Climate change is a phenomenon that is
changing our world rapidly before our eyes. It is increasing our ocean
temperatures, and thus becoming a problem for corals, leading to events such as
coral bleaching, coral diseases and coral mortality. Many of these diseases are
opportunistic and prey on the thermally stressed corals.
White plague disease is one of these
opportunistic pathogens. It shows up on coral as a white ring of necrotic
tissue, usually radiating from the base of the colony, and leaving behind a
bare skeleton. It can infect the same colony many times, and has been shown to
create many white areas, showing multiple areas of infection.
In summer 2014, the Florida Keys had some
of the warmest sea surface temperatures on record, leading to a massive coral
bleaching event due to the corals being thermally stressed. Precht et al (2016)
monitored 115 coral colonies with 13 coral species at 4 different sites at the
inner reef tract in Miami-Dade county. They were monitored 40 times between
October 2013 and July 2015. The first white plague disease outbreak was seen in
September 2014, and appeared to have affected 61% of the coral species that
were monitored. When the affected species were looked at separately from the
coral colonies, this number increased to 79%. When recently dead coral species
were added, the number reached an obscene 81%. When looking at the individual
species, the most heavily affected were Eusmilia
fastigiata, Meandrina meandrites and
Dichocoenia stokes, which had lost
more than 97% of their coral colonies.
These results were compared to other white
plague disease outbreaks from the 1970’s until the 1990’s, and in 2005. Whilst
these previous years showed a decrease over 95% in Acroporid populations, and a
60% loss of coral cover in the Virgin Islands respectively, none of them showed
the number of species affected, the high prevalence of disease or the extent of
coral mortality that 2014 showed.
This study was successful in showing
arguably one of the most lethal coral disease outbreaks ever recorded, and this
was linked to the incredibly warm summer that occurred in 2014. I
think this paper was a big breakthrough in showing the links between coral
disease/bleaching and climate change, and will be highly cited in the future.
Reviewed paper: Precht, William. F.,
Gintert, Brooke. E., Robbart, Martha. L., Fura, Ryan., and Van Woesik, Robert.
(2016). Unprecedented disease-related coral mortality in Southeastern Florida.
Scientific Reports. 6: 31374. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979204/
Hi Amy thank you for your review, I did some further reading into the subject and found a paper that has documented a rise in relative dominance of the coral species Siderastrea sidereal in the Florida area (Kuffner and Toth, 2016) Siderastrea sidereal has been shown to be unaffected by the white-plague disease. Siderastrea sidereal is considered to be a hardy coral species and is resistant to high temperature stress, this resistance gives it an advantage over other corals who become heat stressed which as you mentioned in your review is likely leading to diseases such as white plague disease by opportunistic pathogens. Climate change is a huge threat and is not just leading to the decline of coral coverage but also the coral community structure, areas are likely to be dominated by only the most hardy coral and even then there is no certainty that they will be able to tolerate the changing condition as every species has its physiological limit.
ReplyDeleteReference
Kuffner, I. and Toth, L. (2016). A geological perspective on the degradation and conservation of western Atlantic coral reefs. Conservation Biology, 30(4), pp.706-715.
Really interesting paper Alisha - it's fascinating that we are already seeing notable shifts in coral community structures! Perhaps we a there looking at a not-so distant future with reefs dominated by these hardy, thermotolerant species!?
DeleteI agree its interesting that we are already beginning to see these shifts in community structure, which on the surface it might seem that even if we end up with a reef that is dominated by only these hardy coral at least there will still be some coral, but I think it will have dramatic impact in terms of the wider picture of ecology. With the loss of species that rely on coral species that are no longer able to survive in these areas and therefore unable to provide important ecosystem function even though there will still be a coral community they are likely going to be noticeable difference to the overall ecosystem due to the lost of niches and services from some coral species of course further research would be needed to confirm this.
DeleteThis comment has been removed by the author.
ReplyDeleteHi Alisha,
ReplyDeleteIt's really interesting to see that this pattern hasn't been shown in other coral species such as Siderastrea sidereal, and as you said it's supposably a good thing that hopefully this coral species will survive the increasing temperatures seen even if others don't - a positive in amongst the negative effects on other coral species. Unfortunately with the increasing temperatures I fear that the only thing we can do is to wait and see what the knock on effects of this will be for other species that rely on the diseased and dying corals.
Hi Amy,
ReplyDeleteYou mention that these diseases prey on thermally stressed corals, are you aware of any work that was kept temperature constant and used other stressors such as salinity to see if it left the coral as susceptible?
Thanks
Hi Evan,
ReplyDeleteThis paper mentions that this disease may be caused by a number of environmental factors, but doesn't seem to mention any work that has been done towards testing this. Previous work also seems to suggest that certain environmental factors may have an effect, but unfortunately don't seem to go beyond that. After having looked for papers on this disease related to other stressors, it looks to me as if this stressor was the first one to be tested, and I can't seem to find any papers on any other factors that may have been tested. Due to this and the results that they found in this study, I expect that others may follow in their footsteps and test for an effect with other environmental factors in the near future.
Thanks