Plankton is not the name of a plant or animal but more of a category for any drifting organism that inhabits the middle to upper levels of the ocean, namely the pelagic zone.
Most vets do spays, neuters, bone surgeries, spleen surgery, tumor removals, and intestinal surgeries. Heart surgery and more complicated surgeries are done by specialists that requires more schooling. If you want to be a vet, you have to have REALLY good grades and Vet school is MUCH harder to get into than human medical school.
Veterinarians rely on technologists and technicians to conduct a variety of clinical and laboratory procedures, including postoperative care, dental care, and specialized nursing care. Veterinary technologists and technicians who work in research-related jobs do similar work.