But we can and should do something about our own waste which always seems to tip the balance away from the norm of happy stable ecosystems.
I agree. I'm not arguing that we shouldn't. There are numerous problems on the reef that we can clearly attribute to man-made pollution, but COTS outbreaks aren't one of them.
As for raising larvae to juvenile and adult, well, they may be lacking the diversity of the lagoons and reefs in their tanks to do it properly. Try breeding tangs. Havent heard of much success with them, or other larval reproducers.
I think you misunderstood. It's not that the researchers couldn't raise the larvae successfully. That's been done several times. The first researchers just stopped raising them after the second larval stage, satisfied that they had done enough to show that larval survival was food limited. Other researchers after them were successful raising the larvae all the way to settled juveniles, but found that phytoplankton concentration didn't seem to make a difference in survival to settlement.
As for pelagic spawners, there has been a lot of success breeding commercial game and food species, but the techniques took decades to develop. Culture of ornamentals is still far behind and it seems like people are trying to reinvent the wheel. The success doesn't have anything to do with a lack of diversity, just a lack of resources to figure it out. It takes a lot of time, money, and hard work to figure out how to breed these fish before they ever start making money, so it's not a very attractive endeavor from a business standpoint and a bit out of the range of most hobbyists.
Concerning predation, I thought the COT was pretty much imune to most carnivores because of it's toxins. only a few, low density predators seem capable of eating it. The triton , as they say is a low level predator, not many around, even in balanced ecosystems. Certainly not enough to stem the tide.
Well, predation of the stars is poorly studied so it's nearly impossible to say whether predation was ever a controlling factor and if it was, whether or not that has changed.. As adults, they've got at least 11 known predators of varying abundance. Large proportion of adult show evidence of recent, non-lethal predation. As larvae almost any zooplanktivore such as clownfish, corals, some tangs, some angels, anthias, damsels, etc. will eat them. Obviously these are in high abundance. There is some evidence that juveniles and sub-adults see high predation, but this is probably the hardest stage of the cycle to study because they're cryptic.
I think they make a very good case for runoff pollution feeding the bloom of COT. Correcting that runoff might not only stem the tide of COT outbreaks, but also much of the rest of the pollution pressure on the health of reef corals and critters and fish.
There's a good case that COTS blooms are correlated with runoff, but there really isn't a case to be made yet whether pollution plays any role in the COTS outbreaks. 1) It hasn't been shown that there is extensive nutrification. Local nutrification near some sites that are suspected primary outbreaks has been recorded, but not near others. 2) It hasn't been shown that the larvae are food limited. If they aren't, then whether terrigenous nutrients are causing algae blooms is a moot point. 3) There's no explanation for why similar organisms, such as
Echinometra aren't blooming as well. 4) It's still not known whether there even
is an increase in COTS abundance. There is a lot of work suggesting that periodic outbreaks of COTS have been occurring for as long as 8000 years on the GBR. The idea that they're a new phenomenon is based in large part on the fact that they weren't reported prior to 1962, but then again very few people were looking and no one was keeping records. The only tangible evidence that they're new is from looking at growth and damage of massive corals. Without knowing what populations were in the past we can't say that survival is increasing, much less that X is causing it.
Lots of inverts have what are called mast settlements. That means recruitment is typically low, but rarely there are years with unusually high larval recruitment. In the Caribbean I've seen it with
Acropora and
Diadema. Both were killed off in the 80s and had almost zero recruitment in the area I worked in for the next 20-25 years, then suddenly a few years ago there were two stellar years for
Diadema and a great year for
Acropora, but they've both had very poor recruitment since then. The same thing seems to be true for the COTS. The periodicity and pattern of the outbreaks shows that these guys are generally having poor/moderate survival, but every 20 years or so you get extremely good settlement and a primary outbreak. From there density effects take over and start secondary outbreaks downstream. Genetic evidence supports this.
The evidence leads me to believe that these outbreak cycles aren't something new, but their intensity may be increasing. I strongly suspect, as many others do, that humans are exacerbating the natural cycle, but the jury is still out on that one and science doesn't work on hunches.
