- Phytoplankton is a kind of plant
- Phytoplanktons are found in bodies of water
- An ocean is a kind of body of water
- Therefore, 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
- Therefore, 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
- Hence, 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
- So, 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
- Hence, 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
- Therefore, ocean pollution can cause the amount of oxygen to decrease in the ocean

So, ocean pollution can cause the amount of oxygen to decrease in the ocean
One effect of ocean pollution is that it can reduce populations of phytoplankton and algae. The reduction of these populations might have which impact on an ecosystem?
- Ocean pollution can decrease the number of phytoplanktons and algae 
- Phytoplankton is a kind of plant 
- Plants are a source of oxygen through photosynthesis 
- Algae is found in bodies of water 
- Phytoplanktons are found in bodies of water 
- Algae is a kind of plant 
- An ocean is a kind of body of water 
- As the amount of a source of something decreases , the amount of that something will decrease