Ecosystem

Morphometry

BASIN DATA
Surface elevation:	1,657 m (5435 ft)
Lake surface area:	0.20 km2
Basin surface area:	0.81 km2
Ratio of drainage to lake surface area:	4.0
Maximum depth:	35 m
Average depth:	11.4 m
Lake volume:	2.29 x 106 m3
Shoreline development: (Ratio of shoreline distance to the circumference of circle with the same surface area)	1.36
Trophic status:	meso-oligotrophic

Basin

Castle Lake lies within a low lying basin that collects the runoff and groundwater and incorporates that water into the lake. As such, lakes are affected by features of the basin they are in. The part of the basin filled by water is called the lake basin. The shape of the lake basin affects its volume, area, depth, and the extent of different habitats, as well as the formation of currents and the thermocline. The type of bedrock, surrounding vegetation, and soils in the basin affect the amount and type of nutrients that reach the lake. The granite rocks around Castle Lake have little nutrients in terms of Nitrogen and Phospherous. Most of the Nitrogen that enters the lake is from the leaves of nearby alder trees and other vegetation. Phospherous also comes from terrestrial runoff, as phospherous is binded into the soil.

Climate

While there is interannual variation, Castle Lake enjoys four distinct seasons of the year. The influence of the climate on the processes occuring at Castle Lake is great. Please consult the references at the bottom of this page for further study.

Spring and Fall Mixing

In the fall and spring, "overturns" occur which equalize the temperature of the water in the lake. This mixing of the water temperatures brings up essential nutrients that accumulate at the bottom of the lake. This often initiates "blooms" of phytoplankton which stimulate productivity in the whole lake.

Summer Stratification

Castle Lake. During the summer, a phenomenon known as thermal stratification occurs in lakes. Sunlight heats the top of the lake, forming a layer of warm water over a cooler zone. These warm and cold zones are separated by a zone of mixed water where there is a sharp decline in temperature. Summertime swimmers often experience these temperature layers as their feet hit the sudden cool waters.

Winter Icecover

Castle Lake frozen in the early spring. With the onset of winter and continuous nights of 0° C temperatures, Castle Lake begins to freeze. Unlike other liquids which are heavier at 0° C, water is heaviest at 4° C. Therefore the bottom of the lake contains water at 4° C while colder water is layered above. This prevents Castle Lake from freezing all the way to the bottom and allows life to remain in the lake throughout the winter. When the ice is solid on Castle Lake, there are also opportunities for great ice skating or ice fishing.

Thermocline & Stratification

This is the zone in the lake where temperature changes most rapidly with depth. Since solar heating from above is typically the dominant heat source, lakes gain heat from their surface layers. If a temperate lake is deep enough, the deeper waters never warm up and stay at a consistant 4° C (water is most dense at 4° C) all year round. Castle Lake is such a lake.

During the winter the lake is covered with ice, which begins to melt in spring. Once the weather warms up and the sun begins to warm the surface layers, the entire lake becomes the same temperature at 4° C. When heating gets more intense, the warmer surface layers (less dense) float on top of the colder more dense layers. By late summer the surface waters reach 25° C, but at 10 M deep the water is only 10° C. The thermocline varies between 5 and 7 M deep during the summer. Having such a strong temperature (and density) gradient prevents water layers of different density to mix. In other words, the thermocline traps the lighter, warmer water on top of the heavier, colder water. Strong wind waves can shift the depth and gradient of the thermocline, but the main thermocline remains until fall. When sunlight decreases and the air gets colder, surface waters begin to cool and sink. This eventually destroys the thermocline and the lake mixes from bottom-up to reach a constant 4° C. Further cooling forms ice on the lake, which floats during winter. Lake mixing is critical for algal growth because nutrients vital to algae tend to sink to the deeper layers. Nutrients are mostly trapped in the deep layers during summer, while maximum solar energy, also vital for algae, is at the surface. This causes algae to be nutrient limited until the lake mixes and nutrients previously trapped in deep waters are delivered to the surface. The combination of adequate nutrients and sunlight make the algae bloom during this mixing events.

Climate References

• Goldman, C. R. and E. de Amezaga. 1984. Primary productivity and precipitation at Castle Lake and Lake Tahoe during twenty-four years, 1959-1982. Verh. Int. Ver. Theor. Angew. 22: 591-599.
• Goldman, C. R., A. Jassby and T. Powell. 1989. Interannual fluctuations in primary production: Meteorological forcing at two subalpine lakes. Limnol. Oceanogr. 34:310-323.
• Jassby, A. D., T. M. Powell and C. R. Goldman. 1990. Interannual fluctuations in primary production: Direct physical effects and the trophic cascade at Castle Lake, California. Limnol. Oceanogr. 35:1021-1038.

Benthic Invertibrates

Overview

Historically, limnology has focused primarily on the open water or Pelagic portion of lakes. However, the bottom or benthic region of lakes is also bustling with life. Recently, new emphasis has been placed on the study of benthic organisms and the way they interact with and affect the rest of the aquatic ecosystem.

The term benthic invertebrate encompasses a large group of organisms. At Castle Lake this group includes crayfish, bottom dwelling zooplankton, chironimid larvae, and the aquatic larval phase of insects such as caddis flies, stone flies, dragon flies and damsel flies.

In the spring the midge fly makes up a large part of the insect population in Castle Lake. Their main source of food is algae. In the larval stage the midge fly burrows in the silt at the bottom of the lake where it is often found by the fish. As the midge matures it floats to the surface, where it is vulnerable to fish predation. Once the adult midge fly is free of the larval case it flies away to reproduce.

Species List

Insects

Odonata
Dragonflies
Damselflies

Trichoptera
Caddisflies (Oecetis inconspicua)

Ephemeroptera
Mayflies - several spp.
Diptera - many spp. in Chironomide

Other Invertebrates

Decapoda
Pacific Crayfish (Pacifastacus leniusculus)
Cladocera (Alona guttata)

Mollusca
Pill Clam (Psidium sp.)

Cnidaria
Green Hydra
Porifera
Green Sponge

Sediment References

• Beatty, K. W. 1968. An Ecological Study of the Benthos of Castle Lake, California. Ph.D., University of California Davis.
• Carlton, R. G. 1984. Forms and distribution of carbon in sediments of Castle Lake (California, U.S.A.). pp. 578-582
• Hagley, C. A. 1988. Seasonal and spatial biomass variation of the submerged macrophyte, Isoetes occidentalis, in a subalpine lake. Verh. Internat. Verein. Limnol. 23:1920-1926.
• Kimmel, B. L. 1978. An Evaluation of Recent Sediment Focusing in Castle Lake (California) Using a Volcanic Ash Layer as a Stratigraphic Marker. Verh. Int. Ver. Theor. Angew. Limnol. 20:393-400.
• Kimmel, B. L. and C. R. Goldman. 1977. Production, sedimentation and
  accumulation of particulate carbon and nitrogen in a sheltered subalpine lake, p. 148-154. In H. L. Golterman [eds.], Interactions between sediments and fresh water.
• Marzolf, Erich R. 1991. The Mechanisms of Benthic Nutrient Release
  and its importance to subalpine Castle Lake, CA. Ph. D. Thesis, University of California Davis.
• Neame, P. A. 1975. Benthic oxygen and phosphorus dynamics in Castle
  Lake, California. Ph. D. Thesis, University of California-Davis.
• Neame, P. A. and C. R. Goldman. 1980. Oxygen uptake and production in sediment-water microcosms. U.S. Dept of Energy. 267-278.
• Paulsen, S. G. 1987. Contributions of sediment denitrification to the nitrogen cycle in Castle Lake, California. Ph.D., University of California Davis.
• Reuter, J. E., S. L. Loeb, R. P. Axler, R. G. Carlton and C. R. Goldman. 1985. Transformations of nitrogen following an epilimnetic nitrogen fertilization in Castle Lake, CA: 1. Epilithic periphyton responses. Arch. Hydrobiol. 102:425-433.
• Sanders, F. S. 1976. An investigation of carbon flux in the sediments of Castle Lake, California. Ph.D., Univ. California Davis.

Birds

Overview

The osprey, feeding entirely on fish, can often be seen in the spring and summer around Castle Lake. This beautiful hawk nests on the top of dead trees near lakes and streams. It catches fish by hovering, then plunging talons first into the water, catching its prey, then flying back to its nest to feed its young.

Partial Species List

Raptors

Osprey (Pandion haliaetus)
Bald Eagle (Haliaectus leucoephalus)
Golden Eagle (Aquila chrysaetos)
Turkey Vulture (Cathartes aura)
Peregrine Falcon (Falco peregrinus)
Kestrel (Falco sparverius)
Merlin (Falco columbarius)

Water Birds

Wood Duck (Aix sponsa)
Belted Kingfisher (Megaceryle alcyon)

Other

Brown Creeper (Certhia familiaris)
Steller's Jay (Cyanocitta stellere)
Blue Grouse (Dendragapus obscurus)

Fish

Overview

Castle Lake contains three types of fish--the Golden Shiner, the Brook Char (Brook Trout), and the Rainbow Trout. The Golden Shiner is a minnow that was introduced into the lake by anglers who were using them as bait and left their remaining bait in the lake. The Brook Char was originally stocked by the Department of Fish and Game and now reproduces naturally in the springs on the east side of the lake. The Rainbow Trout is stocked annually by the Department of Fish and Game for sport fishing.

The Golden Shiners and other young fish spend the daylight hours in the shallow areas of the lake among logs and other obstructions hiding from the larger predatory fish and birds. In the evening these fish move into the open lake to feed on zooplankton.

During the spring Rainbow Trout and Brook Char feed mainly on insects like the Midge Fly. In the summer when the surface temperatures are too warm for these trout, they go deeper to feed mainly on zooplankton.

This explains why anglers are usually more successful during the spring and fall when surface temperatures are lower than in the summer. The most successful fishing strategy during the summer is trolling 15 to 20 feet deep where the lake is cooler.

Species List

Rainbow Trout (Oncorhynchus mykiss)
Brook Char (Salvelinus fontinalis)
Golden Shiner (Notemigonus crysoliecas)

Fish References

• Cordone, A. J. and S. J. Nicola. 1970. Influence of molybdenum on the
  trout and trout fishing of Castle Lake. Calif. Fish and Game.
  56:96-108.
• Swift, M. C. 1970. A qualitative and quantitative study for trout food in Castle Lake, California. Calif. Fish and Game. 56:109-120.
• Wales, J. H. 1946. Castle Lake trout investigation: First Phase: Interrelationships of four species. Calif. Fish and Game. 32:109-143.
• Wurtsbaugh, W. A., R. W. Brocksen and C. R. Goldman. 1975. Food and distribution of underyearling brook and rainbow trout in Castle Lake, California. Trans. Am. Fish. Soc. 104:88-95.

Flora

Overview

Algae needs more than sunlight to grow. The mountain alders on the southeast side of Castle Lake help to provide the algae with the essential nutrient nitrogen for their growth. All species of alder have the unique ability to convert nitrogen from the atmosphere into the soil. From the soil, the nitrogen is then filtered into the water which feeds the algae.

Partial Species List

Trees

Ponderosa Pine (Pinus ponderosa)
Red Fir (Abies Magnifica)
White Fir (Abies Concolor)
Lodgepole Pine (Pinus Contorda)
Incense Cedar (Libocedrus decurrens)
Alder

Plants & Bushes

Green Manzanita (Arctostaphylos patula)
Dwarf Mountain Manzanita (Arctostaphylos neuadensis)
Tan Oak (Lithocarpus densiflorus)
Pitcher Plants (Darlingtonia californica)

Flowering Plants

Wood Rose (Rosa gymnocarpa)
Shasta Lupine (Lupinus albicaulis)
Red/Crimson/Scarlet Columbine (Aquilegia truncata)
Tiger Lily (Lilium pardalinum)
Pine-drops (Pterospora andromedae)
Douglas Spiraea (Spiraea douglasii)
Scarlet Paintbrush (Castilleja pinetorum)
Alpine Paintbrush (Castilleja arachnoidea)
Dwarf Paintbrush (Castilleja miniata)
Alpine Saxifrage (Saxifraga nidifica)
Shasta Pentstemons (Pentstemon laetus)
Alpine Buckwheat (Eriogonum pyrolaefolium)
Tofield's Swamp Lily (Tofieldia occidentalis)

Mammals

Partial Species List

Black Bear (Ursus americanus)
Mountain Lion (Felis concolor)
Blacktail Deer (Odocoileus hemionus)
Bobcat (Lynx rufus)
Pine Marten (Martes americana)
River Otter (Lutra canadensis)
Western Grey Squirrel (Sciurus griseus)
Chipmonk (Eutamias)
Black-tailed Jackrabbit(Lepus californicus)

Reptiles & Amphibians

Partial Species List

Snakes

Garter Snake (Thamnophis sirtalis)
Rubber Boa (Charina bottae)
Ring-necked Snake (Diadophis punctatus)
Rattlesnake ( Crotalus viridis)

Amphibians

Rough-skin Newt (Taricha granulosa)
Cascade Frog (Rana cascadae)

Zooplankton

Overview

Zooplankton are the microscopic animals that are adapted to life in the open water. Most zooplankton are about 0.5 to 1 mm in length--just a dot to the human eye, but under a microscope they resemble tiny shrimp, a relative to zooplankton. Some are herbivorous, eating algae, or predaceous, eating other zooplankton.

Species List

Cladocera

Daphnia rosea
Holopedium gibberum
Bosmina longirostris
Daphnia middendorfiana
Polyphemus pediculus

Copepods

Diaptomus novamexicanus
Diaptomus kenai
Tropocyclops prasinus
Macrocyclops albidus

Rotifers

Asplanchna girodi
Collotheca mutablis
Conochilus unicornis
Filinia terminalis
Gastropus stylifer
Synchaeta pectinata
Polyarthra
Keratella

Zooplankton References

• Axler, R. P., G. W. Redfield and C. R. Goldman. 1981. The Importance of Regenerated Nitrogen to Phytoplankton Productivity in a Subalpine Lake. Ecology. 62:345-354.
• Carlson, J. S. 1968. Primary productivity and population dynamics of zooplankton in Castle Lake, California. Ph.D. Thesis, University of California.
• Hoenicke, R. 1984. The effects of a fungal infection of Diaptomus novamexicanus eggs on the zooplankton community structure of Castle Lake, California. Verh. Int. Ver. Theor. Angew. Limnol. 22: 573-577.
• Janik, J. J. 1988. Nutrient cycling in Castle Lake California: phytoplankton-zooplankton interactions. Ph. D. Thesis, University of California-Davis.
• Redfield, G. W. 1979. Temporal variation in diel vertical migration and the ecology of zooplankton in Castle Lake, California. Ph.D. Thesis, University of California-Davis.
• Redfield, G. W. 1980. The effect of zooplankton on phytoplankton productivity in the epilimnion of a subalpine lake. Hydrobiologia. 70:217-224.
• Redfield, G. W. and C. R. Goldman. 1978. Diel Vertical Migration and Dynamics of Zooplankton Biomass in the Epilimnion of Castle Lake, California. Verh. Int. Ver. Theor. Angew. Limnol. 20: 381-387.