Warmer waters also encourage some poisonous marine bacteria to grow and lead to illness in humans whenever taken with raw seafood, like oysters.

这个句子中，不定式to grow and lead to illness作宾补，when taken为省略了主语+be的时间状语从句，修饰动词不定式。when从句的主语和不定式的逻辑主语一致，且从句谓语含有动词be,所以从句省略了they are。they指不定式的逻辑主句，即动词encourage的宾语—poisonous marine bacteria. 从句的意思为：当有毒海洋细菌随生的海产品一起被食入时。