(swooshing)
- [Narrator] Dive beneath the ocean waves
and you'll find a bright, bustling city.
Full of diverse residents, swimming,
eating, and sharing homes together.
At the California Academy of Sciences,
our mission is to explore,
explain, and sustain coral reefs,
like this one in the Philippines.
Each of the thousands of
species that live here
have their own unique role and
place within the ecosystem.
But it's not all just predator and prey,
the relationship between these species are
as diverse as the ecosystem itself.
In this video, we'll investigate
the following key questions.
How do species interact on a coral reef?
What are the effects of
abiotic and biotic factors?
And how do these interactions
influence patterns
of distribution and abundance
within the ecosystem as a whole.
Take for instance this bubble-tip anemone.
Notice anything strange?
Instead of avoiding
its stinging tentacles,
a fish seems to be relaxing in them.
These two reef residents
have formed what is known
as a mutualistic relationship.
In exchange for defending the anemone
from predators like butterflyfish,
the maroon clownfish receives
shelter and a safe nest site,
both benefit from their interaction.
In fact, while the bubble-tip can live
with up to 14 species of clownfish,
this partnership is so important
to the maroon clownfish
that it can't survive without
a bubble-tip anemone host.
Let's take a closer look.
Imagine you're a biologist exploring
the relationship between
bubble-tip anemones
and maroon clownfish in the Philippines.
You visit the same coral reef every year
and sample only bubble-tips
that host maroon clownfish.
Look over your field notes now.
What trends do you see?
How are the populations of these
two coral reef residents connected?
Take a moment to pause the
video and examine the table.
Let's hear from academy
scientist, Luiz Rocha.
- When diving around coral reefs,
we always find maroon
clownfish living in pairs
with their bubble-tip anemone host.
You can see this 2:1 population
ration in your field notes.
Understanding this relationship allows us
to make predictions about the population
of maroon clownfish based on what we know
about the population
of bubble-tip anemones.
- [Narrator] Now imagine you travel back
to the same reef to
continue your research.
What trends do you notice
over the following two years?
(mild playful music)
Given what you know about
this mutualistic relationship,
can you predict the effect this
drop on bubble-tip anemones
will have on maroon clownfish populations?
Pause the video and make your prediction.
- [Luiz] In this example,
extreme temperatures led
to decrease in anemones.
And given what we learned
about the population ratio,
we can predict a similar
drop in maroon clownfishes.
It's important to keep in mind
that this just a theoretical example.
Natural coral reef
systems are very complex
and involve a wide variety of factors
that need to be taken into account.
- [Narrator] Exploring further,
we find another example
of cooperation among reef residents.
This whitetip reef shark sits peacefully
while a bluestreak wrasse swims
around its head and mouth.
Why so calm?
The whitetip has come for a cleaning
and the wrasse, which feeds on dead skin,
is happy to provide it.
Relationships like this
one are so beneficial,
the positive impacts spread
across the entire coral reef system.
Cleaner fish attract a wide diversity
of fish to their cleaning stations.
And as a result of their cleaning care,
improve the overall health of the reef.
Not all interactions on the
coral reefs are win-win however.
Take this saber-toothed blenny.
It looks like a wrasse but instead
of providing a beneficial cleaning,
it usually takes a bite
from its client's body.
This parasitic relationship
means one organism benefits
while the other is harmed.
Passing overhead, a slender fish clings
to the side of a whale shark.
Remoras like this one live
directly on other fish.
Feeding on discarded food
without negatively impacting their host.
This relationship benefits one
without affecting the other.
Which is why we call it commensal.
On a coral reef, species interactions
and the various symbiotic relationships
that arise from them are fundamental
to the functioning of
the entire ecosystem.
Understanding these interactions allows us
to predict patterns of diversity
and most importantly, come
to a better understanding
of these biologically
rich cities under the sea.
