Pii: S0025-326x(99)00037-5

Studies were conducted to assess factors that may in ̄uence the rate and extent of biodegradation of polyaromatic hydrocarbons (PAHs) in waters of Guayanilla Bay (latitude, 18°N; longitude, 66.45°W) Puerto Rico. Phenanthrene was used as a model PAHs compound. Both the rate and extent of phenanthrene degradation by natural microbial ̄ora present in seawater samples from Guayanilla Bay were quite slow. Addition of KNO3 as a source of inorganic nitrogen (N) resulted in a 10-fold increase in the rate of phenanthrene degradation within a 125 h period, whereas, addition of K2HPO4 as a source of inorganic nutrient phosphorus (P) had no e€ect. Phenanthrene degradation was strongly inhibited when seawater pH was adjusted to 10.0. Phenanthrene in seawater samples degraded rapidly when ®rst pretreated with hydrogen peroxide (H2O2) and then inoculated with a known indigenous phenanthrene degrading bacterium, Alteromonas sp. Pretreatment of phenanthrene with Triton-x-100 had little or no e€ect on its degradation by the same bacteria, whereas, degradation in samples preheated at 60°C was somewhat inhibited. Ó 1999 Elsevier Science Ltd. All rights reserved