Living coral is a marine organism, often mistaken for a plant or a rock due to its appearance and stationary nature. These structures are colonies of tiny invertebrate animals. They form intricate underwater landscapes that are integral to the health and biodiversity of our oceans, highlighting why their preservation is a global concern.
What is Living Coral?
Living coral is a marine invertebrate animal, specifically a polyp, belonging to the phylum Cnidaria, which also includes jellyfish and sea anemones. Each coral polyp has a sac-like body with a mouth surrounded by tentacles. These tentacles contain stinging cells called nematocysts, used to capture small prey from the water and sweep it into their digestive cavity.
Many corals engage in a symbiotic relationship with microscopic algae called zooxanthellae, which live within the coral’s tissues. The zooxanthellae perform photosynthesis, converting sunlight into energy, and provide the coral with up to 90% of its nutritional needs in the form of sugars and proteins. In return, the coral offers the algae a protected environment and essential compounds like carbon dioxide. Hard, or stony, corals secrete a rigid external skeleton of calcium carbonate, which accumulates over time to form reef structures. Soft corals, in contrast, do not produce a hard external skeleton but instead have a wood-like core and soft bodies that sway with ocean currents.
The Coral Ecosystem and Its Vital Role
Individual coral polyps reproduce and grow, building upon previous generations’ calcium carbonate skeletons to form massive structures known as coral reefs. These reefs thrive in warm, clear, shallow, and sunlit waters, typically within a temperature range of 68–90°F (20–32°C), as the zooxanthellae require sunlight for photosynthesis. Reef formation begins when coral larvae, called planulae, settle on a solid surface and develop into polyps, forming these complex underwater structures over thousands of years.
Coral reefs are often called “rainforests of the sea” because they are biodiversity hotspots, providing habitat and food for an estimated 25% of all marine species, including over 4,000 species of fish. These natural barriers protect coastlines by reducing wave energy and buffering against storms, preventing erosion and property damage. Coral reefs also hold substantial economic value, supporting fisheries and attracting tourism through activities like diving and snorkeling. They serve as a source for new medicines, with compounds from reef organisms being explored for treatments for cancer, arthritis, and other diseases.
Threats to Coral Health
Coral reefs face threats, primarily from climate change. Rising ocean temperatures cause corals to expel their symbiotic zooxanthellae, leading to coral bleaching, where the coral turns white. Ocean acidification, resulting from the ocean’s absorption of increased atmospheric carbon dioxide, lowers the water’s pH, making it more difficult for corals to build and maintain their calcium carbonate skeletons.
Local pollution also impacts coral health. Runoff from agriculture, sewage, and industrial waste introduces harmful substances, such as pesticides, fertilizers, and heavy metals, which can smother corals, promote algal blooms, and weaken coral immune systems. Plastic pollution physically damages reefs and acts as carriers for pathogens. Destructive fishing practices, like dynamite fishing or bottom trawling, directly destroy coral structures and disrupt reef ecosystems. Increasing prevalence of coral diseases, often linked to environmental stressors, can lead to widespread coral mortality.
Global Efforts to Conserve Coral
Strategies are being implemented worldwide to protect and restore coral reefs. Establishing Marine Protected Areas (MPAs) safeguards reefs by limiting human activities like fishing and tourism within designated zones. These areas help preserve biodiversity and allow fish populations to recover, benefiting coral health by maintaining balanced ecosystems.
Coral restoration projects rebuild degraded reefs. Methods include coral nurseries, where coral fragments are grown in controlled environments before being outplanted onto damaged reefs, and coral gardening, which involves transplanting healthy coral pieces to assist recovery. Promoting sustainable tourism and fishing practices is also key, encouraging responsible interactions with reefs and supporting local economies through ecotourism. Individuals can contribute by making responsible seafood choices, reducing their carbon footprint, and supporting conservation organizations. Ongoing scientific research improves our understanding of coral biology and the threats they face, leading to new techniques and strategies for their long-term survival.