Changes in the concentrations of short‐chain carboxylic acids and gases during decomposition of the aquatic macrophytes, Lemna paucicostata and Ceratophyllum demersum

Abstract

SUMMARY. Samples of two species of aquatic macrophytes, Lemna paucicostata and Ceratophyllum demersum, with which snail hosts of schistosomes are commonly associated, were homogenized, together with their epiphytic flora, and allowed to decompose in closed systems for up to 42 days. After 10 days of incubation it was found that populations of rod and coccoid shaped bacteria had greatly increased. Fermentation proceeded only to the acid forming stage and no methane was produced. Despite the differences in the morphologies, habitats and epiphytic flora of the two species, it was found that the short chain carboxylic acids, acetate, propanoate, butanoate and hydrogen were the major end products of microbial decomposition in both cases. There was also some oxygen production from photosynthetically active zones within the homogenates. Most of the accumulation profiles for the acids conformed to logistic growth curves, whereas the hydrogen values fluctuated. The reasons for the biochemical changes, the differences between the patterns of decomposition in Lemna and Ceraiophyllum. and the ecological relevance of the results to the plants, micro‐organisms and the snails are discussed.