Is anything known about allelopathy?

[MartinM]

Is anything known about allelopathy other than what it is? I know for data-driven approaches we typically have to turn to commercial aquaculture, but I don’t know of any commercial studies on allelopathy, and I know it would have to be a on per-species basis, so wouldn’t necessarily be helpful to us in this hobby. Some searches here on R2R also didn’t yield much. Just wondered if anything additional had been discovered in the ~9 years I’ve been away!

 

[Randy Holmes-Farley]

There's plenty of scientific research, but not much that I've seen that tells reef hobbyists to do anything different than they have been.

Here are a couple of typical papers:

Octocorals outcompete scleractinian corals in a degraded reef

Radware Bot Manager Captcha

Seaweed-coral competition in the field: effects on coral growth, photosynthesis and microbiomes require direct contact

https://royalsocietypublishing.org/doi/full/10.1098/rspb.2020.0366

 

[MartinM]

Thanks! I should have clarified: anything known about controlling it? Does activated carbon media adsorb allelopathic chemicals? Does ozone use oxidize them? Are there other methods of removal? Thanks!

 

[taricha]

anything known about controlling it? Does activated carbon media adsorb allelopathic chemicals? Does ozone use oxidize them? Are there other methods of removal?

Interesting Q. Here's a couple of observations, though it still may not be relevant to your actual interest, if it is coral-on-coral allelopathy.

In the context of toxic dinoflagellates harming corals, ostreopsis toxin is closely related to palytoxin. Palytoxin is dramatically removed from aquarium water by GAC
"Activated carbon adsorbed 99.7% of PLTXs contained in the seawater and this represents a good strategy for preventing aquarium hobbyist poisonings."
Also other dinoflagellate toxins causing ciguatera are also treated with charcoal
"Like similar marine polycyclic ether poisonings, current therapy for ciguatera is primarily supportive. Gastric emptying, activated charcoal, and catharsis are recommended in the acute phase."

That said, we observe that Ostreopsis / prorocentrum outbreaks still kill a LOT of corals. Even while the hobbyist is using and changing out GAC continuously. So either this means that some cells are directly attaching to the coral and thus toxin removal from the water isn't effective, or it's possible that some of the other measures taken against the dinos are harming the coral.
It's more likely the direct attachment, because in cases where we can observe visible dino accumulations directly on coral flesh, the coral flesh is often dead in ~1 day or so later at the attachment site. (Although we can't totally rule out something like O2 deprivation).

There are some algae that have been shown to have allelopathic effects that prevent the normal diatoms, dino, cyano epiphytes from attaching. It's not very practical because most of these algae are nasty (dictyota) and the allelopathic chemicals that suppress nuisance dinoflagellates also make it something you wouldn't want in your system, and would be hard to find grazers to eat it. Ulva might be an exception, this thread here on that idea, but evidence in the hobby systems is thin.

My overgeneralized understanding is that the allelopathic chemicals are large organics that both bind to GAC and have sites vulnerable to being disrupted by ozone. I've never run across any discussion of allelopathic chemicals that are small.
edit : now that I type that, saxitoxin is a fairly small (molar mass 299) dinoflagellate toxin that apparently is poorly removed by ozone, but GAC does a good job with it.

 

[MartinM]

Great info and very thorough, thanks!