BIO 475 Lecture Notes - Lecture 8: Coralline Algae, Beachrock, Oahu
Geology
● Reefs require antecedent structures, and they have to be shallow, 100 ft and shallower
is best condition
● Most reefs located near australia because it is more shallow
● 7,000 years sea level has been at present level
○ Prior, sea level was lower due to glaciation (water frozen in ice).
○ 18,000 years ago (modern man and mammoths), sea level was 100m lower than
today
● LAst ½ million years on average was 50m (150ft) lower than it is today
● Climate change may be good because if sea level rises, provides antecedent structure
for reefs
● Corals not growing up. Staying where they were before sea levels rose.
Bank/Shelf Reefs
● Florida Keys
● Great Barrier Reef
Fringing Reefs
● Oahu, Hawaii
● Bailey’s Bay, Bermuda
Atoll
Barrier
● Palau
● Bermuda
Patch reefs
● Reefs within a lagoon
Windward barrier reef geomorphology
Seaward slope
Spur and Groove zone; where there is a lot of wave energy
● Corals and algae grow on spur
Algal ridge; reef crest
● Ridge of algae, CCA
● Crustose Coralline Algae
Waves break from fore reef, spur and groove, until the algal ridge
Reef flat mantled with sand and gravel
● If there is an island you may get beachrock or erosion
Lagoonal reef flat
Lagoonal reef slope
Patch reefs
● Typically bigger , if there's corals stuck together; knolls
Cells
● Where patch reefs grow together;cells
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Document Summary
Reefs require antecedent structures, and they have to be shallow, 100 ft and shallower is best condition. Most reefs located near australia because it is more shallow. 7,000 years sea level has been at present level. Prior, sea level was lower due to glaciation (water frozen in ice). 18,000 years ago (modern man and mammoths), sea level was 100m lower than today. Last million years on average was 50m (150ft) lower than it is today. Climate change may be good because if sea level rises, provides antecedent structure for reefs. Staying where they were before sea levels rose. Spur and groove zone; where there is a lot of wave energy. Waves break from fore reef, spur and groove, until the algal ridge. If there is an island you may get beachrock or erosion. Typically bigger , if there"s corals stuck together; knolls.
