Biology 5868
Ecotoxicology
Final Exam
May 13, 2009
Remember – each question has multiple parts. Be sure to address each part and provide a complete and
detailed answer.
1. Anthropogenic contaminants such as PCBs and perfluorooctane sulfonate (PFOS) have been found in
significant quantities in the tissues of humans, fish, and marine mammals in the Arctic region. Assuming
that these chemicals were produced in temperate industrial regions, explain in detail how they end up in
high concentrations in humans and other top predators thousands of miles from their point of origin or
use. Include in your explanation the time scale involved as well as interactions with different biotic and
abiotic phases. (15 points)
The answer should address two points: 1) How persistent organic pollutants (POPs) move from
temperate areas to the Arctic, and 2) Once there, how POPs move through the food web to
concentrate in top predators.
Certain compounds move from temperate to Arctic regions through a process called global distillation.
Key characteristics of these chemicals are they are A) fairly volatile and B) resistant to physicochemical and biological degradation.
POPs volatilize at their point of origin or use and enter the atmosphere in the vapor phase; prevailing
winds in the Northern hemisphere carry the POPs northward.
In some cases, POPs can be carried from temperate regions to the poles in one air movement,
resulting in hemispheric transport of POPs in weeks or months. In other cases cooler temperatures,
either at high altitude or related to seasonal changes, cause POPs to condense out of the vapor phase
onto dust, soil, water, and biota in a region north of their original entry into the air column.
As seasonal temperatures increase, POPs re-volatilize and the pattern of movement and recondensation is repeated. Over several years this process can result in the progressive movement of
POPs to northern regions where they cannot volatilize because the ambient seasonal temperatures
are too low.
Lipophilic (high Kow/Koc) POPs can enter the food web at any point via bioaccumulation at lower
trophic levels, and biomagnify through higher trophic levels. Since they are not likely to be degraded,
they are available for re-volatilization after the death and decomposition of the organism. The
combination of global distillation and biomagnification results in high concentrations of bioavailable
POPs in the Arctic and especially in top predators/consumers.
2. Polycyclic aromatic hydrocarbons (PAHs) are known contaminants produced by oil sands mining
processes. Your task is to design and conduct a community-level NOEC test to establish an acceptable
concentration for PAH releases. Your community must consist of at least 3 members at different trophic
levels (you do not need to list the exact species, just taxa and trophic level), including at least one
invertebrate and one vertebrate. You can use an existing community or create a hypothetical
community. The community (or one similar to the hypothetical community) must reside in a habitat
found within the oil sands project region, in the Athabasca region, or in any area affected by
contaminants from the Athabasca oil sands project. Please answer the following questions (please label
your answers). (35 points)
A. In which abiotic phase or phases are PAHs likely to be found? Why? (3 points)
Lower ring number (lower molecular weight) PAHs tend to either volatilize into air or into
water; higher molecular weight PAHs have a higher KOC and will partition to sediments
B. What species or taxa in your community are likely to have the highest PAH body burden?
Why? (3 points)
Invertebrates will generally have higher body burdens than vertebrates.
Invertebrates cannot metabolize PAHs, while vertebrates can. Therefore, invertebrates
would be expected to have higher body burdens.
C. Would you expect the oil sands process PAHs to bioaccumulate? Why? (3 points)
Yes and no.
Higher molecular weight PAHs tend to bioaccumulate more than lower MW PAHs. In
addition, invertebrates will bioaccumulate PAHs more than vertebrates.
D. Would you expect the PAHs to biomagnify in any food web? Why? (3 points)
PAHs might biomagnify in “invertebrate only” food webs, but not in most conventional
food webs. Since vertebrates can metabolize PAHs, they would actually contain fewer
PAHs than their invertebrate food sources.
E. List the community members and describe a test that would confirm their trophic position.
(3 points)
Organisms:
Comparative trophic level position can be established using stable isotope discrimination.
F. What biomarker(s) would you use for PAH exposure for each community member? Why?
(3 points)
Biomarkers for PAH exposure include P450 enzyme gene activation, immunoassay, or
activity (e.g. EROD) for almost all organisms; tumor formation in vertebrates. P450 activity
would indicate exposure (detoxification); tumors are good effects biomarkers.
G. Describe the community-level NOEC test(s); include the type of test(s), organisms used,
(including age, sex, etc, if applicable), test parameters, and endpoint(s). (6 points)
Community-level NOEC tests are designed to estimate the lowest concentration of the
contaminant that will cause an effect in various individuals in a community or in the
community as a whole. Tests should be dose-response experiments using PAH
concentrations that include those likely to be experienced in the contaminated settings.
Organisms (as well as their sex, age, developmental or metamorphic stage) will vary,
depending on the community of interest, but could include native species or surrogate
(model) species. Test duration depends on the experimental organisms and the endpoints;
for example, P450 enzyme induction tests in invertebrates or vertebrates could last hours
to days, while tumorogenesis in bird or mammals could last months and reproductive
studies in birds or fish could be carried out for many months.
Alternative community-level NOEC test designs include the most sensitive species test
(weighted NOECs) and the modified most sensitive species test (i.e. pooled NOECs).
H. How would you use the data from the test to regulate allowable PAH releases? (4 points)
Your community-level test(s) should result in a PAH concentration that caused no effect
(at the 95%, or p ≤ .05 level) for one or more of the species in the community. You can use
this information to set allowable PAH release levels based on concentrations that protect
the most sensitive species, the keystone species, or protect at the pooled NOECs for
multiple species.
I. List and discuss two reasons why your community-level NOEC test might be inadequate to
protect similar communities in the oil sands mining region. (3 points)
e.g. does not protect most sensitive species
e.g. protection level not adequate for protection of community
e.g. not enough known about community
J. Describe a test of PAH effects at a level of biological organization above the community level
and one at a level below the community level that could be conducted in the oil sands
region. For each of these tests describe the information that you would expect to gain and
explain how it would enhance your understanding of the oil sands contamination issues.
(3 points)
Bonus question. On May 8, 2009 a UN environmental organization banned the production and use of
nine chemicals, including the pesticides hexachlorocyclohexane (lindane) and chlordecone. These
additions bring the total of internationally banned or restricted chemicals to 22, which also include the
pesticides aldrin, dieldrin, and chlordane, as well as PCBs and dioxins. What characteristics put these
chemicals on the banned list? (3 points)
Toxic
Persistent (resists both physical and biological degradation)
Bioaccumulate/biomagnify (lipophilic, poorly biodegradable)