Carbon - Freshwater Ecology: Concepts and Environmental Applications - page 243

variety of metabolic pathways, including aerobic respiration,
anaerobic respiration using oxidized inorganic compounds to release
energy from organic molecules in the absence of O 2 , and
fermentations.
5. Methanotrophic organisms rely on oxidation of methane as a primary
energy source and generally are situated close to anoxic habitats
where methane is produced.
6. Methanogenic organisms produce methane from CO 2 and H 2 under
extremely low redox conditions. These organisms in aquatic habitats
have a significant input to the global atmospheric methane.
QUESTIONS FOR THOUGHT
1. Why may global warming alter deposition rates of organic carbon in
peat bogs?
2. Should wetlands be preserved even though they are a net source of
greenhouse gasses?
3. Why might the microlayer at the surface of lakes be important in
determining influx and efflux rates of lake water CO 2 ?
4. Do the processes of manganese reduction and iron reduction by
bacteria have to occur in regions of different redox in the
environment?
5. Why is CO 2 more likely to limit production of benthic organisms
than phytoplankton?
6. Why is it important to know the pH when conducting experiments to
measure photosynthetic rate with 14 CO 2 ?
7. Why is alkalinity generally high in limestone watersheds?