nutrient cycles eutrophication nitrogen –chemical forms in the aquatic environment –chemical...
TRANSCRIPT
Nutrient Cycles• Eutrophication
• Nitrogen– Chemical Forms in the Aquatic Environment– Chemical Transformations– Cycle
• f-ratio
• Carbon
Nutrient Cycles and Eutrophication
• Light penetration with depth
• Mixing and stratification
• Phytoplankton nutrient use
• Ocean circulation
Eutrophic
• Refers to areas that contain high nutrient concentrations and support high biological productivity
Eastern Boundary Currents
Upwelling
Eutrophication
• An increase of nutrients in a system (N or P) which promotes excessive plant growth (and decay) and is likely to cause severe reductions in water quality
Increase in nutrient loading
Experimental Lakes Area
Point and Nonpoint sources of chemical inputs
Algal Bloom in Lake
Before After
Adverse effects of eutrophication on lakes,
reservoirs, rivers and coastal marine waters • Increased biomass of phytoplankton • Toxic or inedible phytoplankton species • Increases in blooms of gelatinous zooplankton • Increased biomass of benthic and epiphytic algae • Changes in macrophyte species composition and
biomass • Decreases in water transparency • Taste, odor, and water treatment problems • Dissolved oxygen depletion • Increased incidences of fish kills • Loss of desirable fish species • Reductions in harvestable fish and shellfish • Decreases in perceived aesthetic value of the water
body
New species invasion
• Eutrophication may cause competitive release - nutrient normally limiting ↑↑.
• ↑ nitrogen might allow new, competitive species to invade and outcompete original inhabitant species
The changes in nutrient levels and biology can directly affect humans:
• The water can be injurious to health• The amenity value of the water may decline• Increased vegetation may impede water flow and
navigation• Commercially important species of fish may disappear• Treatment of drinking water may be difficult and supply
can have an unacceptable taste or odor
Prevention of eutrophication
The main effects caused by eutrophication:
1. Species diversity decreases and the dominant biota changes
2. Plant and animal biomass increase
3. Turbidity increases
4. Rate of sedimentation increases, shortening the lifespan of the lake
5. Anoxic conditions may develop
Gulf of Mexico
Algal Bloom
Oligotrophic Lake Eutrophic Lake
Oligotrophic Lake Eutrophic Lake
Chemical Forms – Nitrogen
Chemical Forms – N
• NO32- (Nitrate)
• NO2- (Nitrite)
• NH4+ (Ammonium)
• CO(NH2) 2 (Organic, Urea)
• N2 (Dissolved gas)
• N2O (Nitrous Oxide)
Annual Surface Nitrate Concentration
The Marine Nitrogen Cycle
The Marine Nitrogen Cycle
*
The Marine Nitrogen Cycle
**
The Marine Nitrogen Cycle
***
Denitrification
Nitrification
NO32- (Nitrate) → NO2
- (Nitrite) → NH4+ (Ammonia)
Heterotrophic microbes (anerobic)
NH4+ (Ammonia) → NO2- (Nitrite) → NO32- (Nitrate) Heterotrophic microbes (aerobic)
Nitrate Uptake into the Cell
Reduction steps: Reduced forms of nitrogen are ‘preferred’
NO3 NO3 NO2 NH4
Reduction steps
Diffusional Gradient
Proteins
Phytoplankton other Autotrophs - Assimilatory N Reduction
NitratePhytoplankton
Up
wel
lin
gM
ixin
g
Ver
tica
lF
lux
N2 FixationRiversDeposition
PONDIN
Euphotic Zone
f-ratio
Upwelling Zone 0.8Gyre 0.1Global Average < 0.5
New Production
New + Regenerated Production
Sediment traps
to catch
sinking particles
Sustainable yields
NitratePhytoplankton
Up
wel
lin
gM
ixin
g
Ver
tica
lF
lux
N2 FixationRiversDeposition
PONDIN
Euphotic Zone
Fishing
New Production
Oligotrophic gyres
Upwelling regions
