Exam 2 Chapter 5- Coral Reefs

What are the benefits of coral reefs

1. food

2. tourism

3. medicine

4. fish nurseries

5. habitat for marine life

6. shoreline protection

7. aquarium industry

8. high species diversity

Coral reef paradox

tropical waters surrounding coral reefs are nutrient poor but reef supports large amounts of sea life

The coral reef is efficient at

cycling nutrients

Coral reefs are

biological (corals) and geological structures (secretion of limestone)

Coral reefs are found

worldwide

Coral reefs are restricted to

shallow, regular salinity, clear waters in 20-30*C range

Corals deposit what to build reefs?

calcium carbonate (CaCO3) or limestone

Major groups of corals

Phylum Cnidarian; Class Anthozoan

The anthozoan class lacks

a medusa stage and lives as polyps

Scleractinian corals

Stony/true corals

Scleractinian corals are the

main reef builders, almost all have zooxanthellae

Soft corals are not

reef builders, most have zooanxthellae

Coral morphologies

variety of coral structure

Coral structure

- plate like

- foliaceous (leaf-like)

- columnar

- massive branching

- encrusting

- free-living

Zooxanthellae ex

symbiotic single cell dinoflagellates

Zooxanthellae are

photosynthetic algae living inside many corals

When does coral bleaching occur

when zooxanthellae are expelled

When can zooxanthellae be expelled?

When temps are too high or other stressful conditions

Coral polyp

sessile sac-like structure, ring of tentacles armed with nematocysts

Nematocysts are

released from cnidocytes, sting prey

Reproduction of corals

- asexual by budding/fragmentation

- sexual by release of gametes into water

What larvae of coral settles on substrates?

planula larvae

Photosynthetic zooxanthellae provide corals with

nutrition to survive

Most corals will also eat

zooplankton

Whats caught by their tentacles?

detritus

Mesenterial filaments

coiled tubes attached to wall of coral's gut secrete digestive enzymes

Corals also absorb

dissolved organic matter (DOM)

Types of Coral Reefs

- fringing reef

- barrier reef

Fringing reefs are

the most common, near shore

Fringing reefs are vulnerable to

human activity, freshwater run-off and sedimentation

Fringing reefs basic structure

Reef flat, reef slope, reef crest

Fringing Reef flat

shallow up to shore, gradually becomes deeper

Fringing Reef slope

steep slope at edge of reef flat, more dense coral growth than flat

Fringing Reef crest

edge of reef flat where the slope begins, often most corals

Barrier reef

along coast, further away from shore than fringing reef

Lagoons are

between shore and barrier reef ( soft sediment with seagrass)

Lagoons can have

patch reefs, coral knolls or pinnacles

Black-reef slope is

on lagoon side, wave action limits coral growth

Barrier Reef flat is

- shallow

- can have seagrass beds

- some patch reefs

Barrier Reef crest

- edge of fore-reef slope

- richest coral growth usually

Barrier fore-reef slope

descent away from shore

Barrier sand cays/keys

sand builds up

Barrier spur and groove formations

sand channels along fore reef slope caused by wave and wind action

Different shapes of corals grow at

different depths along slope

Top depth

massive corals that can withstand wave action

Mid-slope depth

vertical growing to maximize space competition

Lower depth corals

spread out to capture more light

Atolls are a

ring of reef surrounding central, shallow lagoon

Most atolls occur in

indo-west pacific region

Atolls can occur

far from shore (unlike barrier, ringing reefs)

The outer and inner slopes of atolls

same as fore and back reef areas

Windward side of atolls

tougher coralline algae

Leeward side of atolls is

the sheltered side

The outer reef atoll is

vertical, becomes deep fast

In atolls, what prevents coral growth from bottom?

deep water

Darwin proposed theory of Atoll formation

1. new volcanic mountain emerged

2. fringing reef formed

3. mountain sinks

4. reef flat becomes lagoon and barrier reef

5. island disappears, leaves only atoll

Coral reef communities are

very complex ecosystems

Space competition is

when space is limited on a reef; light competition

Corals competition uses

mesenterial filaments to digest neighboring corals; sweeper tentacles

Corals compete with

algae and seaweeds (grow faster)

Coral Reef communities can be

nutrient limited, though grazed by herbivores

Why is grazing on algae important

algae can take over reefs if left ungrazed

What can remove grazers?

overfishing

What is Diadema

long-spined urchins

What can increase algae too?

Eutrophication from run-off

Other coral reef primary producers

cyanobacteria, turf algae and coralline algae

Other reef inhabitants

vertebrates and invertebrates

Invertebrates being

mollusks, echinoderms, crustaceans, polychaete worms

Vertebrates being

- herbivorous, carnivorous and omnivorous fish

- reptiles (snakes, sea turtles)

Corallivores

eat coral, break off skeleton which breaks into smaller bits (bioerorsion)

Bioersion and corallivores help build

beaches near coral reefs

Symbiosts: Clownfish/Anemone

-clownfish protected by predators

- anemones stinging, gain nutrients from clownfish

Symbiosts: Cleaning stations

- small invertebrates

- fish clean off parasites from other larger fish and marine reptiles

Symbiosts: Shrimp goby/ pistol shrimp

- shrimp build tunnels for goby

- goby signals vision impaired shrimp of danger

Mangroves

land trees/ shrubs adapted to being in marine environment

Northern reach of mangroves is where

hard frost can regularly occur

3 main types of mangroves (of many)

1. red mangrove 2. black mangrove 3. white mangrove

Red mangrove

most salt-tolerant and found closest to shoreline

Black mangrove

Found slightly more inland

White mangrove

Least salt-tolerant and therefore found furthest inland

All 3 species of mangroves must have

special adaptations to deal with low oxygen levels

Special adaptations for mangroves

1. lenticels

2. pneumatophores

3. salt excretion

Lenticels are

pores that bring up O2

Pneumatophores

lateral roots that grow upward out of the mud and water to bring in oxygen

Salt excretion occurs through

leaves too

Reproduction in mangroves

elongated seedling attached to the parental tree

Seedling also called

propagule

In reproduction, the propagules

float in water until suitable habitat found

Mangrove distribution

coastal areas in tropics and subtropics, climate change moving some further north

Mangrove benefits

- fish nurseries

- shoreline protection

- filtration of runoff from land

Mangrove loss

worldwide loss of mangroves due to development, shrimp farms