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Crater Lake
Captain Clarence Dutton was the
next man to make a discovery at
Crater Lake.
Dutton commanded a U.S.
Geological Survey party which
carried the Cleetwood, a half-ton
survey boat, up the steep slopes of
the mountain then lowered it to the
lake.
From the stern of the Cleetwood, a
piece of pipe on the end of a spool of
piano wire sounded the depth of the
lake at 168 different points.
Dutton's soundings of 1,996 feet were
amazingly close to the sonar readings
made in 1959 that established the
lake's deepest point at 1,932 feet.
Crater Lake
Ø It
is the deepest lake in the United States
Ø 7th deepest lake in the world
Ø Surface area of 53.2 km2
Ø Maximum depth of 589 m
Ø Mean depth of 325 m
Feature
Metric unit
Imperial unit
maximum depth (July 2000)
594 m
1,949 ft
maximum depth (Year 1959)
589 m
1,932 ft
average depth
457 m
1,500 ft
max diameter of caldera at the
rim
9.7 km (east-west)
6.02 mi (east-west)
min diameter of caldera at the
rim
7.3 km (north-south)
4.54 mi (north-south)
surface area
52.9 km2
20.42 mi2, 13,069 acres
record clarity depth (August
1994)
40.8 m
134 ft
average clarity depth
27.4-30.5 m
90-100 ft
Crater Lake
Ø Formed
by catastrophic collapse of the
sides of Mount Mazama following a violent
eruption about 6,800 years ago
Ø Present
caldera has steep walls and is
between 8 and 10 km in diameter
Lake Level
Ø
Lake level has exhibited considerable
long-term variation since the late 1890's.
Ø From 1910 to 1942 the lake dropped about
4 m in elevation, but returned to the 1910
level by the late 1950's.
Ø The lake fluctuated by 1 m above and
below a bench mark level of 1882 m
observed from 1958 to 1985.
Lake Level
Ø Between
1986 and 1994, the level
dropped to about 3.5 m below the longterm average elevation.
Ø Since then the lake has risen to nearly the
bench mark level.
Mixing
Ø The surface of Crater Lake seldom freezes
over, owing to the heat content of the
massive lake volume and wind mixing.
Ø In winter and spring the water mass in
Crater Lake circulates to a depth of
between 200 and 250 m by wind action
and cooling.
Mixing
Ø In
late spring or early summer the
temperature of the lake near the surface
increases and a thermocline forms
between July and September.
Ø The
depth of the epilimnion is between 5
m and 20 m.
Crater Lake
Ø
Ø
Ø
Ø
Orthograde nitrate-N depth profile
Low concentrations of nitrate-N in the epilimnion
The relatively high concentrations of total
phosphorus in Crater lake is in the range usually
associated with mesotrophic lakes.
Some of the chemical properties of Crater lake
do not conform to the entire range of criteria
usually associated with oligotrophic status
Crater Lake
Ø Changes
in the amount of chlorophyll and
primary production appear to be related to
deep-water mixing of the water column
during winter and spring.
Ø This upwelling phenomenon moves
nutrient-rich waters in the deep lake to the
upper 200 to 250 m of the water column.
Phytoplankton
Ø 157 phytoplankton taxa
Ø 55
diatoms
Ø 53 chrysophytes
Ø 1 xanthophyte
Ø 21 chlorophytes
Ø 12 dinoflagellates
Ø 6 cryptomonads
Ø 7 cyanobacteria,
Ø and 2 unknown taxa.
were identified
Phytoplankton
Ø In
winter the flora was uniformly distributed
to the depth of mixing.
Ø During
the period of thermal stratification,
phytoplankton are spatially segregated
within the water column to a depth of 200
m
Crater lake
Ø Nitzschia gracilis
was the dominant taxa in
the upper 40 m of the water column.
Ø Ankistrodesmus
spiralis, Dinobryon
sertularia, Tribonema sp., Rhodamonas
lacustris and Gymnodinium inversum were
the dominant taxa from 60 to 100 m.
Ø From
120 to 200 m the dominant taxa
were the same as during winter
Zooplankton
Ø During
periods of thermal stratification the
zooplankton were spatially segregated
within the water column
Zooplankton
Ø Polyarthra
was the dominant taxon in the
upper 40 m of the lake, but it occurred in
low density.
Ø Between
40 m and 80 the dominant taxa
were Bosmina, Polyarthra, Kellicottia and
Asplanchna.
Zooplankton
Ø From
80 to 120 m the dominant taxa were
Daphnia, Keratella, Synchaeta, Filinia and
Polyarthra
Ø The
dominant taxa from 120 to 200 m
were Philodina, Conochilus, Keratella and
Collotheca.
Crater Lake
Ø Daphnia abundances
appear linked with
periods of increased primary productivity
Ø Predation by kokanee salmon probably
impacts their abundance and may be the
reason for its reduced abundance in 1990
and disappearance in quantitative samples
by 1993
Crater Lake
Ø
Ø
Ø
Ø
Crater Lake was naturally barren of fish. Several
salmonid species were introduced into the lake
between 1888 and 1941.
Kokanee salmon and rainbow trout were the
only species of fish collected from the lake
between 1986 and 1999.
Kokanee salmon were cyclic in abundance.
Rainbow trout appeared to be less cyclic in
abundance than were kokanee salmon.
Crater Lake
Ø Kokanee salmon
primarily live in the
pelagic zone of the lake from the surface
to a depth of about 100 m.
Ø They prey on small emerging benthic
macroinvertebrate pupae and larvae and
terrestrial insects landing on the lake
surface.
Ø They also prey on Daphnia.
Crater Lake
Ø Rainbow
trout live in the nearshore area of
the lake.
Ø They prey on large bodied terrestrial
insects from the lake surface and benthic
macroinvertebrates.
Ø Rainbow trout also prey on kokanee
salmon.
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