Research Product

Estuarine surface films from Escambia Bay, Florida, and adjacent waters were sampled by using the membrane adsorption technique to enumerate microbial populations. Samples of the upper 10 µm of estuarine surface films yielded microbial populations up to 108 ml-1 or 105 cm-2. These populations were 10 to 100 times greater than those in underlying waters of 10 cm. Predominant bacteria in surface films as isolated on Marine Agar (Difco) were motile, nonpigmented, gram-negative rods. Colony-forming units of yeasts and molds on Mycological Agar (Difco) prepared with 50% seawater were found in concentrations to 104 ml-1 or 28 cm-2. The predominant surface film isolates from Marine Agar were proteolytic and amylolytic but exhibited only weak to negligible hydrocarbonoclastic and lipolytic activities. A greater proportion of the surface-film bacteria, as compared to those at 10 cm depth, were capable of growth on freshwater media. With selective isolation media, amylolytic, and lipolytic bacteria appeared to comprise a more significant proportion of the total population. Twenty-one representative bacteria, yeasts, and filamentous fungi from initial sampling of surface microlayers were tested for the effects of selected pesticides on utilization of various substrates. One bacterium was sensitive to PCB formulations. In subsequent studies with 53 isolates representative of more diverse physiological groups, o-chlorophenol, 1-chloronaphthalene, PCB 1016, and pentachlorophenol were inhibitory to a large portion of the isolates. Heptachlor inhibited 2 isolates and methoxychlor inhibited only 1 isolate. In contrast, with hydrocarbon as a substrate, microorganisms were more frequently inhibited by various aromatic or chlorinated hydrocarbons. For example, heptachlor, biphenyl, pyrene, and PCB 1016 significantly reduced hexadecane utilization by representative surface film bacteria. In a few instances, trace concentrations of pesticides enhanced hydrocarbon utilization. In studies with yeasts, high concentrations of heptachlor appeared to have a slight stimulating effect on utilization of hexadecane by C. maltosa, but no effect with C. lipolytica. The complex nature of metabolic responses with varying substrate and pesticide indicates that multiple assay procedures are required to detect the altering capability of pesticides within the surface film ecosystem.