Transcript ES 120 TOXICS IN THE ENVIRONMENT

ES 120 TOXICS IN THE
ENVIRONMENT
LECTURE 16-17: Effects on
populations, communities and
ecosystems
SCOPE OF LECTURE
• How can we recognize toxic effects on
populations, communities and
ecosystems?
EFFECTS ON HIGHER LEVELS OF
BIOLOGICAL ORGANIZATION
• Population: group of individuals of same
species in an area
– Change in abundance
– Change in age distribution
– Change in genotypes
• Community: group of populations in an
area (see lecture on biomonitoring)
• Ecosystem: interaction of biotic and abiotic
factors in an environment
2 PARADIGMS OF POPULATION
MODELS (CONTINUOUS)
- Population growth rate is density independent and constant:
Exponential growth:
dN
rN
=
dt
- Population growth rate is density dependent, e.g.:
Logistic growth:
dN
dt
N)
r
N
(1
= max
K
CONTINUOUS POPULATION GROWTH
TOXICANT EFFECT ON LOGISTIC GROWTH
WHY IT IS DIFFICULT TO DISCERN EFFECTS
OF STRESS ON REAL POPULATIONS
1. There are multiple stressors, some density
dependent and some density independent
2. Intensity of stressors varies in time
3. Population growth may be discrete
4. Real populations are age/size structured: birth
and death rates depend on age/size
5. Dynamics of real populations depend on other
species: competition, mutualism, parasitism,
predation
6. A population may develop resistance to a
stressor
INTENSITY OF STRESSOR VARIES IN TIME:
POPULATION OF BLUE HERONS DECLINES
AFTER SEVERE WINTER
DISCRETE POPULATION GROWTH MAY CAUSE
FLUCTUTATIONS (LOGISTIC GROWTH)
‘PREDATOR-PREY’ DYNAMICS
MAY LEAD TO FLUCTUATIONS
Producer
SUBLETHAL
EFFECTS ON
CONSUMER
MAY INCREASE
BOTH
PRODUCER
AND
CONSUMER
DENSITIES
Consumer
Producer
???
Consumer
RESISTANCE IN INSECTS
DEVELOPMENT OF RESISTANCE TO
PYRETHROIDS IN COTTON BUD WORM
(ANNUAL APPLICATION IN JANUARY/
FEBRUARY)
EFFECTS ON HIGHER LEVELS OF
BIOLOGICAL ORGANIZATION
• Population: group of individuals of same
species in an area
• Community: group of populations in an
area
• Ecosystem: interaction of biotic and abiotic
factors in an environment
– Changes in elemental fluxes (C, N)
MICROBIAL RESPIRATION IN SOILS
AMMENDED WITH A HERBICIDE
BIOMAGNIFICATION ACROSS TROPHIC
LEVELS IN LAKE WASHINGTON
(1 FULL TROPHIC LEVEL: d15N INCREASES 0.34%)
DDT
Predators
Grazers
Next Lecture
• Linking toxic effects across biological
levels of organizations
• Review
• Homework:
– Read PE 15
– Study ‘Part 1’: PE 1 – 6 plus lecture material
EXTRAPOLATION ACROSS LEVELS OF
BIOLOGICAL ORGANIZATION
• How can we relate the biochemical effects
of pollutants to changes at the population
level?
Or:
• How can we ‘proof’ that observed effects
at higher levels of organization are caused
by pollutants?
THREE POSSIBLE APPROACHES
1. Apply mathematical models to translate effects at
the biochemical level to population, community or
ecosystem level
•
Methodology largely undeveloped
2. Conduct large scale mesocosm, field enclosure or
field trials with varying pollutant levels including
controls
•
Elaborate, time consuming, expensive
3. Use ‘mechanistic’ biomarkers with effects that are
quantitatively ‘calibrated’ to population effects
•
Scope of chapter 15
FOUR EXAMPLES
• Effects of organophosphorus pesticides on
central nervous system
• Effects of DDT on central nervous system
• Effects of DDT on Ca-ATPase
• Effects of synthetic estrogens on
development
ORGANOPHOSPHORUS INSECTICIDES
BIOCHEMICAL
INTERACTION
OP
inhibits
Acetylcholine
esterase
Accumulation
of
Acetylcholine
in
synaptic cleft
PHYSIOLOGICAL
EFFECT
EFFECTS ON
INDIVIDUALS
Continuing
signal
transduction
leading
to
cramped
muscles
reduced
feeding
rates,
escape
from
predators;
death
EFFECTS ON
POPULATIONS
increased
mortality;
reduced
production
EFFECT OF DDT ON CENTRAL NERVOUS SYSTEM (CNS)
BIOCHEMICAL
INTERACTION
DDT
inhibits
Sodium
channel
in CNS
Retarded
restoration
of
Na/K
gradient
after
passage
of signal
PHYSIOLOGICAL
EFFECT
EFFECTS ON
INDIVIDUALS
Disturbed
signal
transduction
leading
to
tremors
and
convulsions
reduced
feeding
rates,
escape
from
predators;
death
EFFECTS ON
POPULATIONS
increased
mortality;
reduced
production
EFFECT OF DDT ON EGG SHELL PRODUCTION
BIOCHEMICAL
INTERACTION
DDT
inhibits
CaATPase
PHYSIOLOGICAL
EFFECT
Reduced
transport
of Ca
over
membrane
in
egg shell
gland
Reduction
of
egg shell
thickness
EFFECTS ON
INDIVIDUALS
EFFECTS ON
POPULATIONS
When
thinning
exceeds
17%,
eggs
may break
Reduced
breeding
success
SYNTHETIC ESTROGENS (EE2)
BIOCHEMICAL
INTERACTION
EE2
binds to
receptors
of
cells in
various
tissues
PHYSIOLOGICAL
EFFECT
EFFECTS ON
INDIVIDUALS
Development
of female
secondary
sexual
characteristics;
In liver of fish:
production of
vitellogenin
Reduced
sperm
production
male
sterility
EFFECTS ON
POPULATIONS
Reduction
in
recruitment
ADDITIONAL REMARKS
• Not all biomarkers indicate effects at
higher levels of biological organization
• Most sites are subject to multiple
pollutants/ sources of stress, which
obscure the clean relationship between a
‘mechanistic’ biomarker and effects on
populations and beyond
• Expression of biomarkers may depend on
environmental conditions, season, time of
day, etc