Suppose that the chemist does not find that the pH of the pond has changed significantly since the time when large numbers of the fish were found in the pond. After further research, the biologist discovers that the same fish species has been dying in large numbers in other bodies of water because of an infestation of a microscopic, parasitic protist. What type of expert should the biologist seek, and why? (**Will award Brainliest to best answer**)