Chlorophyll is also contained by every single photosynthetic plant and algae that we know. For that reason, most plants and algae and phytoplankton are green. In addition to chlorophyll, there are many different kinds of photosynthetic pigments that absorb light and, thus, alter the shape of the absorption spectrum. The little bumps you see in this graph are caused by some of these different pigments. These pigments come in two varieties, photoprotective pigments and accessory pigments.
Photoprotective pigments act like sunglasses for the phytoplankton cell.
Accessory pigments act like ball gloves to catch wavelengths of light that chlorophyll isn't good at catching. These accessory pigments ultimately pass on their photons to chlorophyll and, thus, they help in the process of photosynthesis. Recall that phytoplankton cause the biggest change in the absorption properties of the ocean. Our discussion of the optical properties of seawater and the components suspended and living within it has taken us into deep into the frightening coves of physics and quantum dynamics. However, I trust you have survived.