Coral Reefs

Marine Biology Unit #9

Introduction Most complex & diverse ecosystem in our oceans Not only biological, but geological Spectacular!

Coral Polyps Member of Phylum: cnidaria, Class: anthozoa Related to sea anemones Most corals are colonial Few are solitary

Soft Corals (ahermatypic)Non-reef building coralsNo hard skeletonSea fans

Stony Corals (hermatypic)Reef-building coralsCalcium carbonate skeleton (secreted by

polyps)

Stony Corals (hermatypic)

Colonial Polyps Polyps housed in cups called corallite cups Polyps connected by mesentery (tissue) Polyps are clones

Zooxanthellae Symbiotic algae residing in polyp tissue Hermatypic corals Help deposit calcium carbonate Provide nourishment for polyps (via photosynthesis) Give coral coloration

Zooxanthellae

Coral Reefs Conditions for optimal growth:

Shallow water with plenty of light

Started on hard substrate Islands, shores

Clean, clear water

Warm water

Coral Reefs

Reef Formation Three main types of coral reefs:

Fringing Barrier Atolls

Fringing Reefs Close to shore (newly formed island; coast of mainland) Vulnerable to sediments, runoff, human disturbance

Fringing Reefs Rarotonga, Cook Islands

Moorea, Tahiti

Barrier Reefs Reef further from shore Lagoon between shore and reef

Barrier Reefs Back - reef slope (inner slope) is protected Reef flat may begin to form sand cays Outer reef crest/slope is where most growth occurs

Barrier Reefs Back - reef slope (inner slope) is protected Reef flat may begin to form sand cays Outer reef crest/slope is where most growth occurs Spurs and grooves allow lagoon circulation

Barrier Reefs Great Barrier Reef

Atolls Island has receded, leaving only coral “ring” Often contains islands or sand cays

Atolls Majority of atolls occur in the Indo-West Pacific Many atolls are inhabited

Bikini Atoll

Bikini Atoll

Reef EcologyNutrients recycled very effecientlySpace is major limiting factorCompetiton

overgrowing attacking

Reef Ecology Predation on coral

FishButterfly fishParrot fish

Reef Ecology Predation on coral

Parrot fish make coral sand

Reef Ecology Predation on coral

Crown-of-thorns (seastar)

Reef EcologyCoral bleaching

Temperature increasing Acidification

Reef Ecology Symbiotic relationships

Mutualism

Reef Ecology Symbiotic relationships

Commensalism

Reef Ecology Symbiotic relationships

Parasitism