SS2.01 Effects of Biotic Interactions on the Structure and Function of Microbial Food Webs
Date: Wednesday, June 12, 2002
Time: 11:15:00 AM
Location: Saanich
 
NobleRT, UNC Chapel Hill Institute of Marine Sciences, Morehead City, USA, rtnoble@email.unc.edu
Paerl, H, W, UNC Chapel Hill Institute of Marine Sciences, Morehead City, USA, hans_paerl@unc.edu
Peierls, B, L, UNC Chapel Hill Institute of Marine Sciences, Morehead City, USA, bpeierls@email.unc.edu
Piehler, M, F, UNC Chapel Hill Institute of Marine Sciences, Morehead City, USA, mpiehler@email.unc.edu
 
FUNCTIONAL INTERACTIONS OF VIRAL, BACTERIAL, AND PHYTOPLANKTON ASSEMBLAGES IN RESPONSE TO VARYING NUTRIENT SCENARIOS IN ESTUARINE ENVIRONMENTS
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Estuaries are rich, productive systems that are the subject of constant and increasing anthropogenic pressure. Estuarine environments can be seasonally and/or chronically impacted by ‘loading’ with excess nitrogen and phosphorus, causing rapidly changing nutrient scenarios. Microbial assemblages, virioplankton, bacterioplankton and phytoplankton, are dynamic in these systems. The Neuse River Estuary-Pamlico Sound (NRE-PS) system is part of the 2nd largest estuary system in the United States and an important larval fish hatchery. Phytoplankton doubling times generally range seasonally in this system from 1 to 3 days, with varying responses to nutrient pulses by specific functional groups. Cryptomonads appear to respond rapidly to pulses of N, with doubling times on the order of 0.5 d, and slower doubling times are commonly associated with cyanobacteria, and diatoms. Bacterial and viral production rates indicate turnover times of the bacterial population on the order of ca. 1 day, with strong impacts on bacterial mortality by viral populations. Previous work indicates a N-dominated system with important regeneration processes conducted by the heterotrophic bacterial population. We are examining the consortial interactions among viruses, bacteria, cyanobacteria and eukaryotic phytoplankton, paying special attention to responses to changing nutrient conditions with the use of classic and novel molecular techniques. We will discuss the microbial response to varying nutrient scenarios by examining changes in microbial biomass, growth rates, community composition, and group specific responses to nutrient conditions. Information on interactions between microbial consortia will yield better information regarding causes of and responses to eutrophication, and potential nutrient-input reduction strategies for water quality improvement.