Air Pollution Water pollution DDT Bioaccumulation Ecology Air Pollution Water pollution DDT Bioaccumulation

Introduction 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

Introduction 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 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 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 dioxide Component of killer smog Mixture of smoke and fog Remains at lower layers of the atmosphere due to air inversion.

Lead Source: Burning of leaded petrol Accumulates in the body Effects: cramps, loss of control of hands and feet, coma and death

Water Pollution

Water 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)

Eutrophication

Eutrophication 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

Eutrophication 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--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--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--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 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 organisms

DDT 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 The goal of lesson two is to introduce the concepts of bioaccumulation and biomagnification and their importance in the environment. Additionally, lesson two introduces students to the natural history of osprey and bald eagles in the context of food webs. Finally, students will be encouraged to visualize what type of graph they can expect with various datasets.

Recap: What is a Food Web? At this point it may seem that a completely new topic is being introduced. To transition to the explanation of food webs, ask students how the toxicity of DDT is related to food webs.

Food Web = A summary of the feeding relationships within an ecological community. Osprey Sucker Trout In lesson three the students will work with an osprey dataset. To familiarize students with some of feeding habits of osprey,the example food web focuses on osprey. For additional information about osprey refer to the osprey information sheet. The osprey is often mistakenly called the fish hawk or fish eagle. Historically, ospreys were reported as numerous, nesting in forested areas near water because they favored dead trees or trees with flat or dead tops. Unlike most birds of prey, osprey are tolerant of human activities and will build nests on almost any suitable structure close to water and with an abundant supply of fish. Ospreys are able to catch fish by hovering, and then plunging three feet into the water to capture fish. Their dense oily feathers make them suited to repel water and quickly regain flight. USGS. 2002. Osprey in Oregon and the Pacific Northwest. USGS FS-153-02.  Students will be asked to define food web on their worksheet. Silverside Bay Shrimp Water Plants Plankton ORGANIC DEBRIS

Food Chain = One thread of the food web Osprey Large Mouth Bass This is the same picture of food web but with one chain highlighted. It is assumed that most students are familiar with the basic concept of food webs and food chains. If food webs and food chains are new material, please refer to the suggested reading site for additional information. The following website also has additional information about food webs: http://www.saunderscollege.com/lifesci/titles.html Crayfish ORGANIC DEBRIS

Components 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  Students have a copy of this pyramid on their worksheet and are to identify primary producers, primary consumers, secondary consumers, and tertiary consumers.

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.  The students will be asked to write down the definitions to bioaccumulation and biomagnification. Both terms will be define in the upcoming slides.

What is bioaccumulation? 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. Chemicals that are soluble in fat, like DDT, particularly tend to bioaccumulate compared to those soluble in water. Chemicals that are soluble water are removed from the body in urine, whereas those soluble in fat, do not have a means to leave the body and remain in tissue.

What is biomagnification? 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.

In the body of an animal, DDT is metabolized 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 Damage Reproductive failure (in birds- eggshell thinning) Immune system problems Nervous system damage Death  Students will be asked to list some of the damage caused by DDT on their worksheets.

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. After DDT is applied, some DDT residue remains on the plant material and some washes off the plant into the soil eventually making its way to a body of water. The DDT that remains on the leaves of plants is taken up by primary consumers such as insects and rodents. As for the DDT that has washed into a stream, river or lake, it enters the food chain through consumption by bottom-feeding fish or through absorption by fish gills and skin.

Biomagnification of a DDT in Aquatic Environment Level Amount of DDT in Tissue Tertiary Consumer 3-76 µg/g ww (fish eating birds) Secondary Consumers 1-2 µg/g ww (large fish) This is an example of actual concentrations of DDT as it passes through the heron food chain. It is important that the students notice the units in which DDT is measured and to become familiar with the relative amount of DDT that accumulates in organisms of different trophic levels. Students will also be given another example using osprey to demonstrate this point. There are several factors that contribute to the problem of bioaccumulation and biomagnification in aquatic environments. When DDT is applied it runs off into water and collects in lakes, streams, wetlands and other bodies of water. Fish are then exposed to DDT through consumption of organic debris on the floor of a water body and/or through their gills when it is suspended in water. Thus, water dwelling creatures are at higher risk of bioaccumulating DDT. 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?

Plant material and algae Osprey Food Web DDT Concentration Osprey 3-76 µg/g ww Large Mouth Bass 1-2 µg/g ww Osprey are at the top of the aquatic food chain, and are thus exposed to many pollutants found in the environment. Toxic chemicals are present in water, air, sediments, and aquatic biota throughout osprey breeding and wintering ranges. Many of these contaminants bioconcentrate from water passed through fish gills, and bioaccumulate in the fish from their food. The efficient transfer of chemicals from food to consumer through two or more trophic levels results in biomagnification, a systematic increase in tissue residue concentrations from one trophic level to another. USGS. 2002. Osprey in Oregon and the Pacific Northwest. USGS FS-153-02.  Students will be asked to fill in the food chain given here and the relative concentrations of DDT. 0.2- 1.2 µg/g ww Crayfish Plant material and algae 0.04 µg/g ww

Units of Measurement 1 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. This slide will give a quick introduction to the units of measurement that are used for measuring concentrations. Micrograms per gram is in several of the slides in lesson 2 and wet weight and dry weight are in lesson 3 and 4. For additional information about units of measurements the following website is a useful reference: http://www.unc.edu/~rowlett/units/index.html

The Effects of DDT on Reproduction Species Effect on Reproduction DDT: Critical Concentration (measured in egg contents) Bald Eagle None < 3µg/g 1 Failure 16 µg/g 1 Osprey 17.6 µg/g 2 Because both bald eagles and osprey are at the top of the food chain, the DDT biomagnifies in their tissue and this results in eggshell thinning. This slide combines results from two different studies measuring the concentration of DDT in eggs and comparing it to the reproductive success of bald eagles and osprey. This slide shows the DDT concentration level that results in total reproductive failure, and this level of DDT concentration would result in an immediate local extinction. In other words, if bald eagles or ospreys were exposed to the above levels of DDT, within one generation there would be a local extinction. It is important to note that levels between three and 16 µg/g impair reproduction. Intermediate levels of DDT concentration would result in a slow decline in the bald eagle and osprey populations, and this would likely lead to an eventual extinction. 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. 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.  Students have fill-in-the-blank questions to answer questions about this slide. It is important that students understand that high levels of DDT result in female osprey to lay thin eggs with thin eggshells.

How is the impact of DDT on osprey and eagle reproduction measured? In Lesson 3 and Lesson 4 students will be working with real data. In order for students to have a clear picture of how and why data was collected, the next slide introduces the data collection method.

One 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.

The above graph depicts data where eggshells with higher levels of DDT concentration are thinner.

DDT reduces reproductive rates at moderate concentrations DDT reduces reproductive rates at moderate concentrations. At high concentrations it causes total reproductive failure.

At moderate DDT concentration there is slightly lower reproductive success than at low DDT concentrations and at a certain high concentration of DDT there is total reproductive failure.