phytoplankton is a kind of plant & phytoplanktons are found in bodies of water & an ocean is a kind of body of water ->  phytoplanktons are plants that can be found in the ocean  algae is found in bodies of water & algae is a kind of plant & an ocean is a kind of body of water ->  algae is a plant that can be found in the ocean  phytoplanktons are plants that can be found in the ocean & algae is a plant that can be found in the ocean ->  phytoplanktons and algae are plants that can be found in the ocean  phytoplanktons and algae are plants that can be found in the ocean & plants are a source of oxygen through photosynthesis ->  phytoplanktons and algae are source of oxygen in the ocean  phytoplanktons and algae are source of oxygen in the ocean & ocean pollution can decrease the number of phytoplanktons and algae ->  ocean pollution can decrease the source of oxygen in the ocean  ocean pollution can decrease the source of oxygen in the ocean & as the amount of a source of something decreases , the amount of that something will decrease -> ocean pollution can cause the amount of oxygen to decrease in the ocean