- Coral reefs are one of the most diverse
and important marine ecosystems,
providing homes to hundreds of thousands of species,
including almost a third of the world's marine fish.
Humans have been migrating to coastal regions
and increasing the populations of those areas
on a global scale that far outpaces
the overall growth of the human population.
Artificial light at night
is affecting roughly 22% of the world's coastlines today
and about 35% of protected marine areas.
Hi guys and girls, I'm Reefman,
and just how much damage
are those crazy bright blue moonlights doing to our corals?
I recently did a video all about moonlights,
and another video about replacing the bright blue LEDs
with some more realistic white ones.
That got me thinking,
we know that light pollution impacts coral spawning
and we know that it impacts clownfish egg's ability to hatch
but does it do any real damage to coral?
Well, we're in luck!
There was a paper recently published that's all about that.
So, I grabbed the paper and it's,
"Red Sea Corals under Artificial Light Pollution
"at Night undergo oxidative stress
"and photosynthetic impairment"
and it was published in Global Change Biology recently
and the authors studied this question
in two different species of coral,
an Acropora and a Pocillipora, both from the Red Sea
off the coastline of Israel and Jordan.
I'm sure that most of you have noticed
that there's a marked difference
in your tank from day to night.
Polyps extend, L-P-S puffs up in hopes of catching food,
all sorts of critters come out of hiding
once the fish go to sleep.
Zooplankton rises up from the depths,
and with it comes a host of other organisms
that are important to the health of a reef ecosystem.
There's unfortunately not much research on the impact
that light pollution has on all of these different things
but at least we have this one paper now
on the effect that it has on coral.
For their study they collected coral,
they split it into two groups,
one would experience natural light and lunar cycles,
and the other was lit with LED strips
that were tuned to output 35 to 40 lux.
Keep in mind that natural moonlight is about 0.1,
or maybe 0.2, lux.
So the experimental light pollution
is far outstripping a natural amount of light.
They turned on the LEDs at sundown each night,
and then turned them off at sunrise,
simulating a natural light pollution level.
They picked 35 to 40 lux
because that's what they measured on the reef
that they were studying and where they got the corals from.
They set up additional tanks on top of these
to explore the effect of different colors of LEDs
on the coral.
In these tanks, they used white, blue,
and yellow colored LEDs.
And they studied the effect of the light pollution
in these individual colors on corals.
And then they wanted to look at the fluorescence
as well as oxidative stress that would be caused.
And have you ever hear of antioxidants?
It's the same idea here,
we like to eat antioxidants to combat oxidative stress
in our own bodies.
Corals can't do that.
So, what do you think they found?
First off, fluorescence.
They measured this by looking at the electron transport rate
that the tissues of the corals exhibited at certain times
after exposure to the light pollution.
They found that fluorescence decreased significantly
when corals were exposed to artificial light,
no matter what color it was.
You can see this in the graphs from the paper,
it increases and then significantly drops off
but in every case the light polluted tanks did worse.
That's the line on the bottom there.
Second, oxidative stress.
Lipid peroxidation was also increased in every sample,
but interestingly blue light was far worse than white light
and yellow light, almost no effect there.
The corals produced a lot more reactive oxygen compounds
under blue light than either of the other light colors,
although white light also caused an increase over time.
These chemicals lead to tissue, DNA damage.
This all happens over time.
Which is why we like to eat a lot of antioxidants
to combat them.
There were other effects that they found too.
Changes in their zooxanthellae symbionts
and such and chloroplast
but these were more species specific.
An interesting side note,
how would you measure the surface area of a coral skeleton?
Well, you dip it in paraffin wax to coat it,
and then measure the weight of the wax
that clings to the surface.
I thought that was pretty cool.
With this paper in mind,
I went ahead and ordered a lux meter off Amazon.
I'm very keen to make sure that
I'm not blasting too much light
into my tank at night,
now that I know that it does actually trigger changes.
And that those are actually bad for our coral.
The paper is linked down below in the description.
It's an open access paper,
so I would strongly encourage you to check it out,
if you're at all interested, it has a lot more details.
I know I only covered the basics of what they describe
in these videos.
Also, take a moment to subscribe if you haven't already,
it really does make a difference.
It's always neat to see that so many of you
watch these videos,
and to be honest, I can't believe that so many people
are interested in this, kind of like, reef science stuff.
It's really cool, I think,
and I'm glad you enjoy it as well.
Thanks for watching.
Have a fantastic day, and I will see you next time.
Bye!