The evolution of coral

The building blocks to every marine ecosystem

    

Fig 1: Coral Reef
Photographer: NOAA 2015

Corals are the backbone of marine ecosystems and provide food, shelter and habitat for marine organisms.  Due to climate change and human pressure, 15% of coral has been lost and a further 35% is at risk of bleaching (Wilkinson 2008).

Fig. 2: Craysfort Reef, a comparison of damage between 1975 and 2004
Photographer:Phillip Dunstan 2015

Thankfully, some corals have adapted to rising sea temperatures by developing heat shock resistant proteins (Guest et al 2012).

Given the corals quick ability to adapt, scientists such as Van Oppen and Mascerelli are talking about experimenting with ‘Assisted evolution’ whereby corals can be genetically altered to better prepare them for future global warming (Van Oppen et al 2015)(Mascerelli 2014).

Fig 3. Acropora hyacinthus: a heat resistant coral
Franco Banfi 2013

What is assisted evolution?

In this context, assisted evolution is when scientists genetically modify a species outside of its natural environment then place it back with a better chance of surviving global warming (Mascerelli 2014).

Although this sounds like a good idea, experimenting with keystone species could produce a whole range of ecological disasters (Oppen et al 2015). 

Fig 4: A Stanford researcher testing the heat tolerance of corals between normal water and +2 degrees
Photographer: Tom Oliver 2009

What could go wrong?

According to Van Oppen (Van Oppen et al 2015) some of the things that could go wrong include the altered coral becoming invasive, the introduction of a new pathogen from the altered species or an entire ecosystem collapse.

How is it done?

There are a range of different ways corals can be ‘adapted’ to rising temperature, these include:

Selective breeding

Fig 5: Researcher measuring coral for selective breeding 
Photgrapher: Ken Nedimyer 2015

Priming

 Growing corals in a heated environment to acclimatize them and possibly induce trans-generational plasticity (Van Oppen et al 2015).

  Fig 6: Stanford research on coral  heat tolerance and plasticity

Anonymous 2015

Changing algae

Fig 7: Symbiotic algae (Zooxanthellae) shown in yellow growing on coral 
Anonymous 2012

Another short term solution is to change the algae that live inside coral with a more heat resistant species ,this can increase a corals heat tolerance by 1- 1.5 degrees (Birkelmans and Van Oppen 2006).

Thank-you for reading J check back next week for more information on marine evolution.

References

Anonymous 2015, Stanford research on heat tolerance and plasticity, http://stanford.edu/~rbay/stanford/Research.html retrieved 22/3/15

Anonymous 2012, Symbiotic algae (Zooxanthellae) shown in yellow growing on coral http://deepbluehome.blogspot.com.au/2011/08/after-coral-bleaching-winner-is.html retrieved 22/3/15

Banfi F 2013, Acropora hyacinthus: a heat resistant coral, https://www.sciencenews.org/article/corals-beat-heat-being-prepared retrieved 22/3/15

Birkelmans R, M J H Van Oppen 2006, ‘The role of zooxanthellae in the thermal tolerance of corals: a ‘nugget of hope’ for coral reefs in an era of climate change’, Proc. R. Soc. B, vol 273, pp.2305-2312, doi: 10.1098/rspb.2006.3567

Dunstan P 2015, Craysfort Reef, a comparison of damage between 1975 and 2004, http://www.zoo.ox.ac.uk/group/oceans/research/shallowreef.html retrieved 22/3/15

Guest J R, Baird A H, Maynard J A, Muttaqin E, Edwards A J, Campbell S J, Yewdall K, Affendi Y A, Chou L M 2012, ‘Contrasting patterns of coral bleaching susceptibility in 2010 suggest an adaptive response to thermal stress’, PLOS ONE, vol 7, no 3, doi:10.1371/journal.pone.0033353

Mascarelli A 2014, ‘Climate-change adaptation: Designer reefs’ Nature, vol 508, no 7497 pp. 444–446, doi:10.1038/508444a

Nedimyer K 2015, Researcher measuring coral for selective breeding, http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/florida/interactive-media-staghorn-coral-17.xml retrieved 22/3/15

NOAA 2015, Coral Reef, http://www.noaa.gov/features/economic_0708/images/coralreef.jpg retrieved 22/3/15

Oliver T 2009, A stanford researcher testing the heat tolerance of coral between normal water and +2 degrees http://news.stanford.edu/news/2009/may20/corals-052009.html retrieved 22/3/15

Reusch T B H 2014, ‘Climate change in the oceans: evolutionary versus phenotypically plastic responses of marine animals and plants’, Evolutionary Applications, vol 7, no.1, pp.104 – 122, doi: 10.1111/eva.12109

Van Oppen M J H, Oliver J K, Putnam H M, Gates R D 2015, ‘Building coral reef resilience through assisted evolution’, PNAS, vol 112, no. 8, pp.2307-2313,  doi: 10.1073/pnas.1422301112

Wilkinson, C (ed.) 2008, Status of the coral reefs of the world: 2008, Global coral reef monitoring network and reef and rainforest research center, Townsville, Australia 

Marine life and climate change: An evolutionary advantage

The Crown of Thorns Starfish

We have all heard the term ‘climate change’

But we don’t often hear about how climate change affects an individual species. The crown of thorns starfish is one example of how climate change can benefit a species.

The crown of thorns starfish (Acanthaster Planci) is a massive multi-limbed starfish that can even survive even being cut in half (Engelhardt and Lassig  1993, p71-79). So how could such a resilient creature benefit from climate change?

Acanthaster Planci: Crown of thorns starfish

Starfish life

The Crown-of-thorns starfish (COTS) eat coral polyps and live in the Indo Pacific region of the ocean. Under normal conditions, the COTS population is regulated by predators such as the Triton sea snail. However, in the past 30 years COTS population has increased by up to 6 fold in waves causing mass loss of reefs (Birkeland and Lewis 1990)

Above: The Triton Sea Snail attacking a starfish

The cause

Crown of Thorns Starfish outbreak

Scientists have found that the two most likely causes of outbreak are nutrient run-off and climate change. Evidence has shown that excess nutrients in the ocean increase the number of phytoplankton that larval COTS feed off (Brodie et al, 2005). Another study (Uthicke et al. 2015) found that increased sea temperature of 2 degrees increases larval growth rate by 240%. This along with a reproduction rate of approximately 50 million eggs per female per spawn is causing outstanding issues for coral reefs (Birkeland and lewis, 1990).

Coral damage caused by Starfish

The change

With an increased larvae survival rate, COTS are more likely to disperse to new areas, face new challenges and evolve (Benzie 1999). It also allows starfish that would normally die in the larval stage to reproduce and change the gene distribution within the population rapidly (Nishida and Lucas 1988). This can and has led to some genetic drift within populations (Benzie and Wakeford 1997). This is just example of how climate change can benefit a species.

For more information on the COTS click here

Check back next week for more information on how climate change is affecting marine life. Thanks for reading. J

References:

Benzie J, Wakefore M, 1997, ‘Genetic structure of crown-of-thorns starfish (Acanthaster planci ) on the Great Barrier Reef, Australia: comparison of two sets of outbreak populations occurring ten years apart’, Marine Biology, vol 129, no.1, pp. 149-157, viewed 15/3/15, url: http://link.springer.com/article/10.1007/s002270050155#page-1

Birkeland C, Lucas J, 1990, Acanthaster Planci: Major Management Problem of Coral Reefs, CRC Press, United States.

Brodie J, Fabricus K, De’ath G, Okajc K, 2005, ‘Are increased nutrient inputs responsible for more outbreaks of crown-of-thorns starfish? An appraisal of the evidence’, Catchment to reef: water quality issues in the Great Barrier Reef region, vol.51, no.1-4, pp.266-278, viewed 15/3/15, doi: 10.1016/j.marpolbul.2004.10.035

Engelhardt U, Lassig B (ed) 1993, The possible causes and consequences of Outbreaks of the Crown-of-thorns Starfish, Great Barrier Reef Marine Park Authority, Australia.

J.A.H. Benzie, 1999, ‘Genetic differences between Crown of thorns starfish (Acanthaster Planci) populations in the Indian and pacific oceans’, Evolution, vol.53, no. 6, pp.1782-1795, viewed 15/3/15, url: http://www.jstor.org/discover/10.2307/2640440?sid=21106116781373&uid=4&uid=2

Nishida M, Lucas J, 1988, ‘Genetic differences between geographic populations of the Crown-of-thorns starfish throughout the Pacific region’, Marine Biology, vol.98, no.3, pp. 359-368, viewed 15/3/15, url: http://link.springer.com/article/10.1007/BF00391112#page-1

Uthicke S, Logan M, Liddy M, Francis D, Hardy N, Lamare M, 2015, ‘Climate change as an unexpected co-factor promoting coral eating seastar (Acanthaster planci) outbreaks’, Nature, no. 8402, viewed 15/3/15, doi: 10.1038/srep08402