>>NARRATOR:
Reaching up into the water

like the branches of trees,
they are thousands of organisms

living together as one.

And together they provide
shelter and protection

for many more.

>>This is really important
for a lot of different

marine organisms and provides
a refuge for these organisms.

>>NARRATOR:
Once a common sight,

elkhorn and staghorn corals
were the dominant

shallow reef building corals
in the Caribbean and Florida.

>>Coral reefs are under
extreme stress toda

from a variety of causes,
both globally and locally.

>>In the past 30 years,
elkhorn and the staghorn

have declined dramatically,
between 90% and 98%,

throughout the Caribbean.

They're now listed
as threatened under

the U.S. Endangered
Species Act...

>>And are much reduced
from their former glory.

>>NARRATOR: Primarily, disease
as well as some other factors

has led to the drop in numbers

of elkhorn and staghorn
colonies.

But while these corals
have declined in recent years,

their hybrid appears
to be increasing

in parts of the region.

>>What's really cool
about this hybridizing system

is that the hybrid is not found
in the fossil record.

They seem to be
increasing recently,

likely due to the decrease
in the parental species.

>>NARRATOR: Often found in
really shallow water,

this hybrid, commonly called
fused staghorn,

closely resembles its parents.

>>You have some that look
very much like staghorn

and then others
that look like elkhorn.

Most of the ones that I've seen
throughout all my study sites

in the Caribbean have more
of a staghorn look to them,

but they're more tightly clumped
than the branching staghorn.

>>NARRATOR: Could these hybrids
be better equipped

at dealing with
environmental stressors?

Might they be filling
a niche left behind

by the decline of their parents?

>> Major funding for this
program was provided

by the Batchelor Foundation,
encouraging people

to preserve and protect
America's underwater resources.

And by Divers Direct,
inspiring the pursuit

of tropical adventure
scuba diving.

>>NARRATOR: Dr. Nicole Fogarty
is an Assistant Professor

at Nova Southeastern
University's

Oceanographic Center.

She studies the hybrids
at various sites

across the Caribbean.

>>I was really interested
in this hybridization

between these two
threatened species.

There's very little that's known
about the hybridization.

>>NARRATOR: Since 2005,
she's been making

regular research trips
to a small island

off the coast of Belize.

>>The island is out on
the Mesoamerican Barrier Reef,

so you really can literally
roll off the island

and be on a coral reef.

There's just a very nice reef,
very, very close to the island.

>>NARRATOR: The Mesoamerican
Reef stretches along

the coasts of Mexico, Belize,
Guatemala and Honduras.

It is considered
the largest barrier reef

in the Western Hemisphere,
covering nearly 700 miles

from the northern tip
of the Yucatan Peninsula

down to the
Honduran Bay Islands.

Carrie Bow Cay is located
15 miles offshore

from the Belizean town
of Dangriga.

It has been a research facility
of the Smithsonian Institution

since 1972.

>>We just celebrated
our 40th year anniversary,

and we've got
over 930 scientific publications

that have come from the island,
including a few books

that have all resulted
from the work at Carrie Bow.

It's really contributed a lot
to our understanding

of coral reef ecosystems
in the Caribbean.

>>NARRATOR: The island is an
ideal place to study the hybrid

because of its proximity
to all three types of corals.

>>There's a wonderful
population just off

the southern end of the island.

It has both the staghorn,

the elkhorn and the hybrid
of those two species.

>>NARRATOR:
When Nicole first started coming

to Carrie Bow Cay, she wanted
to understand why the hybrids

might be increasing in numbers.

>>One possibility
is that there's

an actual increase
in hybrid formation,

so the egg and sperm
of staghorn and elkhorn

are mixing to form an embryo
that's a hybrid

that will eventually
go and settle and grow

into an adult hybrid coral.

The other possibility
is that we have an increase

in asexual fragmentation.

These corals
are branching corals,

and so they can break off
and fragment, reattach

to the bottom and then
continue to grow.

So that's a very
important aspect

of their life history stage.

So you could imagine
if there's just a few rare

hybrid events that formed
decades ago, these hybrids

could just fragment repeatedly
over the years.

The other possibility
is that the hybrid

is actually more viable
than the parental species

and might show
increased fitness.

It's called "hybrid vigor."

And so we have hybrids that have
been established over the years.

And when you have
the disease outbreak

and disturbance and other things
that have led to the decline

in the parental species,
the hybrid's actually able

to withstand all those
different events.

And that's why
they're increasing in numbers

and are higher in abundance
at some of the sites.

>>NARRATOR:
To test these hypotheses,

Nicole decided to conduct
a number of experiments

when the corals were spawning.

>>Staghorn and elkhorn coral
only spawn once a year,

usually in late summer-- July,
August, or September.

So that means one night
out of the year, they release

gamete bundles,
and those gamete bundles

are full of both egg and sperm.

Each individual polyp
that makes up a coral colon

will form one gamete bundle.

It takes the polyp
about nine months

to create the egg
and about six months

to create the sperm.

So there's a lot of energy
being invested in forming

these gametes.

The gamete bundles are released
in one synchronized pulse.

They float up to the surface,
break apart, mix with

other gametes from
other individual corals

from the same species,
or sometimes hybridize,

and then fertilization occurs
at the surface.

The resulting embryos
then float around

for a couple of days
before developing into larvae.

And then the larvae
will float around

for a few more days
before they start swimming

down to the bottom, looking for
a good place to settle.

They'll attach to the bottom,
metamorphose, and grow into

an adult coral.

>>NARRATOR:
Staghorn and elkhorn corals

are very plantlike creatures.

>>And so really, when you're
thinking about corals,

even though they're animals,
their evolutionary background

and evolutionary trajectory
are much more like plants.

They are hermaphrodites.

They are attached to the bottom
just like adult plants are.

They broadcast spawn their
gametes like many plants do.

They're long-lived like plants,
and they also can

asexually fragment.

They asexually propagate
like many plants.

>>NARRATOR:
Using a tentlike net,

Nicole collected the gametes of
both elkhorn and staghorn corals

on the nights
they were spawning.

>>We bring those gametes
back into the lab.

We can separate the gametes
out to sperm and stock solution

and then we can play
"mad scientist," where we do

all kinds of different
fertilization assays.

Now that we've separated them
out into our sperm

and egg solutions, we're going
to conduct a series

of fertilization experiments.

And so, we're looking
at fertilization between

the elkhorn and the staghorn,
and this is crosses between

the staghorn eggs
and the elkhorn sperm.

And now I am going to add one
milliliter of eggs to the vials.

After I complete this cross,
then we'll do

the reciprocal cross
and mix staghorn sperm

with the elkhorn eggs.

And then we can do it
with sperm competition.

That's when we mix
both the staghorn

and the elkhorn sperm together
and then introduce the sperm

to the staghorn eggs
or introduce the sperm mixtures

to the elkhorn eggs.

And that's more likely
what occurs during

coral spawning, because
these species spawn

at the same time,

and so the sperm
are going to be mixing,

competing for who's going to
actually fertilize the eggs.

Once all the crosses are done,
we'll let them sit

for three hours and then
we'll score fertilization.

When we score fertilization,
what we are looking for

is the number
of unfertilized eggs

and the number
of dividing embryos.

>>NARRATOR: With these
fertilization experiments,

Nicole tried to determine
if there may be

gametic incapability,
which means one species' sperm

can't fertilize
the other species' eggs.

>>What we found out
is that both the staghorn eggs

and the elkhorn eggs
are able to hybridize,

but the elkhorn eggs
are a little more resistant

to hybridization
than the staghorn eggs.

The staghorn eggs
can be fertilized

by the elkhorn sperm just as
easy as their own species sperm.

In the sperm competition assays,
we found the similar result.

The eggs of elkhorn
are a little more resistant,

and then the eggs of staghorn
are more easily fertilized

by not only their
own species sperm

but the elkhorn sperm, as well.

So it can happen
in both directions,

but hybridization occurs
more frequentl

with the staghorn eggs.

>>NARRATOR: Next, Nicole
looked into the viabilit

of the hybrids.

>>The hybrid might be sterile,
such as the mule example,

when a donkey and a horse mate.

Or it might just be inviable,
so it has decreased fitness,

and it's not able to persist
in an environment.

Perhaps it's more
susceptible to disease

or temperature fluctuations.

So these are the type of things
that I wanted to look at.

And what we found
was that the hybrid

was not inferior across
any life history stage

that we looked at.

That includes the larval stage,
during settlement,

throughout metamorphosis,
and also as an adult.

We also found that
hybrids can persist

in the shallow
marginal environments

they're often found,
but also can persist and grow

in the parental species habitat
without a problem.

>>NARRATOR: And Nicole made
another interesting discover

at her study site in Belize.

>>The hybrid, even though
they're often in just

two or three feet of water,
are no more likely to bleach

than the parental species
that are in deeper water.

And so this could be
that the hybrid is more tolerant

of fluctuations in temperature--
not only increase in temperature

during the summertime,
but those shallow areas

also cool off really quickly
during the wintertime.

And there's also a lot of UV
irradiance blasting those corals

in that really shallow,
clear water.

So that's something that I'm
going to be exploring further.

>>NARRATOR: Coral bleaching
occurs when the animals

are very stressed.

There are a variety of stressors
that can cause bleaching,

including exposure
to extreme temperatures.

Extreme temperatures
are likely going to increase

in frequency in the future
because of climate change.

>>Coral bleaching is when
the corals lose

their symbiotic dinoflagellate
that's in the tissues

of the coral.

So corals have
a symbiotic relationship

with a dinoflagellate
we call zooxanthellae,

and the zooxanthellae
is in the coral tissue.

It gives the coral the golden
or brown colors that you see.

And what occurs
is when the coral

gets stressed out,
that symbiotic relationship

is going to break down.

And so they lose
that zooxanthellae,

and then what you see
is the white coral skeleton

through the translucent tissues.

Now the dinoflagellate,
the zooxanthellae,

is important for the corals
because it gives the corals

a lot of its nutrition.

Corals can capture
small zooplankton

in their tentacles,
but most of the nutrition

that the coral gets
is through the zooxanthellae.

So when the symbiotic
relationship breaks down,

the coral is going to have
decreased growth rates,

it's going to have reduced
reproductive capabilities,

and so it's going to really
negatively affect the coral.

>>NARRATOR: one thing that
is still unknown at this point

is whether or not the hybrids
can mate with each other.

>>We know that hybrids
aren't sterile because

from the molecular signature,
we know that the staghorn

and the hybrid can mate.

>>NARRATOR: However, to date,
no second generation of hybrids

has been discovered.

>>There's a couple
of different hypotheses

of why we might not see
a second generation,

one of which is that the
sampling effort was pretty low.

It was only at three
geographic sites

and pretty low sample size.

So perhaps second generation
hybrids are out there,

but it'll take further sampling,
and that's something

I am looking at
as part of my research

at Nova Southeastern University.

The other possibility
is that if hybridization

is increasing, as I believe
it is, then we might have

more generations
in the decades to come.

It's just such a new event
that they're increasing

in numbers that they haven't had
an opportunity to create

a second generation.

What's really interesting
about this system is that

the parental species
are found in the fossil record

for millions of years,
but the hybrid

has no fossil record.

So it's a relatively recent
event, and there is evidence

that it is increasing
in some sites.

There are sites in Belize,
in Curacao, in Florida

where we know the hybrid
was not at that site

just five years ago, and now
we see hybrids there.

We also know
from genetic studies

that the hybrid populations
are composed of

multiple genotypes, meaning
that there are separate

hybridization events
that have occurred

and not just one
rare hybridization event

that has asexually fragmented.

What I think is currently
going on in this system

is that, with the decline
of the parental species

over the past 30 years,
we actually have an increase

in hybridization.

And how that would work
is that if you imagine back

before the 1980s,
you had really extensive

thickets of both staghorn
and elkhorn.

They were the primary
reef builder in the shallow

reef environments.

And so when staghorn or elkhorn
spawn, the eggs

are immediately going to be
swamped

by their own species' sperm.

And occasionally you might have
had hybridization

if a couple of the eggs
went unfertilized,

but it was a pretty rare event.

Well, now you have these
populations of elkhorn

and staghorn that are
really sparse, and so if you can

imagine when they spawn,
the eggs are going to go

unfertilized.

And at least with
the staghorn eggs,

whatever sperm they run into,

whether it's their own species'
sperm or an elkhorn sperm,

that's going to fertilize it.

So, we have this increase
in hybrid formation

because the parental species
have decreased in numbers.

>>NARRATOR: Long-term
monitoring is necessar

to truly understand the changes
occurring on the reef.

>>Only through long-term
observations over time

can you evaluate and find
new discoveries, and I think

it's paid off in a big way.

>>NARRATOR:
In 2011, Nicole created

a demographic study
off the south end of the island.

>>As far as we know,
we're the only demographic stud

Caribbean-wide that looks at
both the elkhorn, staghorn

and the hybrid.

We established
seven circular plots,

and these are permanent plots.

So every three to four months,
we go back and look at

every individual elkhorn,
staghorn or hybrid

in these plots.

>>NARRATOR: Each of the seven
plots has a buoy at its center.

>>And then we took
a transect line and extended it

seven meters from the center.

We then tagged every single
coral colon

within that seven-meter radius
in that circular plot.

We also mapped it,
and how we do that is

we take the transect line
from that center buo

and extend it out
to the focal colony.

And then someone at the center
buoy has a compass,

looking at their compass,
and then will give us

the different numbers
for that compass bearing.

Whoever is at the focal colony
will then write down

the distance from
the center buoy, and then also

that compass bearing
that the person at the center

then gave them.

That way, we can mark
each individual coral colon

and where it is.

>>NARRATOR:
Next, tissue samples were taken

for genetic analysis.

>>We take small tissue
samples-- about a centimeter,

just like the very end
of your pinky.

It's only about one month
of growth for these corals,

so it doesn't hurt the corals
at all.

We take that tissue sample
and preserve it.

Then we take it back
to the laborator

and we use micro-satellite
markers to be able to genotype.

And then that gives us an idea
of how many separate genotypes

are in our population
and how man

of the different colonies are
actually from asexual fragments.

So far, we have nearly
600 corals tagged and followed

over that period of time.

The elkhorn coral out there
is really genotypically diverse.

We have over 30 genotypes
out there.

The staghorn
is less genotypically diverse

and there's only a couple
unique genotypes, and the hybrid

has about four or five
unique genotypes.

>>NARRATOR: Nicole based
her demographic stud

on a protocol designed and used
by other scientists

in the Caribbean.

>>We can compare our results
in the Western Caribbean

with their results
in Florida and elsewhere

in the Eastern Caribbean.

Every three to four months,
we come back and we photograph

each individual colony.

We also assess each individual
colony and so see if there's

any damselfish bites,
see if there's any predation,

coral bleaching, disease,
et cetera.

>>NARRATOR: Nicole also takes
length, width and height

measurements of each individual
colony and then estimates

the percentage of live coral
for each colony.

>>We're also interested in how
quickly these corals grow.

So what we do is we take
a beaded cable tie and put it

about two centimeters away
from the tip of the coral.

The coral grows from the end,
and so it will continue to grow

and extend so we can measure
from that beaded cable tie

to the very end of the coral
and see how much it grows

every time period that we
come out here and sample.

We're going to be doing
a lot of spatial analyses

and being able to look
how disease spreads

across this population
and coral bleaching, predation,

and see how that changes
year after year and how it

affects different colonies
and may spread

to neighboring colonies.

>>NARRATOR: In the few
short years that this project

has been ongoing,
Nicole has already made

several interesting discoveries.

>>We established this project
just a few months before

a major disease outbreak.

The other aspect is that
we've already lost

individual genotypes
from that disease event,

and lastly we're seeing
some new recruits--

at least colonies that we think
are new recruits.

Once they get a little bit
larger, we'll be able to take

a tissue sample
and genotype them

and verify that it's
a unique genotype

compared to the rest of the
individual colonies out there.

>>So, it's really
a valuable data set.

There's nothing else quite like
it in the Western Caribbean.

There is some similar monitoring
going on in the Florida Keys,

and also in the Virgin Islands,
but this will add a new data set

for a region, the Mesoamerican
Barrier Reef Region,

which is really
much less explored.

>>What we ultimately would like
to do is put this data

into population models.

And so, then, we can determine
whether this

particular population is stable,
increasing or decreasing.

>>NARRATOR: There are still
many questions left unanswered

that Nicole hopes to study.

>>Because the elkhorn
and the staghorn corals

are the only current threatened
species in the Caribbean,

it's really important
that we have a better handle

of what's going on with them

both from an ecological
standpoint

and also an evolutionary
standpoint.

And so this information
not only will provide

some data needed to understand
the evolutionary trajector

of these species, but also
what's going on

from the ecological perspective.

If the hybrid is more tolerant
to increased temperature

or UV irradiance,
then it's going to be able

to withstand some of these
harsh environmental changes

that we may see associated with
global climate change.

If we lose one or both
of the parental species,

it will be interesting to know
if the hybrid can reproduce

among itself and can provide
a genetic reservoir

for some of these genes
that we have lost

through the extinction
of the parental species.

>>It's an avenue that's worthy
of research and may provide

some great information
on how coral reefs

can be restored and thrive
in the future.

>> Major funding
for this program was provided

by the Batchelor Foundation,
encouraging people

to preserve and protect
America's underwater resources.

And by Divers Direct,
inspiring the pursuit

of tropical adventure
scuba diving.