. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DECOMPOSITION OF SPARTINA 65 ploited the more easily decomposable fractions of the litter. The second step of nitrogen build-up in the remaining 80 days could indicate a shift of the microbiota in response to a depletion of the more readily utilizable substrates. This in turn causes a buildup of a population which attacks the less available bio-polymers (see Swift et al., 1979, Section ). In Spartina litter, Lee et al. (1980) found a similar pattern for fungal biomass calculated from the ergosterol content but only a one
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DECOMPOSITION OF SPARTINA 65 ploited the more easily decomposable fractions of the litter. The second step of nitrogen build-up in the remaining 80 days could indicate a shift of the microbiota in response to a depletion of the more readily utilizable substrates. This in turn causes a buildup of a population which attacks the less available bio-polymers (see Swift et al., 1979, Section ). In Spartina litter, Lee et al. (1980) found a similar pattern for fungal biomass calculated from the ergosterol content but only a one step increase of bacterial biomass in the same litter (direct counts). Since the more recalcitrant lignocellulosic components of the litter are degraded primarily by fungi, it is likely that a shift from primarily cellulolytic fungal population to lignolytic types was responsible for the two step enrichment. Extrapolation of lignin miner- alization data gathered in vitro strongly indicates that most (approx. 70%) of the lignin fraction of Spartina alterniflora is not decomposed by the microbial com- munity present during the initial stages of decomposition (MacCubbin and Hodson, 1980). Further decomposition of this litter requires a subsequent increase in the population of a lignolytic microbiota. The second step of nitrogen enrichment of the litter correlated with the increase in nitrate and nitrite in the outflow waters (Fig. 5) so it is possible that nitrifying bacteria contributed to the organic matter. To test this, the maximum contribution of chemoautotrophic microbial biomass to the litter was calculated from the amount of ammonia oxidized to nitrite and then to nitrate. This value was derived from the nitrate production data and from published conversion factors (Focht and Ver- straete, 1977) and is about 105 cells • mg NO3-N~'. I assumed some diameters and densities for small rod-shaped nitrifying bacteria (Ferguson and Rublee, 1976), and then calculated a mean dry w
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
