POTENTIAL ROLE OF ACRYLIC-ACID IN BACTERIOPLANKTON COMMUNITIES IN THESEA

Since the early work of Sieburth (1960; Science 132: 676-677) acrylic acid has frequently been mentioned as inhibiting bacterial growth in t he sea, although this has not been tested thoroughly. Recent focus on dimethylsulfoniopropionate (DMSP) and its cleavage into equimolar conc entrations of dimethylsulfide (DMS) and acrylic acid has led to increa sed speculation that acrylic acid may retard bacterial growth. In orde r to test the role of acrylic acid in controlling bacterial metabolism we performed experiments with bacterioplankton originating from the u pper mixed layer of the Adriatic Sea. In short-term experiments (20 mi n incubation period) leucine as well as thymidine incorporation into b acteria were reduced by greater-than-or-equal-to 50% at acrylic acid c oncentrations greater-than-or-equal-to 1 mM while in long-term incubat ions of seawater cultures (24 to 110 h) bacterial activity was retarde d at acrylic acid concentrations > 10 muM. In order to test potential effects of pH deviations, experiments with seawater cultures amended w ith 10 mM acrylic acid and adjusted pH (8.0) were performed, indicatin g that in pH-adjusted cultures bacterial production is reduced to ca 4 0% of the production rate in unamended cultures while bacterial produc tion in cultures with unadjusted pH is reduced to ca 2%. Although few data are available, we assume that acrylic acid concentrations in natu ral waters are similar to those of DMS (in the nM range). If this is t rue, then bacterioplankton will rarely experience growth inhibition by acrylic acid in the environment. Only under specific conditions when phytoplankton forms aggregates, e.g. marine snow or Phaeocystis coloni es, could acrylic acid play a role in reducing bacterial metabolism.