Question

if there is a toxin present in the primary producer population, how might this affect organisms at higher topic levels?

Answer 1

Biomagnification.
When a toxin is present in a producer population. Other organisms are affected by this. How?
As the primary consumers eat large amounts of plants in their lifetime, their tissues become filled with the toxin. As secondary consumers eat many of their preys(primary consumers) in their lifetime, their the tissues become filled with the toxin in higher scale that those of the primary consumers. As the top-predators eat many organisms that contain hundreds of accumulated toxins in their lifetime, the tissues of the top-predators reach the enough level of accumulation of toxins. This accumulation of toxins causes top-predators to die. :v

Review. (Dots represent toxins)
Biomagnification
Consumer: ..
1^ consumers: ...
2^consumers: .....
3^consumers: ........... = X_X