Coupled biogeochemical cycles: eutrophication and hypoxia in temperate estuaries and coastal marine ecosystems

Nutrient fluxes to coastal areas have risen in recent decades, leading to widespread hypoxia and other ecological damage, particularly from nitrogen (N). Several factors make N more limiting in estuaries and coastal waters than in lakes: desorption (release) of phosphorus (P) bound to clay as salini...

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Bibliographic Details
Published in:Frontiers in ecology and the environment 2011-02, Vol.9 (1), p.18-26
Main Authors: Howarth, Robert, Chan, Francis, Conley, Daniel J, Garnier, Josette, Doney, Scott C, Marino, Roxanne, Billen, Gilles
Format: Article
Language:English
Subjects:
algal blooms
biogeochemical cycles
clay
Coastal ecology
coastal water
coasts
Crustacea
desorption
Earth and Related Environmental Sciences
Environmental Sciences
Estuaries
Eutrophication
Freshwater ecosystems
Geologi
Geology
Geovetenskap och miljövetenskap
Hypoxia
lakes
Marine
Marine ecosystems
Mollusca
molluscs
Natural Sciences
Naturvetenskap
nitrogen
nitrogen fixation
ocean acidification
oceanography
Oceans
Oxygen
phosphorus
physics
pollution
REVIEWS
salinity
Sea water
Sediments
silica
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Summary:Nutrient fluxes to coastal areas have risen in recent decades, leading to widespread hypoxia and other ecological damage, particularly from nitrogen (N). Several factors make N more limiting in estuaries and coastal waters than in lakes: desorption (release) of phosphorus (P) bound to clay as salinity increases, lack of planktonic N fixation in most coastal ecosystems, and flux of relatively P-rich, N-poor waters from coastal oceans into estuaries. During eutrophication, biogeochemical feedbacks further increase the supply of N and P, but decrease availability of silica -– conditions that can favor the formation and persistence of harmful algal blooms. Given sufficient N inputs, estuaries and coastal marine ecosystems can be driven to P limitation. This switch contributes to greater far-field N pollution; that is, the N moves further and contributes to eutrophication at greater distances. The physical oceanography (extent of stratification, residence time, and so forth) of coastal systems determines their sensitivity to hypoxia, and recent changes in physics have made some ecosystems more sensitive to hypoxia. Coastal hypoxia contributes to ocean acidification, which harms calcifying organisms such as mollusks and some crustaceans.
ISSN:1540-9295
1540-9309
1540-9309
DOI:10.1890/100008