The Marine Park has unique natural values and a rich biodiversity with more than 1800 identified species and many more yet to be discovered. To this high biodiversity contribute the different types of habitats found within the park, which provide food and shelter for many species, some of high economic value.
These forests made of large brown algae are extremely productive habitats that many marine animals use as nurseries, refuge or for feeding. Very sensitive to environmental changes,
these habitats have been declining, but the Marine Park has already started recovery efforts.
In the waters of the Marine Park we find different gardens… they are not plants or algae, but animals - gorgonians. They are soft corals that live on rocks and feed on small beings that they filter from the water. They serve as habitat for many other species, some with commercial value. These corals live for tens of years and grow very slowly, which makes them especially sensitive to impacts and good indicators of the health status of coastal systems.
Essential to many species, rocky reefs are one of the most important habitats in the Marine Park. The quantity and diversity of the marine life associated to rocky reefs along the entire coast has been monitored to assess the effectiveness of the Park's management measures and its conservation status.
The Marine Park protects important habitats such as seagrass meadows, also known locally as “sebas”. These plants with flowers perform an essential role in the ecosystem. They improve water quality, hold the sand on the beaches, reduce the impact of waves and currents, help to remove carbon from the atmosphere and provide refuge, food and a safe breeding area for many fish and invertebrates. Until the end of the 1980s, the bay of Portinho da Arrábida (between the Fort and the figueirinha beach) was covered by an extensive seagrass prairie, which housed an oasis of life. At least 10 hectares of marine grasslands have been destroyed since then. With its disappearance, Arrábida lost a great source of wealth. The Park has been promoting its recovery.
The Marine Park has extensive bivalve beds, which were extensively explored before their protection. For many species, some of great commercial value, such as the octopus, these bivalves are a source of food. The prohibition of fishing with dredges and capture of bivalves with autonomous scuba diving within the limits of the park aimed to reverse the degradation of these resources and protect the habitats where they are found.
Below 60 meters deep, there are important habitats made of corals and sponges, some of which are quite rare species. In the deepest rocky reef areas of the Marine Park we can find black corals, gorgonians and orange corals that create an important habitat for other species as well.