**Disclaimer: Poor internet connection restricted my ability to add graphics and gifs. I’m deeply sorry for the absence of Spongebob in this post.**
Paper: Hock, K., Wolff, N. H., Condie, S. A., Anthony, K., & Mumby, P. J. (2014). Connectivity networks reveal the risks of crown‐of‐thorns starfish outbreaks on the Great Barrier Reef. Journal of Applied Ecology, 51(5), 1188-1196.
Have you ever seen something so beautiful, you could cry?
But I’m actually talking about something so beautiful yet so awful.
This beaut is a Crown-of-Thorns Starfish – a COTS. And it’s the worst.
COTS can wreak havoc on coral reefs during outbreaks. An outbreak is when the density of COTS on a reef exceeds the amount of food available to the COTS. And unfortunately, COTS like to eat coral.
Gobbling up a lot of a reef’s coral is extremely detrimental to the reef. Reef-building coral are the ecosystem engineers of reefs. They do not have a degree in physics, but they are a major component of habitat substrate in reefs. Their nooks and crannies provide places for prey, such as different types of fish and critters, to hide from predators, like sharks. Thus, coral is smart, coral is kind, but actually tho – coral is important.
So you might be thinking COTS outbreaks are the most terrible thing ever, but COTS outbreaks are actually like wildfires.
But aren’t wildfires bad?
Wildfires can actually be a good thing. They kill off a lot of vegetation, but then new vegetation can grow. There’s a whole ecological concept behind what I just said, but you’re sick of my ramblings from last week so just google: intermediate disturbance hypothesis I linked he wikipedia article to that for you because I love and want you to be happy.
Similar to how the destruction of vegetation in forests can be a good thing, the destruction of coral by COTS in reefs can be a good thing.
Ocean warming, ocean acidification, pollution, and other whatnot that have resulted from our treating the ocean like a garbage can intensify COTS outbreaks to the point where it gets really, really hard for a reef to recover before the next outbreak.
This study looked at COTS outbreaks in the Great Barrier Reef, which I’ll refer to as GBR because acronyms are the best.
COTS outbreaks in the GBR are mainly a local thing. —you wouldn’t understand—jk jk.
What I mean by local is that COTS are NOT eating up all the coral on the seafloor in the Great Barrier Reef like a vacuum sucking up all the stuff on a carpet.
No no no no.
They mainly just eat up the coral in the reef of their roots.
So how are COTS outbreaks a threat to so many reefs in the Great Barrier Reef (GBR)?
Like many marine critters, COTS produce planktonic larvae – larvae that goes with the flow, and rides with the tides, to wherever they begin to grow.
COTS larvae can travel in the water column from 9 to 42 days. What a huge range!!
So they have the potential to end up in pretty far places from their birth (making sure to call Mom at least every Sunday). Which means they can end up in new reefs, ready to prey on the untouched coral there. How delicious.
Reefs that have a lot of COTSs can lead to COTSs outbreaks. Outbreaks have been documented to occur in Cooktown-Cairns – northern end of the GBR and Swains region – southern end of GBR.
This study aimed to see how connectivity between reefs influenced a reef’s potential threat of COTS outbreak and predict COTS epidemics.
A COTS epidemic is the spreading of COTS outbreaks through connectivity between reefs.
A major theme of this study is POPULATION CONNECTIVITY.
I’m gonna focus on one point of the study because I’m already at 622 words and you’re proabably already bored.
Hypothesis: Reefs with connections to many other reefs have greater potential for COTS outbreaks.
What they did: This study was kinda math-y.Since larvae disperse in the water and “ride with the tide,” they generated simulations on a computer of larvae moving in water. Larvae were represented as particles. They used data collected from the spawning seasons of COTSs from 2006 til 2011.
Each reef was represented by a polygon and 10,000 particles representing COTS larvae were dispersed from each reef in the model. Since the larvae travel at such a range of time length, like I had mentioned above, the model generated larval movement over 28 days – as a compromise of the range.
The connectivity network was then analyzed. Arrows went between reefs representing the movement of a larva from one reef to another during the simulation. The more arrows incoming to a reef, the more larvae that reef received.
With this network, “superspreader” reefs could be identified. Superspreader reefs were described as those that have lots of connections to different reefs, and can, thus, cause COTS epidemics.
What they found: The superspreader reefs identified in the model matched the reefs that had been historically known for COTS outbreaks – the reefs at Cooktown-Cairns and Swains region.
Basically, the reefs that have the greatest potential to spread COTS and cause COTS epidemics were the reefs that have had COTS outbreaks in the past.
Omg. The world is ending.
COTS outbreaks can be controlled, but the best solution is prevention. Like Smoky said, only YOU can prevent wildfires, only WE can really prevent COTS outbreaks.
Why this study matters: Only a small, select few of us can do the labor-intensive and expensive process of controlling COTS populations. Rather than treat COTS outbreaks only after they occur, the results of this study identified the superspreader reefs that could be focused. By controlling these reefs before outbreaks occur, other outbreaks can be prevented.
But remember, outbreaks can be a good thing. So our control of these hotspots can also mean allowing outbreaks to develop. But this way we can manage the extent.