Scientists have identified around 300,000 different marine and ocean species, making up about 15% of all know plants and animals on the planet. Our oceans are so vast with so much left to explore, it is said that a million or more undiscovered species might live in its waters.
The marine food chain is made up of a complex series of interconnected energy producers, such as plants and phytoplankton, and consumers from plant eaters (herbivores) and meat eaters (carnivores). Most marine species are tied together in a food web with multiple different layers.
- Level One: Photoautotrophs
- Level Two: Herbivores
- Level Three: Carnivores
- Level Four: Top Predators
The bottom level of the food chain is largely visible and made up of billions of single-cell organisms called phytoplankton.
These tiny organisms fill sunlit upper ocean waters around the world. It could be said that phytoplankton work like plants using the sun’s energy and through photosynthesis, turn nutrients and carbon dioxide into organic compounds.
These tiny organisms play a huge role, being the main producers of the organic carbon that all ocean animals need to survive. They also produce more than half of the oxygen that we breathe.
Plankton shows remarkable bursts of productivity, called blooms, at certain times of the year, particularly in the spring with longer days and greater sunlight.
The next level of the food chain is made of of plant eaters, or herbivores. Many are so small that they can not be seen with the naked eye. These tiny creatures are known as zooplankton. These tiny organisms drift across the oceans surface grazing on whatever they can. There are also larger herbivores such as turtles and manatees as well as certain types of fish.
Together these herbivores each a large amount amount of ocean plant life, and in turn become food for the carnivorous animals further up the food chain.
The small zooplankton become food for the carnivores. This includes plentiful smaller fish such as herring which are extremely successful hunters, but often fall prey to larger animals further up the food chain.
Large predators sit at the top, or apex of the food chain. This is a widely varied group including finned animals, such as dolphins and whales, feather animals such as eagles and sea gulls and flippered animals such as seals and sea lions. These top predators tend to be large, fast and extremely efficient at catching prey. They also tend to have longer life-spans and reproduce much more slowly.
The top predators are common prey for the most deadly hunters of all: humans. When populations of top species shrink due to overfishing, it can take years for them to recover. This is due to their slow rate of reproduction. The loss of these species can create problems throughout the entire food chain. For example, populations of the smaller animals they normally feed on can become too large. These smaller animals might then nearly wipe out populations of even smaller animals. or, they might eat too much plant life.