Joshua Kale

2016-07-20-23.13.31Project Title: Ecology at the Microbial Scale: The importance of Microscale Interactions between Heterotrophic Bacteria and Phytoplankton in Marine Environments

Mentors: Olivia Ahern and Tatiana Rynearson

Abstract: Climate change is one of the most pressing issues facing the world today and has the capacity to drastically alter marine food webs and biogeochemical cycles through ocean stratification and changing nutrient regimes. Despite their diminutive size, phytoplankton are the basis of all marine food webs and are responsible for about 20% of the worlds primary production. Bacteria are also key players in global biogeochemical cycling by remineralizing and recycling inorganic nutrients from detritus to organic nutrients that can be readily used by phytoplankton. Insights into the interactions between the two can help us understand how these organisms can adapt and survive in light of climate change. Using a fluorometer and Fluorescence Induction and Relation machine (FIRe), I tested the relationship between two strains of the cosmopolitan diatom Thalassiosira rotula and the two associated heterotrophic Proteobacteria Roseovarius and Marinobacter under nutrient replete and phosphorus limited conditions. I found that T. rotula had a higher growth rate with the bacteria Roseovarius but not from Marinobacter. This suggests that different bacteria may influence the physiological state of diatoms.