Decomposition of sewage sludge in drying beds at Ley Creek (LC) and Meadowbrook‐Limestone (MB) Wastewater Treatment facilities in metropolitan Syracuse, N.Y. was monitored. LC and MB beds were derived from an anaerobically digested, primary sludge and an aerobically digested, activated sludge, respectively. Fluxes of O2, CH4, and CO2, as determined by in situ incubation of cylinders and analysis by gas chromatography, showed that at LC, aerobic and anaerobic, decomposition and photosynthesis occurred concomitantly due to high moisture. Similar analyses for two separate trials at MB found that both total decomposition rate and percentage of anaerobic decomposition (1 to 90%), as indexed by CH4 evolution vs. O2 consumption, decreased with time and were inversely related to sludge moisture content. O2 consumption rates, when standardized to 15°C, ranged from 10 to 80 µliter/g dry wt. For both LC and MB sludge, aerobic and anaerobic bacteria were abundant (3 × 107 to 6 × 108 colony‐forming units/g dry wt) and dominant bacteria were not enteric. Nematode densities ranged from 7 to 814 individuals/g dry wt. A computer simulation model on the role of macroinvertebrates in decomposition was used for analyzing the effects of the earthworm, Eisenia foetida. This oligochaete was introduced into one‐half of the MB cylinders and was shown to accelerate decomposition and decrease the proportion of anaerobic decomposition if the sludge was below 375% moisture dry weight and 40% anaerobic decomposition. This stimulation was also reflected in increased nematode density and elevated Eh. Flooding of drying beds caused mortality to E. foetida.

The distribution of zinc-tolerant bacteria in sediments from three stream sites containing high (3125 sg g -1 ), medium (291 µg g -1 ), and low (109 µg g -1 ) concentrations of Zn was determined . Zinc tolerance was estimated by the ability of bacteria to grow on media amended with Zn concentrations ranging from 4 to 512 mg 1 -1 . The presence of Zn-tolerant bacteria was correlated with the degree of heavy metal contamination ; this correlation' was more closely associated with readily extractable heavy metal concentrations than with the more rigorously extracted heavy metals . Low concentrations of Zn in media (4 to 16 mg 1 -1 ) were stimulatory to growth of bacteria from contaminated sites while concentrations as low as 4 mg 1 -1 were inhibitory to bacteria from the control site.

Artificial streams were used to study the effect of chronic zinc dosing (0.00,0.05 or 1.00 mg Zn 1-') on epilithic communities during summer and early fall, 1984 and 1985. Following zinc addition, epilithon was periodically measured for '4C-glucose and 14C-glutamate respiration, ash-free dry weight (AFDW), protein, carbohydrate, chlorophyll a (Chl a), pheophytin a (pheo a), and colony forming units (CFU) on zinc amended and unamended media. Transient peaks in glucose respiration rates mg-' protein and AFDW occurred within 5 to 10 days in streams dosed with 1.0 mg Zn 1-' and coincided with decreases in AFDW, protein, carbohydrate, Chl a, and pheo a. Respiration of glutamate did not show a significant response to dosing (a = 0.05). Epilithic plate counts demonstrated more total and zinc-tolerant CFU in dosed than in control epilithon after 20 days. After 30 days, greater biomass and lower protein: carbohydrate ratios were evident in epilithon dosed with 1.0 mg Zn 1-' compared to unamended treatments. Peaks in glucose respiration suggested the presence of zinc-tolerant heterotrophs transiently capable of increased respiration of glucose but not glutamate. Concurrently, minimal but measurable biomass inferred the persistence of zinc-tolerant microorganisms in zinc-dosed epilithon. By the end of the studies, results indicated that metal-tolerant populations replaced metal-sensitive organisms under conditions of elevated zinc concentration. These zinc adapted communities had lower potential value as a food source to grazers (low protein: carbohydrate ratio) and were no longer distinctive with respect to glucose respiration.

Levels of polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography in indigenous oysters (Crassostrea virginica) from three rivers in the southern Chesapeake Bay. Accumulation and depuration rates of PAHs in oysters were measured in sttu by relocation experiments between industrially impacted and nonimpacted sites. Elizabeth River oysters at Norfolk, Virginia, contained the highest PAH tissue burdens among oysters from the rivers sampled; the sum of six PAHs identified was 3 9 ppm dry weight. PAH levels in James River oysters ranged from 0 to 2 3 ppm at Wreck Shoals near Newport News, Virginia No PAHs were detected in oysters from the Piankatank River In accumulation experiments, PAH levels increased from 0 to as much as 11 7 ppm dry weight within 3 d of exposure in the Elizabeth River, they then stabilized Depuration or transformation of PAHs in Elizabeth River oysters to undetectable levels occurred within 4 d of relocation to the Ware River Differences in oyster PAH levels generally corresponded with the degree of industrial and urban development and shipping traffic in the habitats.

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