Transcript Wetland Ecosystem Management - Nutrient

Aquatic Plants and the Environment
(SWES, ECOL, WFSc 474/574)
Nutrient Cycles in Wetlands
Dr. Kevin Fitzsimmons
Professor – University of Arizona
Carbon Cycle
digestion and
respiration + 3O2
C6H12O6
sugars and
other organics
anaerobes,
fermentation, and
methanogens
Photosynthesis
6 H2O + 6 CO2
water and
carbon dioxide
C6H12O6 + 3O2
sugars and
other organics
and oxygen
CH3CH2OCOOH (lactic acid)
other acids (humic and tannic)
CH4 + COx
Carbonate Cycle
CO2 + H2O
H2CO3
H+ + HCO3-
carbon dioxide
dissolved in water
carbonic
acid
bicarbonate
ion
H+ + CO32carbonate
ion
Carbonate cycle
Calcium, Silica, Carbon cycles
Nitrogen cycle
• Nitrogen is often a limiting element in freshwater
aquatic system
• Adding nitrogen will cause rapid increase in
primary productivity
• Nitrogen in anaerobic sediments
- denitrification (reduction to NH3 or N2 gas)
Nitrogen cycle in aquatic systems
Phosphorus cycle
Phosphorus and
orthophosphate.
Organic P
decomposes and
releases PO4,
taken up by algae
and plants or
adsorbs to clay
particles and
precipitates.
Anaerobic
conditions can
re-release P to
water.
Sulphur cycle
Organic sulphur, digested
to sulphates, then
reduced
to sulphur dioxide,
elemental sulphur
or hydrogen sulfide
Saturated Soils
•
•
•
•
Bacteria decompose organics, quickly use available DO
Anaerobic conditions, anaerobes scavenge O release H+
Reducing conditions
Redox reactions in sediments / soils
Oxidized
Form
Reduced
Form
Eh
(mV)
O2
H2O (CO2)
350
Aerobic respiration
NO3-
N2
250
Denitrification
Mn4+
Mn2+
250
Fe3+
Fe2+
160
Fe Reduction
Gray (gley)
SO42-
H2S
-150
Sulfate Reduction
Rotten Eggs
CO2
CH4
-250
Methanogenesis
oxidizing conditions
reducing conditions
Hydric Soils
Wetland Ecosystem Management