What is a coral polyp, and how does it build a reef?

A tiny, soft-bodied animal (related to anemones) that secretes a hard calcium carbonate cup around itself; billions of these cups accumulate over thousands of years to form a reef A type of algae that hardens and cements together to form reef structures A microscopic bacterium that forms colonies that solidify over time The larval stage of a jellyfish that settles and grows into a hard structure

What is the relationship between zooxanthellae and coral polyps, and what happens when it breaks down?

Zooxanthellae are photosynthetic algae living in coral tissues, providing up to 90% of coral's energy; when stressed by warm water, corals expel them, causing bleaching and starvation Zooxanthellae are parasites that cause disease in coral; their removal by bleaching is a coral immune response Zooxanthellae provide color to coral; bleaching occurs when dye leaches from the reef Zooxanthellae filter toxins from the water; bleaching means the coral is healthy and clean

Why do coral reefs require clear, shallow water to thrive?

Their photosynthetic zooxanthellae need sunlight; turbid or deep water blocks light and prevents photosynthesis, starving the coral Reef fish need shallow water to breathe air; the fish create the structure Coral polyps need to be partially exposed at low tide to survive Coral requires warm surface water to produce calcium carbonate; depth makes water too cold

What is coral biodiversity, and why is it so high on tropical reefs?

The enormous variety of species on a reef results from the complex three-dimensional structure creating thousands of distinct microhabitats, each supporting different species Tropical reefs have high biodiversity because tropical water contains more nutrients than other oceans High temperatures increase mutation rates, rapidly generating new species on reefs Reef biodiversity is high because coral poisons competing organisms, leaving space only for the most adaptable species

What is the role of parrotfish on a coral reef?

They bite off chunks of coral and rock with their beak-like teeth to eat algae and zooxanthellae, producing fine sand as a byproduct and keeping reefs free of algae overgrowth They build nests inside coral heads to protect their eggs from currents They are venomous fish that protect coral from predatory crown-of-thorns starfish They produce chemicals that prevent algae from settling on coral surfaces

What is coralline algae, and what role does it play in reef construction?

Calcified algae that secretes calcium carbonate, helping to cement reef pieces together and create a hard surface on which new coral larvae can settle A type of soft algae that provides food for coral polyps Algae that produces oxygen used by coral for respiration Harmful algae that competes with coral for space

What is a 'phase shift' on a coral reef?

A transition from a coral-dominated reef to an algae-dominated reef, usually triggered by overfishing of herbivores, nutrient pollution, or coral bleaching The natural seasonal cycle of coral growth and dormancy When a new coral species colonizes a reef, displacing existing species The transition from a fringing reef to a barrier reef over geological time

What is coral spawning, and why do many species do it simultaneously?

Mass spawning is when many coral species release eggs and sperm into the water on the same night, triggered by lunar and temperature cues, maximizing fertilization success and overwhelming predators Corals spawn individually year-round; mass spawning is a myth Corals only reproduce asexually by budding, not by releasing eggs Mass spawning is triggered by storms that mix the water column

What are coral reef restoration techniques being used today?

Coral gardening (growing coral fragments on underwater nurseries and transplanting them), assisted evolution, and removing algae or invasive species manually Adding fertilizer to reef water to stimulate faster coral growth Covering reefs with shade cloth to reduce bleaching Introducing new reef-building species from other oceans to replace lost corals

What is the 'Coral Triangle' and why is it significant?

A region spanning parts of Indonesia, the Philippines, Malaysia, Papua New Guinea, and the Solomon Islands that contains the highest marine biodiversity on Earth A deep-ocean zone in the Pacific where three tectonic plates meet, forming hydrothermal vents The three largest coral atolls in the Indian Ocean The area of the Caribbean where the first coral reefs were scientifically described