July 2, 2025 • 13 mins
Bioluminescent tides are often described as the northern lights of the ocean.
Marine biologist, Dr Yasmin Meeda, has only witnessed this natural phenomenon once. She says seeing bioluminescence is one of the most magical things she’s ever experienced.
Yaz takes us into the strange world of bioluminescent life to meet the species whose bodies light up from the inside, due to a chemical reaction.
From bioluminescent tides caused by microscopic dinoflagellates to angler fish and glow worms, uncover nature's light displays in the dark.
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Production:
Host: Rosie Holdsworth
Producer: Michelle Douglass
Sound Editor: Jesus Gomez
Special thanks to Dr Yasmin Meeda @marinebiologywithyaz for exploring the weird world of bioluminescence with Wild Tales.
Follow Yaz @marinebiologywithyaz on instagram
Image (c) Kezan24 | iStock
Discover more:
Find out about the UK Glow Worm Survey and look for organised walks:
https://glowworms.org.uk/
Follow Wild Tales on your favourite podcast app or on Instagram @wildtalesnt
If you'd like to get in touch with feedback, or have a wild tale you’re like to hear, you can contact us at podcasts@nationaltrust.org.uk
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
YASMIN MEEDA (00:39):
I have seen bioluminescence only once and it
was honestly the most magicalthing that I have ever seen.
ROSIE HOLDSWORTH (00:56):
It's a bucket list natural phenomenon every
traveller would love toexperience. Bioluminescent tides
or sea sparkles are a rare andethereal looking sight. And
we're heading to the ocean tomeet the strange species who use
light to send signals throughthe dark. I'm Ranger Rosie
Holdsworth. Welcome to WildTales, Bioluminescent Baywatch.
(01:28):
You might have seen the pictureson Instagram of lagoons of
electric blues and greens.People on the shore at night
splashing in waves that look litup as if by magic. This natural
phenomenon is called abioluminescent tide.
So, what causes the sea to lightup in this eerie way? What's it
(01:52):
like to experience it? And whyis Bioluminescence itself found
in so many mysterious oceancreatures? To find out, we need
to go down to the ocean whereit's... Dark at night or in deep
deep waters where light shows upin the pitch black.
YASMIN MEEDA (02:14):
I'm Yasmin Meeda, I'm a marine biologist by
training and I'm now working asa postdoctoral researcher at
Cranfield University.
ROSIE HOLDSWORTH (02:23):
Dr Yasmin Meeda who goes by Yaz is not
your typical marine biologist.You might imagine people in
Yaz's profession out in researchboats, studying dolphins,
turtles, fish or other big faunaof the seas. But Yaz is
interested in somethingdifferent. She specialises in a
branch of marine biology calledmicrobiology.
YASMIN MEEDA (02:45):
I deal with all the tiny hidden wonders of the
ocean that nobody really thinksabout. It's often overlooked.
I'm really interested inunderstanding how these
microbial life actually sustainall the bigger species in the
ocean that we know and love,like whales and sharks. But we
really need to understand thesetiny organisms.
ROSIE HOLDSWORTH (03:03):
Yaz is usually found in her white coat in her
lab, pouring over the littleguys, the weird and wonderful
hidden microscopic organismsthat don't get a lot of love,
but they're essential for allocean life.
Yaz has another great passion,to make sure science is for
everyone.
YASMIN MEEDA (03:24):
I'm really trying to champion the fact that
science should be accessible toabsolutely everyone. Myself, I
actually failed my A-levels whenI was at school. And then
suddenly I really had a passionfor science. And I believe that
you don't have to have straightA's to actually get through and
become a scientist.
ROSIE HOLDSWORTH (03:42):
Yaz's drive to open up science to more people
led to her creating herInstagram account.
YASMIN MEEDA (03:48):
So I post on social media with a handle
@marinebiologywithyaz. And itstarted just as showcasing to
family and friends what I get upto. I mainly made this page to
showcase the hidden wonders ofthe ocean.
ROSIE HOLDSWORTH (04:00):
As a marine biologist, Yaz knows all about
bioluminescence. But she's onlyever actually seen it once. And
the experience has stayed withYaz as one of the most memorable
of her career.
YASMIN MEEDA (04:15):
I have seen bioluminescence. Only once. And
it was honestly the most magicalthing that I have ever seen. I'm
an ambassador for the MarineStewardship Council in the UK.
We were fishing for sardinesusing ring net fishing. So this
is a way to reduce bycatch soyou're only fishing for what you
want.
I was fortunate enough to go outon a sardine fishing boat in
(04:38):
Newlyn in Cornwall and I'venever been on a fishing boat and
as a marine biologist I'm alwaysin the lab. I'm hardly ever out
at sea so this was a really newexperience for me. So we set off
at around 8pm in the evening.And I was told it should be
quite calm. It should be OK. Butwe're going out at night and
we'll be back early hours of themorning.
(05:01):
So there's me, never been evenfishing before. And so I'm now
on this fishing vessel thatwe're going out. We're going out
quite far into the ocean. AndI'm like, wow, there's nothing
around me. It's pitch black. Icould see the stars. I could see
the milky way.
I've never even seen that sovivid because obviously with
light pollution, you can't seeit. And as we were fishing, once
(05:23):
they'd deployed the net, this iswhen I saw so many birds just
coming down. And there wereloads of seabirds, some
seagulls, other species of birdsI didn't even know. And it was
so loud.
The noise was just immense. Andthen as I was looking at these
birds, I could see that they hadthese specks or these sparkles
of a greeny blue hue. And I waslike, this looks interesting.
(05:47):
And then one of the fishermenwas like, it's the phosphorus.
It's the phosphorus.
ROSIE HOLDSWORTH (05:51):
Phosphorus is a chemical element that can
sometimes glow in the dark. ButYaz knows what they're seeing is
something different.
YASMIN MEEDA (05:59):
And I was like, what are you on about? And they
were like, that's what we callit, the phosphorus. And I was
like, no, I think that'sbioluminescence. And they were
like, oh, is that what it'scalled? And I said, yeah, I've
never seen it in real life. I'veonly ever seen videos. The
colour was definitely like abluey-green. You only see
bioluminescence when there'smovement in the water.
(06:21):
So as the waves are crashing andthe birds are diving into the
water, you then get this kind ofdifferent shades of this
bioluminescence coming up andit's brighter in some areas and
it's dimmer in others. Andhonestly it was just like an
alien world to me because wewere the only vessel I could see
for a while. We were in themiddle of the ocean I couldn't
(06:42):
even see land and yet all aroundme were just these birds and
bioluminescence and it wasincredible.
ROSIE HOLDSWORTH: ROSIE HOLDSWORTH (06:50):
Bioluminescent
tides occur all around the worldand some of the best known spots
include beaches in Australia,Thailand, Puerto Rico and
California. These sea sparklesalso appear here in the UK.
Wales has some of the mostfamous bioluminescent tides and
it's found in other places too,like Yaz's experience in
(07:11):
Cornwall.
What you see in photos andvideos can look a little
different to with the naked eye,though no less magical to
witness.
YASMIN MEEDA (07:24):
But I think what people see on photos or on
documentaries can be slightlyover-exaggerated. This is a
little bit similar to myexperience with the northern
lights. I think your camera canreally overexpose the green hue.
You could definitely see it. Andit was more like a, almost a
neon green.
ROSIE HOLDSWORTH (07:44):
We know bioluminescent tides look
magical, but what exactly ishappening? Bioluminescence, when
an organism lights up frominside its body through a
chemical reaction, is found innature in certain species. In
the case of tides like those Yazsaw, these are caused by a type
of algae called dinoflagellates.
(08:07):
In these dinoflagellates,bioluminescent light is created
when two chemicals, luciferinand luciferase, interact with
oxygen. This chemical reactionis triggered when water
containing the dinoflagellatesis disturbed, like when waves
crash on the shore or when birdsdive into the sea to catch fish.
YASMIN MEEDA (08:29):
Bioluminescence happens in loads of different
organisms but in the ocean it istypically from dinoflagellates
which are a group ofphytoplankton and they are
microscopic so you can't seethem with the naked eye you'd
need a microscope to see themnormally. But when they create
this bioluminescence you can seeit as light and that's because
there are thousands of them socollectively you'll be able to
(08:52):
see this light.
ROSIE HOLDSWORTH: ROSIE HOLDSWORTH (08:55):
Bioluminescent
light isn't just found in thesetiny dinoflagellates. It's found
in lots of species, occasionallyon land but by far most
widespread in the ocean.
YASMIN MEEDA (09:07):
Fireflies are a really good example of
bioluminescence and so theycause bioluminescence within
themselves but I've neveractually seen fireflies myself.
The anglerfish that are found inthe deep sea, I want to say ugly
but maybe that's unfair. They'rethe ones that if you've seen
Finding Nemo, it's got the biglight on the end of its head.
(09:29):
And the bacteria that are withinthese anglerfish are responsible
for the Bioluminescence that yousee. So that's how they can see
in the dark when they're in thereally deep sea.
For different species, therecould be different reasons as to
why they have bioluminescence.Sometimes it could be because of
mating. So it could attract amate. Or for the case of
(09:51):
dinoflagellates in the ocean, itcould be to deter a predator.
And then that will deter thepredator because they'll think,
oh, there's something there andit will scare them off, which I
think is pretty cool.
ROSIE HOLDSWORTH (10:05):
And perhaps the most mysterious is the
centuries-old story of milkyseas. Sailors talked of an eerie
phenomenon of looking out to theocean at night and seeing it
transformed, as if blowingghostly white all the way to the
horizon.
In the 1990s, scientists lookingat satellite images finally
(10:25):
confirmed these milky seas werea type of Bioluminescence, this
time caused by bacteria, andthat the light could be seen all
the way from space.
Bioluminescent tides like inYaz's story are relatively rare
(10:48):
but they occur often enough foryou to have a chance of
witnessing them. So what are thetop tips for seeing them for
yourself?
YASMIN MEEDA (10:57):
My top tips if you want to see bioluminescence
would definitely be to look outon the coast. There are certain
areas within the UK that youcould see it such as in Wales
I'd definitely say Cornwall is areally good spot.
My experience was not from theshore so I don't know how
prominent it will be if you'rejust watching from a beach and
want to go and hunt for it. Butif you can get on a boat and go
(11:17):
and explore I think definitelylooking at either Facebook
groups or looking online atdifferent travel blogs or
Instagram or TikTok I think youcould definitely find it and
spot it from there.
ROSIE HOLDSWORTH (11:29):
I've seen bioluminescence myself just one
time, on land. In glowworms'shining green bums in Leeds. It
was really, really magical. ButI've never seen bioluminescent
tides in the ocean. They'rereally high on my bucket list.
The fact this phenomenon evenexists reminds us that our world
is still so full of mystery andwonder.
YASMIN MEEDA (11:57):
I think the fact that bioluminescence is really
unique is something that I thinkis quite alien to the world. And
for me, I think that's one ofthe most amazing things about
evolution and just the naturalworld, is that these things have
just sprung up in nature basedon either it could attract a
mate, it could deter predators.
(12:19):
And so I just think it'sabsolutely incredible that
different organisms have suchdifferent traits that help them
survive in our planet.
ROSIE HOLDSWORTH (12:35):
If you'd like to look for bioluminescence for
yourself, do search for groupsdedicated to spotting it along
the Welsh coast and other partsof the UK. Just please don't do
anything daft and follow safetyadvice when you're mixing with
water, tides and the dark.
Summer is a great time to seethe UK's glowworms. You can find
out more about them in ourepisode show notes. Until next
(12:57):
time, follow Wild Tales on yourpodcast app. Find us on
Instagram @wildtalesnt. Andshare your stories with us with
#wildtaleswednesday. See younext time.
I have seen bioluminescence only once and it
was honestly the most magicalthing that I have ever seen.
ROSIE HOLDSWORTH (00:56):
It's a bucket list natural phenomenon every
traveller would love toexperience. Bioluminescent tides
or sea sparkles are a rare andethereal looking sight. And
we're heading to the ocean tomeet the strange species who use
light to send signals throughthe dark. I'm Ranger Rosie
Holdsworth. Welcome to WildTales, Bioluminescent Baywatch.
(01:28):
You might have seen the pictureson Instagram of lagoons of
electric blues and greens.People on the shore at night
splashing in waves that look litup as if by magic. This natural
phenomenon is called abioluminescent tide.
So, what causes the sea to lightup in this eerie way? What's it
(01:52):
like to experience it? And whyis Bioluminescence itself found
in so many mysterious oceancreatures? To find out, we need
to go down to the ocean whereit's... Dark at night or in deep
deep waters where light shows upin the pitch black.
YASMIN MEEDA (02:14):
I'm Yasmin Meeda, I'm a marine biologist by
training and I'm now working asa postdoctoral researcher at
Cranfield University.
ROSIE HOLDSWORTH (02:23):
Dr Yasmin Meeda who goes by Yaz is not
your typical marine biologist.You might imagine people in
Yaz's profession out in researchboats, studying dolphins,
turtles, fish or other big faunaof the seas. But Yaz is
interested in somethingdifferent. She specialises in a
branch of marine biology calledmicrobiology.
YASMIN MEEDA (02:45):
I deal with all the tiny hidden wonders of the
ocean that nobody really thinksabout. It's often overlooked.
I'm really interested inunderstanding how these
microbial life actually sustainall the bigger species in the
ocean that we know and love,like whales and sharks. But we
really need to understand thesetiny organisms.
ROSIE HOLDSWORTH (03:03):
Yaz is usually found in her white coat in her
lab, pouring over the littleguys, the weird and wonderful
hidden microscopic organismsthat don't get a lot of love,
but they're essential for allocean life.
Yaz has another great passion,to make sure science is for
everyone.
YASMIN MEEDA (03:24):
I'm really trying to champion the fact that
science should be accessible toabsolutely everyone. Myself, I
actually failed my A-levels whenI was at school. And then
suddenly I really had a passionfor science. And I believe that
you don't have to have straightA's to actually get through and
become a scientist.
ROSIE HOLDSWORTH (03:42):
Yaz's drive to open up science to more people
led to her creating herInstagram account.
YASMIN MEEDA (03:48):
So I post on social media with a handle
@marinebiologywithyaz. And itstarted just as showcasing to
family and friends what I get upto. I mainly made this page to
showcase the hidden wonders ofthe ocean.
ROSIE HOLDSWORTH (04:00):
As a marine biologist, Yaz knows all about
bioluminescence. But she's onlyever actually seen it once. And
the experience has stayed withYaz as one of the most memorable
of her career.
YASMIN MEEDA (04:15):
I have seen bioluminescence. Only once. And
it was honestly the most magicalthing that I have ever seen. I'm
an ambassador for the MarineStewardship Council in the UK.
We were fishing for sardinesusing ring net fishing. So this
is a way to reduce bycatch soyou're only fishing for what you
want.
I was fortunate enough to go outon a sardine fishing boat in
(04:38):
Newlyn in Cornwall and I'venever been on a fishing boat and
as a marine biologist I'm alwaysin the lab. I'm hardly ever out
at sea so this was a really newexperience for me. So we set off
at around 8pm in the evening.And I was told it should be
quite calm. It should be OK. Butwe're going out at night and
we'll be back early hours of themorning.
(05:01):
So there's me, never been evenfishing before. And so I'm now
on this fishing vessel thatwe're going out. We're going out
quite far into the ocean. AndI'm like, wow, there's nothing
around me. It's pitch black. Icould see the stars. I could see
the milky way.
I've never even seen that sovivid because obviously with
light pollution, you can't seeit. And as we were fishing, once
(05:23):
they'd deployed the net, this iswhen I saw so many birds just
coming down. And there wereloads of seabirds, some
seagulls, other species of birdsI didn't even know. And it was
so loud.
The noise was just immense. Andthen as I was looking at these
birds, I could see that they hadthese specks or these sparkles
of a greeny blue hue. And I waslike, this looks interesting.
(05:47):
And then one of the fishermenwas like, it's the phosphorus.
It's the phosphorus.
ROSIE HOLDSWORTH (05:51):
Phosphorus is a chemical element that can
sometimes glow in the dark. ButYaz knows what they're seeing is
something different.
YASMIN MEEDA (05:59):
And I was like, what are you on about? And they
were like, that's what we callit, the phosphorus. And I was
like, no, I think that'sbioluminescence. And they were
like, oh, is that what it'scalled? And I said, yeah, I've
never seen it in real life. I'veonly ever seen videos. The
colour was definitely like abluey-green. You only see
bioluminescence when there'smovement in the water.
(06:21):
So as the waves are crashing andthe birds are diving into the
water, you then get this kind ofdifferent shades of this
bioluminescence coming up andit's brighter in some areas and
it's dimmer in others. Andhonestly it was just like an
alien world to me because wewere the only vessel I could see
for a while. We were in themiddle of the ocean I couldn't
(06:42):
even see land and yet all aroundme were just these birds and
bioluminescence and it wasincredible.
ROSIE HOLDSWORTH: ROSIE HOLDSWORTH (06:50):
Bioluminescent
tides occur all around the worldand some of the best known spots
include beaches in Australia,Thailand, Puerto Rico and
California. These sea sparklesalso appear here in the UK.
Wales has some of the mostfamous bioluminescent tides and
it's found in other places too,like Yaz's experience in
(07:11):
Cornwall.
What you see in photos andvideos can look a little
different to with the naked eye,though no less magical to
witness.
YASMIN MEEDA (07:24):
But I think what people see on photos or on
documentaries can be slightlyover-exaggerated. This is a
little bit similar to myexperience with the northern
lights. I think your camera canreally overexpose the green hue.
You could definitely see it. Andit was more like a, almost a
neon green.
ROSIE HOLDSWORTH (07:44):
We know bioluminescent tides look
magical, but what exactly ishappening? Bioluminescence, when
an organism lights up frominside its body through a
chemical reaction, is found innature in certain species. In
the case of tides like those Yazsaw, these are caused by a type
of algae called dinoflagellates.
(08:07):
In these dinoflagellates,bioluminescent light is created
when two chemicals, luciferinand luciferase, interact with
oxygen. This chemical reactionis triggered when water
containing the dinoflagellatesis disturbed, like when waves
crash on the shore or when birdsdive into the sea to catch fish.
YASMIN MEEDA (08:29):
Bioluminescence happens in loads of different
organisms but in the ocean it istypically from dinoflagellates
which are a group ofphytoplankton and they are
microscopic so you can't seethem with the naked eye you'd
need a microscope to see themnormally. But when they create
this bioluminescence you can seeit as light and that's because
there are thousands of them socollectively you'll be able to
(08:52):
see this light.
ROSIE HOLDSWORTH: ROSIE HOLDSWORTH (08:55):
Bioluminescent
light isn't just found in thesetiny dinoflagellates. It's found
in lots of species, occasionallyon land but by far most
widespread in the ocean.
YASMIN MEEDA (09:07):
Fireflies are a really good example of
bioluminescence and so theycause bioluminescence within
themselves but I've neveractually seen fireflies myself.
The anglerfish that are found inthe deep sea, I want to say ugly
but maybe that's unfair. They'rethe ones that if you've seen
Finding Nemo, it's got the biglight on the end of its head.
(09:29):
And the bacteria that are withinthese anglerfish are responsible
for the Bioluminescence that yousee. So that's how they can see
in the dark when they're in thereally deep sea.
For different species, therecould be different reasons as to
why they have bioluminescence.Sometimes it could be because of
mating. So it could attract amate. Or for the case of
(09:51):
dinoflagellates in the ocean, itcould be to deter a predator.
And then that will deter thepredator because they'll think,
oh, there's something there andit will scare them off, which I
think is pretty cool.
ROSIE HOLDSWORTH (10:05):
And perhaps the most mysterious is the
centuries-old story of milkyseas. Sailors talked of an eerie
phenomenon of looking out to theocean at night and seeing it
transformed, as if blowingghostly white all the way to the
horizon.
In the 1990s, scientists lookingat satellite images finally
(10:25):
confirmed these milky seas werea type of Bioluminescence, this
time caused by bacteria, andthat the light could be seen all
the way from space.
Bioluminescent tides like inYaz's story are relatively rare
(10:48):
but they occur often enough foryou to have a chance of
witnessing them. So what are thetop tips for seeing them for
yourself?
YASMIN MEEDA (10:57):
My top tips if you want to see bioluminescence
would definitely be to look outon the coast. There are certain
areas within the UK that youcould see it such as in Wales
I'd definitely say Cornwall is areally good spot.
My experience was not from theshore so I don't know how
prominent it will be if you'rejust watching from a beach and
want to go and hunt for it. Butif you can get on a boat and go
(11:17):
and explore I think definitelylooking at either Facebook
groups or looking online atdifferent travel blogs or
Instagram or TikTok I think youcould definitely find it and
spot it from there.
ROSIE HOLDSWORTH (11:29):
I've seen bioluminescence myself just one
time, on land. In glowworms'shining green bums in Leeds. It
was really, really magical. ButI've never seen bioluminescent
tides in the ocean. They'rereally high on my bucket list.
The fact this phenomenon evenexists reminds us that our world
is still so full of mystery andwonder.
YASMIN MEEDA (11:57):
I think the fact that bioluminescence is really
unique is something that I thinkis quite alien to the world. And
for me, I think that's one ofthe most amazing things about
evolution and just the naturalworld, is that these things have
just sprung up in nature basedon either it could attract a
mate, it could deter predators.
(12:19):
And so I just think it'sabsolutely incredible that
different organisms have suchdifferent traits that help them
survive in our planet.
ROSIE HOLDSWORTH (12:35):
If you'd like to look for bioluminescence for
yourself, do search for groupsdedicated to spotting it along
the Welsh coast and other partsof the UK. Just please don't do
anything daft and follow safetyadvice when you're mixing with
water, tides and the dark.
Summer is a great time to seethe UK's glowworms. You can find
out more about them in ourepisode show notes. Until next
(12:57):
time, follow Wild Tales on yourpodcast app. Find us on
Instagram @wildtalesnt. Andshare your stories with us with
#wildtaleswednesday. See younext time.
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