240
A. A. Ansari et al.
2011a; OECD 1982; Henderson-Sellers and Markland 1987;
Ryding and Rast 1989; Harper 1992; Thornton et al. 1999).
It is now evident that the nutrients are primarily responsible for limiting productivity in lakes and rivers, which are
well-known as the limiting nutrient controversy (Likens
1972). Scientists working on fresh waters have mainly concentrated on phosphorus as a key element in controlling eutrophication. The consequences of cultural eutrophication
caused by excessive inputs of phosphorus and nitrogen are:
• Increase in biomass of phytoplankton and macrophytes
• Domination of algal bloom forming species which is
toxic to consumers of eutrophic ecosystem
• Change in species composition of macrophyte vegetation
and increase in biomass of consumer species owing to
increase of biomass of benthic and epiphytic algae
• Frequent fish kills
• Decline in species diversity of aquatic ecosystem
• Decrease in harvestable fish biomass
• Decrease in water transparency
• Anoxic conditions in the aquatic ecosystem
• Problems related to the quality of water and its aesthetic
value
The empirical models describe the declining inlake concentrations of chemical elements; especially phosphorus which
results in reoligotrophication (Jeppesen et al. 2005; Jensen
et al. 2006). The water bodies can be divided into various
trophic levels such as autotrophic, nutrient-regulated heterotrophic, and external carbon-controlled state. The autotrophic state in flowing waters depends mainly on phosphorus
and nitrogen levels. Algal biomass is positively correlated
to gross primary production in streams and rivers (Dodds
2006).
In addition to increasing scientific knowledge, answers to
the questions related to eutrophication can influence strategies for ecosystem restoration or rehabilitation (Hecky 2009).
Initially, P and C has drawn the attention of limnologists and
ecologists as primary causes of eutrophication. However,
now it is proved that N also contributes in increasing eutrophication especially in estuaries where it is a limiting factor
under normal conditions. Therefore, now it is evident that N
is a primary cause of eutrophication in many coastal ecosystems (Paerl et al. 2003).
17.2 The Global Scenario
Most of the countries of the world have now realized the
serious threat posed by eutrophication. The water bodies of
countries such as India, China, Bangladesh, Pakistan, Indonesia, Switzerland, Poland, Austria, Denmark, Croatia, Ireland, France, Greece, Estonia, Russia, Italy, Turkey, Japan,
and the great lakes states of the USA and Canada are under
the direct threat of eutrophication (Ansari 2005). In the midtwentieth century, eutrophication had been recognized as one
of the causative factors of pollution in European and North
American lakes and reservoirs. Since then, it has become
more widespread and surveys showed that 54 % of lakes in
Asia, 53 % in Europe, 48 % in North America, 41 % in South
America, and 28 % in Africa are in eutrophic state (Colin
et al. 2007). In Spain 80 % of the lakes, 70 % of the reservoirs and 60 % river sites were eutrophic in the 1990s with
hypertrophy increasing downstream (Alvarez-Cobelas et al.
2001).
A number of lakes and water reservoirs in China are in
eutrophic state. The main pollution indicators of these lakes
were TN (total nitrogen) and TP (total phosphorus ) as recorded by China lake database, CAS Nanjing Institute of
Geography and Limnology, searched in April 2009 (CAS
2009). Eutrophication has become a threat to floral and faunal diversity in the coastal areas that are receiving direct
input of nutrients from some of the major rivers like the Amazon, Nile, Ganges, Mississippi, Brahmaputra, and Thames.
(Khan and Ansari 2005).
17.3 Aquatic Plant Diversity in Eutrophic
Ecosystems
Eutrophication causes undesirable changes in species composition of an aquatic ecosystem (Romermann et al. 2008).
Acidification and eutrophication have been identified as
the two major threats to the survival of aquatic ecosystems
which are also causing potentially severe changes to plant
diversity (Murphy et al. 2003). The plant species play a vital
role in the functioning of soft water lake ecosystems. Lake
area, altitude, trophic state, and water quality have been
found directly related with the macrophyte species richness.
The global changes in the plant diversity of soft water lake in
northern Europe are potentially severe (Murphy 2002).
An aquatic system takes thousands of years to become
eutrophic which is a natural process. However, a high rate of
input of nutrients because of anthropogenic activities significantly enhance the condition in a very short period of time.
This is called an artificial eutrophication. The high-nutrient
concentrations enhance the excessive growth of phytoplankton and macrophytes in aquatic ecosystem (Rovira and Pardo
2006). Eutrophication causes an increase in plant and animal
biomass, frequency of algal blooms, growth of rooted plants
and decreases the species diversity which further results in
high degree of competition. The high chemical or physical
stress also enhance the struggle for survival in eutrophic systems. As a result the diversity of organisms declines in eutrophic than in oligotrophic systems (Ansari 2005).
A. A. Ansari et al.
2011a; OECD 1982; Henderson-Sellers and Markland 1987;
Ryding and Rast 1989; Harper 1992; Thornton et al. 1999).
It is now evident that the nutrients are primarily responsible for limiting productivity in lakes and rivers, which are
well-known as the limiting nutrient controversy (Likens
1972). Scientists working on fresh waters have mainly concentrated on phosphorus as a key element in controlling eutrophication. The consequences of cultural eutrophication
caused by excessive inputs of phosphorus and nitrogen are:
• Increase in biomass of phytoplankton and macrophytes
• Domination of algal bloom forming species which is
toxic to consumers of eutrophic ecosystem
• Change in species composition of macrophyte vegetation
and increase in biomass of consumer species owing to
increase of biomass of benthic and epiphytic algae
• Frequent fish kills
• Decline in species diversity of aquatic ecosystem
• Decrease in harvestable fish biomass
• Decrease in water transparency
• Anoxic conditions in the aquatic ecosystem
• Problems related to the quality of water and its aesthetic
value
The empirical models describe the declining inlake concentrations of chemical elements; especially phosphorus which
results in reoligotrophication (Jeppesen et al. 2005; Jensen
et al. 2006). The water bodies can be divided into various
trophic levels such as autotrophic, nutrient-regulated heterotrophic, and external carbon-controlled state. The autotrophic state in flowing waters depends mainly on phosphorus
and nitrogen levels. Algal biomass is positively correlated
to gross primary production in streams and rivers (Dodds
2006).
In addition to increasing scientific knowledge, answers to
the questions related to eutrophication can influence strategies for ecosystem restoration or rehabilitation (Hecky 2009).
Initially, P and C has drawn the attention of limnologists and
ecologists as primary causes of eutrophication. However,
now it is proved that N also contributes in increasing eutrophication especially in estuaries where it is a limiting factor
under normal conditions. Therefore, now it is evident that N
is a primary cause of eutrophication in many coastal ecosystems (Paerl et al. 2003).
17.2 The Global Scenario
Most of the countries of the world have now realized the
serious threat posed by eutrophication. The water bodies of
countries such as India, China, Bangladesh, Pakistan, Indonesia, Switzerland, Poland, Austria, Denmark, Croatia, Ireland, France, Greece, Estonia, Russia, Italy, Turkey, Japan,
and the great lakes states of the USA and Canada are under
the direct threat of eutrophication (Ansari 2005). In the midtwentieth century, eutrophication had been recognized as one
of the causative factors of pollution in European and North
American lakes and reservoirs. Since then, it has become
more widespread and surveys showed that 54 % of lakes in
Asia, 53 % in Europe, 48 % in North America, 41 % in South
America, and 28 % in Africa are in eutrophic state (Colin
et al. 2007). In Spain 80 % of the lakes, 70 % of the reservoirs and 60 % river sites were eutrophic in the 1990s with
hypertrophy increasing downstream (Alvarez-Cobelas et al.
2001).
A number of lakes and water reservoirs in China are in
eutrophic state. The main pollution indicators of these lakes
were TN (total nitrogen) and TP (total phosphorus ) as recorded by China lake database, CAS Nanjing Institute of
Geography and Limnology, searched in April 2009 (CAS
2009). Eutrophication has become a threat to floral and faunal diversity in the coastal areas that are receiving direct
input of nutrients from some of the major rivers like the Amazon, Nile, Ganges, Mississippi, Brahmaputra, and Thames.
(Khan and Ansari 2005).
17.3 Aquatic Plant Diversity in Eutrophic
Ecosystems
Eutrophication causes undesirable changes in species composition of an aquatic ecosystem (Romermann et al. 2008).
Acidification and eutrophication have been identified as
the two major threats to the survival of aquatic ecosystems
which are also causing potentially severe changes to plant
diversity (Murphy et al. 2003). The plant species play a vital
role in the functioning of soft water lake ecosystems. Lake
area, altitude, trophic state, and water quality have been
found directly related with the macrophyte species richness.
The global changes in the plant diversity of soft water lake in
northern Europe are potentially severe (Murphy 2002).
An aquatic system takes thousands of years to become
eutrophic which is a natural process. However, a high rate of
input of nutrients because of anthropogenic activities significantly enhance the condition in a very short period of time.
This is called an artificial eutrophication. The high-nutrient
concentrations enhance the excessive growth of phytoplankton and macrophytes in aquatic ecosystem (Rovira and Pardo
2006). Eutrophication causes an increase in plant and animal
biomass, frequency of algal blooms, growth of rooted plants
and decreases the species diversity which further results in
high degree of competition. The high chemical or physical
stress also enhance the struggle for survival in eutrophic systems. As a result the diversity of organisms declines in eutrophic than in oligotrophic systems (Ansari 2005).