1. Describe a Predator/Prey interaction (not hare and lynx)
Welcome to Class
Describe a Predator/Prey interaction (not hare and lynx)

2. Agenda
Finish Predator/Prey Lab
Food Webs, Bioaccumulation

3. Bioaccumulation

4. DDT is a pesticide used for mosquito control and pest control
About DDT
DDT is a pesticide used for mosquito control and pest control
DDT accumulation in some bird species resulted in death, nervous system damage, and reproductive failure
DDT was banned in the United States in 1972
If students had difficulty with concepts from lesson one, review the examples from the previous day.
The answer to Review Questions 1 and 2 are on this slide.
Review Question 1: What are two sources of bias? 1) Sampling Bias 2) Measurement Bias
Review Question 2: What year was DDT banned in the United States? 1972

5. What kind of damage can DDT cause to birds?

6. In the body of an animal, DDT is changed (metabolized) to DDE.
DDE dissolves in fat, not in water, and is stored in fatty tissues.
DDE tends to remain in the body and can cause several problems

7. DDE: Kinds 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 DDE on their worksheets.

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

9. DDT on leaves of plants:
After DDT is applied,
Some volatizes
Some remains on the plant
Some washes off into the soil
eventually going into a stream, river, or lake
DDT on leaves of plants:
ingested by primary consumers (insects and rodents)
DDT in water:
remain in the sediment
consumed by bottom-feeding organisms
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.

10. Is DDT still used today? YES
Insect control on crops
Used for mosquito control

11. Food Web ORGANIC DEBRIS Osprey Sucker Trout Silverside Bay Shrimp
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 Osprey in Oregon and the Pacific Northwest. USGS FS
 Students will be asked to define food web on their worksheet.
Silverside
Bay Shrimp
Water Plants
Plankton
ORGANIC DEBRIS

12. Food Chain Osprey Large Mouth Bass Crayfish ORGANIC DEBRIS
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:
Crayfish
ORGANIC DEBRIS

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

14. bioaccumulation biomagnification
Ospreys and eagles are tertiary consumers and this makes them particularly vulnerable to DDT because of and
bioaccumulation
biomagnification
 The students will be asked to write down the definitions to bioaccumulation and biomagnification. Both terms will be define in the upcoming slides.

15. Bioaccumulation = the accumulation of a contaminant or toxin in or on an organism from all sources (e.g., food, water, air)
accumulate in living things and stored faster than they are broken down (metabolized) or excreted
Chemicals that are soluble in fat, like DDE, 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.

16. Biomagnification = the increase in concentration of toxin as it passes through successive levels of the food web DDE accumulates at higher levels in organisms that are higher in the food chain

17. Biomagnification of a DDE in Aquatic Environment
Level
Amount of DDE in Tissue
Tertiary Consumer µg/g ww
(fish eating birds)
Secondary Consumers µg/g ww
(large fish)
Primary Consumers
(small 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 DDE.
µg/g ww
Primary Producers
(algae and aquatic plants)
0.04 µg/g ww

18. Considering biomagnification, how could DDE harm an osprey?

19. Plant material and algae
Osprey Food Web
DDE 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 Osprey in Oregon and the Pacific Northwest. USGS FS
 Students will be asked to fill in the food chain given here and the relative concentrations of DDE.
µg/g ww
Crayfish
Plant material and algae
0.04 µg/g ww

20. The Effects of DDE on Reproduction
Species
Effect on Reproduction
DDE: 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 DDE biomagnifies in their tissue and this results in eggshell thinning. This slide combines results from two different studies measuring the concentration of DDE in eggs and comparing it to the reproductive success of bald eagles and osprey.
This slide shows the DDE concentration level that results in total reproductive failure, and this level of DDE 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., Organochlorine pesticide, polychlorobiphenyl, and mercury residues in bald eagles, , and their relationship to shell thinning and reproduction. Arch. Environ. Contam. Toxicol., 13, 529.
Johnson, D.R. et al., DDT and PCB levels in Lake Coeur d’Alene, Idaho osprey eggs, Bull. Environ. Contam. Toxicol., 13, 401.

21. Effects of DDE
High levels of DDE 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 DDE, female ospreys can also lay eggs that contain high enough concentration of DDE 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 DDE result in female osprey to lay thin eggs with thin eggshells.