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The Chickadee's, Nicole Iversen |
Lakes
A lake is a low spot in the terrain that captures and holds water. Lakes are classified into different types based on the geologic nature of the basin. Several types include Glacial lakes, Tectonic lakes, Landslide lakes, Volcanic lakes, Fluviatile lakes, Shoreline lakes,
Solution basins, Resevoirs, Glacial Lakes: A glacial lake is created by an action of a glacier carving over bedrock and low spots become filled with water. Sierra Nevada is most abundant with these types of lakes, ex: Dollar Lake. Other lakes of glacial origin owe their existence to the moraine left behind when the glacier retreated. Ex: Big Pine lake
Tectonic Lakes: lie in basins formed by warping, folding, fracturing, and faulting of the earths crust. Fault block mountains of the Basin-Range Province alternate with valleys that may contain impounded water. This is known as horst-graben topography, a lake formed in such a basin is called a graben lake.Ex: Lake in Saline Valley.
Landslide Lake: Created by the movement of rock slides and mud flows. These lakes are often short-lived because the river , once impounded, overflows the dam, subsequent erosion carries away material, restoring the area to a river.
Volcanic Lakes: because volcanoes occur on a fault line, the combination of volcanic and tectonic activity cooperate to create a lake basin. Ex: Clear Lake, two arms of the lake lie in grabens, but water is impounded by a lava dam. Another kind of volcanic lake is a caldera, which results when the summit of a volcano collapses Ex: Crater Lake
Fluviatile Lakes: lie in depression caused by flowing water. When rivers flow over the flat gradients, the meander back and forth across a flood plain, which consistently change direction. Such lakes are present in the Great Central Valley Ex: Peter Slough, near the San Joaquin River.
Shoreline Lakes: are those impounded by barriers of sand. In California these occur within a mile of the ocean. The sand accumulates by the combined action of wind and water Ex: Nipomo dune, near Pismo Beach
Solution Basin: Some rocks are water-soluble. Pits and depressions may occur in granite where water-soluble minerals have been dissolved. In deserts these depressions catch rain water and provide an important water source for animals.
Resevoirs: are man-made bodies of water formed by damming rivers. True reservoirs are primarily for storing water, which is released at a later time for irrigation, drinking or industrial use. Some reservoirs are constructed for hydroelectric power. Nearly every river in California has been dammed. Ex: Grant Lake and Lake Thomas Edison
Streams
Flowing water may be characterized in several different ways, creek, river, brook.
Sometimes the appearance of the flow is used as a basis for comparing streams. Water that flows smoothly is said to be laminar, a situation that occurs in large rivers where the water flows slowly.
Another means of comparison is based on the rate of fall, a combination of speed and turbulence based on stream gradient. Water moves fastest when it flows straight down with out friction on the streambed. This is called a waterfall. Falling water directs a great deal of energy at the stream bottom
When large volumes of water are involved, discharge is often expressed in acre-feet per year. One acre-foot covers an acre to a depth of one foot Ex: The Mississippi River discharges 450million acre-feet per year.
Formation of Stream Channels
At upper elevations stream channels and valleys have a U-shaped bottom. As the waters flow toward lower elevation, they pass through the V-shaped river valleys. A river as it flows cuts a notch into its bed, as the notch becomes deeper, weathering, gravity, and side streams work to eliminate the steep walls of the notch.
A stream may be thought of as having the "goal" of flowing in a smooth arc from its headwater to its mouth. At its upper end, where less water is involved, the curve is steep. At its lower end, the curve flattens out. If an ideal curved is achieved the stream uses all its energy to carry sediment over a smooth bed.
Controlling rivers with dams and concrete channels disrupts the natural order of things. Without rejuvenation, soil is lost, not gained. Fertilizer must be applied artificially.
Aquatic Animals in Streams
In lakes and rivers, there are three sources of nutrients: photosynthesis, material carried by downflow n streams, and material from the land. An analysis of the relative importance of these three sources has indicated that most nutrients enter the system from the outside. Leaf litter and other debris washed off the land or dropped by tress represent the greatest amount of input in streams and lakes.
In stream ecosystems, the amount of organic material washed in is roughly equivalent to the amount washed out. As material is carried downstream in a river, however, the system becomes more productive
In lakes, attached and floating microorganisms play an important role. The contribution of photosynthesis increases in direct proportion to the nutritional state, or degree of eutrophication.
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Chapter 11: Inland Waters |
"Lakes are often classified into different types based on the geologic nature of the basin. Limnologists have recognized at least 11 categories." (p. 553).
Glacial Lakes
"The carving and scouring actions of a glacier as it passes over bedrock leaves behind an irregular terrain. Low spots that become filled with water are glacial lakes called tarns. One of the largest lakes in the Sierra Nevada, Thousand Island Lake, at the head of the San Joaquin River, is a huge but shallow tarn."(p. 553).
Tectonic Lakes
"Tectonic lakes lie in basins formed by warping, folding, fracturing and faulting of the earth's crust. Graben lakes are formed by a combination of uplift and subsidence, usually along a dip-slip fault." (p. 556) Lake Tahoe is a graben lake.
Landslide Lakes
"Many lakes throughout the world owe their existence to impoundment of stream valley by rock slides or mud flows. On the Kern River at the southern end of the Sierra Nevada are two landslides lakes, known as Kern and Little Kern lakes."(p. 558) Mirror Lake is a landslide lake.
Volcanic Lakes
"Volcanos often occur along faults, so it is not surprising that a combination of volcanic and tectonic activity might cooperate to create a lake basin."(p. 558). Clear Lake is a volcanic lake.
Fluviatile Lakes
"Fluviatile lakes lie in depressions caused by flowing water. When rivers flow over the gradients, they meander back and forth across a flood plain."(p. 560). Murphy Lake is a good example.
Shoreline Lakes
"Shoreline lakes are those impounded by barriers of sand. The sand accumulates by the combined action of wind and water. In the large Nipomo dune field near Guadalupe, south of Pismo Beach, there are several such bodies of fresh water. Flaco Lake is a popular example."(p. 560).
Solution Basins
"Some rocks are water-soluble. Pits and depressions may occur in granite where water-soluble minerals have become dissolved. Where limestone is the bedrock, water can create large cavities. In the Sierra Nevada, Boyden and Crystal caves are limestone caverns." (p.560).
Reservoirs
"Reservoirs are man-made bodies of water formed by damming rivers."(p.560). Many times they are created to generate electricity. Some examples are Lake Thomas Edison and Huntington Lake.
Water Quality
"Various characteristics of lake water may be measured as indicators of eutrophication."(p.563). Nutrient content is important to Aquatic biologists because the use it to measure what types of organisms live there. Also biomass and growth rates are estimated.
"Another indicator of eutrophication is the amount of photosynthesis that occurs in phytoplankton over some period of time. This is known as primary production."(p. 566). Artificial eutrophication can occur when nutrients such as nitrates and phosphates are added to a lake. This can be very harmful to the fish population.
Streams
"Terms such as river, creek or brook are based on relative size. Sometimes the appearance of the flow is used as a basis for comparing streams."(p.569).
Freshwater fish are the most common marine vertebrate and comprise three families:
Primary freshwater fish fall in three families:
minnows and suckers make up the bulk of state fish, as bass, bluegill, crappie, and catfish are all introduced game-fish species.
Minnows are the most widely distributed family, streamlined to live in fast running water; they are seriously localized. Speckeled Dace are the most widespread with downward facing mouths for bottom feeding on small invertebrates and snails. They live in rocky, and turbulent riffles, on the shores of Lake Tahoe, and desert springs.
Explanation for the wide distribution of minnow species, even across mountain ranges, is headwater stream capture. This is the summit of two drainages during heavy rainfall, eroding back into each other and mixing fish species.
native species are endangered by 50 introduced species, the largest:
Colorado Squawfish reach up to 5 feet long, 100 pounds, live in the lower colorado river, and are an endangered species
The next largest is the Sacramento Squawfish which reach up to 3 feet long
Both are carnivorous and from big river systems
They swim upstream to lay eggs, but do not die afterward
Dams on river systems have blocked spawning runs
Fish and Game is replenishing razorback suckers and colorado squawfish
Page 593, Figure 11.19 "A Natural history of california" by the UC Press, 1992
Primary Freshwater Fish:
Salmonidae
Cyprinidae
CATOSTOMIDAE
CENTRARCHIDAE
EMBIOTOCIDAE
CHUB DISPERSAL IS SO WIDESPREAD THAT IT IS HYPOTHESIZED THAT PLATE TECTONICS CAUSED THE ROTATION OF LAND MASSES SUCH AS THE TRANSVERSE MOUNTAINS AND THE KLAMATH MOUNTAINS.
EVIDENCE OF ROTATION LIES IN THE PRESENCE IN THE MAGNETIC LINES OF FORCE, CAPTURED IN THE VOLCANIC ROCKS DATING FROM THE MIOCENE PERIOD.
ANOTHER THEORY IS THAT OF HEADWATERS STREAM CAPTURE, WHERE THE LAND SHIFTS ALLOW SPECIES TO COLONIZE HYBRIDIZE IN ANOTHER AREA.
OWENS TUI CHUB AND THE MOHAVE TUI CHUB ARE CAUSED BY DEWATERING OF HABITAT AND THE HYBRIDATION WITH ARROYO TUI CHUB.
THE MOST BEAUTIFUL MINNOW IS THE LAHONTAN REDSIDE, A BRIGHT GOLD AND RED LINED MINNOW. THEY LIVE IN LAKE TAHOE AND SCHOOL IN LARGE GROUPS AND RUN AROUND 3 INCHES LONG, SPAWN IN SHALLOWS.
THE PLASTICITY OF GENETIC SYSTEMS IN THE COLORADO RIVER CONTAIN ROUNDTAIL CHUBS IN SLOW WATER, EXCEPT THE STREAMLINE IN FAST WATER.
BONYTAIL CHUB IS ENDANGERED IN THE COLORADO RIVER, THE ENLARGED HUMP HELPS THEM STAY ON THE BOTTOM,
THE RAZORBACKED AND BONYTAILED SUCKER IS ENDANGERED
INTRODUCED FISH SUCH AS THE THREADFINNED SHAD ARE SUPPLANTING THE NATIVE HITCH.
THE HARDHEAD IS THREATENED BY INTRODUCED INLAND SILVERSIDES, CARP, LAND GOLDFISH
SMALLER STREAMS SUCH AS SPECKLED DACE ARE BEING THREATENED BY RED SHINERS, GOLDEN SHINERS, AND FATHEAD MINNOWS.
THICKTAIL CHUB IS EXTINCT DUE TO DRAINING THEIR WETLANDS AND CHANNELING, THE SACRAMENTO BLACKFISH AND SPLITTAIL CHUB ARE THREATENED
SUCKERS ARE SECOND MOST COMMON IN CALIFORNIA, RELATED TO MINNOWS AND ARE BOTTOM FEEDERS
RAZORBACK SUCKER’S LARGEST IN THE COLORADO RIVER SYSTEM
THERE ARE 4 SUB-SPECIES THAT GO UP TO 18 INCHES
11 NATIVE SPECIES LIVE IN CALIFORNIA
TAHOE SUCKER
MOUNTAIN SUCKER FROM THE LAHONTAIN DRAINAGE, EAST SIDE
OWENS SUCKER FROM THE OWENS RIVER
SANTA ANA SUCKER FROM THE L.A. BASIN
MODOC SUCKER IS ENDANGERED
KLAMATH DRAINAGE
LOST RIVER SUCKER IS ENDANGERED
KLAMATH LARGESCALE SUCKER IS ENDANGERED
KLAMATH SMALLSCALE SUCKER IS ENDANGERED, (SMALLEST BUT MOST COMMON)
SUCKERS ARE GOOD TO EAT!!!
LAKE TAHOE TO PYRAMID LAKE, HONEY AND EAGLE LAKE ARE PART OF THE LAHONTAN DRAINAGE, LAKE LAHONTAN USED TO COVER MOST OF EASTERN NEVADA AND NORTH EASTERN CALIFORNIA
MOUNTAIN WHITEFISH IS LAHONTAN ONLY
LAHONTAN CUTTHROAT TROUT
LAKES OF THE HIGH SIERRA WERE FISHLESS, EXCEPT FOR LAKE TAHOE
COASTAL RAINBOW TROUT WERE DISCOVERED IN 1855 IN REDWOOD CREEK, IN THE EAST BAY HILLS. STEELHEAD LIVE IN SALT WATER, BUT SPAWN IN FRESH WATER
REDBAND TROUT ARE AN INLAND VERSION OF THE RAINBOW TROUT
GOLDEN TROUT IS THE STATE FRESHWATER FISH
1876, GOLD AND SILVER MINERS INTRODUCED TROUT TO STREAMS AND LAKES TO SUPPLY FISH FOR THE MINERS
1891, SAWMILLS PLANTED TROUT AT ELEVATIONS ABOVE 9,000 FEET IN WATER TEMPERATURES BELOW 70 DEGREES FAHRENHEIT
1894, LOCK LEVEN TROUT FROM SCOTLAND WERE PLANTED
1894, BROWN TROUT
1895, GERMAN BROWN TROUT
CHARS
1872, BROOK TROUT FROM NEW HAMPSHIRE AND WISCONSIN
BROOK TROUT DO NOT HYBRIDIZE AS THEY SPAWN IN THE FALL, ALL OTHERS IN THE SPRING
NON-MINNOW OR SUCKERS
TULE PERCH
SECONDARY FRESH WATER FISH ARE EURYHALINE
SCULPIN
COTTIDAE (PAGE 604, FIGURE 11.21)
CYPRINODONTIDAE
GASTEROSTEIDAE
PRICKLY SCULPIN MIGRATE DOWNSTREAM TO BREED, SOMETIMES INTO SALT WATER.
KILLIFISH OR TOOTH CARP ARE SOUTHERN FISH
PUPFISH OR KILLIFISH ARE MOjAVE DESERT FISH
THE OWENS PUPFISH LIVES UNDER THE ICE AT FISH SLOUGH NORTH OF BISHOP
THE SALTON SEA EXISTS DUE TO IRRIGATION RUNOFF FROM THE COACHELLA AND IMPERIAL VALLEYS, IT USED TO BE THE OUTLET FOR THE COLORADO RIVER, INTERESTING WATERLINES:
STICKLEBACKS ARE THE THIRD GROUP OF FRESHWATER FISH IN CALIFORNIA, THREESPINE STICKLEBACK
THE ARMOR IS A FUNCTION OF THE PREDATION PRESSURE
ANADROMOUS FISH BREED IN FRESH WATER AND LIVE IN SALT WATER
CHINOOK 31 INCHES, , STEELHEAD
COHO OR SILVER SALMON MAY BECOME 2 FEET IN LENGTH AND 22 POUNDS
FIGURE 11.25, PAGE 612
ANADROMOUS FISH
LAMPREYS ARE EEL-LIKE WITH NO PAIRED FINS, THEY HAVE A LONG LARVAL STAGE AND ADULT STAGE IS SHORT, 5 TO 7 YEARS AS SENDENTARY FILTER FEEDERS. SUCTION CUP MOUTH, THEY ATTACH THEMSELVES TO A BELLY AND ITS ALL OVER. THE ADULT STAGE IS FOR REPRODUCTION ONLY.
ACIPENSERIDAE
over a 100 year lifespan. They produce tasty roe or American caviar.
Sacramento-San Joaquin Delta.
SALMONIDAE
in the north coast rivers.
OSMERIDAE
CATADROMOUS FISH LIVE IN FRESH WATER AND BREED IN SALT WATER
MUGILIDAE
high in the water and land loudly on their sides, tasty eating.
TRUE MARINE FISHES
SYNGNATHIDAE
Family, eggs incubated in brood pouches of the males. Live in green algae of the Navarro River.
GOBIIDAE
water. Alien species from the orient.
PLEURONECTIDAE
flat on their side on the bottom.
RANIDAE - Frogs, though amphibian are largely aquatic.
Valley and deserts. Breed at night and sing for mates. Amplexus is the mating ritual whereby he grabs her under the armpits and fertilizes her eggs by manipulating her under the armpits. Floating masses of fertilized eggs turn into tadpoles.
Large, tasty legs. They reach up to 8 inches in length and feed on crayfish, frogs, and small fish and small snakes. It has made the Red-Legged Frog scarce.
the Red-legged frog. 3 inches with yellow bellies. Occurs in rivers and streams north of the San Gabriel Mountains
species, up to 12,000 feet. Sometimes the larvae over-winter for two seasons, postponing metamorphoses, gives them more toleration for low oxygenation under the ice. They reproduce after the ice melts. Large frog populations indicate that the fishing is poor, as trout eat the tadpoles when they leave the warm shallows in the evening, to bask in the warmer deep waters.
Adult Yellow-Legged Frogs produce an odorous mucous that reduces predation, though fish, garter snakes, and birds still eat them. Gulls and Blue Herons eat the tadpoles. Thanks to the introduction of trout, both species are disappearing.
and pools.
Mountains and Mount Lassen. Unlike the Yellow-Legged Frog, they do sit motionless on the bottom when threatened, but swim to safety.
Barely existing in California, released from schools and laboratories until it now has a wide range throughout the state.
survives well in aquariums. The adults have no predators in streams and ponds because the mucous secretions are poisonous. In large reservoirs, predatory fish eat the tadpoles
They are predatory and compete with Sticklebacks and other endangered species. Can live up to 15 years.
BUFONIDAE, Frogs and Toads are often confused. Toads as adults are mostly
Terrestrial and have stripes down their backs along the midline. Hind legs are shorter than those of frogs, and they walk more than hop unless excited. The web between their toes is not as well developed.
except deserts. Like frogs, they breed in water, and during the dry season they sometimes bury themselves in loose soil or enter rodent burrows.
I t grows up to 6 inches long with infamous toxic secretions. Becoming scarce due to the dams on the Colorado River.
Feet, and are diurnal with sexual dimorphism. Males and females are distinctly different. Females run to 3 inches, gray or brown, the males are smaller and a blotchy olive green.
The silent males that attempt to sneak a female away from a calling male are weird.
These toads hibernate in rodent burrows or in cracks under rocks and logs until the snow melts. California Gulls and Clark’s Nutcrackers prey on them when they first emerge and cross the snowfields to water. Their secretions are partly wiped off by passes scraping across the toads before they fly them away. Dehydration because of inadequate time to metamorphose is the leading cause of death. Variable emergence from hibernation ensures that they will not die out as weather controls the survival of the hatchlings.
HALIDAE, or Treefrogs are common and about 2 inches long. Long legs with adhesive toe pads, they are agile jumpers sometimes over 3 feet high.
occur in various colors, in fact, they can change colors to match a background similarly to a chameleon. Most commonly heard frog in California, they occur in vegetation around marshes, ponds, and roadside ditches. They call from shallow water near the shore.
Southern California’s Transverse and Peninsula Mountain Ranges often with its cousin the Pacific Tree-Frog.
ASCAPHUS TRUEI,Tailed Frog, sometimes incorrectly called a Bell Toad. These are impressive in their adaptation for survival. The larvae have suction cups enabling them to cling to rocks in fast moving water, even in waterfalls where predators cannot reach them. These Toads even have internal reproduction!
THAMNOPHIS, (= Nerodea) or garter snakes, get their name from their looks and can reach up to 4 feet in the largest ones. They have a yellow stripe down the back and two lateral stripes. Good swimmers and heads wider than bodies, often get them confused with water moccasins. They remain motionless until they can feed on small fish, salamanders, frogs, toads, small mammals, and birds. Their defense to predators is unusual, they wrap themselves around the attacker and defecate an excrement that contains an objectionably odorous secretion from their musk glands.
The state, especially in Southern California
feet in the Sierras.
red on the sides and may have blue-green bellies, common in the Coast Range.
CLEMMYS MARMONATA, The Western Pond Turtle is the only native turtle to California occurs in the Coast Ranges, Transverse Ranges, Peninsula Ranges, and the Great Central Valley. The only occurrence in the desert in the Mohave River.
Their habitat is disappearing in Southern California.
CHELYDRA SERPENTINA, The Snapping Turtle is a long nosed turtle and is an introduced species, Large head with a sharp ridge along its back whose powerful jaws can inflict serious damage. It is an introduced species.
PSEUDEMYS (Trachemys) SCRIPTA, The Common Slider or Red-eared Slider resembles the native pond turtle, but has a red line on each side of its face. It is an introduced species.
CHRYSEMYS PICTA, Painted Turtle resembles the Pond Turtle and is common in pet stores. Also an introduced species.
TRIONYX SPINIFERUS, Spiny Softshell Turtle was introduced into the lower Colorado River. Pancake shaped up to a foot long, floats with the current with just its head showing. In quiet backwaters they bury themselves, only extending their necks to breathe above the surface. They have a long, narrow, flat tipped nose with two large nostrils at the tip.
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Chapter #11 INLAND WATERS |
LAKES
Lakes owe their origin to geologic processes. A lake is a low spot in the terrain that captures and holds water. Lakes are often classified into different types based on the geologic nature of the basin.
Glacial Lakes
The carving and scouring action of a glacier as it passes over bedrock leaves behind an irregular terrain. Low spots that become filled with water are glacial lakes called tarns. Most tarns are small mountain lakes that lie in depressions produced by glacial scouring. Large, glacially carved valleys commonly have tarns scattered about on their bottoms.
A moraine may occur at the outlet of a tarn, forming a dam that enables the lake to hold more water. Other moraines may form nearly the entire lake basin. These large moraine lakes are often at the mouths of canyons on the east side of the Sierra.
Tectonic Lakes
Tectonic lakes lie in basins formed by warping, folding, fracturing, and faulting of the earth’s crust. Fault-block mountains of the Basin-Range Province alternate with valleys that may contain impounded water. This is known as horst-graben topography, and a lake formed in such a basin is known as a graben lake. The name graben is German for "grave," implying that the lake lies in a low place.
Landslide Lakes
Many lakes throughout the world owe their existence to impoundment of stream valleys by rock slides or mud flows. These lakes are often short-lived because the river, once it is impounded, overflows the dam, and subsequent erosion carries away material, restoring the area to a river.
Volcanic Lakes
Volcanoes and tectonic activity often lead to the formation of
volcanic lakes. Clear lake was by volcanic processes as a lava
dam at the southern end blocked the water flow. Volcanic mud
flows, landslides of volcanic rock, and collapsed calderas contribute
to the formation of lakes. Crater lake is the deepest in the
state at nearly 2000 ft. Closed-basin lakes such as Mono Lake
lie in a region of interior drainage, with no outlet. It is
hypersaline because minerals (such as salt) accumulate as water
evaporates. Tufa towers, the product of precipitation of
limestone, have formed along the shore of Mono lake.
Fluviatile Lakes
Fluviatile lakes lie in depressions caused by flowing water.
The remnants of meandering streams they become known as oxbow
lakes. Several occur in the Great Central Valley. Lakes
may also form when sediment deposits from tributaries block the flow
of the river. Lake Cahuilla is an example of this sort of
fluviatile lake.
Shoreline lakes-
Formed by the impounded barriers of sand, shoreline lakes occur
within a mile of an ocean. Sand accumulates and can block
estuaries creating freshwater lakes.
Solution Basins: Water-soluble rocks such as granite may dissolve
creating pits and depressions where water accumulates. The
depressions are known as tinajas "tanks". Limestone can
dissolve and create large cavities or caves.
Reservoirs: Reservoirs are man-made bodies of water formed after the damming of rivers. They are used for water storage or to generate hydroelectric power, a cheap source of energy. Many have multiple uses such as Lake Mendocino which is used for water storage for irrigation, drinking water, and recreation. Nearly every river in California has been dammed. Animals, such as beavers, also dam small rivers, altering natural stream flow and creating bodies of water.
Lake Succession
As lakes become older, they go through a process leading to their own demise. By their very nature, lake basins accumulate material and become filled with sediment. A lake ultimately becomes a meadow. Virtually all nutrients come from outside a lake, and as a lake becomes older, water becomes enriched with these minerals and nutrients. This process is known as eutrophication; the term trophic means "nourish."
Eutrophic lakes usually occur in lowland areas. Having had long periods of time to accumulate materials, they contain water that is murky. The sediment in such a lake is rich in organic material, forming a muddy ooze. In California, most eutrophic lakes become stratified during the summer. This means that there is a distinct layering of water of different temperatures and density.
Water Quality
Various characteristics of lake water may be measured as indicators of eutrophication. Aquatic biologists want to know the nutrient state of a lake so they may estimate what kinds of organisms live there and what sort of biomass and growth rates should be expected. In areas of habitation, these types of measurements are used to determine if the water is suitable for human consumption. Humans prefer to drink oligotrophic water.
Measuring biological oxygen demand and primary productivity requires specialized equipment and skilled technologists. The best results are obtained from analyzing water samples in a laboratory.
Seasons in a Lake
In high-mountain lakes there are only two seasons: winter and summer. During winter the duration of ice cover is the critical factor. Because wind is the source of oxygen for latke water, a lake that is covered by ice for too long cannot sustain a fish population. The larger the lake, the greater the oxygen reservoir; therefore large, deep lakes are able to maintain fish populations under ice for a longer period of time.
During summer concentrations of phytoplankton are low because dissolved nutrients such as nitrates and phosphates have been exhausted. Plankton that were abundant in spring have died and settled to the bottom. As autumn approaches the cooler waters sink and produce s stirring effect known as autumn turnover. When this happens, nutrient-rich water from the bottom rises to the top. If there is a cover of ice during the winter, a second turnover during spring may occur when the ice melts. It is less dense and slightly warmer, when it sinks to the bottom it initiates a spring turnover. During spring, day length increases. As the surface water becomes warmer, phytoplankton become more numerous, absorbing abundant nitrates and phosphates. This is the spring bloom.
Cultural Eutrophication
If nutrients such a nitrates and phosphates are added to a lake artificially, eutrophication may occur at an accelerated rate. This type of artificial eutrophication can be serious enough that an oligotrophic lake can become green and murky in a short period of time.
STREAMS
Flowing water may be characterized in several different ways. Terms such as river, creek, or brook are based on relative size.
Types of Flowing Water
Sometimes rivers are described according to permanence of flow. A permanent stream flows year-round. An intermittent stream dries up during a portion of the year. An interrupted stream is one that flows aboveground in portions of its run and underground in others.
Sometimes the appearance of the flow is used as a basis for comparing streams. Water that flows smoothly is said to be laminar, a situation that occurs in large rivers where the water flows smoothly. Most rivers are characterized by various degrees of turbulence, reflecting a combination of speed and irregularities of the stream bottom.
The Sierra Nevada abounds in waterfalls, cataracts, and rapids. For example, some of the most spectacular waterfalls in the world are found in Yosemite National Park. Falling water directs a great deal of energy at the stream bottom. In a waterfall, nothing remains that is not attached. In a cataract, only large boulders remain. In a rapids, large and small boulders remain in the flow.
The speed of the water depends on the stream gradient. If it moves too fast, it not only carries along sediment, but organisms as well. The optimal flow for a typical stream is only about 1 to 3 feet per second.
The correct classification of a stream requires careful examination of a detailed topographic map, which would be complicated by intermittent streams and would be only as reliable as its level of detail.
Inland Waters |