The deep sea, a vast and largely unexplored realm, hosts unique life forms adapted to intense pressure, perpetual darkness, and frigid temperatures. Discoveries in these depths continue to unveil the planet’s incredible biodiversity, offering glimpses into ecosystems far removed from the sunlit surface.
Unveiling Savalia
Savalia, commonly known as gold coral, is a colonial false black coral belonging to the family Parazoanthidae. It forms large, tree-like structures with a horny, brown or black skeleton from which its yellow polyps extend. Each polyp, about 3 cm (1.2 inches) tall, has an oral disc surrounded by approximately thirty tentacles arranged in two whorls. These tentacles are not pinnate, a characteristic that helps distinguish Savalia as a zoanthid from other coral types.
A colony often begins by growing on the surface of another gorgonian coral, such as Paramuricea clavata or Eunicella singularis. Over time, Savalia engulfs its host and develops its own rigid, self-supporting skeleton. These colonies can reach impressive sizes, growing up to 2 meters (6 feet) in height with a main trunk diameter of 14 cm (5.5 inches).
Deep-Sea Dwellings
Savalia is found in the deep ocean, particularly in the northeastern Atlantic Ocean and the Mediterranean Sea. Its geographic range includes the western Mediterranean, from the Straits of Gibraltar to Sardinia, and into the Atlantic, encompassing the Canary Islands, Madeira, and the coasts of Spain and Portugal. While it is generally uncommon, it appears more frequently in areas like the Gulf of Corinth and the Sea of Marmara.
This coral typically inhabits depths ranging from 10 to 120 meters (33 to 394 feet), though some reports indicate a wider distribution down to over 600 meters. Research suggests its preferred habitat is a rough seafloor with steeply sloping rocks, typically at depths between 34 to 77 meters (112 to 253 feet). In these environments, it attaches to hard substrates like rocks on continental slopes or seamounts, enduring cold temperatures, high pressure, and low light conditions.
How Savalia Thrives
Savalia polyps obtain nutrients by filter feeding, capturing plankton and other suspended particles from the surrounding water. They can also absorb dissolved nutrients, supplementing their diet in the nutrient-scarce deep-sea environment. The skeleton of Savalia contains unique compounds, including an amino acid and an ecdysterone previously known only from terrestrial plants.
This coral exhibits a remarkably slow growth rate, with radial growth estimated at 14 to 45 micrometers per year. This slow growth contributes to its extraordinary longevity; carbon-14 dating has revealed that Savalia colonies can live for up to 2,700 years, making it one of the longest-lived organisms on Earth. Savalia colonies are either male or female, and sexual reproduction has been observed, with spawning occurring in December as seawater temperatures begin to cool. While larval stages and dispersal strategies are not yet fully understood, asexual reproduction also contributes to its survival.
Its Role in Ocean Ecosystems
Savalia acts as an ecosystem engineer within its deep-sea habitat due to its large, rigid, and long-lived three-dimensional structures. These complex, tree-like colonies modify their environment by reducing current velocity and stabilizing sedimentation, which increases the local deposition of fine particles. Such modifications create diverse microhabitats that support a variety of other deep-sea organisms, including squat lobsters, brittle stars, and sea spiders, offering them shelter from predators.
The presence of Savalia colonies enhances benthic biodiversity and faunal biomass in areas that might otherwise be barren. Larger marine animals, such as fish, sharks, and squid, are attracted to these areas due to the abundance of smaller prey, establishing a complete food web. Savalia plays a significant role in sustaining high levels of biodiversity and ecosystem functioning over long temporal scales in the deep-sea twilight zone.
Protecting Savalia
Savalia faces numerous threats, primarily from human activities in the deep sea. Deep-sea trawling, where heavy nets are dragged across the seafloor, is a widespread threat that can physically destroy these slow-growing coral colonies. Its slow growth rate makes Savalia particularly vulnerable to disturbance, as damaged colonies can take hundreds to over 1,000 years to recover, if at all.
Seabed mining and the deployment of underwater cables also pose risks by disturbing or destroying deep-sea habitats. Climate change presents additional challenges, including potential impacts from ocean acidification, which can weaken coral skeletons, and rising ocean temperatures, which although less directly impactful on deep-sea corals than shallow-water species, contribute to overall ocean stress. Conservation efforts include establishing marine protected areas and implementing regulations on deep-sea fishing activities, like prohibiting destructive gear in specific zones. Savalia is recognized for its rarity and vulnerability and is included in international agreements like Annex II of the Barcelona Convention and Annex II of the Bern Convention, aiming to ensure its maximum possible protection and recovery.