The most common marine plants found around the world are the seagrasses, which can form extensive underwater growths known as meadows. These are plans which produce fruit and flowers, much in the same way as plants on land. An example is Posidonia oceanica (Neptune Grass), which is endemic to the Mediterranean Sea, which is considered as a keystone species due to its different roles in plays in marine ecosystems (if the species in the oceans formed a football team, Posidonia oceanica would be one of the most important players in the team!).

For example, it forms a complicated network which is home to a large variety of marine species, including molluscs (snails), echinoderms (starfish and sea urchins), and even fish species which use the plant’s meadows to lay their eggs and as a nursery for their young. In addition, the seagrass meadows shield the coast from erosion arising from intense storm activity, whilst also oxygenating the water.

Besides seagrass meadows, some other important marine habitats include boulders, caves and coral reefs. The latter are mostly found around the tropics and are on the decline due to harmful fishing techniques used, coastal development and due to damage from more frequent major storms. The Great Barrier Reef, measuring 1,243 miles, is the largest living structure on Earth. It can be seen from the Moon.