RAPID MICROBIAL-DEGRADATION OF PHENOLIC MATERIALS IN CALIFORNIA (USA)COASTAL ENVIRONMENTS

Phenolic materials are common in terrestrial and freshwater environmen ts, yet their distribution is limited in marine systems. Since these c ompounds are common pollutants as well as important structural compone nts of terrestrial and riverine humic materials, we used a phenolic mo del compound for the study of organic carbon dynamics in coastal envir onments. Concentrations and microbial utilization rates of p-cresol we re determined in various waters off the coast of California, USA. Leve ls of p-cresol ranged from 9.26 ng l(-1) in Humboldt Bay in Northern C alifornia to 303 ng l(-1) near the White's Point Outfall in Southern C alifornia. Levels of 37.1 to 61.1 ng l(-1) were found at 3 other sampl ing locations in San Diego Bay and San Francisco Bay. Microbial utiliz ation rates of p-cresol were determined by measuring cellular incorpor ation and respiration of H-3-p-cresol. Utilization rates ranged betwee n 1.02 (Spanish Landing in San Diego Bay) and 35.5 ng l(-1) h(-1) (San Francisco Bay). Residence times for added tracer ranged from 10 (San Francisco Bay) to 28 h (at White's Point Outfall). Turnover times calc ulated from biodegradation rate and ambient concentration of p-cresol ranged from 1.7 h (San Francisco Bay) to 37 h (Spanish Landing in San Diego Bay). These rapid turnover times indicate high anthropogenic inp ut of p-cresol and possibly natural input as a component of humic type materials. In areas where freshwater input is significant, utilizatio n kinetics may suggest biodegradation of more complex, phenol-containi ng humic materials. We conclude that accumulation of phenols is not ge nerally observed in coastal waters a short distance from input sources due to rapid microbial utilization.