- Paralytic Shellfish Poisoning
- peduncle
- pellicle
- periflagellar area
- periflagellar collar
- periflagellar flange
- periflagellar plates
- periflagellar pore
- phagotrophy
- photosynthesis
- phytoplankton
- pigments
- plankton
- plastid
- pore
- poroid
- post-cingular plates
- posterior
- pre-cingular plates
- premedian cingulum
- prokaryote
- prorocentroids
- pustule
- pusule
- pyrenoid