1. Explain how HIPPO factors contribute to population changes
Readings: Read about Daniel Pauly and overfishing linked on the Week 6 module
Also watch the linked EO Wilson TED talk
P is for Pollution
Nitrogen Cycle Nitrogen is contained in all living things:
proteins, DNA and RNA
The atmosphere contains: N2 gas
Nitrogen must be fixed into nitrate (NO3-) or ammonium (NH4+)
to be used by plants
1) N fixation occurs in the soil by bacteria (sometimes in
symbiotic association with certain plant roots)
2) Ammonium can be assimilated or converted into nitrite
(NO2-), then nitrate (NO3-) by bacteria
3) NO3- can be assimilated by plants through their roots
QUESTION: How do alders obtain nitrogen when they grow in
soils lacking in nitrogen?
QUESTION: Where do organisms like squirrels or salmon
obtain nitrogen that they need to make protein or nucleic acids
(DNA and RNA)?
4) Excess NO3- may be converted back to N2 gas by bacteria
5) N-containing organic materials pass through trophic levels, wastes and dead organic material is deposited
6) activity of decomposers return N to soil for plants use
Nitrogen loading - Eutrophication = Addition of inorganic nutrients (human-induced)
In estuaries and coastal ecosystems N is limiting so addition of
N to coastal water causes eutrophication This is when high
nutrient levels results in excessive growth of phytoplankton or
algal bloomswhen they die decomposers take O2 out of water
for their own respiration while breaking down dead algae .
There is not enough O2 in water and there is no mixing of water
to add O2 which means that fish and other organisms die =
Black Sea Gulf of Mexico Dead zones
Saanich inlet also has a small dead zone
This same phenomenon of eutrophication occurs in lakes due to the addition of P
(phosphorus, usually as phosphates). The added phosphates promote the rapid
growth of algae. The algae form a green scum on the lake. As the algae die they sink
into the water and become food for aquatic decomposers. The decomposers deprive
other aquatic organisms of dissolved oxygen causing their death.
QUESTIONS: What nutrient is usually lacking to prevent the growth of algae in
healthy lakes? How could you test if this nutrient is lacking in coastal waters?
Phosphate is lacking. You can test this by adding it to the soil and seeing if there is
Agriculture: growing crops depletes soil N
Because crops removed from fields there is no decomposition to return N to soil. Instead…
Fertilizers added –farms, golf courses, gardens runoff to lakes and rivers
Nitrates contaminating groundwater affect the health of amphibians, animals and humans (babies)
-also causes acidification of lakes and soils (QUESTION: What effect could this have?)
QUESTION: How is nitrogen added back to forest soils? Hint: you observed it happening in Pacific
Spirit Park on your field trip.
It is added back to soil by decomposers and dead organisms that die off after eating the trees… or
the trees dying off themselves.
Other sources of nutrient loading:
-phosphate containing detergents
-sewage and factory wastes
Where does your sewage go? Iona Island Sewage treatment station
Sewage is kept in holding tanks to let the
solids settle out and to add oxygen to speed
up decomposition (Most decomposers need
oxygen to work)
-most “nutrients” are removed from water before
returning water to the natural environment but…
In the past when released partially treated sewage
close to shore-had a type of eutrophic effect:
phytoplankton zooplankton crustaceans RATS!!
Now drain empties farther offshore and down deeper
QUESTIONS: Why could adding the treated sewage into deep water have less of a eutrophic effect?
a. Benthic (deep water organisms) inhibit decomposers
b. There is not enough oxygen for decomposers to be able to live and decompose the sewage
c. The sewage forms sediments which turn into rock (forming rock is a secondary thing. This is
not the main reason for a eutrophic effect)
d. There is no light to allow plankton to grow from the nutrients liberated by composers (no
phytoplankton or even decomposers down at that depth)
e. All of the above but b
What environmental event could cause this sewage to still have a eutrophic effect?
a. A storm with large waves (waves allow the sewage to be mixed up some more)
b. Increase temperature
c. Increase salinity (increased salt)
d. Formation of ice on the surface
e. All of the above
POPs (Persistant Organic Pollutants ) and other toxic wastes (heavy metals)
[organochlorines, organobromines] [lead, mercury, arsenic]
Sources: Pesticides e.g. DDT
Industrial chemicals e.g. PCB (polychlorinated biphenyls)
Waste by-products e.g. dioxins
Why are we concerned about these wastes?
Many have been implicated in causing cancer and disrupting natural hormones.
Exposure to or consumption of these compounds can cause
Decreased ability to produce antibodies
Decreased resistance to infection
Disruption of hormone production
A global threat - These compounds are primarily produced in industrial countries.
POPs when released (as smoke) into the atmosphere are transported through air currents far from
the point of origin.
In colder climates particulate matter in the atmosphere is more likely to precipitate
POPs enter the food chain/web as they are absorbed by
The POPs do not break down, they are stored in oils or
With each link in the food chain (subsequent trophic
level) the POPs become more concentrated.
In this Arctic food chain
POPs preciptate dissolved in sea water (FILL IN THE BLANKS BELOW based on your knowledge)
⇒ absorbed by phytoplankton
⇒ consumed by zooplankton
⇒ which are consumed by fish
⇒ consumed by seals
⇒ consumed by polar bears
⇒ hunted by humans
QUESTION: Why is this a form of biomagnification? How does it fit?
POPs concentrate in fat. They do not breakdown. As you move up the food chain they become more
concentrated in organisms higher up the chain.
Concentration of PCBs in Canadian arctic polar bear: 10 ppm
Norwegian arctic polar bear: up to 100 ppm
After 2 decades of polar bear studies they found that young bear cubs had 2X the PCB levels of their
mothers. Researchers concluded: PCBs pass through the placenta
Young cubs consume milk with concentrated PCB levels
Documented effects on human health – Traditionally the Inuit of Northern Canada consume a diet of
fish and sea mammals. In a study published in 1994, comparisons of breast milk from Inuit and
Caucasian women in northern Quebec indicated that the Inuit women had PCB levels that were 4X
higher. These higher PCB levels were correlated with:
Developmental problems in infants
Smaller birth weights and growth rates
Reduced immune function, more susceptible to disease
More recent studies have found:
Decreased testosterone levels in males and increased rates of infertility.
QUESTIONS: Are caribou likely to show high levels of POPS? Are arctic hares? Are walruses?
QUESTION: which animals from arctic food webs are likely to show high levels of POPS
d. a and b
e. b and c
O is for Overconsumption/overuse Eg.: Decline of global fisheries
When John Cabot explored Newfoundland his crew could gather cod by putting buckets over the
side of the ship. Thus began fishing for Atlantic cod. Initial fishing was done in small boats with nets
by fishers from Newfoundland, Spain and Portugal. They brought the fish to shore for processing as
Factory ships developed in the mid 1950’s increased the catch of cod but also included by-catch
(non-target species) and disrupted spawning. Their fishing methods scraped the ocean’s bottom
which caused great damage to the bottom-dwelling species. They were also very efficient at catching
cod and as seen the graph above the amount of fish caught greatly increased. The stocks began
declining until the population completely crashed in the 90s. It has not recovered.
UBC Fisheries Professor Dr. Daniel Pauly has won the Cosmos prize (likened to the
Environmental Nobel prize) for his work on fish conservation. He has monitored
global fish populations for many years observing that current fishing practices are
not sustainable and global fisheries are in decline.
He has observed that the average trophic level of fish
caught in both marine and freshwater ecosystems has
declined. There is a greater dependence on organisms
low on food webs. = “fishing down the food web”
QUESTIONS: What are some examples of organisms at
higher trophic levels? (which have greatly diminished
a. Swordfish, shark
b. Tuna, salmon
c. Mussels, prawn
d. A and b
e. A and c
What are some examples of organisms at lower trophic
levels? (that are beginning to be overharvested now)
a. octopus, cod
b. tuna, salmon
c. mussels, prawn
d. a and b
e. a and c
QUESTION: What is Dr. Pauly advocating? (What can we do to prevent collapse of aquatic
a. close high trophic fisheries but increase quotas for shellfish and other spp. At lower trophic
b. reduce quotas (amount fishers are allowed to take) for all commercial species
c. create a number of marine protected areas
d. all of the above
e. b and c
Consider the various elements of HIPPO as you undertake this next activity.
Salmon Farming in BC
A case study
The aquaculture or farming of fish started in Norway in the 1960’s. Fish farms were located in deep
fjords with high water replacement rates. The industry developed technologies to support a
successful industry and as a result has provided Norway, the rest of Europe and Russia with a
reliable source of Atlantic salmon for over 40 years.
The pristine BC coast was identified for the potential development of a fish farming industry. With
encouragement from the BC government the Norwegian technologies were adapted for BC and in
1971 the first salmon farm was in operation in BC. Following an optimistic beginning, which lead to a
peak of 135 fish farms, the number of fish farms decreased. There are now only 12 fish farms along
the southern BC coast. As the difficulties of catching the dwindling stocks of wild salmon increase the
politicians’ reason that there are social and economic benefits to be gained in supporting this industry.
A BIOL 111 task force is being set up to investigate and evaluate the economic, social, environmental
and ecological impact of this industry.
After forming groups of 4 or 5 students collect an envelope.
In this envelope you will find descriptions of different interest groups each on a different colour of
Each member of your group needs to select one of these and return the envelope.
Prepare answers to the questions appropriate for the role.
The researched information will be discussed next class.
Keep track of sources of your information (lobby groups, organizations, government websites,
Next week your group will need to prepare and hand in a one-page position paper.