Case Study: Tidal Bay Ecological Assessment
Answers
1. What are the benefits of comparing contaminant concentrations and biological
impact in Tidal Bay sediments with those of a reference area? This allows
researchers to be able to compare what they believe to be a contaminated area
with an area that is not. Because it is a similar area they are comparing it to, they
can see what is considered to be normal for that environment.
2. What are some of the limitations (problems) associated with the use of a
reference area and with the choice of Shipshape Inlet as this area? There are
significant differences, specifically in the type of sediment at the bottom of the
bays. Another issue is that Shipshape Inlet is more pristine that Tidal Bay but is
by no means an ideal comparison – it is still contaminated, just not as much. This
contamination exists because it is still in an industrial area and is associated with
the same large basin that includes Tidal Bay.
3. Can you think of another approach that might work? There are a lot of chemicals
at play in Tidal Bay (more than 150) which makes it difficult to see how specific
chemicals are affecting the environment of Tidal Bay. So being able to compare
the two areas is probably a good strategy.
4. What impact do you think the presence of multiple types of hazardous waste will
have on the ability of investigators to establish a cause-and-effect relationship
between specific chemicals and adverse (negative) biological changed in Tidal
Bay? When there are that many chemicals present in one area, you cannot tell
how those chemicals are going to interact together (like the Love Canal). This
means that they will not be able to establish a relationship between the
chemicals and the effect on the environment.
5. Do you feel these measurements are relevant to this aquatic ecosystem? Yes,
the measurements done on the species at the bottom of the food chain because
if their levels are high(er) then they will be passing those toxins up the food
chain. Also, it states that these species are very sensitive to toxins, are therefore
are because of their location would be exposed to the toxins.
6. Are these measurements likely to give the kind of data required to fulfill the
purpose of the assessment? If not, how would you change the approach? Using
a variety of chemical and biological tests adds validity to the assessment.
7. Investigators characterized degradation of benthic macroinvertebrate
communities in terms of a decrease in the abundance of total amphipods,
molluscs, polychaetes, or total macrofauna. However, many conditions can
influence the overall abundance of benthic macroinvertebrates including an algae
bloom that depletes oxygen in the water. Did the investigators consider all factors
that could have altered macroinvertebrate numbers? No. Some species will
increase because of an abundance of chemical pollutants.
8. Could apparent effects thresholds be determined for bioaccumulation and
histopathology in fish? Why do you suppose investigators did not do this? Yes,
they could of but the purpose of apparent effects threshold was to rank specific
problem areas in the bay. They did not do this because it could not be
determined how much hazardous waste the fish had been exposed to in the
water and food chain.
9. What are some major strengths of the apparent effects thresholds and what are
some limitations? Strengths are that they are very sensitive to the amount of
toxins present. However, its limits is that it is only for a specific site.
10. Name one point you learned that you feel is most interesting.