EcologyEcology

Air PollutionWater pollution

DDT Bioaccumulation

IntroductionIntroduction

Until the last 10, 000 years, living systems evolved in response to changes in the abiotic environment, unaffected by human activity.

Development of agriculture and technology, and widespread industrialisation has led to potentially damaging pollution

IntroductionIntroduction Pollution: process by which harmful substances

are added to the environment.

Problem becomes more serious due to increased industrialisation and urbanisation

Many products of modern technology find their way into the air and water

Air PollutionAir Pollution Was considered a local problem associated with urban and

industrial centers Now known that pollutants may be transported long

distances in the air, causing adverse effects in environments far removed from sources of emission

Mainly results from incomplete burning of fuels

2 main pollutants: Sulphur dioxide Lead

Sulphur dioxideSulphur dioxide

Source: Burning of fossil fuels Effects: SO2 enters leaves through stomata, damaging

leaves and killing the plants Combines with oxygen and rain water to form

sulphuric acid (acid rain)

Sulphur dioxideSulphur dioxide

Component of killer smog Mixture of smoke and fog Remains at lower layers of the atmosphere due

to air inversion.

LeadLead

Source: Burning of leaded petrol

Accumulates in the body Effects: cramps, loss of control of hands and

feet, coma and death

Water PollutionWater Pollution

Water PollutionWater Pollution

Inorganic wastes are discharged by industries into rivers and seas.

Examples:-phosphate ions from detergents-fertilizers leeched from the soil-non-biodegradable wastes (mercury, nickel etc)

EutrophicationEutrophication

EutrophicationEutrophication

Inorganic wastes decrease the amount of oxygen that is dissolved in water

Inorganic wastes and fertilizer encourage the growth of bacteria and algae

Algae form “mats” on water surface-- generally more competitive species dominate, hence reduction in phytoplankton diversity

EutrophicationEutrophication Algae mats reduce light penetration to lake bottoms Aquatic plants at bottom of lack unable to

photosynthesize Food chains in habitat affected; many organism deaths Algae not eaten enter the decomposition pathway Decomposition is an O2 demanding process, triggers

more organism deaths and greater organic matter released (vicious cycle)

Eutrophication--EffectsEutrophication--Effects

Species diversity decreases Plant, algal and animal biomass increase Water turbidity increases Rate of sedimentation increases, shortening the

lifespan of the lake Anoxic conditions (lacking oxygen) develop

Eutrophication--ProblemsEutrophication--Problems

Water not suitable for human consumption Increased vegetation impedes water flow and

blocks navigation of important waterways Commercially important species may disappear Amenity/ recreational value of water decreases

Eutrophication--SolutionsEutrophication--Solutions

Legislation to control fertilizer use Crop rotation (including legumes) Chemical removal of nutrients Monitoring of Biological Oxygen Demand (BOD)

to warn of possible algal blooms Monitoring of water supplies for nitrate content Incorporating Rhizobium into crop plants

Water PollutionWater Pollution Other Examples:- discharge of untreated sewage (direct health hazard for

humans and marine organisms)- land drainage containing heavy metals or hydrocarbons

(hazard for organisms due to biomagnification)- excessive slit discharge (hazardous to coral reefs)

Plastic bags strangle marine organismsPlastic bags strangle marine organisms

DDT BioaccumulationDDT Bioaccumulation

Background:- Between 1940 and 1960, DDT was a commonly used

pesticide- DDT was very persistent and remained in the

environment for long periods without being broken down- DDT accumulated across the food chain and had

devastating effects on carnivores at the top of the food chain

Recap:What is a Food Web?Recap:What is a Food Web?

Food Web = A summary of the feeding relationships within an ecological community.

Food Web = A summary of the feeding relationships within an ecological community.

ORGANIC DEBRIS

Osprey

Water Plants

Sucker

Bay Shrimp

Trout

Plankton

Silverside

Food Chain = One thread of the food webFood Chain = One thread of the food web

ORGANIC DEBRIS

Osprey

Large Mouth Bass

Crayfish

Components of a food webComponents of a food web Tertiary Consumers –

Animals that eat animals that eat animals

Secondary Consumers – Animals that eat animals that eat plants

Primary Consumers – Animals that eat plants

Primary Producers – Plants and Phytoplankton: organisms using the sun for energy

Why is food web knowledge important for understanding the impact of DDT on ospreys and eagles?

Why is food web knowledge important for understanding the impact of DDT on ospreys and eagles?

Ospreys and eagles are tertiary consumers and this makes them particularly vulnerable to DDT because of

bioaccumulation and biomagnification.

Ospreys and eagles are tertiary consumers and this makes them particularly vulnerable to DDT because of

bioaccumulation and biomagnification.

Bioaccumulation = the accumulation of a contaminant or toxin in or on an organism from all sources (e.g., food, water, air).

An increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.

Bioaccumulation = the accumulation of a contaminant or toxin in or on an organism from all sources (e.g., food, water, air).

An increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.

What is bioaccumulation?What is bioaccumulation?

Biomagnification = the increase in concentration of toxin as it passes through successive levels of the food web

DDT accumulates at higher levels in organisms that are higher in the food chain

DDT accumulation in some bird species resulted in death, nervous system damage, and reproductive failure.

As a result DDT was banned in the United States in 1972.

Biomagnification = the increase in concentration of toxin as it passes through successive levels of the food web

DDT accumulates at higher levels in organisms that are higher in the food chain

DDT accumulation in some bird species resulted in death, nervous system damage, and reproductive failure.

As a result DDT was banned in the United States in 1972.

What is biomagnification?What is biomagnification?

In the body of an animal, DDT is metabolized.

Metabolised DDT dissolves in fat, not in water, and is stored in fatty tissues. Thus, DDT tends to remain in the body and can cause several problems.

In the body of an animal, DDT is metabolized.

Metabolised DDT dissolves in fat, not in water, and is stored in fatty tissues. Thus, DDT tends to remain in the body and can cause several problems.

DDT: Types of DamageDDT: Types of Damage

Reproductive failure (in birds- eggshell thinning)

Immune system problems

Nervous system damage

Death

How does DDT move into lakes, streams and oceans?How does DDT move into lakes, streams and oceans?

After DDT is applied, some DDT vapourises, some remains on the plant, and some runs off the plant

into the soil, eventually making its way to a a stream, river, or lake.

The DDT that remains on the leaves of plants may be ingested by primary consumers such as

insects and rodents.

DDT that has washed into a waterbody, remains in the sediment or is consumed by bottom-feeding organisms or absorbed by fish gills and skin.

Biomagnification of a DDT in Aquatic EnvironmentBiomagnification of a DDT in Aquatic Environment

Tertiary Consumer 3-76 µg/g ww

(fish eating birds)

Level Amount of DDT in Tissue

Secondary Consumers 1-2 µg/g ww

(large fish)

Primary Consumers

(small fish)0.2-1.2 µg/g ww

Primary Producers

(algae and aquatic

plants)

0.04 µg/g ww

Considering biomagnification, how could DDT harm an osprey?

Considering biomagnification, how could DDT harm an osprey?

Osprey Food Web

Large Mouth Bass

Crayfish

Plant material and algae

3-76 µg/g ww

1-2 µg/g ww

0.2- 1.2 µg/g ww

0.04 µg/g ww

DDT Concentration

Osprey

Units of MeasurementUnits of Measurement1 gram = 1000 milligrams (mg) = 1,000,000 micrograms (µg)

microgram (µg) = one millionth of a gram

To describe concentrations: µg/g = number of micrograms (of toxin) per gram (of tissue)

2 µg/g DDT in egg content means there is 2 parts of DDT in 1,000,000 parts of an egg contents

ww or wet weight refers to the fresh weight of animal tissue.

dw or dry weight refers to the weight of animal tissue after it has been dried in an 65°C oven to remove all the water.

The Effects of DDT on ReproductionThe Effects of DDT on Reproduction

Species Effect on Reproduction

DDT: Critical Concentration (measured in egg contents)

Bald Eagle None < 3µg/g 1

Bald Eagle Failure 16 µg/g 1

Osprey Failure 17.6 µg/g 2

1. Wiemeyer, S.N. et al., 1984. Organochlorine pesticide, polychlorobiphenyl, and mercury residues in bald eagles, 1969-1979, and their relationship to shell thinning and reproduction. Arch. Environ. Contam. Toxicol., 13, 529.

2. Johnson, D.R. et al., 1975. DDT and PCB levels in Lake Coeur d’Alene, Idaho osprey eggs, Bull. Environ. Contam. Toxicol., 13, 401.

High levels of DDT cause the female ospreys to lay eggs with thin eggshells.

Thin eggshells have a greater chance of breaking, leading to embryo death.

With high levels of DDT, female ospreys can also lay eggs that contain high enough concentration of DDT to prevent embryo development.

High levels of DDT cause the female ospreys to lay eggs with thin eggshells.

Thin eggshells have a greater chance of breaking, leading to embryo death.

With high levels of DDT, female ospreys can also lay eggs that contain high enough concentration of DDT to prevent embryo development.

How is the impact of DDT on osprey and eagle reproduction measured?

How is the impact of DDT on osprey and eagle reproduction measured?

One Method for Measuring the Impact of DDT on Osprey ReproductionOne Method for Measuring the Impact of DDT on Osprey Reproduction

Collect eggs from abandoned osprey nests.

Measure the thickness of the eggshells.

Measure the amount of DDT in the egg.

Determine the association between eggshell thickness and DDT residue.

Relationship Between DDT Concentrations and Eggshell Thickness

0.440.450.460.470.480.490.5

0.510.52

0 1 2 3 4 5 6

DDT Concentration

Eg

gsh

ell

Th

ickn

ess

low concentrations high concentration

normal

thin

DDT reduces reproductive rates at moderate concentrations. At high

concentrations it causes total reproductive failure.

Relationship Between DDT Concentrations and Eggshell Thickness

0

20

40

60

80

100

0 2 4 6 8 10 12

DDT Concentration

Re

pro

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cti

ve

Su

cc

es

s

high concentrationlow concentration

high

low