Another would be that some species of pennate diatoms are motile, meaning they are able to push themselves through the water column. This helps them maintain a planktonic existence because they are able to stay at the top of the water column where there is more sunlight. Then there is the siliceous frustola, it is thought to have developed so that it could help protect the diatom from grazers. Another thought about the siliceous frustule is that it could help capture light energy for photosynthesis, which would help the diatom because it needs photosynthesis to live. These are some of the morphological adaptations that diatoms have evolved to help them maintain a planktonic existence. Dinoflagellates have a pair of flagella, transverse flagella, which are wrapped around the body and then, when whipped in a wave-like manner, cause the cell to enter a rotary motion, which gives it forward propulsion. This helps dinoflagellates maintain their planktonic existence because it can help them stay at the top of the water column, making it easier for them to perform