The Freshwater Biome
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1/26/2016 The freshwater biome http://www.ucmp.berkeley.edu/exhibits/biomes/freshwater.php 1/3 A lake at Acadia National Park, Maine. See the world (and its fossils) with UCMP's field notes. SEARCH | GLOSSARY | SITE MAP Online exhibits : The world's biomes The freshwater biome Freshwater is defined as having a low salt concentration — usually less than 1%. Plants and animals in freshwater regions are adjusted to the low salt content and would not be able to survive in areas of high salt concentration (i.e., ocean). There are different types of freshwater regions: Ponds and lakes Streams and rivers Wetlands Ponds and lakes These regions range in size from just a few square meters to thousands of square kilometers. Scattered throughout the earth, several are remnants from the Pleistocene glaciation. Many ponds are seasonal, lasting just a couple of months (such as sessile pools) while lakes may exist for hundreds of years or more. Ponds and lakes may have limited species diversity since they are often isolated from one another and from other water sources like rivers and oceans. Lakes and ponds are divided into three different “zones” which are usually determined by depth and distance from the shoreline. The topmost zone near the shore of a lake or pond is the littoral zone. This zone is the warmest since it is shallow and can absorb more of the Sun's heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects, such as dragonflies and midges, only the egg and larvae stages are found in this zone. The vegetation and animals living in the littoral zone are food for other creatures such as turtles, snakes, and ducks. From left: a view across Manzanita Lake toward Mt. Lassen, California; a forest pond near Donnelly, Idaho; a Great Blue Heron; Paranagat Lake, southeastern Nevada. The nearsurface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is welllighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without
description
Based off article from educational website
Transcript of The Freshwater Biome
1/26/2016 The freshwater biome
http://www.ucmp.berkeley.edu/exhibits/biomes/freshwater.php 1/3
A lake at Acadia National Park, Maine.
See the world(and its fossils)with UCMP's field
notes.
SEARCH | GLOSSARY |SITE MAP
Online exhibits : The world's biomes
The freshwater biomeFreshwater is defined as having a low saltconcentration — usually less than 1%. Plants andanimals in freshwater regions are adjusted to thelow salt content and would not be able to survive inareas of high salt concentration (i.e., ocean). Thereare different types of freshwater regions:
Ponds and lakesStreams and riversWetlands
Ponds and lakesThese regions range in size from just a few squaremeters to thousands of square kilometers. Scatteredthroughout the earth, several are remnants from thePleistocene glaciation. Many ponds are seasonal, lasting just a couple of months (such as sessilepools) while lakes may exist for hundreds of years or more. Ponds and lakes may have limitedspecies diversity since they are often isolated from one another and from other water sources likerivers and oceans. Lakes and ponds are divided into three different “zones” which are usuallydetermined by depth and distance from the shoreline.
The topmost zone near the shore of a lake or pond is the littoral zone. This zone is the warmestsince it is shallow and can absorb more of the Sun's heat. It sustains a fairly diverse community,which can include several species of algae (like diatoms), rooted and floating aquatic plants,grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects,such as dragonflies and midges, only the egg and larvae stages are found in this zone. Thevegetation and animals living in the littoral zone are food for other creatures such as turtles,snakes, and ducks.
From left: a view across Manzanita Lake toward Mt. Lassen, California; a forest pond near Donnelly, Idaho; a Great BlueHeron; Paranagat Lake, southeastern Nevada.
The nearsurface open water surrounded by the littoral zone is the limnetic zone. The limneticzone is welllighted (like the littoral zone) and is dominated by plankton, both phytoplankton andzooplankton. Plankton are small organisms that play a crucial role in the food chain. Without
1/26/2016 The freshwater biome
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aquatic plankton, there would be few living organisms in the world, and certainly no humans. Avariety of freshwater fish also occupy this zone.
Plankton have short life spans — when they die, they fall into the deepwater part of thelake/pond, the profundal zone. This zone is much colder and denser than the other two. Little lightpenetrates all the way through the limnetic zone into the profundal zone. The fauna areheterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration.
Temperature varies in ponds and lakes seasonally. During the summer, the temperature can rangefrom 4° C near the bottom to 22° C at the top. During the winter, the temperature at the bottomcan be 4° C while the top is 0° C (ice). In between the two layers, there is a narrow zone calledthe thermocline where the temperature of the water changes rapidly. During the spring and fallseasons, there is a mixing of the top and bottom layers, usually due to winds, which results in auniform water temperature of around 4° C. This mixing also circulates oxygen throughout the lake.Of course there are many lakes and ponds that do not freeze during the winter, thus the top layerwould be a little warmer.
Streams and riversThese are bodies of flowing water moving in one direction. Streams and rivers can be foundeverywhere — they get their starts at headwaters, which may be springs, snowmelt or even lakes,and then travel all the way to their mouths, usually another water channel or the ocean. Thecharacteristics of a river or stream change during the journey from the source to the mouth. Thetemperature is cooler at the source than it is at the mouth. The water is also clearer, has higheroxygen levels, and freshwater fish such as trout and heterotrophs can be found there. Towards themiddle part of the stream/river, the width increases, as does species diversity — numerous aquaticgreen plants and algae can be found. Toward the mouth of the river/stream, the water becomesmurky from all the sediments that it has picked up upstream, decreasing the amount of light thatcan penetrate through the water. Since there is less light, there is less diversity of flora, andbecause of the lower oxygen levels, fish that require less oxygen, such as catfish and carp, can befound.
From left: McArthurBurney Falls State Park, California; trout; Green River, Utah; Brooks River, Alaska.
WetlandsWetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs areall considered wetlands. Plant species adapted to the very moist and humid conditions are calledhydrophytes. These include pond lilies, cattails, sedges, tamarack, and black spruce. Marsh floraalso include such species as cypress and gum. Wetlands have the highest species diversity of allecosystems. Many species of amphibians, reptiles, birds (such as ducks and waders), andfurbearers can be found in the wetlands. Wetlands are not considered freshwater ecosystems asthere are some, such as salt marshes, that have high salt concentrations — these support differentspecies of animals, such as shrimp, shellfish, and various grasses.
1/26/2016 The freshwater biome
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From left: Pescadero Marsh, California; coastal marsh at Umpqua Dunes, Oregon; trees and bogs on Esther Island, Alaska.
Visit our gallery of wetlands images, which illustrate the amazing diversity of wetland ecosystems.
Freshwater Marine Desert Forest Grassland Tundra
Top photo by David K. Smith, UCMP. Ponds & lakes photos, from left: Glenn and Martha Vargas © 2004 California Academy ofSciences; David K. Smith, UCMP; Gerald and Buff Corsi © 2001 California Academy of Sciences; Glenn and Martha Vargas © 2004California Academy of Sciences. Streams & rivers photos, from left: Dr. G Dallas and Margaret Hanna © 1999 California Academy ofSciences; Susan Middleton © 2003 California Academy of Sciences; Lorraine Elrod © 2000 California Academy of Sciences; Dr. RobertThomas and Margaret Orr © 2004 California Academy of Sciences. Wetlands photos, from left: Dr. Robert Thomas and Margaret Orr ©1999 California Academy of Sciences; David K. Smith, UCMP; Gerald and Buff Corsi © 2005 California Academy of Sciences.
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