Eutrophication

Eutrophication is an important process involving enrichment of water by excess nutrients. The different processes and effects of coastal eutrophication are well documented (Cloern, 2001) and it has been considered as one of the biggest threats to marine ecosystem health for decades (Nixon, 1995).

What is eutrophication about?

1. It’s about increased productivity (conversion of light and carbon dioxide into living organic matter – a process being limited by nitrogen and/or phosphorus) and unacceptable ecological effects as algal blooms, oxygen depletion, kills of benthic animals and fish
2. It’s caused by increased inputs of nutrients from
   1. point sources
   2. activities in the upstream catchment (e.g. losses from agriculture)
   3. atmospheric deposition
3. It’s about money!

What are we really talking about?

Eutrophication 

“eu” = “well” or “good”

“trope” = “nourishment”

But is “eutrophication” good?

• In general: NO … it is actually ”bad” …
• ... too many nutrients in wrong places may cause problems and result in changes in structure, function and stability of the marine ecosystems …

• Eutrophication is ”too much of a good thing”

Some definitions:

Eutrophication 

An increase in the supply of organic matter (Nixon 1995)

A condition in an aquatic ecosystem where high nutrient concentrations stimulate growth of algae which leads to imbalanced functioning of the system” (HELCOM).

Alternative proposal 

The enrichment of water by nutrients, especially nitrogen and/or phosphorus and organic matter, causing an increased growth of algae and higher forms of plant life to produce an unacceptable deviation in structure, function and stability of organisms present in the water and to the quality of water concerned, compared to reference conditions (Andersen et al. (2006))

The process of eutrophication

Eutrophication schematic. Source: US EPA

European Coastal Areas

The main source of nitrogen to European coastal waters is agricultural runoff discharged into the sea via rivers, identified as originating from sources of ammonia evaporation in animal husbandry and partly from fossil fuel combustion in traffic, industry and households (EEA Topic report 7/2001). For phosphorus the major sources are treated and untreated discharges to the sea from households and industry as well as soil erosion (EEA Topic report 7/2001).

EU Directives:

• EC Urban Waster Water Treatment Directive http://ec.europa.eu/environment/water/water-urbanwaste/directiv.html
• EC Nitrates Directive http://ec.europa.eu/environment/water/water-nitrates/directiv.html
• EU Water Framework Directive http://ec.europa.eu/environment/water/water-framework/index_en.html
• Marine Strategy Directive http://ec.europa.eu/environment/water/marine.html

Nixon, S. W. (1995) Coastal marine eutrophication: a definition, social causes, and future concerns. Ophelia, 41, 199–219.[ISI]

http://www.helcom.fi/environment2/eutrophication/en_GB/front/

Andersen, J. H., Schlüter, L. and Ærtebjerg, G. (2006) Coastal eutrophication: recent developments in definitions and implications for monitoring strategies. J. Plankton Res. 28(7): 621-628.

Ærtebjerg, G. et al., Eutrophication in Europe’s Coastal Waters. Topic Report No 7/2001. European Environment Agency. (http://reports.eea.europa.eu/topic_report_2001_7/en)

Ærtebjerg, G. et al., Eutrophication in Europe’s Coastal Waters. Topic Report No 7/2001. European Environment Agency. (http://reports.eea.europa.eu/topic_report_2001_7/en)