Contemporaneous Nitrogen Fixation and Denitrification in Intertidal Microbial Mats: Rapid Response to Runoff Events
Joye SB and Paerl HW. 1993. Contemporaneous Nitrogen Fixation and Denitrification in Intertidal Microbial Mats: Rapid Response to Runoff Events. Marine Ecology Progress Series. 94(3):267-274
We examined the contemporaneous responses of N sub(2) fixation and denitrification to inorganic nitrogen-enriched runoff in 2 intertidal microbial mats in Tomales Bay (California, USA). Prior to runoff, N sub(2) fixation rates averaged 3 mmol N M super(-2)/d. Denitrification rates were lower, corresponding to 0 to 25% of N sub(2) fixation rates. After the initiation of runoff, N sub(2) fixation rates decreased, approaching zero at both sites. In contrast, denitrification rates increased by an order of magnitude. We developed a simple model to examine the magnitude of N removal from creek water by mat denitrification before, during and after runoff. Model results show that during peak runoff, N removal was limited by the residence time of creek water in the intertidal region. As runoff volumes decreased and residence times increased, N removal became limited by the supply of organic matter. Our results illustrated the rapid metabolic adaptation of microbial mats to altered N fluxes. Changes occurring in the mat N cycling after the initiation of runoff led to 2 fundamental ecological changes: (1) mats became sinks for rather than sources of fixed N and (2) denitrification became limited by the availability of organic carbon rather than nitrate.
- Type
- Journal Article
- Authors
- Joye, S; Paerl, H
- Units
- PORE
- Keywords
- Agricultural runoff, biological production, California, community studies, denitrification, Ecosystem, Energetics, Environmental Regime Marine, INE, Lyngbya, Microcoleus, Mud flats, Nitrogen Fixation, Organic Matter, Oscillatoria, Salicornia, Spirulina, Tomales Bay ER, USA