Some would argue that the Copepoda is one of the most important groups of the crustaceans. They are found in abundance and constitute an important source of protein in the oceans. Their fecal pellets also accumulate onto the ocean floor and greatly accelerate the flow of nutrients and minerals from the ocean surface to the ocean floor.
Many copepods are parasites. However, several groups are free-swimming and are food to many fish and the whales of the northern hemisphere. You can read more about the different groups of copepods at the systematics page.
Often many copepod species occur in the same area. This observation raises questions about the resource partitioning of those copepods. Click life history to read more about copepod ecology and behavior.