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BIOL3219, Sandie L03
Geological history of coral reef distribution II
| Question | Answer |
|---|---|
| What are the 5 major geological events? | 1. Cambrian explosion (>500 mya) 2. Tethys ocean becomes circumglobal around equator (152 mya) 3. Formation of )modern continents as Laurasia and Gondwana split (50 mya) 4. Terminal Tethyan event (12 - 18 mya) 5. Isthmus of Panama (1 -6 mya) |
| What is IWP? | IWP = IndoWest Pacific |
| What is IAA? | IAA = Indo-Australian Archipelago |
| What is IMT? | IMT = IndoMalay Triangle (Coral Triangle) |
| If most species in the IAA hotspot are older than the Pleistocene, this suggests that the IAA is a current hotspot of biodiversity because? | So many species that originated via some other (earlier) mechanism in the IAA have STAYED in the IAA. So many species that originated earlier elsewhere have now ended up in the IAA. |
| What evidence about hotspot dynamics is there against most species arising form the Pleistocene? | The number of genera (α-diversity) of large benthic foraminifera (LBF): - Mid-Eocene West Tethyan and Arabian hotspots (38-40)mya) - Early Miocene Arabian and IAA hotspots (18 -23 mya) - Early Miocene Arabian to recent IAA hotspots |
| What is the relevance of 'hotspot dynamics'? | There have been multiple hotspots, allowing testing of ecological patterns or evolutionary processes that contribute to their formation. Hotspots are dynamic entities with 'lifecycle'; they arise, age and disappear. |
| What is the role of tectonic plates for hotspots? | A key feature of the three hotspots, is that each marks the location of a major collision between tectonic plates. The primary drivers of hotspot formation may operate over temporal scales beyond those traditionally used to examine diversity. |
| What is control #3: Ocean circulation? | These geologic events setup the current oceanic conveyor-like global circulation which heavily influences earth’s climate, and has done through geological time. |
| What is control #4:sea levels? | There have been enormous fluctuations in sea levels through cyclic phases of icehouse and greenhouse. |
| How fast can sea levels rise? | During the last deglaciation phase, peak sea rise rates were 50mm/yr. Sea rise rates have been much slower in the last 6000 years (during Holocene period) until NOW! |
| How can reefs respond to sea level rise? | There are THREE modes of reef accretion during sea level rise. These are keep up, catch up of give up. |
| What are the characteristics of the KEEP up the mode? | Accretion patterns: rapid Coral types: branching corals Water depth: shallow throughout |
| What are the characteristics of the CATCH up the mode? | Accretion patterns: Slow at first; faster as water shallows Coral types: branching over heads Water depth: shallowing through time |
| What are the characteristics of the GIVE up the mode? | Accretion patterns: variable until stops altogether. Coral types: variable Water depth: variable |
| How are the three modes of coral accresion represented graphically? | The keep up, catch up and give up modes can be plotted on a depth relative to present sea level VS time graph. |
| What is the take home message from lectures 2 and 3? | Plate tectonics, oceanic circulation, & sea level changes, combined with biotic evolution & extinction, controls the geographic distribution of coral reefs. Present day true coral reefs are currently restricted to the equatorial tropics and sub tropics. |
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