Scent of Survival: How do Heatwaves Impact Bumblebees? (Ep. 45)

Bees + flowers = pollination. Climate change is turning up the heat on our native bees. A new study shows that when temperatures soar, bumblebees struggle to pick up on the scents of flowers, which is very important for their role in pollination. This is the sizzling predicament we’re talking about today with Dr. Sabine Nooten.

Dr. Sabine Nooten is an insect ecologist at the Julius Maximilians University of Würzburg in Germany. This is the study we discussed and you can learn more about her and her work here. Follow her on X (formerly Twitter).

Good to know

How exactly did Sabine and her team conduct this study? She has climate chambers in her lab where they can house bumblebees under controlled conditions, and expose them to different temperatures (like heat waves). After exposing them to a “heat wave”, they remove the antenna from the bumblebee and insert it into a tiny glass tube attached to electrodes in a large apparatus, to measure the electrical responses to puffs of floral scented air. To keep a controlled environment, the apparatus sits in a metal cage called a Faraday cage to avoid outside interference when recording the electrical signals.

Transcript

[00:00:00] Welcome to the Bee’s Knees. I’m your host, Jacy Meyer. The Bee’s Knees is a podcast wild about native bees. Wild and native bees are under threat worldwide. In each episode, we look at actionable things we can do to support these adorable little guys whose pollination work is crucial for maintaining biodiversity.

Thanks for being here.

It’s December in the Northern Hemisphere, and heat waves are far from our minds. But many people may have been impacted by one this past year. The World Meteorological Organization is predicting 2024 may be the hottest year on record, with a global average 1. 5 degrees Celsius above the pre industrial average.

We’ve talked before about the effects of heat waves and drought on native bees, but today we’re going to focus on how the heat may impact the important pollination work these little guys do. Dr. Sabine [00:01:00] Nooten led a study looking at the effects of high temperatures on bumblebees ability to detect floral scents.

Her research found that extreme heat events disrupt the chemical communication between plants and pollinators. I started our discussion by asking her why she was interested in the effects of heat waves on pollination. Well, as an insect ecologist, I saw that studies came out that showed that climate change and also heat waves have an effect on pollinators.

However, explanatory effects can be very complex. There can be all sorts of changes in morphological traits, physiological process, in species richness, and in their abundance. So I wanted to find out not only that there is an effect, but rather what this effect is. So here in the lab, we have the setup and the expertise to do this physiological experiments like electro antenograms.

And I thought it’s a great [00:02:00] opportunity to test the effects of heatwaves on bumblebees ability to detect floral scents. Your study mentions that heatwaves cause reductions in antennal responses to floral scents in bumblebees. Can you explain what an antennal response is and how this change might affect pollination efficiency?

There are sensors on the antennae that detect the auto molecules and pass the information onto the brain in form of electrical signals. And we measure the electrical signal strength using electro antenography. So our experiment shows that hot temperatures impede the physiological processes of the bumblebees to detect these floral scents.

Based on the outcome at this stage of that study, we can only speculate that pollination efficiency might decline due to the bumblebees reduced ability to detect these floral scents. However, I have already acquired funding for a follow up [00:03:00] project, where we are now testing how experimental heat waves affect the bumblebees behavior in terms of finding or locating the floral scents in an experimental setup.

And this project is currently underway. I found this so interesting. You found differences in the antenna responses to floral scents between worker and male bumblebees. What might be the reasons for these differences and what could their impact be? Indeed, we found that reductions in antenna responses were much more pronounced in the workers by up to 80 percent than in males, which only showed reductions of up to 50 percent.

So we can only speculate about this, about the reasons and the impacts of these differences. So let me explain. On one hand, male bumblebees can be surprisingly heat tolerant. You need to imagine that they are being kicked out of their nests once they reach maturity, and so they are exposed to harsh outside temperatures day and night.[00:04:00]

Workers, however, can retreat back into the colony underground or in grassy bushels when the conditions outside are unfavourable. In essence, the male’s purpose is to find and mate young queens to start the next cycle, so they basically spend day and night outside for this purpose. On the other hand, workers Their chief responsibility is to locate and gather food for the colony, and this task requires a highly developed olfactory system.

We could imagine that workers have much more olfactory receptors tuned to the volatiles, which are released by flowers, and that makes them more sensitive to odor cues. And we can imagine that any damage to these receptors may then have a greater impact on the worker’s ability to locate food and perform their tasks efficiently compared with males.

How do you think the [00:05:00] increasing frequency of heat waves may affect plant pollinator interactions and the broader ecosystem services they support? So our study showed that heat waves diminish the bumblebee’s ability to detect floral scents. in terms of a physiological process. That could mean that bumblebees spend more time to detect the floral resources outside.

And if this is so, we speculate that ecological services like pollination could be diminished if bumblebees olfactory system does not adjust to these environmental changes. Or if bumblebees cannot adjust in any other way. And that, for instance, could be changes in their behavior, the time when they go out forage.

So, what, if anything, can we do, and what research still needs to be done? Well, unfortunately, we cannot influence the occurrence of heat waves. However, we can generally help our native pollinators by planting native plants in the [00:06:00] garden and making sure that they provide flowers and nectar resources throughout the entire year.

We definitely need follow on studies and we are already well on track to look at the behavior part of the effects of heatwaves. And that is to investigate the bumblebee’s ability to locate floral scents in experimental setups. And we also need to investigate the quantitative aspects in this regard.

For example, how much pollen are bumblebee workers collecting after a heatwave exposure as compared to before that? Why do you do what you do? Why bees? I’m passionate about wild bees and bumblebees in particular, not only because they are widely diverse in form, shape, color, and they’re very beautiful insects, but also because they’re really important in their habitats.

They provide important ecological services by pollinating wildflowers and whereby maintaining floral biodiversity in all sorts of ecosystems. [00:07:00] However, they’re also vastly important for us in an economical sense. Because they pollinate a wide, wide range of crops, which we highly value, like for example, strawberries and blueberries and apples and tomatoes.

And so without them as helpers for this pollination services, we would not only lose biodiversity, but we would also struggle to get our most favorite fruits and vegetables. Bees pollinate crops that make up one third of our food supply. One third! High temperatures affect their physiology, and if bees can’t find their food effectively, they can’t pollinate effectively, which directly impacts the food we eat.

Thanks so much for listening today, and thanks to Sabine for talking with us. Be sure to visit the website, thebeesknees. website, to read how Sabine conducted this research in her lab. And, we will try and talk to Sabine again when she completes her follow up study. Such a fascinating way to end season two.[00:08:00]

I hope you enjoyed the people we met this past year, like Gary Connolly, whose organization helps plant orchards in Ireland, and Justina Block, who works to promote biodiversity in our own backyards. We talked about how non native bees impact native ecosystems, the nutritional habits of bees, and of course, the ongoing dangers of pesticides and climate change.

What was the biggest takeaway for you this year? Let me know, and let me know what you’d like to learn more about in Season 3. You can send me a message on the website, and also subscribe to our newsletter, The Hive. I’ll be back in January with a preview of Season 3. Until then, keep buzzing.