Microbial Organic Matter Utilization in High-Arctic Streams: Key Enzymatic Controls

Area of Science:

• * Arctic stream ecology
• * Microbial biochemistry
• * Biogeochemical cycles

Background:

• * Climate change increases organic matter mobilization in Arctic streams.
• * Microbial extracellular enzymes are key to processing stream organic matter.
• * Limited data exists on Arctic stream enzyme activity.

Purpose of the Study:

• * Investigate microbial extracellular enzyme activity variability in high-Arctic fluvial biofilms.
• * Understand how geomorphology and nutrient availability influence enzyme activity.
• * Assess the coupling between terrestrial and stream ecosystems in the Arctic.

Main Methods:

• * Studied 12 stream reaches in Northeast Greenland with diverse geomorphology and soil organic matter.
• * Measured stream nutrients (nitrogen, phosphorus), dissolved organic carbon, algal biomass, and bacterial density.
• * Quantified extracellular enzyme activities (e.g., β-glucosidase, phosphatase, phenol oxidase).

Main Results:

• * Significant differences in microbial organic matter utilization were observed across geomorphological features.
• * Phosphatase and phenol oxidase activities were higher in solifluction areas compared to alluvial areas.
• * Nitrogen availability, alongside dissolved organic carbon, primarily controlled enzyme activities, suggesting enhanced mineralization with increased nutrients.

Conclusions:

• * Terrestrial and stream ecosystems are strongly coupled in the high-Arctic.
• * Nitrogen availability is a key factor controlling microbial organic matter processing in Arctic streams.
• * Findings are crucial for predicting impacts of increased nutrient availability due to climate change in Arctic ecosystems.