Prospective experimental field evaluation of genetically engineered microorganisms, such as microbial pest control agents, raises issues of how to properly ascertain their fate and survival in the environment. Field trials with recombinant organisms must reflect requirements for sampling and monitoring. Field trials were conducted at Tulelake, Calif., to monitor the numbers of viable cells of a nonrecombinant strain of Pseudomonas syringae that entered the atmosphere and landed on plants and soil during and after an aerosol spray application. An exponential decrease in numbers of viable cells deposited at increasing distances from three sprayed plots was observed. The relative rate of survival of cells sprayed directly on plants was more than 10 times higher than that of cells dispersed through the air to similar adjacent plants. Results are being used to gain experience with the characteristics of a release site that influence containment or dispersal and to develop appropriate sampling methodologies for evaluating survival and dispersal characteristics of genetically engineered bacteria released into the environment. The ability to make predictions about microbial dispersal and survival will reduce the uncertainties associated with environmental releases of recombinant organisms.

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The Atchafalaya Basin comprises an 8 345 km 2 lowland area within Louisiana . Annual organic carbon fluxes were determined for the 2 129 km2 Atchafalaya Basin Floodway (subject to frequent and prolonged natural flooding) and two subunits within the Floodway . Comparisons are made with an area not subject to extensive overflow due to its isolation from the Atchafalaya River by manmade levees . Comparisons are also made with some other areas reported in the literature . Overflow areas were found to have a large areal net export of dissolved organic carbon while the non-overflow area had a low net export . Areal export of particulate organic carbon was high in the non-overflow area while the overflow areas acted as sinks for particulate organic carbon . Prolonged overbank flooding, with the annual inundation of additional land areas and the decomposition of herbaceous materials and forest litter, renews the supply of organic carbon .

The relationship between chlorophyll u, total phosphorus, secchi disk depth, and trophic state were examined using data on U.S. lakes collected by U.S. EPA's National Eutrophication Survey. By comparing predicted secchi disk depths with observed summer secchi disk depths in 757 lakes, it was determined that in many lakes non‐chlorophyll related light attenuation is important in controlling the amount of chlorophyll u produced per unit of total phosphorus. Ranking of 44 lakes by 18 different trophic state measurements and single and multivariable indices were compared with rankings provided by mean summer ambient total phosphorus and chlorophyll u. The trophic state measurements and indices were much more successful in ranking the lakes against total phosphorus than chlorophyll u, indicating that there are differences in the relative trophic rankings of many of the lakes depending upon whether primary nutrients or biological manifestations are used as the ranking mechanism. If the manifestations of nutrients rather than their absolute levels are the primary criteria for beneficial use of lakes, the use of many of the commonly employed trophic state measurements, which assume or imply that there is a constant relationship between total phosphorus or secchi disk and chlorophyll, can lead to erroneous conclusions and unnecessary costly management controls. Secchi disk measurements may be more useful as a predictor of ambient lake total phosphorus concentrations than of chlorophyll.

Fish populations in seven backwater lakes were sampled by rotenone poisoning. On the average, 397 pounds of fish per acre comprising 103 pounds of game fish and 169 pounds of commercial fish were recovered from the lakes. Recoveries from individual lakes ranged from 142 to 651 pounds of fish per acre. Non‐predaceous fish made up 56 percent of the total population. Bluegill sunfish, warmouth sunfish, gizzard shad, fresh‐water drum, largemouth bass, black crappie and spotted gar were the principal fishes in the lakes. An average of 78 pounds of available game fish (harvestable‐size game fish) per acre was recovered from the lakes. Fairly large concentrations of fish occurred in relatively small areas in some of the backwater lakes. A total of 974 pounds of fish, of which 475 pounds were game fish, was recovered from a single 1 acre sampling area. On the average, there were 1.9 pounds of non‐predaceous fish per pound of predaceous fish. There were considerably less available forage fish (by weight) for the predators than they themselves made up in the population. The predaceous fish in the backwater lakes must be partly dependent on some type of forage other than fish, and swamp crayfish are probably important in their diet. A large increase in the area of the lakes during high water periods in the spring creates a favorable habitat for a rapidly expanding fish population. The quality of the sport fishing on the backwater lakes is excellent.

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