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Freshwater Biomes

Unit 10

Historically, people have settled and thrived by freshwater. Freshwater is used for cooking, bathing, transporting, irrigating, supplying energy, and cooling nuclear reactors.

Are people putting too many demands on freshwater?

An understanding of freshwater biomes is important if we are to preserve and keep freshwater needs preserved into the future.

Freshwater Biomes

Describe the factors that characterize the various types of aquatic biomes.

I Can…

Until this point, we have studied land biomes.

However, land only covers 30% of the Earth.

The next two units will focus on aquatic biomes, or habitats where the organisms live in or on water.

Aquatic Biomes

Aquatic biomes are not grouped like land biomes are, and they are very difficult to map.

Aquatic biomes are scattered, and they are determined by water depth, not location.

Aquatic Biomes

The descriptors used to define aquatic biomes are different, too.

The two most important factors in aquatic biomes are salinity and depth of the water.

Other important factors are the amount of dissolved oxygen and rate of flow.

Aquatic Biomes

Aquatic biomes can be divided into 2 groups based on the amount of dissolved minerals in the water. Freshwater Saltwater

All bodies of water contain dissolved minerals, but the ocean has more than most lakes, ponds, or streams.

Salinity

The amount of dissolved salts in a body of water is called salinity.

Salinity is measured in parts per thousand.

The salinity of ocean water is 30 parts per thousand.

Freshwater’s salinity is 0.5 parts per thousand.

Salinity

Water that is more saline than fresh, but less than ocean water is called brackish water.

Brackish water is found often in river deltas, and coastal marshes, where ocean water and freshwater mix.

Salinity

The water in most lakes, ponds, and rivers is fresh.

Some lakes, though, are more saline than the ocean, and can have up to 40 parts per thousand. They are hypersaline. Great Salt Lake Mono Lake, California

Salinity

Salt water is denser than freshwater.

Salinity is tested using a hydrometer.

Because salt water is denser, items in salt water have more buoyancy and float more easily than in freshwater.

Salinity

The second variable that affects the organisms present in water is depth.

The depth is so important because of the ability of sunlight to penetrate the water.

Depth

The amount of sunlight is important in determining the types of plants that grow at certain depths.

As the base of the food chain, the types of plants determine the types of organisms that make up the rest of the ecosystem.

Depth

Bodies of water can be divided into depth zones.

Photic zone Aphotic zone Benthic zone

Depth

The photic zone The top layer of water which

receives enough sunlight for photosynthesis to occur.

The size of the photic zone depends on the clarity of the water.

In the open ocean it is up to 200m.

Sunlight decreases as depth increases

Depth

The aphotic zone Below the photic zone Sunlight never reaches the aphotic

zone Only the ocean and deep lakes have

aphotic zones.

Depth

Benthic zone The floor of a body of water. In shallow water sunlight reaches this

zone In open ocean, contains decomposers

and scavengers. Freshwater dwellers include larvae,

snails, catfish, and turtles.

Depth

Depth

Bodies of water are divided into different zones based on temperature, also. Epilimnion Metalimnion (thermocline) Hypolimnion

Depth

Epilimnion – the top layer of a stratified lake, the warmest layer. Higher oxygen levels and pH levels. Highest plankton levels

Depth

Metalimnion or thermocline – the middle layer that separates the warm top from the cold bottom.

Rapid temperature change Does not always exist Depends greatly on season, lat./long.,

tides, etc.

Depth

Hypolimnion – the deepest layer of water Coldest layer (summer) warmest layer

(winter) Densest layer Usually no sunlight reaches this layer

Depth

Depth

Depth

Identify the characteristics of different types of standing-water ecosystems.

Explain the value of wetlands and the reasons for their decline.

I Can…

Freshwater biomes can be divided into 2 groups. Standing water Flowing water

Standing water ecosystems include: Bogs, prairie potholes, swamps,

marshes There is little flow in/out of the

ecosystem, but water circulates within the system to distribute warmth, oxygen, and nutrients.Standing-Water

Ecosystems

Abiotic Factors Biotic Factors

LakeDeepest standing water; aphotic zone, may be aquifer fed

Producers are floating algae in photic and benthic zone plants at shoreline; complex food webs

PondLight reaches benthic zone, fed by rainfall; may be seasonal

Producers are plants and algae on bottom; food web simpler than lake

MarshShallow; soil saturated; lacks oxygen; tidal: fresh, salt, or brackish, Everglades (fresh)

Plant’s roots underwater, leaves above, grasses, cattails, rushes; ducks, waterfowl, and benthic animals

SwampWater-soaked land w/ poor drainage, along streambeds; Mangrove swamps are salty along coastlines

Large trees and shrubs; muddy oxygen poor soil; Cypresses common in South, willow and dogwoods in N.US

BogInland wetland w/ little in/out flow; acidic soil; slow decay; carbon stored in dead plants

Sphagnum moss dominant; partly decayed moss accumulates as peat.

Standing-Water Ecosystems

Standing-water ecosystems have several levels of habitats

The top level supports the plankton community.

Plankton is a general term for organisms that drift in the water.

Standing-Water Ecosystems

Most freshwater plankton are the size of dust particles.

2 main types of plankton Zooplankton Phytoplankton

Phytoplankton – perform photosynthesis, and are the producers in food web.

Standing-Water Ecosystems

Zooplankton – microscopic animals and protists

Zooplankton eats phytoplankton (consumers)

Standing-Water Ecosystems

Standing-Water Ecosystems

The benthic community in standing water depends on the organic material that sinks down to the bottom.

Many organisms here are scavengers and decomposers.

Standing-Water Ecosystems

Ecosystem where roots of plants are underwater part of the year.

Often where land and water meet.

Include marshes, swamps, and bogs.

Wetlands

Soils are soaked with water and do not have a lot of dissolved oxygen.

Water may be fresh, salt, or brackish.

Some may be flowing water wetlands.

Wetlands

Wetlands act as filters, removing chemicals from the water as it moves through them.

Also are breeding, feeding, and resting areas for animals.

Act as flood control regions and help refill aquifers.

Wetlands

Wetlands are being destroyed at an alarming rate.

People may not care for the smell, or the fact that wetlands tend to be good insect breeding grounds.

Land may be valuable for other uses: waterfront views, landfills, filling in for cities, etc.

Wetlands

Swamp Lands Act 1849 – filling and draining of wetlands.

½ the wetlands in US have been destroyed.

Clean Water Act prohibits filling, but only 8% of wetlands in US are protected.

Wetlands

Once spanned from Lake Okeechobee 160km south to the southern tip of FL.

Water moved in a wide, shallow sheet during the wet season from May – Oct.

Wetlands – FL Everglades

Water was channeled away from Lake Okeechobee to created farmland and much of the southern wetland was drained.

1947 Everglades National Park was established.

1967 a canal was dug to bring water to the Everglades

1983 “Save our Everglades” campaign – clean up and restore natural flow of water 100,000 acres returned to wetland

Wetlands – FL Everglades

Home to huge number of organisms.

Alligators, fish, turtles, birds, etc.

Wetlands – FL Everglades

Wetlands – FL Everglades

Wetlands – FL Everglades

Describe how abiotic factors of gravity, erosion, and sedimentation affect stream ecosystems.

I Can…

Flowing freshwater systems have many names: river, stream, creek, brooks, etc.

The different names suggest size differences, but scientifically, they are all streams.

Freshwater flows through aquifers, too

Flowing-Water Ecosystems

There is life in aquifers, too.

Some contain fish and other animals.

The aquifer would then be their habitat.

Flowing-Water Ecosystems

Organisms that live in streams are adapted to the movement of the water.

Some have hooks and suckers to anchor themselves to plants, rocks, and other animals.

Stream Organisms

Salmon and trout are two fish adapted to live in streams.

Salmon and related fish breed and grow in streams, but live in larger bodies of water.

Stream Organisms

When the fish are ready to reproduce, they swim upstream and return to where they hatched.

It has been shown that they find the same stream and breeding spot by using scent cues in small amounts of chemicals in the water.

Stream Organisms

Most streams begin high in mountains, the result of snow melt and runoff.

Gravity pulls the water downhill toward the ocean (sea level).

The place where the stream begins is called the head of the stream.

Stream Flow

Headwaters are usually cold, high in oxygen, and could support a lot of life.

However, they are usually fast flowing and most organisms can’t survive such a high energy environment.

As the slope of the land declines, the water slows.

Stream Flow

As the water slows, the sediments that were being carried by the water begin to settle to the bottom of the body of water.

Sediments provide a place for plants to grow, which further slows the water and allows for heating.

Stream Flow

The warmer water allows for phytoplankton to grow and sets up the basis for a population of consumers.

Stream Flow

Sedimentation coupled with erosion causes the course of a stream to change over time.

A stream has meanders or bends and curves in it path.

As the water flows, the water on the inside of the curves slows down, allowing for deposition.

At the same time, the outside speeds up and erodes bank, elongating the meanders.

Stream Flow

Stream Flow

The flow of many streams have been changed by humans.

Damming, dikes, and irrigation channels all make changes to ecosystems.

Stream Flow

Flooding is natural and beneficial.

When floodplain are not allowed to flood the soils do not get the benefits from the nutrients provided by the water

Stream Flow