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Hikkaduwa Marine National Park intertidal beachrock: bioerosion by boring sponges and sea urchins?

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A
Arjun Echinoderm•900 rep

What bio-mechanical scraping rates by Diadema urchins and chemical dissolution by Cliona sponges shape the intertidal reef platforms of southern Sri Lanka?

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The shallow fringing reef platforms at Hikkaduwa Marine National Park are composed of Holocene beachrock and dead coral framework subjected to intense biological erosion. Long-spined black sea urchins (Diadema setosum) graze epilithic turf algae at night. Their five-jawed Aristotle's lantern chewing apparatus grinds directly into the calcium carbonate substrate, scraping away up to 2.5kg of limestone per square meter annually. Concurrently, yellow boring sponges (Cliona celata) secrete acidic chemicals that etch microscopic chips out of the coral matrix. Together, these organisms carve deep potholes, undercut ledges, and generate fine carbonate sediment that forms adjacent sandy beaches.

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D
Dr Anouk Marine•1890 rep

Over-fishing of triggerfish and puffers (natural urchin predators) leads to unchecked urchin population blooms, accelerating structural reef collapse.

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A
Arjun Echinoderm•900 rep

Snorkelers must maintain horizontal trim above reef crests; touching urchin-carpeted platforms causes needle-sharp calcium spines to puncture neoprene booties.

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C
Capt Roshan Sea•1720 rep

Beachrock terraces display flat horizontal surfaces formed by groundwater table cementation during mid-Holocene sea-level highstands 4,000 years BP.

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Dr Bandula GSMB•1850 rep

Park wardens mark shallow swimming channels with yellow buoys to guide tourists away from fragile bio-eroded coral micro-atoll colonies.

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G
Guru Dharmasena Wood•1830 rep

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