Coral Reefs & Human Threats

Question 1

What phylum do corals belong to?

Answer 1

Cnidarian

Question 2

What region has the highest coral reef biodiversity?

Answer 2

The coral triangle in the Indo-Pacific

Question 3

Zooxanthellae

Answer 3

• Dinoflagellates in symbiosis with polyps

- Help corals make their calcium carbonate skeletons

Question 4

What is the exoskeleton of a coral reef made of?

Answer 4

Calcium carbonate

Question 5

Coral Polyp-Zooxanthellae Symbiosis

Answer 5

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

Question 6

Soft corals

Answer 6

• Mainly colonial, non-reef forming species

- Fleshy and bendable, very abundant among hard coral reefs

Question 7

List the three types of coral reefs

Answer 7

1. Fringing reef
2. Barrier reef
3. Atolls

Question 8

Fringing Reef

Answer 8

• 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

Question 9

What is the main area of a Fringing Reef called?

Answer 9

The reef flat; exposed in very LT

Question 10

Barrier Reefs

Answer 10

• 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

Question 11

Atolls

Answer 11

• Further from the shoreline
• Associated with a central lagoon
• Winds produce windward and leeward sides

Question 12

How does Darwin relate to coral reefs?

Answer 12

• The three types of reefs were first described by Darwin

Darwin’s hypothesis of coral overgrowth on a sinking island was correct (atolls)

Question 13

What are the most common interactions found between competitors?

Answer 13

• Corals against corals
• Corals against sponges
• Corals against seaweeds (most critical)

Question 14

Corals against seaweeds interaction: which species are in favour of corals?

Answer 14

Grazers that consume seaweeds (sea urchins and king crab)

Question 15

Corals against seaweeds interaction: which species are in favour of seaweeds?

Answer 15

Coral eaters and pollution

- Butterfly fish, crown of thorns

Question 16

Explain the trophic cascade of coral reef systems

Answer 16

Overfishing top predators decreases coral reefs.

Question 17

Crown of Thorns Starfish

Answer 17

• Huge coral reef predator

Question 18

List the stressors to coral reefs

Answer 18

• Pollution, sediments, and nutrients

- Examples include deforestation, dredging, coastal run off

Question 19

List the natural threats to coral reefs

Answer 19

1. Bleaching
2. ENSO
3. Disease

Question 20

What is coral bleaching?

Answer 20

• Major threat to coral reefs
  When water temperature increases, coral expel their zooxanthellae. Without algae, the corals turn transparent (white color is caco3)

Question 21

How does ENSO effect coral reefs?

Answer 21

ENSO causes warming conditions in the Pacific which prompt coral bleaching (major threat)

Question 22

List the diseases that effect coral reefs

Answer 22

• Black band disease
• White plague disease
• White band disease
• Yellow blotch disease

Question 23

What are the main problems with coral diseases?

Answer 23

1. Poor diagnoses (lack of expertise)

2. Interaction with bleaching and other forms of human disturbance

Question 24

What are the two main human threats to marine ecosystems?

Answer 24

1. Overfishing; bycatch of species other than the target

2. Pollution; toxins, acoustic, light

Question 25

What is the main problem with overfishing?

Answer 25

• 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

Question 26

Acoustic pollution

Answer 26

When there are multiple sources of noise, it alters dolphins echolocation and whales stop vocalizing. It also disrupts behaviour, foraging, and navigation.

Question 27

Light pollution

Answer 27

Too much artificial light causes issues with navigation an orientation in species. It also alters day/night cycles, timing of feeding, etc.