Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: A factory in Japan had been dumping mercury into Minamata Bay. Certain microorganisms in the water were able to change the mercury into a form that the plankton could use. Which most likely happened next?
The mercury passed through the food chain.
Plankton absorbed mercury.