Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Conservation > Coral bleachhing > Flashcards

Coral bleachhing Flashcards

1
Q

What are corals

A
  • most primary reef-building corals are calcifying anthozoans
  • Anthozoa is a class of 6000 species (within cnidaria). They only exist as polyps , never medusa
  • True “stony” corals are in the order scleritina
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do corals create

A

Coral reefs - hyper diverse marine environments, they only cover 1% of the sea floor yet hold 1/4 of all marine species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Biology of scleritinian corals

A

Scleratinian reef corals form an aragonite corallum (colonial skeleton) composed of individual cuplike coralites around and under each polyp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

corallum

A

the entire skeleton of a compound coral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does coral growth occur

A
  • Growth occurs on top of previous calcification.

- Growth in some acopora corals can be >100mm annually

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How large can coral colonies get

A
  • Large coral colonies can reach several M in height and tons in weight.
  • The living tissue however is typically <1mm thick on surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What controls the rate of growth/calcification

A

Growth is controlled by function of specific calciloblastic tissue (has a direct role in crystal formation)
- Growth is also controlled by photosynthetic contributions of symbiotic zooxanthellae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is a zooxantehllae

A

In this case it is a coral containing an algal symbiont.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is typical of (hermatypic) scleritinian corals

A

they are typical of shallow seas and almost all are zooxanthellae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are hermatypic corals

A

Hermatypic corals are those corals in the order Scleractinia which build reefs by depositing hard calcareous material for their skeletons, forming the stony framework of the reef. Corals that do not contribute to coral reef development are referred to as ahermatypic (non-reef-building) species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the most common zooxanthellae relationship

A
  • Most scleritinian corals have a symbiotic relationship with dinoflagellates of the genus symbiodinum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how many types of symbiodinum are there

A

> 100 genotypes of symbiodinum , some are widely distributed whilst others are specific to species or environments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

where are zooxanthellae located

A

zooxanthellae are inra-cellular and located within host gastrodermal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how many zooxanthellae are typically within an individual

A
  • 1-3 or more per cell

- typically 1500000 symbiont cells per cm^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the three functions of zooxanthellae

A
  • influence calcification process
  • Provide nutritional material to their hosts
  • take up host waste products
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does light affect calcification rates

A
  • light, photosynthesis and calcification are intimately linked
  • A cloudy day can reduce carbonate deposition by 50%
  • Carbonate production is 3x higher at daytime compared to night
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does the zooxanthellae provide nutrition for the coral

A
  • Carbon fixed by photosynthesis is translocated to the host in the form of amino and fatty acids, glucose and glycerol
18
Q

What is the ratio of photosynthesis to respiration

A

In some conditions photosynthesis to respiration ratio (P:R) can be >1. I.E. all metabolic requiremnts met by photosynthesis

  • symbiosis is autotrophic (in this case)
  • This varies substantially with light, depth ,season ,habitat etc.
19
Q

Are corals autotrophic

A

No , most corals also feed heterotrophically, this significantly increases both tissue growth and calcification rates

feed on planktonic prey

20
Q

How do corals deal with their waste products

A
  • Zooxanthellae take up phospherous and nitrogen from their hosts
  • They transform these into organic compounds and transfer them back to host
  • Ammonium and nitrate are potentially toxis to corals, zooxanthellae act as “metabollic kidneys”
21
Q

what is the main benefit of the symbiotic zooxanthellae relationship

A

Allows reef-building corals to survive in nutrient poor shallow tropical waters

22
Q

Reef corals are intolerant to the following types of environmental change

A
  • reduced salinity
  • prolonged low tides
  • disease
  • pollution
  • temperature extremes (KEY)
  • High light levels
23
Q

What are coral stress responses

A

At threshold levels
- increased mucous secretion and polyp withdrawal (no longer active)

Beyond physiological thresholds
-zooxanthellae symbionts are expelled (bleaching)

24
Q

What is coral bleaching

A
  • A complex reaction based on physiology, biochemistry and traits from both partners
  • Most obvious forms of bleaching result in host appearing transparent (this is through revealing the aragonite skeleton underneath)
25
Q

Not all coral bleaching is worrying and can reflect seasonal variation , what is this called

A

cyclical changes are called physiological bleaching

26
Q

How does severe bleaching affect corals

A
  • Typically a loss of 60-90% of symbiont cells
  • Usually accompanied by a loss of host tissue biomass
  • bleaching is significant injury to the coral , not just loss of photosynthesis
27
Q

How does temperature affect bleaching

A
  • Most reefs are sensitive to small increases in temp
  • Just 1-2 degree celcius increase above summer highs can induce bleaching

-El ninos generate wide swathes of such conditions , 30-32 degrees widespread in the tropics

28
Q

What happens when the corals release the zooxanthellaes

A

-Without the algae (symbiont) , the coral loses its major source of food , turns white/transparent and becomes more susceptible to disease.

29
Q

Examples of previous mass bleaching events

A
  • Super el nino (1998) , caused coral mortality across the tropics. Unprecedented in global scope.
  • Coral coverage was reduced >90% in many parts of the indian ocean
  • similar patterns in pacific + caribbean
  • 16% of the worlds shallow water reefs were lost
30
Q

The role of climate change in coral bleaching

A

climate change interacts with natural processes and variation to increase the severity and extent of bleaching events

31
Q

How does coral bleaching effect reef ecosystem services

A
  • Many species entirely dependant on healthy corals for habitat and food
  • Coral cover and topgraphic complexity especially important to fish
32
Q

Example of bleaching effect on reef species composition

A

Example: Pratchett et al. (2008) Effects of coral bleachng, 1998 on species richness

  • Most species declined/died out
  • Species which suffered the most were coralivores and coral dwellers
  • Herbivores tend to do well as bleached coral gets colonised by macroalgae
33
Q

When did NOAA declare the 3rd ever global bleaching event

A

2015 - NOAA declared 3rd ever global bleaching event

  • > 1/2 of japans coral reef died
  • severe effects predicted globally
  • As the year progressed predictions worsened significantly
  • covered most of the tropics and pretty much everywhere else
34
Q

The 2016 bleaching event and the great barrier reef

A
  • 1000km of the reef was affected
  • Northern areas hit hardest , 95% of reefs between cairns and papau new guinea showed bleaching
  • southern and central regions protected by cooler weather form cyclone winston
35
Q

What was special about the bleaching of the great barrier reef

A

first bleaching event that played out on social media

36
Q

According to Terry hughes what was the extent of damage to the reef

A 
Northern = 26% mortality 
North = 67% mortality 
Central = 6% mortality 
South = 1% mortality
37
Q

How does the future look for bleaching events

A
  • Projected increase in sea suraface temps (1.2/2 -5/10 degree increase by 2100) will increase bleaching events significantly
  • Surface aragonite is going to decrease , this will reduce calcium deposition preventing coral regeneration
  • prediction suggest future seas will be unable to support corals
38
Q

How does aragonite concentration affect corals

A

There is a critical concentration of aragonite below which calcifying organisms such as corals cannot function

39
Q

What is the problem with saying the great barrier reef “died”

A

Russel Bainard , chief scientist at NOAA

there is increasing concern that overstatement of the environmental situations that our planet faces causes people to lose hope and thus reduces efforts to fix the problem.

-only 22% of the reef died , a large proportion of the public think 100% perished

40
Q

Summary

A
  • Coral reefs are dependant on symbiotic relationship with zooxanthellae
  • many stressors can lead to it breaking down
  • temperature is primary driver of bleaching
41
Q

Coral reefs prognosis

A
  • Tropical reef systems are transitioning to a new era in which the interval between bleaching events is too small to allow full coral regeneration
  • median return times between events is no 6 years (decreased since 1980s)
  • Annual bleaching may become the norm

Conservation (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions