(Gently chiming bells)
- Tides are amazing.
The pull of the sun and the moon on our planet
causes water to rise and fall all across the globe.
Sometimes very dramatically.
Right between Nova Scotia and New Brunswick,
there's a Bay that experiences tides
like no other place on our planet.
Between low and high tide,
the water level in the Bay of Fundy,
can change by up to 53 feet.
That's almost as tall as a four story building.
But massive tides can bring with them
more than just tons of water.
Sometimes they can also contain a deadly allergy.
You may have heard of red tides on the news.
These are caused by algal blooms,
which deplete the water's oxygen,
discolor the waves and release toxins into the water.
And these red tides kill.
More specifically fish, dolphins, manatees,
and many other animals in the ocean.
But they can be harmful to humans
without you even ever setting foot near the water.
But more on that later.
With all of that it might surprise you to learn
that the tiny organisms that cause red tides,
are also an extremely important part of our ecosystem.
What are algae?
Are they plants, animals, fungi?
Well, they're not really any of the above.
While they're part of the plant kingdom,
algae aren't really plants,
but a pretty diverse set of organisms
that can photosynthesize.
This means that they use energy from sunlight
to turn CO2 into oxygen and sugar.
They can be single-celled or multicellular.
So it might surprise you to learn
that seaweed and kelp are not plants,
they're actually algae.
- Mmh?
- Algae can live in the water,
in the ground, or even in snow.
Yep. Snow algae.
They can be really simple cells like bacteria
or more complex ones like the eukaryotic cells
in our own bodies.
The type of algae that causes red tides
are often dinoflagellates.
And yes, I know that sounds like little dinosaurs.
But really they're just microscopic single-celled plankton,
free floating organisms carried around
by waves and currents.
And a red tide is actually an algal bloom
where these organisms rapidly reproduce and replicate,
causing a buildup of millions of organisms
in just a gallon of water.
Now dinoflagellates and algal blooms on their own,
aren't necessarily a bad thing.
In fact,
scientists don't love the all-encompassing term of red tide,
and prefer the terms algal bloom and harmful algal bloom,
to distinguish something that is just an overgrowth
from one that's actually harmful.
And a dinoflagellates are a pretty important part
of the ecosystem.
Many are photosynthetic,
creating their own energy from sunlight,
and they become food for lots of ocean dwelling creatures,
passing that energy into the larger food web.
But blooms can form when the water changes,
either due to a lower salt content
or more surface temperatures,
or an increased number of nutrients in the water,
which could potentially come from human activity.
But sometimes these blooms can be dangerous
and that they produce toxins.
These are poisonous substances produced
within living cells or organisms,
things like snake and spider venom.
Many of these dinoflagellates produce exotoxin,
which is just a fancy word for fish poison,
either poisons made by fish or things that kill fish.
Here we're talking about the killing fish kind.
And these toxins can be harmful to humans too,
especially because they can accumulate
in things like shellfish,
which if you were then to eat,
could make you sick or even potentially kill you.
In Florida,
the annual red tide that washes up on its beaches
is caused by a species of algae known as Karenia Brevis,
which produces brevetoxins.
These are tasteless odorless molecules
that affect the central nervous system
of both fish and you.
After eating contaminated shellfish,
you might start off with some stomach symptoms
like vomiting and diarrhea,
and end up with neurological symptoms
like tingling sensations,
problems feeling hot and cold,
vertigo and impaired coordination.
This happens because the brevetoxins
are long cyclical structures,
that combined two membrane channels on our neurons
causing them to fire when they shouldn't.
Other algae species can produce compounds
like saxitoxins,
which also accumulate in shellfish
and can cause paralytic shellfish poisoning.
If you eat those shellfish,
these toxins can cause you to lose control of your muscles
for days or weeks.
Though its molecular structure is much smaller
than the brevetoxins,
it too confined to sodium channels on your neurons,
preventing them from firing.
Again, this is really bad
and can lead to paralysis or death.
And it's not just eating contaminated fish and shellfish
that can be a problem,
waves can break-open algae cells
and release the toxins into the air.
Meaning you could be breathing them in,
standing on the beach.
And breathing in these toxins
can lead to allergy-like symptoms,
including coughing, sneezing, and runny eyes.
Oh, and you don't even have to be close to the water
to inhale these toxins,
they can travel up to a mile inland
if the wind is blowing just the right way.
Meaning you can experience symptoms
without even going to the beach.
And, while rare,
these toxins could even affect your pet your too.
That's not great.
Nature often makes things that are beautiful and deadly.
And red tides are no exception.
Despite what the name says,
not all red tides are red though.
They come in a rainbow of colors,
including brown, orange, yellow, burgundy,
and yeah, red,
based on the exact algal species that is causing the bloom.
Different species contain different pigments,
many of which play a role
in helping them capture light for photosynthesis
or act like a sunscreen.
Before we talk about photosynthesis,
let's zoom in on light waves for just a second.
Light is energy and it can be modeled as a wave.
The visible light that we see
is a part of the electromagnetic spectrum,
which also includes things like x-rays,
microwaves and radio waves.
A side from just high or low frequency,
another way to characterize waves is by their wavelength.
This spectrum is organized by wavelength,
and the shorter the wavelength, the higher the frequency.
High frequency waves like x-rays and UV light
are on one side,
and radio waves are on the other,
with visible light kind of smushed in the middle.
Visible light and other forms of electromagnetic radiation,
can be characterized by their wavelengths.
The measure of distance between one crest of the wave
to the next.
So if we were to compare two colors in the visible spectrum,
you can see that blue light
has a wavelength of around 450 nanometers,
and red light has a longer wave length
of around 700 nanometers.
And we see these different colors in different objects
because of how light interacts with them.
White light,
like the light from the sun,
actually contains all of the wavelengths
of the visible light spectrum.
And you can see that if we send it through a prism.
The prism refracts or bends the light
and each color is refracted by a slightly different amount
based on its wavelength.
This allows the colors to all spread out and be seen.
It's the same thing that happens in a rainbow.
Light from the sun,
it hits water droplets in the sky
and is both reflected and refracted down towards the ground.
The individual wavelengths of light are separated,
resulting in a rainbow.
So let's take this red apple right here.
This apple isn't emitting red light.
That would be really weird.
Instead, white light from the sun outside,
and the lamps in my room is hitting the apple,
and pigments in the apple are absorbing many
of the wavelengths of light in that white light,
but are reflecting back red light,
which then hits your eye.
And pigments are just molecules that do exactly this.
Reflect and absorb light.
They're found in lots of things in nature.
From plants to animals, to minerals,
and can be especially useful for organisms
that make their own energy via photosynthesis.
Now you're probably used to thinking about
the pigment chlorophyll and how it makes plants look green
when we talk about photosynthesis.
Chlorophyll can absorb blue light at 465 nanometers
and red light at 665 nanometers.
It reflects back the green light in between.
But some dinoflagellates have come up with a way
to capture even more light.
Peridinin is a red pigment that can capture light waves
between 470 to 550 nanometers,
where chlorophyll's absorption typically isn't so great.
It's a carotenoid,
the same kind of pigment that gives carrots
their red-orange color.
Dinoflagellates that use a complex
of both peridinin and chlorophyll molecules
are therefore able to extend the range
of light that they capture,
increasing their photosynthetic capability
and the amount of energy they can create.
So the red pigment helps to capture more green light
and reflects more red light back at our eyes,
giving the tides their characteristic color.
But sometimes these tides do emit their own light.
Just look at these images
from a recent red tide in California.
Those bright blue flashes of light in the water,
those are real and they're caused by the algae.
Some of the dinoflagellates that cause red tides
can also emit a flash of blue light
when they're disturbed in the water,
either by a crashing wave or a kayak paddle.
The light comes from a bioluminescent molecule,
called luciferin.
And luciferin molecules show up
in lots of different creatures.
It's the same molecule that gives fireflies their glow.
So how does this humble molecule create light?
Well, it starts with electron energy levels.
Remember that electrons are negatively charged particles
that surround the nucleus of an atom.
They orbit at specific distances from the nucleus,
a bit like rungs on a ladder.
You can use energy to move electrons up to a higher rung
and they can let off energy
when they fall back down to a lower rung.
The dinoflagellates also produce
an enzyme called luciferase,
which adds an oxygen molecule to the luciferin.
This causes an electron to move up an energy level,
and then fall back down, releasing that energy as light.
So how does it know when to do this?
Well, the activity of the enzyme is dependent on pH.
A measure of how acidic or basic something is.
A low pH means that something is very acidic,
like vinegar,
and a high pH means that something is more basic,
like baking soda.
The enzyme is most active at a pH of 6.3,
which is slightly acidic compared to a neutral pH of seven.
And that pH is really a measure of how many hydrogen ions
or hydroxyl ions are present.
If there are lots of hydrogen ions, the solution is acidic.
And if there are lots of hydroxyl ions,
the solution is basic.
The Luciferin and luciferase are located in compartments
within the dinoflagellate cell called scintillons.
When the dinoflagellate is disturbed,
a membrane channel is opened that allows hydrogen ions
to flow into the scintillon.
The pH drops, the luciferase is activated,
and the electron is set into motion,
climbing up an energy level before falling back down,
releasing a photon and causing a flash of light.
These flashes are thought to be a defense mechanism,
startling predators trying to eat the dinoflagellates,
or acting as a kind of alarm
for other organisms attracted to the light
to come eat the original threat.
So these red tides can be dangerous
and they can also be beautiful,
but they don't last forever.
And even blooms of algae that don't produce toxins
can turn deadly for local sea life as they decompose.
As they decay, oxygen levels in the water can drop.
This can cause animals to either leave the area or die.
And all those dead fish and dying algae
become a buffet for new bacteria
and other microbes to feast on what's left behind.
And it produces quite a pungent scent,
which is a good reminder
that nothing in nature is ever wasted.
(Gently chiming bells)