L6 - Tropical Coasts

Question 1

What are continental margins of ocean basins?

Answer 1

The boundaries between continental and oceanic crust

Question 2

What is the continental shelf?

Answer 2

8% of the ocean’s surface area, but biologically richest parts of the ocean

Question 3

What is the tropical seascape?

Answer 3

It is interconnected, Land, mangroves, seagrasses, coral reef, offshore waters

Question 4

What are coral reefs?

Answer 4

Among the most biologically diverse ecosystems - biodiversity hotspots. They provide a habitat structure and facilitate other species by providing a range of niches.

Question 5

What do coral reefs do?

Answer 5

They are ecosystem engineers. They support important subsistence and commercial fisheries. They account for ~5% of the world marine fisheries landings. 22million artisanal fishers worldwide - 6 million of those are on coral reefs.

Question 6

What do coral reefs habitat structure provide?

Answer 6

Tourism/cultural services, biodiversity, shoreline maintenance, coastal protection, fisheries

Question 7

Where are coral reefs distributed?

Answer 7

Within 30 degrees latitude of the equator, bounded by minimum average water temperature ~ 20 degrees.

Question 8

What is the coral triangle?

Answer 8

Centre of diversity. ~76% of the worlds coral species, 37% of the worlds coral reef fish species. 6 out of 7 marine turtle species

Question 9

Where are there no coral species in common between?

Answer 9

The atlantic and indo-pacific ocean

Question 10

What are corals?

Answer 10

Coral is a general term for several different groups of cnidarians. Not all corals species build reefs.

Question 11

What are the two types of corals?

Answer 11

Hermatypic and Ahermatypic

Question 12

What are Hermatypic corals?

Answer 12

Reef building, mostly in the tropical regions.

Question 13

What are Ahermatypic corals?

Answer 13

Non reef-building distributed world wide.

Question 14

Which type of corals are strongly influenced by their physical environment?

Answer 14

Hermatypic

Question 15

What ate scleractinian corals?

Answer 15

Main group of hermatypic corals, coral reefs are colonies of various hermatypic corals. Each coral colony is comprised of tiny animals called polyps. The polyps produce skeletons made of calcium carbonate.

Question 16

What are some characteristics of hermatypic coral reefs?

Answer 16

The corals have a larval stage as a planula - zooplankton, spawning can be synchronised, rarely grow deeper than ~ 50m. Most tropical waters where coral reefs are found are usually nutrient-poor. Little in the way of phytoplankton.

Question 17

Hermatypic coral reefs - What do polyps contain?

Answer 17

Polyps contain symbiotic algae (zooxanthellae)

Question 18

What are some common hermatypic corals?

Answer 18

Acropora, Tubinaria, Porites, Fungia

Question 19

What are the different coral reef zones?

Answer 19

Shore zone, back reef zone, reef flat zone, fore reef zone, drop-off zone.

Question 20

What are the different types of reef?

Answer 20

Fringing reef, patch reef, barrier reef, atoll

Question 21

What is a fringing reef?

Answer 21

Along the coast, most common, susceptible to terrestrial influences.

Question 22

What is a Barrier reef?

Answer 22

Surround many tropical islands, separated from land by lagoons, may develop from fringing reefs after sea level rise.

Question 23

What is a Atoll reef?

Answer 23

Found far from land. Rising from depths of 1000s metres. Ring of reefs, islands and sand cays.

Question 24

What are some reef algae?

Answer 24

Many species of algae are also fundamental to coral reef structure and function. Macroalgae, coralline algae, turf algae.

Question 25

What is macroalgae?

Answer 25

Can be calcified, compete with coral for space and light, shade out coral, mechanical and chemical damage, prevent coral larvae settlement.

Question 26

What is coralline algae?

Answer 26

Slow growing crustose coralline algae, secondary carbonate producer, cements and stabilises.

Question 27

What is Turf algae?

Answer 27

Fast growing, epilithic (grow on rock surface). Cyanobacteria and meiofauna within. Can be drowned by sediment, with zooxanthellae, one of the most important primary producers on reefs.

Question 28

What phase shifts are there on coral reefs?

Answer 28

From coral dominated to algae dominated. This can be triggered by e.g. coral bleaching, cyclones/hurricanes, crown of thorns starfish, eutrophication. Herbivorous fish are important in regulating space competition between corals and algae.

Question 29

What types of herbivorous fish are there?

Answer 29

Browsers, grazers/croppers

Question 30

What are Browsers?

Answer 30

Key for reef resilience, eat large, fleshy macroalgae, e.g. unicornfish, batfishes, rabbitfish.

Question 31

What are Grazers/croppers?

Answer 31

Intensely graze epithilic algal turfs, can limit the establishment and growth of macroalgae, e.g. rabbitfishes, surgeonfishes.

Question 32

What are parrotfishes?

Answer 32

Scrapers/excavators - scrape coral surface and erode reefs, exposing new substrate for larval settlement. Maintain low algal cover, remove live and dead coral, remove and transport sediment.

Question 33

What are mangroves?

Answer 33

Dicotyledonous woody shrubs, 54 true species exclusively in mangrove habitats, confined to tropics, form dense forests - monospecific patches.

Question 34

What do mangroves do?

Answer 34

Can dominate intertidal muddy shores, need soft sediments to get established, stabilise soil, create structurally complex habitats, an example of convergent evolution.

Question 35

What is a mangroves environment?

Answer 35

Periodically inundated by the tides, soils are usually permanently waterlogged and anoxic. Soils are soft and fairly unstable. Fluctuating salinity -> evaporation leads to hypersalinity.

Question 36

What are mangroves adaptations to waterlogged soils?

Answer 36

Buttress roots (pelliciera sp.), Knee roots (bruguiera sp.), prop roots (rhizophora sp.), pencil roots (avincennia or sonneratia)

Question 37

What % can aerial roots account for of above ground biomass?

Answer 37

24%

Question 38

What are some examples of mangroves?

Answer 38

Rhizophora mangrove (red mangrove), avicennia germinans (black mangrove), laguncularia racemosa (white mangrove).

Question 39

How are mangroves adapted to hypersalinity?

Answer 39

Exclusion of salts at the roots (e.g. red mangrove), a physical process. Intracellular partitioning of salt (e.g. black and white mangroves) a chemical process, na+ and cl- in vacuoles, salt glands on leaves.

Question 40

What is productivity and complexity in mangroves?

Answer 40

Mud surface a site for photosynthetic algae, below, bacteria and fungi decompose organic matter. Burrows of deposit and filter feeders, detritivores, herbivores, and predators aerate the mud, trees provide a substrate which other organisms colonise - epibionts. Primary production, nutrient cycling and structural complexity.

Question 41

What are mangroves role as nursery habitats?

Answer 41

Higher species richness, shelter, food, fish : ontogenetic migration.

Question 42

What do mangroves show?

Answer 42

Zonation

Question 43

What are human impacts on coral reefs?

Answer 43

Climate change, human development, eutrophication, overfishing, invasive species

Question 44

What are impacts on mangroves?

Answer 44

Storms - hurricanes and typhoons, tsunamis. Human impacts - deforestation, agriculture, aquaculture, urbanisation, pollution.