Question:
What would be an easy to accomplish easy to understand
method to test algae and/or other microorganisms in
a pond water mini-environment (a gallon jar that
contains pond water and sediment along with various
naturally occurring populations) for the presence of copper
in the food chain? Some students added powered copper
to their pond water to test its effects on the populations.
We would like to know how to see if has actually infiltrated
its way into the microorganisms. We figure if it's in the
primary producer levels, that it's just a matter of time
before it travels up through the trophic levels. Any
help you can offer will be greatly appreciated. Thanks!
Replies:
The first problem is that the copper is water soluble and if ALL of the
organisms are in the same jar, you will not be able to determine if the
copper came from consuming algae or from living in or drinking the water.
The second problem is that copper, unlike fat soluble metals like mercury,
is not conservative. Just because you eat it, does not mean that you keep
it. The levels of copper that most organisms would have are below the
limits of say, your ordinary water test kit that can be found in fish
supply stores. The second problem is that no easy method for copper
detection at low concentrations exist. The best that one could do in
such a case would be to compare biomass and primary productivity in a
non-treated jar with that in a treated jar. In addition, invertebrates
are notoriously sensitive to copper, this is why the navy paints its ship's
hulls with copper based paint. It kills the barnacles. The action of
copper is that of a toxin at high levels, but at low levels it is a
required nutrient. Perhaps a different metal or chemical would be better
suited for studies of movement up trophic levels.
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