Overabundance of serotonin can cause serotonin syndrome.

An overabundance of the neurotransmitter norepinephrine is most likely to be associated with manic episode.

plenty

Overabundance refers to an excessive amount of something, while a huge amount simply suggests a very large quantity. While they both imply a significant quantity, overabundance conveys a sense of excess or surplus beyond what is necessary or desirable.

Eutrophication is the epitome of "too much of a good thing". It happens when nature has an overabundance of nutrients. This overabundance makes everything in the ecosystem suffer.