Touching coral can cause significant harm, often leading to a slow death for the colony. Coral reefs are not rocks but living communities composed of tiny animals called polyps, which secrete a hard, limestone-like skeleton that forms the reef structure. Even a gentle touch from a human hand or fin can disrupt this delicate biological system. This article explores the specific biological vulnerabilities of coral, the mechanisms of damage following contact, and the steps to prevent this harm.
Why Coral Is Biologically Vulnerable to Touch
The reef structure is built by minuscule, soft-bodied coral polyps, which are the living tissue covering the calcium carbonate skeleton. This tissue is remarkably thin, making it susceptible to even minor abrasion. The polyps rely on this fragile tissue layer for gas exchange, nutrient absorption, and their symbiotic relationship with the zooxanthellae algae that live within them.
A transparent, gelatinous layer of mucus covers the entire surface of the living coral colony. This mucus acts as the coral’s primary defense, serving as a physicochemical barrier. It shields the polyps from pathogens, harmful ultraviolet radiation, and environmental stress. The mucus also helps the coral catch fine food particles and clear away sediment.
Contact with a foreign object, such as a hand or fin, immediately compromises this essential outer layer. The physical disruption strips away the mucus, which houses beneficial microorganisms that fight off infections. Without this protective coat, the underlying coral tissue is exposed directly to the surrounding seawater, greatly increasing its vulnerability.
The Mechanisms of Immediate and Delayed Damage
The immediate consequence of touching coral is tissue loss or abrasion against the rough, underlying skeleton. Even a light brush can scrape away the delicate polyp tissue, exposing the white calcium carbonate skeleton beneath. This exposed area is a permanent scar and a dead zone where polyps can no longer feed or grow, and it is highly susceptible to colonization by algae or bacteria.
The delayed damage begins when the protective mucus layer is removed, leaving the coral open to invasion by microbial pathogens. Bacteria and fungi in the water can then establish infections, leading to destructive diseases. Furthermore, the energy a coral expends to repair damaged tissue and regenerate a new mucus layer is diverted away from reproduction and growth. This redirection of resources stresses the coral, making it less resilient to other environmental pressures, such as rising ocean temperatures that trigger coral bleaching.
Severity of Harm Based on Contact Type
The severity of the damage is directly related to the type and force of the contact. A light touch or brushing, often accidental from a diver’s hand or fin, primarily removes the protective mucus layer, leading to the delayed risk of disease and infection. While the immediate physical damage may be minimal, the biological defense system is disabled, creating a lasting vulnerability.
More forceful contact, such as kicking, standing, or grabbing the coral, causes immediate, catastrophic damage. These actions can crush the delicate polyps and fracture the hard calcium carbonate skeleton, especially on fragile structures like branching or foliose corals. Since many coral species grow extremely slowly, a broken branch can represent decades or even centuries of growth that is instantly lost.
Indirect contact from human activity also causes significant harm, such as when boat anchors drag across the reef. The physical scraping from anchors and chains can destroy large swaths of coral. Furthermore, the sediment stirred up can smother polyps, hindering their ability to feed and breathe, and reduces the light penetration needed by the symbiotic algae.
Responsible Viewing and Prevention Techniques
To prevent harm, the absolute rule for all reef visitors is to look but never touch, maintaining a respectful distance from all coral formations. Snorkelers and divers must prioritize mastering buoyancy control to float effortlessly above the reef without making inadvertent contact with their body, fins, or equipment. Wearing appropriate exposure protection, such as a full wetsuit or rash guard, can also prevent accidental contact if a current or surge pushes a person toward the reef.
Another important preventative measure involves the use of personal care products. Many common sunscreens contain chemicals that are toxic to corals and can cause bleaching. Choosing a reef-safe sunscreen, or simply covering up with clothing, helps reduce chemical runoff that further stresses the ecosystem. When visiting a reef, securing all loose equipment and avoiding the stirring of bottom sediment are simple actions that protect the health of the coral colony.