1. Phytoplankton: Microscopic plant-like organisms that drift in the water. They are the primary producers in the marine ecosystem, meaning they convert sunlight into energy through photosynthesis.
2. Zooplankton: Small animals that feed on phytoplankton and other microscopic organisms. Examples of zooplankton include copepods, krill, and protozoans.
3. Small Fish: Small fish such as sardines, anchovies, and herring feed on zooplankton. These small fish are an important food source for larger predators.
4. Medium-Sized Fish: Fish such as tuna, mackerel, and sea bass feed on small fish. These medium-sized fish are also prey for larger predators.
5. Large Predators: Sharks, killer whales, and other large predators hunt and feed on medium-sized fish, as well as seabirds and marine mammals. They are at the top of the food chain in the ocean.
6. Decomposers: Decomposers such as bacteria and fungi break down dead plants and animals, recycling nutrients back into the ecosystem.
Note that food chains are simplified representations of complex ecosystems, and there are many more species involved at each level. In reality, there are multiple interconnected food webs in the ocean, with many species having multiple food sources and predators.