Temperature responses of microbial extracellular enzyme activity associated with decaying submerged leaf litter
Presentation Abstract
The decomposition of leaf litter in aquatic ecosystems is carried out mostly by microorganisms, including bacteria and fungi. They produce extracellular enzymes that aid in the sequestration of carbon and nutrients and lead to the breakdown of complex plant polymers. We evaluated the effects of temperature on extracellular enzyme activity within the framework of the Metabolic Theory of Ecology (MTE). The activity of β-1,4-glucosidase and β-1,4-xylosidase was estimated fluorometrically using artificial substrate analogs. Phenol oxidase activity was estimated spectrophotometrically from oxidation of L-DOPA (L-3,4-dihydroxyphenylalanine). We found that the activity of microbial enzymes involved in carbon sequestration is temperature dependent but does not follow simple monotonous response across experimental temperatures (4-20°C) predicted by the MTE. Instead, we observed greater temperature sensitivity of enzymatic activity at colder temperatures. This may have important implications for stream ecosystems under climate change scenarios since both peak leaf litter availability and microbial activity occur in autumn-winter.
Temperature responses of microbial extracellular enzyme activity associated with decaying submerged leaf litter
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The decomposition of leaf litter in aquatic ecosystems is carried out mostly by microorganisms, including bacteria and fungi. They produce extracellular enzymes that aid in the sequestration of carbon and nutrients and lead to the breakdown of complex plant polymers. We evaluated the effects of temperature on extracellular enzyme activity within the framework of the Metabolic Theory of Ecology (MTE). The activity of β-1,4-glucosidase and β-1,4-xylosidase was estimated fluorometrically using artificial substrate analogs. Phenol oxidase activity was estimated spectrophotometrically from oxidation of L-DOPA (L-3,4-dihydroxyphenylalanine). We found that the activity of microbial enzymes involved in carbon sequestration is temperature dependent but does not follow simple monotonous response across experimental temperatures (4-20°C) predicted by the MTE. Instead, we observed greater temperature sensitivity of enzymatic activity at colder temperatures. This may have important implications for stream ecosystems under climate change scenarios since both peak leaf litter availability and microbial activity occur in autumn-winter.