268
D. Soto and J .G . Stockner
Samples were analyzed using standard limnological methods that are
described in greater detail elsewhere (Soto et al. , 1993; Stockner &
Shortreed , 1985). Although there were some minor differences in laboratory protocol in chemical and biological analyses reported , they were not
of sufficient importance to account for any of the major differences
discussed here. Water samples were taken with a Van-Dorn bottle at
discrete depths within the epilimnion and hypolimnion. Nutrient samples
were analyzed within 24 h of collection and were kept cold prior to
analysis. Total nitrogen (TN) was obtained by summing values of all
inorganic and organic nitrogen analyses.
Chlorophyll a concentrations were obtained by extracting filtered
samples in 90% acetone and measuring absorbance with a Shimadzu UV150-02 spectrophotometer (Chilean lakes) or fluorescence with a Turner
Model 111 fluorometer (BC lakes) (Strickland & Parsons , 1968). Primary
productivity was estimated using the 14C sodium bicarbonate technique
and in situ light and dark bottle incubations over midday at 5 to 10
discrete depths within the euphotic zone (Strickland , 1960). Production
values were integrated over the euphotic zone and over the year based on
measurements from a 12 to 14 month sampling period in Chilean lakes
and from a 7 to 9 month sampling period in BC lakes.
Zooplankton from Chilean lakes were collected with a Ruttner net
(100-um mesh) using 0 to 100m vert ical tows and from BC lakes by a
SCOR-type net (lOO-um mesh) and 0 to 25 m or 0 to 50 m vertical tows
(Rankin, Ashton , & Kennedy, 1984). Zooplankton biomass from Chilean
lakes was estimated using length weight regression s of Dumont, Van de
Velde , Dumont (1975) and Culver , Bouchele, Bean , and Fletcher (1985).
Plankton samples from BC lakes were split and one half dried at 90°C for
24 h and weighted to determine zooplankton dry weights and biomass.
Results and Discussion
Climate, Hydrology
Chile is a long (17° to 56°S) and slender country lying between the Andes
Range to the east and the south Pacific Ocean to the west. Most lakes lie
within three regions: Araucanian , Patagonian, and Torres del Paine (38°
to 52°S) , whose major hydrogr aphic basins run from east to west. The
Province of British Columbia (48° to 60
0N)
, Canada, lies along the north
Pacific Ocean and extends eastward for> 1000km, a region of variable
climatic and biogeographic diversity (Farley , 1979). The greatest number
of lakes (but not the largest) lie in coastal regions, but there are numerou s
large , deep lakes on the vast interior regions east of the coast mountains
(Stockner, 1987, Figure 1).
The Chilean Araucanian study lakes include several large and deep
lakes that have large catchments and one majo r outlet flowing to the
D. Soto and J .G . Stockner
Samples were analyzed using standard limnological methods that are
described in greater detail elsewhere (Soto et al. , 1993; Stockner &
Shortreed , 1985). Although there were some minor differences in laboratory protocol in chemical and biological analyses reported , they were not
of sufficient importance to account for any of the major differences
discussed here. Water samples were taken with a Van-Dorn bottle at
discrete depths within the epilimnion and hypolimnion. Nutrient samples
were analyzed within 24 h of collection and were kept cold prior to
analysis. Total nitrogen (TN) was obtained by summing values of all
inorganic and organic nitrogen analyses.
Chlorophyll a concentrations were obtained by extracting filtered
samples in 90% acetone and measuring absorbance with a Shimadzu UV150-02 spectrophotometer (Chilean lakes) or fluorescence with a Turner
Model 111 fluorometer (BC lakes) (Strickland & Parsons , 1968). Primary
productivity was estimated using the 14C sodium bicarbonate technique
and in situ light and dark bottle incubations over midday at 5 to 10
discrete depths within the euphotic zone (Strickland , 1960). Production
values were integrated over the euphotic zone and over the year based on
measurements from a 12 to 14 month sampling period in Chilean lakes
and from a 7 to 9 month sampling period in BC lakes.
Zooplankton from Chilean lakes were collected with a Ruttner net
(100-um mesh) using 0 to 100m vert ical tows and from BC lakes by a
SCOR-type net (lOO-um mesh) and 0 to 25 m or 0 to 50 m vertical tows
(Rankin, Ashton , & Kennedy, 1984). Zooplankton biomass from Chilean
lakes was estimated using length weight regression s of Dumont, Van de
Velde , Dumont (1975) and Culver , Bouchele, Bean , and Fletcher (1985).
Plankton samples from BC lakes were split and one half dried at 90°C for
24 h and weighted to determine zooplankton dry weights and biomass.
Results and Discussion
Climate, Hydrology
Chile is a long (17° to 56°S) and slender country lying between the Andes
Range to the east and the south Pacific Ocean to the west. Most lakes lie
within three regions: Araucanian , Patagonian, and Torres del Paine (38°
to 52°S) , whose major hydrogr aphic basins run from east to west. The
Province of British Columbia (48° to 60
0N)
, Canada, lies along the north
Pacific Ocean and extends eastward for> 1000km, a region of variable
climatic and biogeographic diversity (Farley , 1979). The greatest number
of lakes (but not the largest) lie in coastal regions, but there are numerou s
large , deep lakes on the vast interior regions east of the coast mountains
(Stockner, 1987, Figure 1).
The Chilean Araucanian study lakes include several large and deep
lakes that have large catchments and one majo r outlet flowing to the