbial transformation of ammonia, and nitrite, variations in microbial populations through time, microbial remediation of water, and other microbial populations. We suggest that small-scale AP systems can be constructed and maintained by students during the course of an academic year at minimal institutional cost, have a very high potential for research and teaching in courses across multiple departments, and provide a unique experiential learning opportunity to students.