Effect of temperature and yeast extract on microbial respiration of sediments from a shallow coastal subsurface and vadose zone

Abstract

As a part of our study on microbial heterogeneity in subsurface environments, we have examined the microbial respiration of sediment samples obtained from a coastal site near Oyster, VA. The sediments at the site are unconsolidated, fine to coarse beach sand and gravel. A Columbus Instruments Micro-Oxymax Respirometer was used to measure the rate of carbon dioxide (CO₂) production during the respiration of the sediment samples. The rate of respiration of the sediment samples ranged from 0.035–0.6 μL CO₂/h/g of the sediment. The sediment samples showing maximum (0.6 μL CO₂/h/g) and minimum (0.035 μL CO₂/h/g) production of CO₂ were selected to study the effect of micronutrientyeast extract (0.5 and 1.0 μg/g of the sediment) and water (0.5 and 1.0 mL) on the rate of CO₂ production. The rate of CO₂ production increased with the addition of water, but increased approx 2 orders of magnitude (from 0.26 to an average of 23.5 μL CO₂/h/g) when 1.0 g/g yeast extract was added to the sediment samples. In these coastal sediments, temperature, depth, and addition of water influenced microbial activity, but the addition of 1.0 μg/g yeast extract as a micronutrient rapidly increased the rate of CO₂ production 2 orders of magnitude.