Transcript What are lotic systems

Freshwater Systems
Lotic Systems
Freshwater Ecosystems
What are the characteristics of freshwater ecosystems?
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A freshwater ecosystem is defined as the living organisms
(biotic) and the non-living (abiotic) environment they inhabit.
The type of freshwater ecosystem —whether it be a pond,
lake, stream, or river— is determined by the watershed
(drainage basin) in which it exists.
Remember that a watershed is a complex system of
components that affect water bodies in a given drainage basin.
Each watershed includes a variety of factors that interact with
the water in the system, including climate, amount of rainfall,
geology and geography of an area (rocks, soil, hills, lowlands,
forests), and human activities (urban and industrial development, agriculture).
What are the characteristics of a
freshwater ecosystem?
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Drainage basins and watersheds that drain into the
body of freshwater
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Drainage basin is an area of land where surface water from rain and melting
snow or ice converges to a single point at a lower elevation, usually the exit of
the basin, where the waters join another waterbody, such as a river, lake,
reservoir, estuary, wetland, sea, or ocean
Including the geology (rocks and soil), geography
and topography (landforms), and human activities
(urban and industrial development and agriculture)
of the area
The red lines describe
the watersheds for the
drainage basins of first
order streams. The
yellow lines define the
watersheds for two
drainage basins from
locations further
upstream. Note that the
first order basins are
components of these
much large drainage
basins. (Source:
PhysicalGeography.net)
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Figure 2: Common drainage pattern types.
(Source: PhysicalGeography.net)
Contribution of watersheds to freshwater
ecosystems
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Components of the
watershed affects the bodies
of water, or habitats, that
they flow into.
Contributing factors include:
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geology (rocks and soil)
geography and topography
(landforms)
human activities (urban and
industrial development and
agriculture)
TYPES OF FRESHWATER
SYSTEMS
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There are generally three types of freshwater
ecosystems: Lotic Systems, lentic systems, and
freshwater wetlands.
Lotic systems include flowing water, such as rivers,
streams, creeks, etc.
 Lentic systems include standing bodies of water, such as
lakes and ponds.
 We will discuss freshwater wetlands at another time.
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General Differences Between Streams and Lakes
Characteristic
Streams (Lotic System)
Lakes (Lentic System)
Water flow
One direction of flow, upstream to
downstream
Various flows, no particular direction
Oxygen content
Normally oxygen rich because of the constant
mixing
Oxygen depletion exists at times in deeper
water or older lakes
General Depth
Size Description
Riparian Zone Description (the riparian
zone is the land area along the banks of
the body of water)
Shallower on average
Narrower and longer
Various effects from different terrestrial
environments along the stream’s course. The
shoreline has more potential to affect water
quality because a larger portion of the water
body is near shore.
Deeper than average
Wider and shorter
Terrestrial environment similar all around the
lake shore. A smaller portion of the water is in
close proximity to the shore.
Changes in shape / depth over time
Stream continually cuts into the channel,
making it longer, wider, and deeper
Lakes become shallower over time from
depositing sediments
Age progression
Age progression of a stream goes from young Age progression of a lake or pond goes from
stream, narrow and shallow, to mature stream, lake to marsh or swamp to land
wider and deeper
Water retention time (how long it holds
water)
Shorter retention time for water (b/c it’s
always flowing)
Longer retention time for water (because it
stores water)
Temperature characteristics
Top and bottom waters generally have the
same temperature (b/c of the constant
mixing)
May have different temperatures from the top
to bottom (b/c it has layers based on density)
LOTIC SYSTEM
A. What are lotic systems?
 Lotic environments include streams and rivers.
 Flowing waters are very diverse, not only in size but
in characteristics.
 Streams and rivers are defined by things like
surrounding land use (urban, agricultural, natural),
size of the watershed, stream order, geology, soils,
topography, flow, and vegetation.
Characteristics of a Lotic System
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Flow in one direction (downhill)
Characteristics of a Lotic System
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Usually high in dissolved oxygen
Shallower than lakes
Narrower and longer than lakes
Characteristics of a Lotic System
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Flowing water continually cuts into the channel,
making it deeper and wider as it ages
Characteristics of a Lotic System
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Water temperature from top to bottom is usually
the same
Water doesn’t stay put for very long
What are the sources of running
water systems?
The places where streams begin are called
headwaters.
a)Many begin in mountain areas from snowmelt.
b)Some begin or are fed by water seeping up from the
water table. (Remember that these are called gaining
streams)
c)Some begin or are fed by other streams flowing into
them. These are called tributaries
What defines a stream?
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Lotic systems consist of flowing bodies of water
Rivers and streams are more diverse than lakes
for many reasons:
Surrounding land use
 Size of the watershed
 Stream order
 Geology and soil type
 Topography
 Rate of stream flow
 Vegetations type
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What are stream orders?
Stream orders are numbered based on their role
in feeding into another body of water.
Stream Types
 Streams and rivers are primarily characterized by
the length of time that they flow.
 There are three main types of streams:
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Perennial streams
 Intermittent streams
 Ephemeral streams
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Three types of streams
1. Perennial streams
 Have
a constant flow of water, flow
year round.
The amount of water can, and will,
vary with the different seasons,
however.
Three types of streams
2. Intermittent streams
May run dry now and then, but have regular periods of
water flow.
 Over 76 percent of the streams in Texas fall into the
intermittent category.
 These usually occur in arid or semi-arid areas or in areas
that are experiencing especially dry conditions. During
times of extreme drought, even perennial streams can
become intermittent.
 Although shallow sections of intermittent streams and
rivers can dry up, perennial pools are often maintained in
the deeper sections of a stream channel. Large pools can
often sustain aquatic life through the hot summer months.
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Three types of streams
3. Ephemeral streams
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rarely have water in them, usually
after rainfall in desert areas
 are intermittent streams that regularly exist
for a short period of time.
 Ephemeral streams are best illustrated by
the dry stream beds in west Texas that
flow only following rainfall and cease to
flow soon after.
Comparing Erosional and
Depositional Habitats of
a Stream
Stream Habitat Types
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There are two types of basic stream habitats,
based on how quickly the water flows:
 Those that have fast-running water (erosional)
 Erosion = take away
 Those that have slow-moving water
(depositional)
 Deposition = Deposit = to place
Comparing Erosional and Depositional Zones of Streams
Characteristics
Erosional Zones
Depositional Zones
Flow
Occurs in relatively shallow area of a stream.
Relatively deep and wide with slow moving
Three areas defined by flow:
water compared to riffles, runs, or glides.
Riffle—fast-moving, turbulent water (rapids)
Primarily found in pools and backwater areas
Run—fast-moving, non-turbulent water
of streams
Glide—slow-moving water
Can also be found at opposite sides of
erosional zones where rivers bend.
Sediment
Coarse sediment consisting of cobble, pebble, and Fine sediment comprised of sand and silt
gravel
Aquatic Plants Plants typically grow on or in coarse sediment.
Submergent vegetation (completely
(pondweed)
underwater) and rooted aquatic plants
Aquatic
Aquatic insects and small fish that require high
Organisms similar to those found in lakes and
Animals
oxygen levels, flowing water for feeding, and are pond systems
adapted to living in swift water through the ability Many fish use the deeper water of the pools
to swim or cling to rocks in riffle areas
and areas along the banks for cover and find
food easier to catch in slower moving water
Organic
Comprised of leaf litter, twigs, and other coarse
Comprised of leaf litter and other matter
materials
matter, usually trapped in stream riffles behind
found at the bottom of pools and backwater
large rocks or logs
areas of streams
Erosional vs. Depositional Habitats
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Erosional Habitats
 Are usually shallower than depositional
 Consist of varying parts:
 Riffles – fast-moving, turbulent water
 Run – fast-moving, non-turbulent water
 Glide – slow-moving water
Riffles, pools, and cascades
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Riffles and pools alternate in somewhat
predictable patterns
www.aquatic.uoguelph.ca/rivers/chphys.htm
Erosional Sediments
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Sediments are coarse (or larger in size)
Consist of cobble, pebbles, and gravel
Aquatic Plants and Animals
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Plants
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Rooted in the coarse
sediment
Are able to withstand the
force of the flowing water
Ex. pondweed
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Animals
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Require high O2 levels
Need flowing water to
feed (filter feeders)
Strong swimmers or cling
to rocks in riffle areas
Erosional Zones
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Usually towards the outer bank (erosion of bank
is high)
Figure
1.21
www.usda.gov/stream_restoration/chap1.html
Depositional Habitats
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Usually deep and wide
Slower moving water as compared to riffles,
runs, and glides
Depositional Sediments
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Sediments tend to build in pools and backwater
areas
Sediment is finer (smaller particles)
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Usually sand and/or silt
Aquatic Plants and Animals
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Plants
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Submergent vegetation
(live completely
underwater)
Able to grow in sand or
silt
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Animals
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Many organisms use
deeper water for cover or
protection
Easier to find and eat
food
Stream Erosion and Deposition
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Streams are constantly changing as water flows
through them.
The actions of the water move sand and rock from
one place, and deposit it at another. The two driving
forces are erosion and deposition.
Erosional zones usually occur in the fast-running water
areas, and may cause high amounts of erosion along the
outer banks of the stream.
 Depositional zones are found in the slower moving water
area, where sediments are able to settle to the bottom.
 Materials such as gravel, pebbles, and sand slowly build,
and may eventually form a bar. Bars often support aquatic
plants.
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Rivers and streams flow downhill seeking a path
of least resistance.
Changing terrain alters the course of a river or
stream creating bends called meanders.
These meanders move over time through the
processes of erosion and deposition.
Meandering Rivers
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Rivers and streams flow with gravity (uphill to
downhill), seeking the path of least resistance
Changing landforms and terrain alters the course
of a river, creating bends, or meanders
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Meander means to wander
Sacromento River, California
Meandering Rivers
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Meandering rivers change
course over time as
sediments build through
deposition, and as banks
erode.
Meandering rivers
A meander becomes more pronounced as the
streamline shifts between the river banks.
Formation of an oxbow lake
http://www.aquatic.uoguelph.ca/rivers/chphys.htm
Effect of the water table
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Rain and snow melt soak into the ground,
becoming part of the water table
When the water table is close to the ground,
springs can form above ground
Effect of the water table
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Gaining streams
Springs above ground that are recharged by
underground sources
 These springs are perennial
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Effect of the water table
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Losing streams
Streams that lose water to replace the water table as
the level of water drops (water from the stream is
lost to the water table)
 These streams are intermittent
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Riparian Zone
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The riparian zone is a vegetated buffer on the banks
of the stream (between nearby lands and the water
itself.)
These areas are important in controlling the
introduction of sediment and nutrients into a river
or stream channel.
The riparian zone includes the stream bank and
portions of the floodplain that are periodically
covered by flood waters.
Interaction between the riparian zone and a stream
is vital for the health of the stream.
Riparian Zone
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“Buffer” comprised of various plant species
Located between the stream and nearby land
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Includes the bank and flood plain areas
http://www.usda.gov/stream_restoration/Images/scrhimage/chap1/fig1-15.jpg
Functions of Riparian Zones
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Many important functions:
Controls the amount of sediments and nutrients that
run-off into the stream
 Protects streams from surrounding land uses
 Helps provide flood control
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E. Stream Habitats and Aquatic
Organisms
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In-stream habitats include pools, riffles, root mats,
aquatic plants, undercut banks, submerged rocks and
logs, overhanging vegetation, and leaf litter.
A combination of these, along with the depth and
flow of the water, are key factors in determining the
type of aquatic organisms found in a stream.
Under natural conditions, a wider variety of habitats
equals greater aquatic life diversity.
Stream Habitats and Aquatic
Organisms
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Low diversity of aquatic life is often caused by
poor quality of in-stream habitats rather than by
poor water quality. In the past, stream quality
was determined by the factors of the water itself.
Now, however, scientist focus just as much as
what is living in the stream.
We will look at what lives here after we look at
lentic systems.
Importance of In-Stream Habitats
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What determines the type of habitat? Habitats in
the stream can be found anywhere:
Pools
 Riffle
 Under or in plant masses and overhanging
vegetation
 Submerged rocks and logs
 Leaf litter on the bottom
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In-Stream Habitats
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The location of the habitat, combined with the
depth of the water and the rate it is flowing are
key factors in determining what type of
organism lives in the stream.
Habitats and Diversity
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The greater the number and types of habitats,
the more diversity there will be
Poor stream quality = low diversity
Determining the Health of a Stream
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The health and quality of a stream is determined
by:
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Water chemistry and physical aspects
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How much dissolved O2, turbidity, pH, temp. etc.)
More recently, we also look at the communities of
organisms living there