From: Gonzalez Meyaui, Maria del Pilar [mailto:[log in to unmask]]
Sent: Friday, July 07, 2006 12:39 PM
To: [log in to unmask]
Subject: [unesco-waterportal-en] EUTROPHICATION: UNESCO WATER PORTAL
WEEKLY NEWSLETTER No. 147
UNESCO WATER PORTAL WEEKLY NEWSLETTER No. 147: EUTROPHICATION
7 July 2006
2005-2015 is the International Decade for Action 'Water for Life'
DID YOU KNOW...? FACTS AND FIGURES ABOUT EUTROPHICATION
* Eutrophication is a slow ageing process during which a
lake or estuary evolves into a bog or marsh and eventually disappears.
During eutrophication, the lake becomes so rich in nutritive compounds
(especially nitrogen and phosphorus) that algae and other microscopic
plant life become superabundant, thereby choking the lake and causing it
to eventually dry up.
* Eutrophication is accelerated by discharges of
nutrients in the form of sewage, detergents and fertilizers into the
* Eutrophication can be a natural process in lakes, as
they age through geological time. Estuaries also tend to be naturally
eutrophic because land-derived nutrients are concentrated where run-off
enters the marine environment in a confined channel and mixing of
relatively high nutrient freshwater with low nutrient marine water
* Lakes and reservoirs can be broadly classified as
ultra-oligotrophic, oligotrophic, mesotrophic, eutrophic or
hypereutrophic depending on the concentration of nutrients in the body
of water and/or based on ecological manifestations of the nutrient
loading. In general terms, oligotrophic lakes are characterized by low
nutrient inputs and primary productivity, high transparency and a
diverse biota. In contrast, eutrophic waters have high nutrient inputs
and primary productivity, low transparency, and a high biomass of fewer
species with a greater proportion of cyanobacteria than in oligotrophic
* Eutrophication can also cause Harmful Algal Blooms
(HABs), which can harm fish and shellfish, as well as the people who
consume them. Some algae can cause negative effects when they appear in
dense blooms, while others have potent neurotoxins and need not be
present in large numbers.
* In the 90s, the regions of Asia and the Pacific had
more lakes and reservoirs with eutrophication problems (54%) than Europe
(53%), Africa (28%), North America (48%) and South America (41%).
* Because of eutrophication, Lake Victoria in Africa has
become turbid to the point that brightly coloured fish species cannot
see each other clearly enough and they have begun to interbreed.
* In China, Lake Dianchi near Kunming and Lake Taihu
near Wuxi both suffer from extreme eutrophication. In these lakes vast
areas are covered by dense algal blooms and fish-breeding has been
almost totally abandoned because there is no oxygen for them to breath,
especially in autumn. Almost all native water plants and many fish
species have been killed. Snails die from lack of oxygen in the bottom
water and in addition the poor water quality makes it very difficult to
supply water for domestic use that meets legal standards.
Information from 2nd United Nations World Water Development Report,
'Water, a shared responsibility'
Vital Water Graphics website (http://www.unep.org/vitalwater/37.htm);
from the article 'Biodiversity studies in Lake Malawi'
(http://newsrelease.uwaterloo.ca/news.php?id=980) and from the section
'How Bad Is Eutrophication at Present?' of the United Nations
Environment Programme website
PUBLICATIONS RELATED TO EUTROPHICATION
Planning and Management of Lakes and Reservoirs: An Integrated Approach
to Eutrophication - A Student's Guide
By the United Nations Environment Programme (UNEP) International
Environmental Technology Centre (IETC), (c) UNEP 2001.
This publication provides an overview of the problems and possible
solutions associated with eutrophication in freshwater lakes and
reservoirs. It takes a look at the origins of the problems, their
consequences, solutions and prognoses under an integrated approach. The
publication also outlines a new approach to water resources management,
emphasizing the need to integrate and solve simultaneously social,
cultural, economic, and other associated problems. The watershed
approach, which should be adopted in successful management strategies
for water quality in lakes and reservoirs, is highlighted.
:: Access the full publication
LINKS ABOUT EUTROPHICATION
Planning and Management of Lakes and Reservoirs focusing on
This website of the United Nations Environment Programme Division of
Technology, Industry, and Economics, explains the eutrophication problem
and contains the environmental modelling tool PAMOLARE 2 that forecasts
the changes in water quality leading to the eutrophication of lakes and
Assessment of Estuarine Trophic Status (ASSETS)
This site, developed by the National Oceanic and Atmospheric
Administration (NOAA) and the Institute of Marine Research (IMAR) from
the United States of America, contains eutrophication-related
definitions, publications, data, models and graphics.
How bad is Eutrophication at Present?
This section of the United Nations Environment Programme website was
done with information from the publication Lakes and Reservoirs vol. 3
by the UNEP Division of Technology, Industry, and Economics. It contains
information about eutrophication and provides examples of different
lakes that suffer from this problem.
This fact sheet from the New Hampshire Department of Environmental
Services, United States, explains what lake aging is, what
eutrophication is, what activities cause eutrophication and what is
meant by trophic state.
:: For a complete list of water links around the world visit
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