Potential role of acrylic acid in bacterioplankton communities in the sea

Since the early work of Sieburth (1960; Science 132: 676-677) acrylic acid has frequently been mentioned a s inhibiting bacterial growth in the sea, although this has not been tested thoroughly. Recent focus on dimethylsulfoniopropionate (DMSP) and its cleavage into equimolar concentrations of dimethylsulfide (DMS) and acrylic acid has led to increased speculation that acrylic acid may retard bactenal growth. In order to test the role of acrylic acid in controlling bacterial metabolism we performed experiments with bactenoplankton originating from the upper mixed layer of the Adriatic Sea. In short-term experiments (20 min incubation period) leuclne as well as thymidine incorporalon into bactena were reduced by 2 50% at acrylic acid concentrations 2 1 mM while in long-term incubations of seawater cultures (24 to 110 h) bacterial activity was retarded a t acrylic acid concentrations > 10 PM. In order to test potential effects of pH deviations, experiments with seawater cultures amended with 10 mM acrylic acid and adjusted pH (8.0) were performed, indicating that in pH-adjusted cultures bacterial production is reduced to ca 40% of the production rate in unamended cultures while bacterial production in cultures with unadjusted pH is reduced to ca 2%. Although few data are available, w e assume that acrylic acid concentrations in natural waters are similar to those of DMS (in the nM range). If this 1s true, then bacterioplankton will rarely expenence growth inhibition by acrylic acid in the environment. Only under speclfic conditions when phytoplankton forms aggregates, e g. manne snow or Phaeocystis colonies, could acrylic acid play a role in reducing bacterial metabolism.