Rapid microbial degradation of phenolic materials in California (USA) coastal environments

Phenolic materials are common in terrestrial and freshwater environments, yet their distribution is limited in marine systems. Since these compounds are common pollutants as well as important structural components of terrestrial and riverine humic materials, we used a phenolic model compound for the study of organic carbon dynamics in coastal environments. Concentrations and microbial utilization rates of p-cresol were determined in various waters off the coast of California, USA. Levels of p-cresol ranged from 9.26 ng l(-1) in Humboldt Bay in Northern California to 303 ng l(-1) near the White's Point Outfall in Southern California. Levels of 37.1 to 61.1 ng l(-1) were found at 3 other sampling locations in San Diego Bay and San Francisco Bay. Microbial utilization rates of p-cresol were determined by measuring cellular incorporation and respiration of H-3-p-cresol. Utilization rates ranged between 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 calculated 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 input of p-cresol and possibly natural input as a component of humic type materials. In areas where freshwater input is significant, utilization kinetics may suggest biodegradation of more complex, phenol-containing humic materials. We conclude that accumulation of phenols is not generally observed in coastal waters a short distance from input sources due to rapid microbial utilization.