DEGRADATION RATES OF SUBSTITUTED PHENOLS BY NATURAL-POPULATIONS OF MARINE-BACTERIA

Phenolic compounds are found in coastal marine environments. They may be naturally produced by marine organisms or enter the ocean from anthropogenic sources. Little is known about the rates of biodegradation of these compounds at low levels by natural populations of marine microorganisms. In this study the growth rates and biodegradation rates using substituted phenols as substrates were determined in batch cultures of natural marine bacteria. Experimental conditions were selected for batch cultures which optimized acclimation and degradation rates. Phenols tested were o-cresol, p-cresol, 2,4-dichlorophenol and 2-bromophenol in concentrations of 100, 500 and 1000 mug.l-1. Growth rates were fastest for cells incubated in cresols and ranged from 2.8 x 10(7) to 7.7 x 10(7) cells.l-1.h-1. They were much slower for populations exposed to halogenated phenols, ranging from 5.8 x 10(5) to 7.9 x 10(6) cells.l-1.h-1 for 2-bromo- and 2,4-dichlorophenol. Biodegradation rates ranged from 2.8 to 19 mug.l-1.h-1 for p-cresol and from 9.2 to 16 mug.l-1.h-1 for o-cresol. Half life values of cresols were calculated and averaged 10 days in Southern California coastal water at 20-degrees-C. Half life values for halogenated phenols are predicted to be much longer.