Light in the Tank: Effect of Light Exposure on pH in a Neotropical Bromeliad

Abstract

Tank bromeliads such as Aechmea nudicaulis tend to have an acidic body of water contained in the center of their tight leaf rosette. This tank of water grows larger with the bromeliad and collects fallen debris and precipitation. These epiphytic bromeliads have evolved to take up water from within their tanks and have no ability to absorb water through their roots which instead only anchor the plant to a host tree. The bromeliads have become dependent on aerobic and anaerobic bacteria living within the tank to break down debris and make nutrients available. Previous investigations of the bacterial communities of neotropical bromeliad tanks found an experimentally supported relationship between tank pH, which can range from 3.5-6.0, and specific bacterial community composition and diversity (Goffredi et al. 2011). To identify if sunlight is a factor determining pH, 32 A. nudicaulis were kept in a growth chamber under 4 different light conditions. After a 2 month long treatment we have determined that there is a significant difference in tank pH of bromeliads exposed to high and low-light conditions (lower pH in higher-light conditions) indicating that light plays a part in determining tank pH and therefore bacterial community composition.