Chapter 10 . Aigal Species Succession in Rivers
197
10.3
Materials and Methods
10.3.1
Data Collection and Analysis
Environmental and limnological parameters (Table 10.1) were measured over a
five-year period (1994-1998). Precipitation data were obtained from 5
representative meteorological stations (Andong, Daegu, Hapcheon, Jinju, and
Miryang) within the Nakdong River basin.
River flow data were obtained from the Flood Control Center. Irradiance and
evaporation data were collected from the Busan Local Meteorologieal Station,
which is closest to the river study site.
Weekly water sampies were collected at a depth of 0.5 m and the following
water quality parameters were measured: water temperature, Secchi transparency,
pH, turbidity, concentrations of dissolved oxygen (DO), nitrate (N0 3 --N),
ammonia (NH/-N), phosphate (P0 4
3 --P), dissolved silica (Si0 2 ), chlorophyll a
(chI. a), phytoplankton biovolume, and zooplankton abundance. Water
temperature and DO (mg L- 1 ) were determined with a YSI Model 58 meter; Secchi
transparencies were determined with a 20-cm disk; pH was measured with an
Orion Model 250A meter; and turbidity (NTU) was detected by Model 11052
Turbidimeter. Water sampies were filtered using 0.45 p.m Whatman GFfC glass
filters to determine nutrient concentrations. The filtrates were frozen and analyzed
by a QuikChem Automated Ion Analyzer (N0 3 --N, No. 10-107-04-1-0; NH/-N,
No. 10-107-06-1-B; P0 4
3 --P, No. 1O-115-01-1-B; Si0 2 , No. 1O-114-27-1-A).
Chlorophyll a concentrations were determined spectrophotometrically after
extraction, using methods described by Wetzel and Likens (1991).
Phytoplankton sampies were collected and immediately preserved with Lugol's
solution. Species were identified by means of a Nikon light microscope (xl,OOO)
and the fOllowing taxonomie references: Foged (1978), Cassie (1989), and Round
et aI. (1990). Phytoplankton was enumerated using an inverted mieroscope
(ZEISS, x400) by the sedimentation method after Utermöhl (1958). The
biovolume of individual species was estimated from mean cell dimensions and the
cellular shape of each species, according to Wetzel and Likens (1991). Mean cell
biovolumes were based on individual cell volume calculations of 10 to 25 cells.
Zooplankton was collected from a depth ofO.5 m using a 3.2 L Van Dorn water
sampier until a total of 8 L of water was obtained. Water sampies were filtered
through a 35-llm net, and the retained zooplankton was preserved with 10%
formalin (final concentration: 4%). Macrozooplankton (almost exclusively
Copepoda and Cladocera) was counted with an inverted microscope at x25-50
magnification. Microzooplankton (mostly Rotifera) was counted with an inverted
microscope at x100-400 magnification. Zooplankton taxa were identified to genus
197
10.3
Materials and Methods
10.3.1
Data Collection and Analysis
Environmental and limnological parameters (Table 10.1) were measured over a
five-year period (1994-1998). Precipitation data were obtained from 5
representative meteorological stations (Andong, Daegu, Hapcheon, Jinju, and
Miryang) within the Nakdong River basin.
River flow data were obtained from the Flood Control Center. Irradiance and
evaporation data were collected from the Busan Local Meteorologieal Station,
which is closest to the river study site.
Weekly water sampies were collected at a depth of 0.5 m and the following
water quality parameters were measured: water temperature, Secchi transparency,
pH, turbidity, concentrations of dissolved oxygen (DO), nitrate (N0 3 --N),
ammonia (NH/-N), phosphate (P0 4
3 --P), dissolved silica (Si0 2 ), chlorophyll a
(chI. a), phytoplankton biovolume, and zooplankton abundance. Water
temperature and DO (mg L- 1 ) were determined with a YSI Model 58 meter; Secchi
transparencies were determined with a 20-cm disk; pH was measured with an
Orion Model 250A meter; and turbidity (NTU) was detected by Model 11052
Turbidimeter. Water sampies were filtered using 0.45 p.m Whatman GFfC glass
filters to determine nutrient concentrations. The filtrates were frozen and analyzed
by a QuikChem Automated Ion Analyzer (N0 3 --N, No. 10-107-04-1-0; NH/-N,
No. 10-107-06-1-B; P0 4
3 --P, No. 1O-115-01-1-B; Si0 2 , No. 1O-114-27-1-A).
Chlorophyll a concentrations were determined spectrophotometrically after
extraction, using methods described by Wetzel and Likens (1991).
Phytoplankton sampies were collected and immediately preserved with Lugol's
solution. Species were identified by means of a Nikon light microscope (xl,OOO)
and the fOllowing taxonomie references: Foged (1978), Cassie (1989), and Round
et aI. (1990). Phytoplankton was enumerated using an inverted mieroscope
(ZEISS, x400) by the sedimentation method after Utermöhl (1958). The
biovolume of individual species was estimated from mean cell dimensions and the
cellular shape of each species, according to Wetzel and Likens (1991). Mean cell
biovolumes were based on individual cell volume calculations of 10 to 25 cells.
Zooplankton was collected from a depth ofO.5 m using a 3.2 L Van Dorn water
sampier until a total of 8 L of water was obtained. Water sampies were filtered
through a 35-llm net, and the retained zooplankton was preserved with 10%
formalin (final concentration: 4%). Macrozooplankton (almost exclusively
Copepoda and Cladocera) was counted with an inverted microscope at x25-50
magnification. Microzooplankton (mostly Rotifera) was counted with an inverted
microscope at x100-400 magnification. Zooplankton taxa were identified to genus