Transcript Eutrophication of Coastal Systems

Eutrophication of coastal systems
1. Our evolving conceptual model of the coastal
eutrophication problem;
James E.Cloern; 2001
2. Submerged aquatic vegetation in relation to
different nutrient regimes;
Carlos M.Duarte; 1995
3. Eutrophication and zoobenthos dynamics;
Carlo Heip; 1995
• Main research question
• Phase I
• Phase II
• Phase III
Main research question;
How does the anthropogenic nutrient
enrichment cause change in the structure or
function of nearshore coastal systems.
Phase I Model
• 1 Signal 1 response
– Nutrient loading
– more phytoplankton biomass, Primary
production, Oxygen concentrations.
Phase I Model
• Vollenweider-type model
Reliability of the model
• Limiting nutrients
• Sediment traps
• Results gathered from temperate latitudes
• Weak signal between signal and response
Advances beyond Phase I model
• Understanding of 1 signal 1 response.
• Data gathering (no experiments).
Advances beyond Phase I model
Responses in the Sediment
• Anoxia
• Release of phosphate
• Inhibition of
nitrification
Advances beyond Phase I model
Responses of fauna
• Step wise change from slow growing plants
to fast growing algae.
Advances beyond Phase I model
Responses of fauna
• From nutrient limitation to light limitation.
• Nutrient availability
• Resuspension of the sediment
Advances beyond Phase I model
Responses of zoo benthos dynamics
• Pearson Rosenberg model
– Slight increase of biomass. Slight change of
species composition
– Strong increase of biomass, replacement by
opportunistic species
– Disappearance of benthic animal species and
azoic sediments
Advances beyond Phase I model
Responses of zoo benthos dynamics
• Bioturbation
• Nutrient regeneration
Advances beyond Phase I model
• Importance of more nutrients like P or Si.
• Changing redfield ratio
• Toxic algal communitities.
• Recovery of the ecosystem
Advances beyond Phase I model
Early responses to enrichment.
• Communities changes at species level.
• Nutrient cycling.
• Change in seasonal timing
The Phase II model
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The major differences
1. A more clearer picture of potential
responses to nutrient enrichment
2. Recognition of system attributes acting as a
filter for responses to change in nutrient
loading
3. The possibility to reverse some of the
direct and indirect responses of increased
nutrient loading
The Phase II model
The Future
Problems to solve
• Nutrient enrichment is thought as operating as
an independent stressor
• Limited experimentation and modeling results
• Results mostly from highly impacted regions
at temperate latitudes
A Phase III model
A Phase III model
1. How does the filter work
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Tidal currents
Salinity gradients
Horizontal transport processes
Light exposure to submerged plants
Particle filtration by suspension feeders
A Phase III model
2. How does nutrient enrichment interact
with other stressors
3. How are responses to multiple stressors
linked
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Climatic system
Human manipulation of coastal hydrology
Human translocation of organisms
Interaction between nutrients and toxic
contaminants.
A Phase III model
4. How does coastal eutrophication impact
the earth systems as a habitat for humanity
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Fishery losses
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Eating of polluted fish
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Methyl bromide or DMS production
contributing to ozone depletion and
acidification.
A Phase III model
5. What synthetic tools can guide
management strategies.
• Restore the function of coastal ecosystems
• Protection of coastal systems
• A model as accurate as possible
A Phase III model
Things to do
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Construction of nutrient budgets
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Development of indices to measure sensitivity
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Experimentation with representations of
coastal systems