Reef Distribution
Where are most tropical shallow-water coral reefs found?
Warm tropical waters, mainly within about 30 degrees of the equator.
What are zooxanthellae?
Photosynthetic symbionts living in coral tissue.
What is the free-swimming coral larva called?
A planula.
What is ecosystem connectivity?
Movement of organisms, materials or energy between habitats.
What is species richness?
The number of species present.
Which three abiotic conditions favour reef-building corals?
Clear sunlit water, suitable warm temperatures and suitable salinity.
What do nematocysts do?
Capture prey and provide defence using stinging capsules.
How does fragmentation reproduce a coral?
A broken fragment survives, attaches and grows asexually.
How do herbivorous fish benefit corals?
They graze algae, reducing competition for light and settlement space.
What does high reef rugosity indicate?
A complex, uneven three-dimensional surface with many refuges.
How does a fringing reef differ from an atoll?
A fringing reef borders a coastline; an atoll forms a ring around a lagoon.
What does each partner gain from coral-zooxanthellae symbiosis?
Coral gains photosynthetic products; symbionts gain shelter, carbon dioxide and nutrients.
What stages connect released gametes to a new coral colony?
Fertilisation, zygote, planula, settlement, polyp and asexual budding.
Why do mangroves and seagrass support some reef fish populations?
They provide juvenile nursery habitat, food and shelter.
Counts are A: 10,10,10,10 and B: 37,1,1,1. Which has greater evenness?
A. Both have four species, but A has equal abundances.
Why does sediment limit coral growth?
It reduces light for photosynthesis and can smother coral tissue.
How do reef-forming hard corals differ from soft corals?
Reef-forming Scleractinia produce rigid calcium carbonate skeletons; soft corals lack the same massive reef-building skeleton.
How do currents and substrate affect recruitment?
Currents transport larvae; suitable substrate permits settlement. Post-settlement survival determines recruitment.
Why are corals ecosystem engineers?
They create complex three-dimensional habitat used by many other organisms.
Calculate SDI = 1 - sum[n(n-1)]/[N(N-1)] for counts 3 and 2.
N = 5. Sum = 6 + 2 = 8. SDI = 1 - 8/20 = 0.60.
How did sea-level changes shape the modern Great Barrier Reef?
Post-glacial rising seas flooded the shelf. Sea level stabilised about 6500 years ago, supporting reef growth near present levels.
How can corals obtain energy in nutrient-poor water?
Zooxanthellae supply photosynthetic products; polyps also capture prey. Nutrients are recycled within the symbiosis.
A reef gains 12 carbonate units but loses 15 annually. What is its net change and implication?
12 - 15 = -3 units per year. Destruction exceeds accretion, causing framework loss.
How could mangrove removal affect a nearby reef fish population?
Nursery loss reduces juvenile survival and subsequent recruitment to reef populations.
Why might removing a stressor not immediately restore an algae-dominated reef?
Hysteresis: feedbacks maintain the altered state, so stronger stress reduction or additional intervention may be needed.