Variability in bacterial community structure during upwelling in the coastal ocean

Over the last 30 years, investigations at the community level of marine bac teria and phytoplankton populations suggest they are tightly coupled. Howev er, traditional oceanographic approaches cannot assess whether associations between specific bacteria and phytoplankton exist. Recently, molecular bas ed approaches have been implemented to characterize specific members of dif ferent marine bacterial communities. Yet, few molecular-based studies have examined coastal upwelling situations. This is important since upwelling sy stems provide a unique opportunity for analyzing the association between sp ecific bacteria and specific phytoplankton in the ocean. It is widely belie ved that upwelling can lead to changes in phytoplankton populations (blooms ). Thus, if specific associations exist, we would expect to observe changes in the bacterial population triggered by the bloom. In this paper, we pres ent preliminary data from coastal waters off New Jersey that confirm a shif t in bacterial communities during a 1995 upwelling event recorded at a long -term earth observatory (LEO-15) in the Mid-Atlantic Bight. Using PCR ampli fication and cloning, specific bacterial 16S ribosomal RNA sequences were f ound which were present in upwelling samples during a phytoplankton bloom, but were not detected in non-bloom samples (surface seawater, offshore site s or sediment samples) collected at the same time or in the same area. Thes e findings are consistent with the notion of specific associations between bacteria and phytoplankton in the ocean. However, further examination of ep isodic events, such as coastal upwelling, are needed to confirm the existen ce of specific associations. Additionally, experiments need to be performed to elucidate the mechanisms leading to the specific linkages between a gro up of bacteria and a group of phytoplankton.