Cliona, often called boring sponges, are marine invertebrates known for their ability to excavate and inhabit calcium carbonate structures. They are widespread globally, influencing both natural formations and human-made installations. Understanding these sponges is important for comprehending their ecological impact and economic consequences.
Understanding Cliona Sponges
Cliona sponges are marine invertebrates, classified within the phylum Porifera. Like other sponges, they are filter feeders, drawing water through their bodies to extract microscopic food particles. Their unique characteristic is creating living spaces within hard, calcareous substrates.
The excavation process involves both chemical and mechanical actions. Specialized cells, called etching cells, secrete an acidic substance that chemically dissolves small portions of the calcium carbonate. These cells then mechanically remove the loosened chips of material. This continuous process creates an intricate network of tunnels and chambers within the substrate, with small, brightly colored papillae typically visible on the surface.
Where Cliona Thrives and What It Impacts
Cliona sponges are found in diverse marine habitats, ranging from tropical coral reefs to temperate coastal waters. They are prevalent in areas with abundant calcium carbonate substrates, such as coral skeletons, mollusk shells (like oysters and clams), and limestone rock formations.
Their boring extends to human infrastructure. Cliona can excavate into concrete structures and other calcareous components. While their activity is a natural part of bioerosion, contributing to the breakdown and recycling of calcium carbonate, their presence in certain locations can lead to significant concerns.
The Ecological and Economic Consequences of Cliona
Cliona sponges have significant ecological and economic consequences through their bioeroding activities. Ecologically, they contribute to coral reef degradation. Their boring weakens the structural integrity of coral skeletons, making reefs more susceptible to damage and breakage from storms and other physical disturbances. This bioerosion can also exacerbate the decline of coral reefs already facing stressors like rising ocean temperatures and ocean acidification.
Economically, Cliona poses a threat to aquaculture, especially shellfish farming. When these sponges infest mollusk shells, such as those of oysters and clams, they weaken the shells, making them brittle and more prone to breakage. This damage can render the shellfish unmarketable, reduce meat quality, and increase mortality rates, leading to financial losses for shellfish producers. Beyond aquaculture, their potential to bore into other calcareous structures, including historical marine artifacts or underwater cables, necessitates monitoring and management in vulnerable areas.
Recognizing Cliona Infestation
Identifying a Cliona infestation involves observing signs on affected surfaces. The most common indicators are small, round holes, typically 5 millimeters or less in diameter, on the surface of shells or corals. These openings often reveal brightly colored sponge tissue within or around them, which can appear yellow, orange, or green.
While visible surface signs might seem minor, the internal damage caused by Cliona is often more extensive. The sponge creates a complex network of tunnels and chambers beneath the surface, weakening the structure. For live shellfish, inspecting the shell surface for these small holes and colored tissue can indicate an infestation, with multiple holes suggesting advanced internal colonization.