19
2 Eutrophication: Global Scenario and Local Threat to Dynamics of Aquatic Ecosystems
trolled growth of primary producers which depletes oxygen owing to decomposition of algal organic matter. The
phosphorous content of eutrophic lakes is between 30 and
100 µg/L and above 100 µg/L phosphorous content is typical
of hypereutrophic lakes (Wetzel 2001).
Irradiance and water temperature in summer limited the
growth of phytoplanktons in Dokoi Bay of Japan (Morishita
et al. 2001). The Hiroshima Bay and Suo Nada of Seto Inland Japanese Sea had significant variation in microbial
communities in spring and autumn and corresponded to seasonal changes in sediment parameters (Rajendran and Nagatomo 1999). Two seasonal peaks of the microzooplankton
populations, one in the month between late spring and early
summer and the other in the autumn season were recorded in
highly eutrophic Tokyo Bay of Japan (Nomura et al. 1992).
High primary production led to high concentration of particulate phosphorus in surface water of Tokyo Bay which later
settled in deeper layers and released orthophosphate on decomposition. This orthophosphate was occasionally advected upwards by wind-induced water mixing and again promoted the phytoplankton growth in upper layers. Increased
phosphorus in summer was attributable to increased input
from river waters and release of orthophosphate from anoxic
sediments (Miyata and Hattori 1986). The phytoplankton
standing crop had a high correlation with nutrient loading in
three experimental ponds in Japan. The relationship between
total phosphorus and chlorophyll-a varied seasonally showing highest correlation in autumn (Aizak et al. 1986). The
continuous input of nutrients from the rivers at their confluence with Kasumigaura Lake (Japan) increased algal primary productivity. The particulate matter varied seasonally and
maintained higher concentration in Takahamairi Bay than in
Tsuchiurairi Bay of the Lake (Ebise 1998).
During wet season, excessive input of organic waste in
Karawang, West Jawa increased chlorophyll-a concentration
(Sachoemar and Yanagi 1999). The phytoplankton biomass
and water quality were influenced by rainfall in Pyeongtaek
Reservoir of South Korea (Shin 2003). In Austrian part of
River Danube, the concentrations of some nutrients were
minimum in summer and maximum in winter (Weilguni and
Humpesch 1999). A succession of phytoplankton dominant
turbid water from macrophyte dominant clear water state in
eutrophic back water of river Denube was recorded between
1992 and 1994 (Kirschner et al. 1999).
In shallow eutrophic Doirani Lake (Denmark), small diatoms (r-species) dominant in the early stage, were replaced
by Microcystis, Anabaena and Cerratium (s-species) in summer. Thermal fluctuation and small depth mixing increased
sediment-water interaction and altered nutrient concentration (Temponeras et al. 2000). The hydrological conditions
in hot season caused eutrophication leading to enhanced
algal growth and reduced floral vitality in nutrient-rich degraded reef in France (Naim 1993). The algal growth, rainfall and winds led to nutrient fluctuations over space and
time in Messolonghi Lagoon of Greece (Friligos 1989). The
wind in shallow lakes played a significant role in seasonal
succession (Padisak 1980).
The long-term studies of nutrient patterns in Kentucky
Lake (USA) revealed that the seasonal variations in nutrient
discharge were more pronounced than the actual variation in
the reservoir with regulated discharge. Greater variations in
nutrient concentrations were found on eastern forested side
of the reservoir than on the western agriculturally dominant
embayment. The annual average of nutrient pattern did not
change and eventually had no impact on the eutrophication
potential during study period from 1989 to 1998 (Yurista
et al. 2004).
2.3 Impact of Fertilizers
Phosphorus and nitrogen inputs owing to excessive use in
agricultural practices, their cycling in the water bodies and
seasonal variability (of temperature, water level, depth, irradiance and winds) are the main causes of eutrophication
(Khan and Ansari 2005). The use of fertilizers in agriculture
has increased several folds during the past 40 years in India
(Anonymous1998, 2002). Several brands of chemical fertilizers containing micro and macro nutrients are being excessively used in addition to compost for optimum crop productivity (Fixen and West 2002). The P-PO 4 concentration
greater than 0.1 µg L
−1
caused eutrophication in three Gorge
Reservoirs of China. Nitrogen and phosphorus runoff from
agricultural, municipal and industrial effluents increased nutrient input in water (Liu et al. 2004).
2.3.1 Impact of Nitrogen
Commercial nitrogen fertilizers (81.7 million MT) account
for approximately half of all nitrogen (N) used in croplands
on a global scale. Current N-efficiency and crop productivity are lower in several parts of Asia than in North America
(Fixen and West 2002). The application of chemical fertilizer
per unit area of farmland in Japan peaked in 1985 (Mishima
2001). Phosphorus and nitrogen in runoff from agricultural
fields are key components of non-point source pollution of
water bodies and can accelerate eutrophication of surface
waters (Zheng et al. 2004). The main source of nitrogen in
underground water of Europe is leaching from agricultural
fields. High nitrogen inputs in the marine environment cause
eutrophication and thus increase algal growth, change biological communities and deoxygenate water (Iverson et al.
1998). Nitrates from fertilizers account for nearly 50 % of
the surface water acidification in watershed. Non-point
source pollution of surface water by nitrate from agricultural
activities is a major environmental problem (Steinheimer
et al. 1998). Biological transformations of N added to ponds
2 Eutrophication: Global Scenario and Local Threat to Dynamics of Aquatic Ecosystems
trolled growth of primary producers which depletes oxygen owing to decomposition of algal organic matter. The
phosphorous content of eutrophic lakes is between 30 and
100 µg/L and above 100 µg/L phosphorous content is typical
of hypereutrophic lakes (Wetzel 2001).
Irradiance and water temperature in summer limited the
growth of phytoplanktons in Dokoi Bay of Japan (Morishita
et al. 2001). The Hiroshima Bay and Suo Nada of Seto Inland Japanese Sea had significant variation in microbial
communities in spring and autumn and corresponded to seasonal changes in sediment parameters (Rajendran and Nagatomo 1999). Two seasonal peaks of the microzooplankton
populations, one in the month between late spring and early
summer and the other in the autumn season were recorded in
highly eutrophic Tokyo Bay of Japan (Nomura et al. 1992).
High primary production led to high concentration of particulate phosphorus in surface water of Tokyo Bay which later
settled in deeper layers and released orthophosphate on decomposition. This orthophosphate was occasionally advected upwards by wind-induced water mixing and again promoted the phytoplankton growth in upper layers. Increased
phosphorus in summer was attributable to increased input
from river waters and release of orthophosphate from anoxic
sediments (Miyata and Hattori 1986). The phytoplankton
standing crop had a high correlation with nutrient loading in
three experimental ponds in Japan. The relationship between
total phosphorus and chlorophyll-a varied seasonally showing highest correlation in autumn (Aizak et al. 1986). The
continuous input of nutrients from the rivers at their confluence with Kasumigaura Lake (Japan) increased algal primary productivity. The particulate matter varied seasonally and
maintained higher concentration in Takahamairi Bay than in
Tsuchiurairi Bay of the Lake (Ebise 1998).
During wet season, excessive input of organic waste in
Karawang, West Jawa increased chlorophyll-a concentration
(Sachoemar and Yanagi 1999). The phytoplankton biomass
and water quality were influenced by rainfall in Pyeongtaek
Reservoir of South Korea (Shin 2003). In Austrian part of
River Danube, the concentrations of some nutrients were
minimum in summer and maximum in winter (Weilguni and
Humpesch 1999). A succession of phytoplankton dominant
turbid water from macrophyte dominant clear water state in
eutrophic back water of river Denube was recorded between
1992 and 1994 (Kirschner et al. 1999).
In shallow eutrophic Doirani Lake (Denmark), small diatoms (r-species) dominant in the early stage, were replaced
by Microcystis, Anabaena and Cerratium (s-species) in summer. Thermal fluctuation and small depth mixing increased
sediment-water interaction and altered nutrient concentration (Temponeras et al. 2000). The hydrological conditions
in hot season caused eutrophication leading to enhanced
algal growth and reduced floral vitality in nutrient-rich degraded reef in France (Naim 1993). The algal growth, rainfall and winds led to nutrient fluctuations over space and
time in Messolonghi Lagoon of Greece (Friligos 1989). The
wind in shallow lakes played a significant role in seasonal
succession (Padisak 1980).
The long-term studies of nutrient patterns in Kentucky
Lake (USA) revealed that the seasonal variations in nutrient
discharge were more pronounced than the actual variation in
the reservoir with regulated discharge. Greater variations in
nutrient concentrations were found on eastern forested side
of the reservoir than on the western agriculturally dominant
embayment. The annual average of nutrient pattern did not
change and eventually had no impact on the eutrophication
potential during study period from 1989 to 1998 (Yurista
et al. 2004).
2.3 Impact of Fertilizers
Phosphorus and nitrogen inputs owing to excessive use in
agricultural practices, their cycling in the water bodies and
seasonal variability (of temperature, water level, depth, irradiance and winds) are the main causes of eutrophication
(Khan and Ansari 2005). The use of fertilizers in agriculture
has increased several folds during the past 40 years in India
(Anonymous1998, 2002). Several brands of chemical fertilizers containing micro and macro nutrients are being excessively used in addition to compost for optimum crop productivity (Fixen and West 2002). The P-PO 4 concentration
greater than 0.1 µg L
−1
caused eutrophication in three Gorge
Reservoirs of China. Nitrogen and phosphorus runoff from
agricultural, municipal and industrial effluents increased nutrient input in water (Liu et al. 2004).
2.3.1 Impact of Nitrogen
Commercial nitrogen fertilizers (81.7 million MT) account
for approximately half of all nitrogen (N) used in croplands
on a global scale. Current N-efficiency and crop productivity are lower in several parts of Asia than in North America
(Fixen and West 2002). The application of chemical fertilizer
per unit area of farmland in Japan peaked in 1985 (Mishima
2001). Phosphorus and nitrogen in runoff from agricultural
fields are key components of non-point source pollution of
water bodies and can accelerate eutrophication of surface
waters (Zheng et al. 2004). The main source of nitrogen in
underground water of Europe is leaching from agricultural
fields. High nitrogen inputs in the marine environment cause
eutrophication and thus increase algal growth, change biological communities and deoxygenate water (Iverson et al.
1998). Nitrates from fertilizers account for nearly 50 % of
the surface water acidification in watershed. Non-point
source pollution of surface water by nitrate from agricultural
activities is a major environmental problem (Steinheimer
et al. 1998). Biological transformations of N added to ponds