Award: OCE-1261359

PROJECT OUTCOMES REPORT Project Title: Growth rates of bacterial taxa in coastal marine ecosystems Project Team: Dr. Barbara Campbell, PI, Clemson University Dr. David Kirchman, coPI, University of Delaware Bacteria are microscopic organisms that are very abundant and diverse in most ecosystems. They are major contributors to biogeochemical cycles, such as the carbon, nitrogen and sulfur cycles. Unlike macroorganisms however, scientists are unable to accurately assess how fast they are growing in situ and contributing to these biogeochemical cycles or how their growth rates and activity change with environmental fluctuations. Therefore, new ways need to be developed to understand the impact of microbes on earth?s multitude of habitats. Estuaries are one of the most productive aquatic ecosystems, where nutrient-laden freshwater meets coastal marine water. In this mixing zone, there generally are enough nutrients and light for microscopic primary producers to fix carbon dioxide into biomass. Primary producers provide needed carbon for upper tropic levels and to the rest of the microorganisms in the ecosystem. Carbon is often also supplied from terrestrial detritus from river or salt marsh habitats. Here, we investigated how the change of carbon source and other environmental factors, such as temperature, salinity or nutrients, affected the activity of bacteria in two east coast estuaries, the Delaware and Chesapeake Bays. We used a combination of culture-based and next generation sequencing approaches to investigate both the composition and activity of microbes in these two estuaries. Examination of bacterial transcription of various growth-related to non growth-related genes correlated measurable differences in transcriptional activity to growth rate. In samples taken directly from both environments, we found that season affects bacterial activity and composition, with their specific microhabitat and salinity also contributing to their activity and function within the ecosystem. However, given the physical closeness of both estuaries, we found differences in bacterial composition and function that was more than expected. The knowledge gained by this NSF-sponsored research will aid scientists in their understanding of microbial activity and function in a variety of ecosystems. This research has been presented to the scientific community by the PIs or their students through various avenues, including scientific publications, seminars and presentations at local, regional, national and international venues. The PIs trained several undergraduate and graduate students in basic microbiological and next generation/high throughput sequencing and bioinformatics approaches. These students are entering the workforce as skilled STEM personnel, who will or have entered careers in either environmental, academic or biomedical fields. In addition, the PIs and their students have interacted with the general public through community outreach efforts in elementary and public open house annual programs. Last Modified: 12/20/2017 Submitted by: Barbara J Campbell