GEOS1100 Lecture Notes - Lecture 10: Ocean Acidification, Spearfishing, Runaway Greenhouse Effect
29 May 2018
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WEEK 10
Coastal processes and management III – Coral reefs
What is a coral?
• Comprises a colonial animal called a polyp
• A coelenterate - an invertebrate related to jelly fish, sea anemones
• And algae called zooxanthellae (or a dinoflagellate)
Corals are symbionts
• Invertebrate stings prey with its nematocysts provides nutrients
• Uses sugars produced as a by-product of the algae
• Algae get protection from stinging cells
• Photosynthesize - which makes the formation of the skeleton possible by facilitating
precipitation of carbonate
Corals form colonies
• Lots of different types of colonial structures which allow reefs to be created
• Only outside edge of structure is alive as the algae must photosynthesize
What is a coral reef?
1. Substrate --> the underlying rock, colonized as sea level rises
2. Framework --> cemented into limestone; unconsolidated rubble - boulders, sand, silt
and mud; mostly CaCO3 - mostly dead coral
3. Living coral colonies - a veneer
4. Other calcifying organisms e.g. a shellfish, calcareous algae
5. Organisms living in the coral rock
6. Organisms living in sediments on the reef surface
7. Organisms living in the waters of the reef
8. Reef islands
9. Organisms living on the reef islands - particularly important as seabird and turtle
nesting areas
What factors control reef growth rates and distribution patterns?
Main factors:
• Temperature (above 18˚c)
• Salinity (fully marine preferred)
• Water movement (needed)
• Light (needed)
• Sediment in water (generally bad)
Coral reefs for human resources
• Reef itself
• Huge % of world's old gas comes from reefal limestones
• Calcium carbonate is key component of cement
• Food resources
• Critical for many countries but in 2007 it was estimated that 60% more reef food (fish,
shellfish etc.) was harvested than could be sustained
-Subsistence versus commercial harvesting
• Tourism
• Major source of income in many countries
How are coral reefs managed?
• Zoning schemes in GBR
• Zoning schemes
• Permitting systems for many activities within the zones
E.g. permits required for research, education and tourist activities
• Supports scientifically - based management
• Sanctioning of existing uses - some problems
• Some activities are prohibited - spearfishing, extractive industry
The GBR is a special case
It works because:
• It is vast
• Generally low previous levels of use
• Reefs are mostly well offshore
• Adjacent human populations are low
Document Summary
Coastal processes and management iii coral reefs. What is a coral: comprises a colonial animal called a polyp, a coelenterate - an invertebrate related to jelly fish, sea anemones, and algae called zooxanthellae (or a dinoflagellate) Invertebrate stings prey with its nematocysts provides nutrients: uses sugars produced as a by-product of the algae, algae get protection from stinging cells, photosynthesize - which makes the formation of the skeleton possible by facilitating precipitation of carbonate. Corals form colonies: lots of different types of colonial structures which allow reefs to be created, only outside edge of structure is alive as the algae must photosynthesize. Main factors: temperature (above 18 c, salinity (fully marine preferred, water movement (needed, light (needed, sediment in water (generally bad) Subsistence versus commercial harvesting: tourism, major source of income in many countries. How are coral reefs managed: zoning schemes in gbr, zoning schemes, permitting systems for many activities within the zones.
