Microbial decomposition of leaf material at 0°C.

The microbial decomposition of leaves (both fresh and autumnshed) at 0°C using stream sediment-water was investigated. The maximum rates of loss of leaf carbohydrate and protein at 0°C were considerable, being about 40% of those at 20°C. These rates were only slightly affected by the type of leaf material present being 1.3-fold higher with fresh leaves as compared with autumn-shed leaves. In addition, an epifluorescence microscopic counting technique was developed and utilized to enumerate the microbial populations colonizing the decomposing leaves. The average microbial densities on fresh and autumn-shed leaves after 35 days of incubation were 1.3 × 10(6) and 9.0 × 10(5) microorganisms cm(-2) at 0°C as compared with 5.5 × 10(6) and 3.3 × 10(6) microorganisms cm(-2) at 20°C, respectively. Antibacterial and antifungal antibiotics were used to estimate the comparative involvement of sediment bacteria and fungi in leaf degradation.