Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Brewers Condensed Solubles (BCS), a by-product of the brewing industry, was evaluated as a nutrient source for rearing juvenile oysters (Crassostrea virginica) and clams (Mercenaria mercenaria). The BCS was used to culture bacteria which were fed to colorless flagellates which were in turn fed to the oysters and clams. The overall growth efficiency of oysters on BCS was 473 mg of oyster (whole weight) per g of BCS (dry weight). Fourteen isolates representing nine genera of bacteria were isolated from BCS enrichment cultures. Specific growth rates of the isolates at &24\sp\circ{lcub}\rm C{rcub}& on a BCS medium ranged from 0.48 &{lcub}\rm h\sp{lcub}-1{rcub}{rcub}& to 0.11 &{lcub}\rm h\sp{lcub}-1{rcub}{rcub}.& The conversion of BCS to bacterial biomass was examined for four isolates with supplements of 0, 38, 76, and 152 mg/l of ammonium sulfate. The largest bacterial biomass (127 mg/g BCS) was obtained with Pseudomonas marina. The largest bacterial biomass when averaged over all bacterial isolates was obtained with 38 mg/l of ammonium sulfate. Yields of P. marina on BCS ranged from 27.4% for no ammonium sulfate addition to 38.5% with 38 mg/l of ammonium sulfate. The effects of dissolved nutrients, salinity, temperature, shaking, bacterial concentration, and bacterial species on the growth rates of five species of colorless flagellates were examined. None of the colorless flagellates could be raised on the dissolved nutrients in BCS, all required a bacterial diet. Shaking, salinity, and the bacterial isolate used as food had little effect on the flagellate growth rates. Temperature and bacterial concentration had pronounced effects. The greatest growth rates were recorded at temperatures between 21 and &26\sp\circ{lcub}\rm C{rcub}.& Growth rates increased with increasing bacterial concentration in a manner suggestive of Michaelis-Menten kinetics. Maximum specific growth rates ranged from 0.11 &{lcub}\rm h\sp{lcub}-1{rcub}{rcub}& to 0.16 &{lcub}\rm h\sp{lcub}-1{rcub}{rcub}.& Yields of colorless flagellates growing on bacteria ranged from 0.30 to 0.42. The growth of oysters and clams fed colorless flagellates. BCS enrichment cultures, and bacteria was compared to the growth of starved controls and animals fed Tetraselmis suecica. Paraphysomonas vestita was the only species of colorless flagellate to consistently result in growth greater than the starved control. The BCS enrichment culture varied greatly in its nutritional value. The average oyster growth on P. vestita was 55% of the growth obtained with T. suecica. Oysters fed combinations of T. suecica and P. vestita did not grow as rapidly as on a pure diet of T. suecica. No growth occurred when oysters and clams were fed a purely bacterial diet.



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