Reef Building
Name the group of corals that are the primary reef builders and are commonly called "stony corals."
Scleractinian corals (stony corals)
Give two abiotic requirements (physical conditions) that limit where reef-building corals can grow
adequate light penetration, warm water temperatures, High salinity,
Name the three main categories of coral reefs
fringing, barrier, atoll
What trophic role do zooxanthellae play in relation to their coral hosts?
Zooxanthellae perform photosynthesis, produce organic matter, and transfer much of it to the coral host
Reef building corals
hermatypic
What photosynthetic symbiont lives inside nearly all reef-building corals and helps them form calcium carbonate skeletons and gain nutrients?
Zooxanthellae
How deep are corals only able to grow? why?
Reefs rarely form deeper than about 50 m because light for photosynthesis of zooxanthellae is limited; depth limits light availability.
What type of reef is characterized by a wide reef flat right up against the coast, a shallow reef crest and ends in a reef slope
fringing reef
Explain how fish grazing contributes to nutrient cycling on reefs and why grazers are important for reef health.
When fish graze on algae they excrete nutrients (nitrogen, phosphorus) that become available to algae and zooxanthellae, recycling nutrients and supporting productivity on otherwise nutrient-poor reefs.
long coiled tubes attached to the wall of a polyp's gut that secretes digestive enzymes
mesenterial filaments
Planktonic coral larvae that becomes the starting individual for a coral colony
Planula larvae
Explain coral bleaching: what causes it at the cellular level and why prolonged bleaching threatens reef survival.
Bleaching occurs when corals expel zooxanthellae (often due to heat stress); without zooxanthellae corals lose major nutritional input and color, and prolonged loss can cause mortality.
What distinguishes a barrier reef from a fringing reef? Include the feature between the reef and shore
Barrier reefs are separated from shore by a relatively deep lagoon; fringing reefs are attached directly to shore
Describe two methods corals use to compete with neighboring corals for space
Describe two methods corals use to compete with neighboring corals for space
erosion caused by organisms
bioerosion
Give me one non-coral organisms that is essential for reef formation and describe one way it contributes to reef structure.
coralline algae
functions: absorbs wave shock; traps sediment; cements coral in place
Describe how sediment build-up negatively affect coral reef health
increased silt blocks light and smothers coral surfaces
Summarize Darwin’s explanation for how atolls form (include the key process of the underlying island).
Darwin proposed they form when a volcanic island subsides while the reef grows upward, leaving a ring as the island sinks.
Which organisms other than coral can have a symbiotic relationship with zooxanthellae?
sea anemones
snails
giant clams
this is usually the widest part of a reef
Reef flat
Define bioerosion and describe two biological agents or behaviors that cause it
Bioerosion is the biological breakdown of reef structure; caused by grazers that scrape/bite (e.g., parrotfish), burrowers (worms, sponges), and other eroders.
El Niño events can cause widespread reef damage. Explain the mechanism by which El Niño typically causes coral stress and connect this to long-term reef decline
El Niño raises sea surface temperatures regionally, causing thermal stress that leads to mass bleaching events; repeated bleaching reduces coral reproductive success and increases mortality, causing long-term reef decline
Which type of reef would you most likely see small patch reefs?
Barrier reef
What two things must sessile organisms on a reef compete for?
light
a hard surface to grow on
the shallow upper edge of a reef
reef crest