Purple corals come in a variety of types. The most common purple corals belong to the Anthozoa class and include soft corals, stony corals, black corals, and sea anemones. Purple corals contain pigments like astaxanthin or other carotenoids that give them their distinctive hue. These corals are found throughout tropical oceans around the world.
Soft Corals
Soft corals, also known as octocorals, are composed of colonies of tiny polyps that resemble eight-limbed sea anemones. There are over 3,000 species of soft corals which come in a rainbow of colors including purple. Some examples of purple soft corals include:
- Purple deadman’s fingers (Alcyonium purpureum)
- Purple reef octocoral (Briareum asbestinum)
- Purple sea whip (Junceella juncea)
- Purple gorgonian (Annella mollis)
These branching corals have a flexible, leather-like texture. The polyps protrude from the surface to feed at night. During the day, they retract back into the colony. Soft corals thrive on coral reefs and rocky substrates from shallow to deep waters. They derive their purple pigmentation from astaxanthin produced by symbiotic algae that live within their tissues. The algae receive nutrients and protection while providing energy to the coral.
Stony Corals
Stony corals, also called hard or scleractinian corals, have colonies composed of hundreds to thousands of individual polyps that secrete external skeletons of calcium carbonate. There are over 1,500 species of stony corals including various purple varieties such as:
- Grape coral (Leptoseris incrustans)
- Metallic coral (Herpolitha limax)
- Purple pore coral (Porites porites)
- Cauliflower coral (Plerogyra sinuosa)
These corals build reef structures as they grow. Their calcareous skeletons come in many shapes like plates, branches, and boulders. Purple stony corals harbor symbiotic algae called zooxanthellae which provide their vibrant coloration along with access to the sun’s energy. They are usually found in shallow, sunlit waters since the algae need light for photosynthesis. Stony corals help build the framework of coral reef ecosystems.
Black Corals
Black corals belong to the order Antipatharia. There are over 230 species, some of which have dark purple hues. These include:
- Purple coral (Antipathes dichotoma)
- Cirrhipathes anguina
- Telopathes magna
Unlike other corals, black corals do not have symbiotic algae. Instead, they get their color from scleroproteins and chitin in their skeletal structure. Black corals grow in branching shapes and can be found at depths up to 9,000 feet. Some species are quite long-lived, with ages over 4,000 years old. They provide habitat for many reef organisms.
Sea Anemones
Sea anemones are predatory animals related to corals and jellyfish. They come in a spectrum of colors with several purple varieties:
- Beaded sea anemone (Zoanthus sociatus)
- Sebae anemone (Heteractis crispa)
- Snakelocks anemone (Anemonia viridis)
- Blood-red anemone (Actinodendron plumosum)
These creatures have a column-shaped body ending in an oral disk surrounded by stinging tentacles. They attach to surfaces on the seafloor or coral reefs. Their bright colors serve as a warning to predators that they are toxic. Sea anemones harbor symbiotic zooxanthellae as well as other pigments that give them their distinctive hues.
Geographic Distribution
Purple corals inhabit tropical and subtropical oceans around the world. They thrive best in warm waters with moderate to high levels of sunlight. Some prime locations include:
- The Great Barrier Reef off Australia
- Coral reefs of the Caribbean Sea
- The Indo-Pacific coral triangle centered in Southeast Asia
- Hawaiian Islands and other Pacific Islands
- The Red Sea near the Middle East
In these shallow, clear waters purple corals can access the light and nutrients they need to survive. Geographic distribution varies by species based on environmental preferences like depth, current, and substrate. While some purple corals live in shallow reef environments, others are found hundreds or thousands of feet deep on seabeds.
Growth and Reproduction
Purple corals exhibit slow growth rates, often less than a centimeter per year for branching varieties. Massive species may grow only a millimeter annually. However, colonies can live for decades to centuries. This slow growth makes them sensitive to environmental disturbances.
They reproduce both sexually and asexually. In sexual reproduction, corals release gametes into the water column where fertilization occurs. The resulting larvae settle onto hard substrates and develop into polyps to start new colonies. Vegetative reproduction happens when fragments break off from parent colonies and reattach to a surface. This cloning process quickly expands the coral.
Threats and Conservation
Many purple corals face threats from both local and global stressors:
- Climate change leading to ocean warming, acidification, and coral bleaching
- Destructive fishing practices like bottom trawling and cyanide fishing
- Pollution from agricultural runoff, sewage, and coastal development
- Physical damage from divers and boat anchors
- Disease outbreaks
These impacts can damage or kill coral colonies. Preserving coral reef habitats is crucial. Strategies include designating marine protected areas, controlling runoff and sedimentation, restricting destructive practices, monitoring coral health, and taking action on climate change. Several purple corals are listed as threatened under the Endangered Species Act. Continued conservation efforts are needed to ensure the future of these unique purple corals.
Unique Traits
Purple corals possess many distinctive traits and adaptations:
- Vibrant colors that come from pigments, fluorescent proteins, and symbiotic algae
- Branching, mounding, plating, and encrusting growth forms
- Stinging cells on tentacles to capture prey
- Hard skeletons of calcium carbonate
- Symbiotic relationships with photosynthetic algae
- Sensitivity to changes in water conditions like temperature, acidity, and sunlight
- Slow growth rates measured in centimeters or millimeters per year
- Long life spans ranging from decades up to millennia
- Ability to clone through vegetative fragmentation
These adaptations allow purple corals to thrive in warm, tropical reef environments. Their diversity of shapes, sizes, and colors contribute to the beauty and biodiversity of coral reef ecosystems. More research is needed to fully understand these unique organisms.
Conclusion
Purple corals comprise a variety of coral species from soft corals, to stony corals, black corals and sea anemones. They derive their distinctive jewel tones from pigments, fluorescent proteins, and symbiotic algae that live within their tissues. These corals provide vital habitat for tropical reef organisms while building the very framework of coral reefs. However, they face mounting threats from both local pollution and global climate change. Preserving these fragile ecosystems will require reducing human impacts and protecting critical marine habitats. The continued survival of diverse purple corals highlights the intricate relationships and adaptations of species that compose coral reef communities. Their biological and ecological uniqueness makes protecting these purple denizens of tropical seas essential.
