Eutrophication of coastal systems

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Eutrophication of coastal systems

• Our evolving conceptual model of the coastal
• eutrophication problem
• James E.Cloern 2001
• Submerged aquatic vegetation in relation to
• different nutrient regimes
• Carlos M.Duarte 1995
• Eutrophication and zoobenthos dynamics
• Carlo Heip 1995

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• Main research question
• Phase I
• Phase II
• Phase III

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Main research question

• How does the anthropogenic nutrient enrichment
  cause change in the structure or function of
  nearshore coastal systems.

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Phase I Model

• 1 Signal 1 response
• Nutrient loading
• more phytoplankton biomass, Primary
• production, Oxygen concentrations.

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Phase I Model

• Vollenweider-type model

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Reliability of the model

• Limiting nutrients
• Sediment traps
• Results gathered from temperate latitudes
• Weak signal between signal and response

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Advances beyond Phase I model

• Understanding of 1 signal 1 response.
• Data gathering (no experiments).

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Advances beyond Phase I model

• Responses in the Sediment
• Anoxia
• Release of phosphate
• Inhibition of
• nitrification

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Advances beyond Phase I model

• Responses of fauna
• Step wise change from slow growing plants to fast
  growing algae.

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Advances beyond Phase I model

• Responses of fauna
• From nutrient limitation to light limitation.
• Nutrient availability
• Resuspension of the sediment

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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

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Advances beyond Phase I model

• Responses of zoo benthos dynamics
• Bioturbation
• Nutrient regeneration

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Advances beyond Phase I model

• Importance of more nutrients like P or Si.
• Changing redfield ratio
• Toxic algal communitities.
• Recovery of the ecosystem

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Advances beyond Phase I model

• Early responses to enrichment.
• Communities changes at species level.
• Nutrient cycling.
• Change in seasonal timing

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The Phase II model

• The major differences
• A more clearer picture of potential responses to
  nutrient enrichment
• Recognition of system attributes acting as a
  filter for responses to change in nutrient
  loading
• The possibility to reverse some of the direct and
  indirect responses of increased nutrient loading

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The Phase II model
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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

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A Phase III model
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A Phase III model

• How does the filter work
• Tidal currents
• Salinity gradients
• Horizontal transport processes
• Light exposure to submerged plants
• Particle filtration by suspension feeders

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A Phase III model

• How does nutrient enrichment interact with other
  stressors
• How are responses to multiple stressors linked
• Climatic system
• Human manipulation of coastal hydrology
• Human translocation of organisms
• Interaction between nutrients and toxic
  contaminants.

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A Phase III model

• How does coastal eutrophication impact the earth
  systems as a habitat for humanity
• Fishery losses
• Eating of polluted fish
• Methyl bromide or DMS production contributing to
  ozone depletion and acidification.

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A Phase III model

• What synthetic tools can guide management
  strategies.
• Restore the function of coastal ecosystems
• Protection of coastal systems
• A model as accurate as possible

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A Phase III model

• Things to do
• Construction of nutrient budgets
• Development of indices to measure sensitivity
• Experimentation with representations of coastal
  systems