Meeting Abstract

P3.32  Friday, Jan. 6  The effects of ocean acidification on biofilm bacterial populations KAO, S.T.*; HADFIELD, M.G.; Univ. of Hawaii, Manoa skao@hawaii.edu

In marine ecosystems, bacteria are major components of biofilms on all surfaces. Marine bacterial films are known to provide essential cues for recruitment of benthic animals and algae. With global climate change occurring at a rapid rate, the natural environment that marine bacterial biofilms occupy has begun to change. Continued atmospheric CO₂ emissions are causing increasing ocean acidification. While previous studies of the impacts of declining ocean pH have focused primarily on calcifying organisms, the current study examined how declining pH may affect bacterial biofilm communities. The effects of three acidity levels on survival and diversity of biofilm bacteria from Pearl Harbor, HI were examined: pH 8.20 (the pH of seawater at Pearl Harbor, HI), pH 7.85, the estimated pH of the ocean by 2105, and pH 7.60, the estimated pH of seawater by 2205. A LIVE/DEAD^® Bac-light^™ viability kit was used to assess bacterial viability and densities after 5 days in the altered pH treatments. The live to dead bacterial cell ratios for all treatments were above 1, confirming that for all test groups the pH treatments were not toxic to bacteria. Bacterial density counts revealed no significant differences between pH treatments and the control. The bacterial communities in seawater of different acidity levels were compared using Denaturing Gradient Gel Electrophoresis (DGGE). A PCR-amplified fragment of the 16s rDNA gene was used in the DGGE analysis. Preliminary results show low and similar diversity in the biofilm bacterial communities across pH treatments. These results may be due to selection of a very few hardy bacterial strains by the warm polluted waters of Pearl Harbor during the summer, a hypothesis being examined in on-going studies.