Eutrophication

Definition of Eutrophication: (1) An increase in the supply of organic matter (Nixon, 1995) (2) A condition in an aquatic ecosystem where high nutrient concentrations stimulate growth of algae which leads to imbalanced functioning of the system (HELCOM 2006) (3) 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 adverse 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) (4) The enrichment of water by nutrients causing an accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance to the balance of organisms present in the water and to the quality of the water concerned” (OSPAR 2003 This is the common definition for Eutrophication, other definitions can be discussed in the article

Eutrophication occurs when a limiting factor on the rate of growth and production of primary producers is released, most frequently via an input of inorganic or organic nutrients (Howarth 1988). High primary production boosted by eutrophication usually leads to oxygen depletion caused by decay of organic matter.

Nutrients for primary production

Nutrients needed in large quantities

• Nitrogen ([math]N[/math]) is often a limiting nutrient to growth. Most common reactive form is dissolved inorganic nitrogen (DIN) found in marine waters as nitrate ([math]NO_3^-[/math]), nitrite ([math]NO_2^-[/math]) and ammonium ([math]NH_4^+[/math]). Nitrogen also occurs in the largely refractory form of dissolved organic matter (DOM) as dissolved organic nitrogen (DON). Small amounts of nitrogen occur in the not directly usable form of particulate organic matter (POM).
• Phosphorous ([math]P[/math]) is often a limiting nutrient to growth. Most common reactive form is dissolved inorganic phosphorus (DIP) found as phosphate ([math]PO_4^{3-}[/math]). Phosphorus also occurs in the largely refractory form of dissolved organic matter (DOM) as dissolved organic phosphorus (DOP). Small amounts of phosphorus occur in the not directly usable form of particulate organic matter (POM).
• Potassium ([math]K[/math])
• Calcium ([math]Ca[/math])
• Magnesium ([math]Mg[/math])
• Sulfur ([math]S[/math])
• Silicium ([math]Si[/math]), mainly as silicic acid [math]Si(OH)_4[/math] can be a limiting nutrient for diatoms

Nutrients needed in trace amounts

• Iron ([math]Fe[/math]) can be a limiting nutrient
• Boron ([math]B[/math])
• Chlorine ([math]Cl[/math])
• Manganese ([math]Mn[/math])
• Zinc ([math]Zn[/math]) can be a limiting nutrient
• Copper ([math]Cu[/math])
• Nickel ([math]Ni[/math])
• Molybdenum ([math]Mo[/math])

Eutrophication indicators

There are no widely applicable indicators of eutrophication due to the high variation in natural conditions and the interaction of multiple factors influencing eutrophication. Often Chlorophyll a ([math]Cl \, a[/math]) is used as indicator of eutrophication, as a proxy for phytoplankton biomass. However, the drawback of using of [math]Cl \, a[/math] as an indicator is that there can be no increase in [math]Cl \, a[/math] after nutrient concentrations have exceeded the threshold beyond which other factors (e.g. light, grazing) are limiting. Additionally, [math]Cl \, a[/math] measures only changes in the abundance of primary producers and cannot indicate any changes in community composition that may occur simultaneously (Jessen et al. 2015).

Articles related to eutrophication

Eutrophication processes

• Eutrophication in coastal environments
• What causes eutrophication?
• Nutrient conversion in the marine environment
• Which resource limits coastal phytoplankton growth/ abundance: underwater light or nutrients?
• Marine microorganisms
• Marine Plankton

Eutrophication impacts

• Threats to the coastal zone
• Coastal pollution and impacts
• Possible consequences of eutrophication
• Algal bloom
• Algal bloom dynamics
• Case studies eutrophication

Eutrophication monitoring

• In situ monitoring of eutrophication
• Plankton remote sensing
• Plankton remote sensing North Sea
• Real-time algae monitoring
• Optical measurements in coastal waters
• Nutrient analysers
• Differentiation of major algal groups by optical absorption signatures
• Sampling tools for the marine environment
• FerryBox - Continuous and automatic water quality observations along transects
• Detecting the unknown - novelty detection of exceptional water reflectance spectra
• The Baltic Algae Watch System - a remote sensing application for monitoring cyanobacterial blooms in the Baltic Sea

Eutrophication modelling

• Coupled hydrodynamic - water quality - ecological modelling
• Nutrient loading of coastal waters

Eutrophication policy

• OSPAR and eutrophication
• OSPAR eutrophication assessment
• European policy on eutrophication: introduction
• European Context of Nutrient Dynamics
• Eutrophication related monitoring tasks and WFD for coastal waters in Greece