They're prolific, natural pollinators and are a huge part of our modern agriculture, I mean a lot of the food we eat relies on pollination from bees.

Unfortunately though they're also in serious danger.

The scientists in our next film symbiosis might have discovered one cause and it could change everything.

We know about bees and their ecosystems.

Starting with the microscopic world that we never knew existed until now.

This is symbiosis from days.

Edge productions bees for more than 100 million years, they've been buzzing around helping plants reproduce.

We're kind of shoulder to shoulder with bee populations in the maintenance and sustenance of plants.

We keep plants because we need them for food.

Bees are in a similar relationship with plants where they're helping the plant and getting something in return, bees collect pollen to feed to their young wings and the larva eat the pollen and develop into adults.

And that's what we've always thought.

But the more we look, the more we realize that bees have this silent partner in their mutual ism with plants and that third silent partner is the microbes.

New research is revealing that these microbes play a surprising role in the lives of nature's most prolific pollinators.

But this discovery raises new questions about the future of wild bees in a world transformed by humans.

If the microbial community is perverted in some way, it can have catastrophic effects in terms of be held, it matters because as with any symbiosis when you remove one of the symbiont, the symbiosis crumbles.

I think when people hear the word B, they typically think of honeybees.

Honeybees are not native to North America.

We brought honey bees here in the 16 hundreds spreading with european colonists.

Honeybees became the most abundant bees on the continent, but there were already wild bees here.

A lot of them In North America.

We have 4000 native bee species.

Some of them are important crop pollinators.

Some of them are also intimately tied to pollination of native wildflowers and native plants.

Whenever there's a flowering plant there is a bee to visit that plant.

And so that pairing that mutual is um between the bees and the plants that has fed the literally and figuratively fed the diversity of bees in North America.

Okay, the vast majority of these are solitary ground nesting bees and by solitary, I mean a single female constructs her own brood cell provisions it with pollen and nectar defends it against parasites and predators and lays her own egg.

Then the grub like larvae eat the pollen and nectar their mothers provision them with and eventually transform into adult bees when the weather conditions are right when the rain comes or when the spring comes, those bees will emerge and they'll start the cycle over again.

But for many of North America's wild bees.

This cycle isn't running as smoothly as it used to.

Native bees are dwindling across the continent and the culprits behind their declines have been hard to pin down.

Mhm.

We started doing research on the native bee fauna of apple orchards in around 2008.

1 of the things we detected is that the species richness and the abundance of bees declined with fungicide use fungicides are agricultural chemicals used to fight disease causing fungi in crops.

But the link between fungicides and bee health was puzzling partly because you can't sell a fungicide in the US until it's been safety tested on bees.

There is a whole lot of data showing that the fungicides are relatively innocuous for the adult being.

If fungicides weren't killing the adults, there had to be another connection.

But what was it?

The first clue came from researchers studying the life cycles of wild bees.

Starting from the very beginning, Mom builds this little brood cell, she digs it out, she lines it, she puts food in it, She lays an egg on it.

And that world is it's a nursery, right?

But mom maybe intentionally, maybe sometimes by mistake, maybe it's just part of being a b.

Mom introduces bacteria.

She introduces funk.

I and it gets sealed off and then it's really literally its own ecosystem.

An ecosystem.

We're only beginning to explore.

Mother bees collecting pollen and nectar.

Also gather microbes like fungi and bacteria And whatever else is on the flowers they visit.

We screened the pollen provisions and we found up to 35 agrichemicals and about half of those were fun designs.

Mhm.

It got the scientists thinking if bees bring fungicides into their nests, could those chemicals throw the tiny brood cell ecosystem out of balance?

And how would that affect the developing bees?

Yeah.

To find the answer, they first had to figure out how bees interact with microbes in healthy brood cells.

We're here at the bodega bay marine lab in northern California to study one of north America's most interesting bees.

And to offer a bomb Boyd's, these bees build massive aggregations.

So we find thousands of nests in one small area of the cliff face.

Mhm.

When we excavate a nest site, we can start getting a glimpse of what's going on inside each of those brood cells.

So here's a brood cell that we've just excavated out.

We see the brute cell is quite a solid structure.

It has a very very strong odor.

It smells a little bit like parmesan cheese or reggiano or cheetos.

There's a fascinating chemical story going on here.

The pungent odor is a sign of microbes at work, just like what happens when microbes transform milk into cheese.

So we have in this vial some provisions that came from the brood cell in the soil.

The provision that smells like cheetos.

Once you put them on these plates, you can start to see some of the diversity of forms and colors and types of interactions of these microbes that otherwise remain unseen.

Take a sample from a brood cell, let it grow for a few days and there they are bacteria, fungi.

It's likely thousands of species of microbes are all these different microbes just getting a free meal in the brood cell Or do they somehow benefit the developing bees?

There's one way to find out.

You knock out the microbes from the fermenting pollen mass and then you see how the B actually fares.

How does that larva, do?

The researchers turned to oz?

Mia bees for an answer.

Also known as mason bees as mia bees are widespread, solitary bees known to be important agricultural pollinators.

Unlike most solitary bees, they nest above ground, often in hollow plant stems.

This makes as mia easier to study than ground nesting bees, but the researchers still had to figure out how to manipulate and observe larvae that normally develop inside sealed individual brood cells.

How do we study these bees?

How do we see what they're doing?

They develop in these opaque chambers.

We don't know what's going on in there and that's when we started opening their nests and looking at them.

It just blew me away.

It was, there was such a brilliant method.

It just appealed to my type, a personality.

I guess it's almost like having your spice jar organized alphabetically.

It was just magnificent like that.

After a few years of trial and error, we figured out that we could actually rare these bees inside our lab inside these bell trays and have better survivorship than recorded in the wild.

Finally, the researchers had a solitary bee they could observe from egg to adult as it grew in a clear plastic brood cell.

What would happen if the bees pollen provisions were sterilized, removing the bacteria and fungi, but leaving the pollen and nectar intact?

And what we found is that when you remove the microbes, the developing larvae just suffer woefully.

Half of them don't even make it to pure peixian.

Those that do tend to be small and sickly and they take a long time to get there.

And so those appear to be huge consequences for A B.

That does not have its microbes.

The larvae developing without microbes were starving even with all the pollen and nectar they could eat.

So what was missing from their diet.

If they're just eating pollen and nectar, these are going to be strictly herbivorous and that has a specific, like chemical signature.

If you pluck a hair out of a vegetarian, they're going to have a different chemical signature than somebody that only eats red.

In other words, analyzing the molecules of the larva is made of can tell us what it's been eating.

We typically think of bee larvae as vegetarians, but in the tiny ecosystem of the brood cell, they have access to a surprisingly diverse menu.

We looked at all major be families and we found every single B was significantly omnivorous.

They're eating huge amounts of this microbial meat.

It's not very often that you think of microbes as food, but that's what we think is exactly going on.

We think that the larva eat pollen.

Yes, but not nearly as much as they eat the microbes that have eaten the pollen.

Mhm.

And if you remove those media microbes and force the larvae to become herbivores, they suffer, it might so be that they consume the pollen because they're trying to consume the microbes and the pollen is just in the way it's I think a massive shift in our understanding beyond their role as a food source.

The microbes could also benefit the larvae by digesting the tough outer shells of pollen grains or even by neutralizing the defensive chemicals present in some plants, pollen and nectar.

The researchers are testing these ideas and more whatever they find, it's clear that the ancient alliance between bees and plants depends on a third partner that's been hidden until now.

We know from our research that there is a broad diversity of fungi within Poland provisions and we know that when they're not there to be suffer, which brings the scientists back to the link between fungicides and B hill In the us alone, we use more than £50 million pounds of fungicide each year connecting the dots from those supposedly be safe fungicides to declining bee populations.

Sean realized that fungicides might not harm bees directly, but instead kill the fungi.

They rely on essentially taking microbial food from the mouths of bee larvae.

Sean and his students tested this idea with a native social bee, the common eastern bumblebee.

We set up an experiment where we had bumblebees in really big cages and we stocked them with lots of flowers.

Um, some cages, the flowers were sprayed with fungicide.

Some cages were just, you know, sprayed with water.

And then we tracked how those bumblebee colonies did.

And we saw this hugely negative effect on the bumblebee colonies that had fungicide residue on the flowers.

The colony's foraging on fungicide treated flowers had fewer workers and smaller queens than colony's foraging on untreated flowers.

That monkey wrenched microbial community results in starving larvae.

So if you ask the question, fungicides be safe not for the larva, and so definitely not.

The data show that the standard practice of testing fungicides only on adult bees has a critical blind spot and we might never have known it without researchers exploring the hidden world of the brood cell.

We're now looking at how fungicides affect other bee species, specifically the solitary bees.

And we're in the midst of that right now, researchers are carefully dozing owes me a bee's pollen provision with various fungicides in the lab mimicking the real world interactions of bee larvae, microbes and fungicides.

Their goal is to identify the threats these chemicals pose to native pollinators.

We really rely a lot on some of these agrochemicals, sadly, if we stopped applying agrochemicals are our food supply would probably be in trouble.

So the answer is not to stop all fungicide sprays.

That's not the answer.

The answer is to figure out a way where spring can be done in a manner that is sustainable and compatible with bee conservation.

The scientists are optimistic that some fungicides will be more bee friendly.

Our findings so far suggest that not all fungicides are created equal.

Some may cause fewer problems for bees than others and beyond choosing less harmful fungicides.

We can also adjust how we apply these chemicals to our crops.

We can spray crops before or after bloom.

So there's less fungicide on the flowers when bees are foraging or even spray at night when most bees aren't active.

One of the fruits of our work has been to say, hey, microbes matter for bees, bees matter to you, the growers.

So can we do this better where we protect our plants but also protect the pollinators.

And we're learning the protecting native bees means protecting the microbes that help them grow and thrive the food we eat.

The air we breathe is in some way shaped by these microbes.

You don't see them, You don't know that they're there, but they shape every every facet of our existence.

Yeah.

24.

Right.

Mhm.

Right.

Yeah.

Yeah.