Coral Reefs & Human Threats Flashcards
What phylum do corals belong to?
Cnidarian
What region has the highest coral reef biodiversity?
The coral triangle in the Indo-Pacific
Zooxanthellae
- Dinoflagellates in symbiosis with polyps
- Help corals make their calcium carbonate skeletons
What is the exoskeleton of a coral reef made of?
Calcium carbonate
Coral Polyp-Zooxanthellae Symbiosis
Coral polyps catch nutrients from zooplankton + fish/invertebrate excretion, which is used by Zooxanthellae during photosynthesis. In return, photosynthesis provides oxygen and sugar to the polyps.
- Deep sea coral do not have Zooxanthellae
Soft corals
- Mainly colonial, non-reef forming species
- Fleshy and bendable, very abundant among hard coral reefs
List the three types of coral reefs
- Fringing reef
- Barrier reef
- Atolls
Fringing Reef
- Band of coral reefs distributed along the shoreline, right under the LT level
- Most common type
- Sensitive to runoffs, pollutants, or estuarine plumes
- Close to beaches, mangroves, rocky shores, and small/shallow lagoons
What is the main area of a Fringing Reef called?
The reef flat; exposed in very LT
Barrier Reefs
- Not restricted to the vicinity of the shoreline
- Usually associated to a deeper lagoon
- In addition to a reef flat, we see fore- and back-reef slopes
Atolls
- Further from the shoreline
- Associated with a central lagoon
- Winds produce windward and leeward sides
How does Darwin relate to coral reefs?
- The three types of reefs were first described by Darwin
Darwin’s hypothesis of coral overgrowth on a sinking island was correct (atolls)
What are the most common interactions found between competitors?
- Corals against corals
- Corals against sponges
- Corals against seaweeds (most critical)
Corals against seaweeds interaction: which species are in favour of corals?
Grazers that consume seaweeds (sea urchins and king crab)
Corals against seaweeds interaction: which species are in favour of seaweeds?
Coral eaters and pollution
- Butterfly fish, crown of thorns
Explain the trophic cascade of coral reef systems
Overfishing top predators decreases coral reefs.
Crown of Thorns Starfish
- Huge coral reef predator
List the stressors to coral reefs
- Pollution, sediments, and nutrients
- Examples include deforestation, dredging, coastal run off
List the natural threats to coral reefs
- Bleaching
- ENSO
- Disease
What is coral bleaching?
- Major threat to coral reefs
When water temperature increases, coral expel their zooxanthellae. Without algae, the corals turn transparent (white color is caco3)
How does ENSO effect coral reefs?
ENSO causes warming conditions in the Pacific which prompt coral bleaching (major threat)
List the diseases that effect coral reefs
- Black band disease
- White plague disease
- White band disease
- Yellow blotch disease
What are the main problems with coral diseases?
- Poor diagnoses (lack of expertise)
2. Interaction with bleaching and other forms of human disturbance
What are the two main human threats to marine ecosystems?
- Overfishing; bycatch of species other than the target
2. Pollution; toxins, acoustic, light
What is the main problem with overfishing?
- Bycatch; the catch of species different from the original target, or the juvenile stages of the target
- Overfishing is a human threat to coral reefs
Acoustic pollution
When there are multiple sources of noise, it alters dolphins echolocation and whales stop vocalizing. It also disrupts behaviour, foraging, and navigation.
Light pollution
Too much artificial light causes issues with navigation an orientation in species. It also alters day/night cycles, timing of feeding, etc.
