- We propagate our coral almost entirely asexually
by fragging the colonies and then growing those small pieces
into whole new colonies.
Then we repeat it and we sell or trade some along the way.
But is there a better way we could do that?
Maybe something that we could use to produce new coral
on a much grander scale?
Hi guys and girls, I'm Reefman,
and this time we're talking about culturing urchins
alongside newborn corals, which results in better growth.
So, take a moment to subscribe if you haven't already.
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So, there is a paper out recently.
It's entitled 'Ex situ culturing
'of the sea urchin Mespilia globulus
'and the coral Acropora millepora
'enhances early post-settlement survivorship.'
All right, so what does that mean?
'Ex situ' just means outside the environment, so in a tank.
Then 'culturing the sea urchin and the coral,'
that's pretty obvious.
And it turns out, raising them together
helps the coral survive!
As always, check below.
There's a link, actually several links,
and you can read the papers for yourself.
You'll get a lot more information that way.
So, coral reefs throughout the world
are under incredible stress right now,
and there's actually a lotta research going on
about how we might mitigate that stress
or even repopulate the reefs once they're gone.
Some people have already figured out
that you can frag a colony and then spread it around
and you end up with a bunch of coral.
But that creates genetic clones,
which isn't so great for an overall reef's health.
So, what could we do differently?
Could we actually breed the coral like we do fish
instead of just fragging 'em?
Well, it turns out we can.
And I did a video all about Project Coral
at the Horniman Gardens in London.
This same team is back now to talk about increasing survival
of those newborn coral larvae.
There was a paper previously published
that found that culturing Trochus snails with the coral
increased survival by about 13%.
But that's not so great;
maybe there's a better creature that we could use.
It turns out, coralline algae actually helps trigger
Acropora larvae to settle out of the water.
But it also tries to prevent coral growth in many ways.
It sheds the outer layer of tissue it has,
it quickly grows over coral,
and some species even release chemicals
that ward off encroaching corals.
After all, if you're coralline algae,
then the last thing you want is to be pushed out
and killed by some coral that's growing over you.
So, it's interesting that even though coralline algae
has such an array of defenses,
it still actually helps trigger
that original settlement of the larvae
outta the water in the first place.
And I'm curious to know why that is.
I'm not really sure, it doesn't make sense.
The one thing in our reef tanks
that consistently eats coralline algae is urchins.
Now, if you have a tiny Acropora millepora larvae,
you can't expect it to survive
a full-grown urchin munching around on it,
so the team cultured urchins alongside the corals.
And a small 10-millimeter urchin does a much better job
of cleaning up around newly-settled corals.
Indeed, Acropora settlement in general
is much more successful in the presence of urchins
where coralline algae growth is heavily controlled.
Urchins help with other algae as well,
and we know that from our tanks.
They keep coralline algae in check,
but they also eat Caulpra, hair algae, and probably others
that we haven't even really identified in the hobby yet.
I've seen algae crowd out even a small frag
that I got from a frag swap.
And if it can do that to a frag, then a newly-settled larvae
is gonna be so much more at-risk.
In the study, the team set up 24 10-liter tanks
and then they put 18 frag plugs
with newly-settled Acropora millepora on each one
or into each tank.
They had four groups of tanks:
a control that had no urchins,
and then three different densities of urchins.
A low-density with four urchins per tank,
medium with nine urchins per tank,
and a high-density group that had 18 urchins per tank.
Now, the urchins are very small.
They're less than a centimeter in size.
But still, 18 urchins in a two-and-a-half-gallon tank
seems like a lot.
The researchers found that in the medium-
and high-density tanks,
the newly-settled Acropora millepora larvae did much better,
almost 40% better in fact.
The urchins did a great job at keeping algae
from crowding out the new colonies,
and the colonies grew significantly more as a result.
You can hardly see the millepora colony
from the control group in this picture.
I also want to mention, the team estimates
that out of 10 spawning Acropora millepora colonies,
they got 46,000 larvae.
From that, they got almost 5,000 new polyps
on nearly 500 frag plugs.
That's significantly more than we can do just by fragging.
Since there is an established procedure
for spawning corals now,
why don't we do this more in the coral reef hobby?
What if we crossed, say, the Walt Disney tenuis
with some other colorful tenuis?
Could we get some entirely new beautiful specimen
that the hobby has never even dreamt of?
I'm sure we could.
Someone just needs to try to do it.
So, thanks for watching!
I would love to see more sexual reproduction of corals
in the hobby.
We do it already with fish,
and we're good enough at raising Acropora
that we really don't need to
collect it off the reefs anymore.
Indeed, mariculture farms now provide
much of the 'wild' coral that we get in the hobby,
and that's great and it provides jobs,
but via selective breeding of captive corals,
the sky really is the limit
on what sorts of corals and colors we could produce.
And that would all be done without any impact
on the world's oceans and reefs.
It would also help drive the research that's needed
to start reintroducing corals back into the ocean
in a way that doesn't impact
the genetic diversity of our reefs.
So, I really hope you enjoyed the video.
Again, don't forget to subscribe if you haven't already.
Check out the papers down below in the description.
Have a fantastic day!
See ya next time, bye.