Carbon monoxide, ethylene, and propylene were produced in illuminated, cell-free distilled water or natural seawater systems to which dissolved organic matter produced by phytoplankton had been added. Methane and the higher saturated gaseous hydrocarbons were not produced. In the dark, little or no carbon monoxide and no hydrocarbons were produced in the distilled water systems; only carbon monoxide was produced in natural seawater, but less was produced than in the light.
Little is known about the nature of bacteria associated with the surface and gut of marine copepods, either in laboratory-reared animals or in the natural environment. Nor is it known whether such animals possess a gut flora. The present report deals with studies of microorganisms isolated from healthy, laboratoryreared copepods of the species Acartia tonsa Dana, from several species of wild copepods collected from a marine or estuarine environment, and from laboratory dishes containing moribund copepods. Evidence for a unique gut flora in laboratory-reared animals is presented; the predominant bacteria were represented by the genus Vibrio. Other organisms such as Pseudomonas and Cytophaga were found less abundantly associated with the copepods and not specifically associated with the gut. Acartia tonsa Dana, an estuarine and neritic calanoid copepod, has proved to be useful as an experimental animal in standardized laboratory culture (25). However, little is known about the effects of associated microorganisms on such marine invertebrates, or, in fact, about the actual associations themselves, either in the natural environment or in laboratory cultures. Ecological relationships and changes in such relationships that might occur when wild copepods are brought into culture should be understood, especially if there is a unique association between copepods and bacteria, such as symbiosis or commensalism. Mass mortalities frequently observed in laboratory culture of copepods may be caused by specific pathogens or opportunistic bacteria, but little is known about bacterial pathogens infecting copepods. In addition, the gut flora of the copepod may confer protection on the animals, but until the existence of a commensal gut flora in the copepod is established, such an hypothesis cannot be proven. Research for the project reported here was initiated on a cruise in the Gulf of Mexico aboard the U.S.N.S. MIZAR. Several species of copepods were collected at four different stations, including sites in the open ocean, off the continental shelf, and in the Mississippi Delta. Samples were also collected in the Anclote River,
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