Transcript snc1d u1 lesson 12 assessing the impact of human activities on ecosystems 2

ASSESSING THE IMPACT OF HUMAN
ACTIVITIES ON ECOSYSTEMS 2
-WATER QUALITY
Lesson 12
September 13th, 2010
ASSESSING WATER QUALITY
 Water
is essential to all life.
 Protecting water quality is essential
for sustainable ecosystems.
 Many aspects of water are used to
assess its quality
AQUATIC ORGANISMS
 Healthy
aquatic ecosystems are full of
organisms.
 These include: Fish, large pants,
invertebrates, plankton, bacteria, and
viruses.
 Sometimes, the types and quantities of
species present in the water can
indicate that the water is unsafe.
AQUATIC ORGANISMS

Indicator organisms include certain insects and
insect larvae, shrimp, clams, and worms.
Different organisms prefer different conditions.
For example, some organisms can survive in
polluted water, while others cannot.
OXYGEN

-Aquatic organisms need the oxygen gas
that is dissolved in the water.
 Dissolved oxygen measurements give
the level of oxygen present in water.
 -If levels of oxygen drop below a certain
level, fewer organisms are able to live in
that body of water.
OXYGEN
BIOLOGICAL OXYGEN DEMAND (BOD)
 Measures
how quickly oxygen is used up
by micro-organisms in a given body of
water
 BOD is an effective test for certain types
of water pollution. Polluted water can
promote the growth of some microorganisms, which feed off the pollution.
These organisms use up oxygen, which
means oxygen is removed from the water
at a high rate
BOD
ACIDITY
Most aquatic organisms prefer a neutral
environment.
 As it increases, the diversity of plants and
animals decreases.
 Most fish die if the water’s pH falls to 4.5.

PHOSPHORUS AND NITROGEN
 Fertilizers
are applied to fields and
gardens to supply plants with nutrients,
such as the elements nitrogen and
phosphorus.
 Water dissolves the fertilizer to provide
nutrients to the plants
 Runoff from fields and gardens runs into
streams causing algae to grow rapidly.
PHOSPHORUS AND NITROGEN
Eutrophication
is the addition of
nutrients to an aquatic ecosystem
causing increased growth of plants such
as algae.
 As
the algae dies and decomposes,
oxygen is depleted from the water.
The resulting low amount of oxygen
in the water may cause fish and
other animals to die.
PHOSPHORUS AND NITROGEN
HEAVY METALS
 Some
kinds of metals cause illness even in
small amounts
 Heavy metals have a density of 5 g/mL or
higher.
 Hg, Cu, Pb, Cd.
HEAVY METALS
 Sources
of heavy metals
 Batteries (Cd, Pb), compact fluorescent
light bulbs (CFLs) (Hg)
 all coal-fired power plants, incinerators,
and steel mills emit mercury from their
smokestacks, because mercury is found
naturally in coal.
 Mercury in the atmosphere usually settles
in water.
HEAVY METALS
 Algae
absorb very tiny amounts of
mercury from the water and builds up in
their tissues.
 Bioaccumulation - The gradual buildup of a substance in an organism’s body
 In a process called biomagnification,
the mercury becomes more and more
concentrated in each link in the food chain
as one animal eats many contaminated
animals
HEAVY METALS
 Many
predatory fish, including some
salmon and trout, have high levels of
mercury and should not eaten by humans
and other animals.
 Health problems caused by heavy metals
include:
 kidney and lung disease, immune
system disorders, cancer, sterility in
men, and infertility in women.
BIOACCUMULATION
PESTICIDES
 chemicals
that kill unwanted organisms
 Some pesticides last a long time in the
environment
 long-lasting pesticides can also
biomagnify
 Example: DDT – accumulated in
peregrine falcons and made their egg
shells weak.
 Modern pesticides are designed to last one
growing season and then break down into
less harmful substances.
HOMEWORK / MSIP
Read 52-57
 Finish the Worksheet and hand in.
