Freshwater ecosystems are classified into lentic (standing water) and lotic (flowing water) types, characterized by low salinity levels and varying ecological conditions influenced by geology and pollution. The document describes various organisms and their classifications within these ecosystems, including autotrophs, phagotrophs, and saprotrophs, along with their habitats and modes of life. It also covers the water cycle, stream dynamics, and the properties of groundwater, highlighting the importance of these ecosystems in nutrient cycling and environmental health.

1. Freshwater Ecosystem
By
Prof. Liwayway Memije-Cruz

2. Freshwater Ecosystem

3. Introduction
 Freshwater Ecosystems include standing
water or lentic such as lakes, ponds,
marshes and wet lands, and the flowing
water or lotic such as spring, streams and
rivers. This ecosystem is normally of with
very low salinity usually between 15 to 30
ppt. They are highly variable and their
characteristics depend upon the
surrounding geology, land use and pollution
levels.

4. State of the Environment:
Issues and Concerns
ECOLOGICAL CLASSIFICATIONS OF
FRESHWATER ORGANISMS
Freshwater ecosystem is classified as
to:
Major niches
Life form or life habit based on
their mode of life
 Region or habitat

5. Freshwater ecosystem is classified as to major niches
based on their position in the energy or food chain
 Autotrophs (producers) are green plants
and chemosynthetic microorganisms.

6. Phagotrophs
 (micro consumers) which are the primary,
secondary, herbivores, predators and parasites.

7. Saprotrophs
 (micro consumers or decomposers) are sub
classified according to nature of the organic
substrate decomposed.

8. Organisms in water may be classified as to their life
form or life habit based on their mode of life as follows:
 Benthos are organism
attached to resting on
the bottom or living on
the bottom sediments.
The animal benthos
maybe conveniently
subdivided into filter
feeders and deposits
feeders (examples are
the clams and the
snails respectively).
.

9. Periphytons
 organisms attached or clinging to stems and
leaves of rooted plants or other plants projecting
above the bottom.

10. Planktons
 floating organisms
whose movement is
more or less
dependent on
currents. They are
sub classified it no
zooplanktons,
netplanktons and
nannoplanktons.

11. Nektons
 swimming
organisms,
which are able
to navigate at
will. Examples
are fish,
amphibians
and swimming
insects.

12. Neustons
 organisms resting or swimming on the
surface.

13. Freshwater organisms maybe classified as to
region or habitat.
 Littoral zone - the shallow
water region with light
penetration to the bottom,
Limnetic zone - the open water
zone to the depth of effective
light penetration called the
compensation level.
 Euphotic zone is the total
illuminated stratum including
littoral and limnetic.
 Profundal zone is the bottom
and deep-water area, which is
beyond the depth of effective
light penetration.

14. Lotic ecosystem or flowing system
 Characterized by inputs of detrital materials from terrestrial
sources and current of varying velocities the carry nutrients and
other material downstream.
 Exhibits continuum physical and ecological variables. There is a
longitudinal gradient in temperature, depth and nature of the
bottom. Changes in physical condition are reflected in biotic
structures.
 Open and largely heterotrophic.
 The major energy source is detrital material carried to it from
the outside. The concurrent of nutrient cycling and downstream
transport has been called spiraling.
 most important erosional agent modifying the Earth’s surface.

15. Water Cycle
 Water cycle is the
movement of water
around, over, and
through the Earth. The
water portion of the
earth is always in
movement. Water cycle,
also referred as the
hydrologic cycle,
describes the continuous
movement of water on,
above, and below the
surface of the Earth.

16. Most of the water that falls as precipitation returns to the
ocean by infiltration and runoff over the surface.
Infiltration
 the process by which
water on the ground
surface enters the soil.
 a measure of the rate at
which soil is able to
absorb rainfall or
irrigation
Run off
 is the flow of water that
occurs when excess
stormwater, meltwater,
or other sources flows
over the earth's surface.

17. Two kinds of surface runoff
 Sheet flow refers to the water flowing over
the surface and not confined to
depressions
 Channel flow is confined to long, trough-
like depressions. The runoff which is
confined to channels is called stream.
Streams flow downhill to a lower elevation
where they empty into another stream, a
lake, or a sea.

18. Stream flow

19. Stream Transport
 The stream loads transported by the stream are sediment dissolved in solution
(dissolved load), sediment dissolved in suspension (suspended load) and those
sediment at the bottom of the channel (bed load). The greatest part of the stream
load is the suspension load and much of the dissolved load is contributed by
groundwater. The bed load is usually the smallest portion of stream’s load.
 A stream’s ability to transport solid particles is based on the capacity and
competence. Stream capacity refers the maximum load of solid particles a stream
can carry while stream competency refers to the maximum particle size a stream
can transport stream competence depends on stream velocity or the speed of the
water in the stream.
 Stream’s velocity is a measure of the downstream distance travelled per unit of
time. The factors that determine a stream’s velocity are gradient (slope of the
stream channel), shape, size, and roughness of the channel, and the stream’s
discharge (amount of water passing a given point per unit of time, prequently
measured in cubic feet per second). As the width, depth, discharge and stream
velocity increases, the gradient and roughness of a stream decrease the
downstream. Stream deposit sediment when velocity slows and competence is
reduced.

20. Stream Deposition
 The process wherein the sediments
carried by the stream water is laid
down or dropped.
 There are different type of stream
deposits which include bars deposit,
floodplain deposit, delta deposit and
alluvian fan deposit.

21. Example of Lotic Ecosystem

22. Lentic Ecosystem or Standing Water
 Exhibits vertical gradients in light, temperature and
dissolved gases.
 In summer, water in deeper lakes and ponds becomes
stratified with a layer warm circulating water on top, the
epilimnion, the thermocline in which the temperature drops
rapidly, and the hypolimnion a bottom layer if denser water
is approximately 4 degrees Celsius often low in oxygen but
high in nutrients.
 In fall and spring, when surface waters cool and warm,
differences in density of water between layers decrease and
water circulates throughout the lake. This is the fall and
spring over turn, which is vital in mixing the bottom water
with top water and circulating nutrients.

23. Examples Lentic Ecosystem
Lake Pond

24. Groundwater
 The largest reservoir of freshwater that is
readily available to humans.
 It occupies the pore spaces in sediment
and rock in a zone beneath the surface
called the zone of saturation. The
upper limit of this zone is called the
water table. Above the water table is the
zone of aeration where the soil,
sediment, and rock are not saturated.

25. Groundwater

26. Two properties of rock that control the flow of
groundwater
 Porosity refers to the volume of open space in
rock.

27. Permeability

28. Thank you!