How Microplastics Impact Honey Bees.

Pretty pervasive pollutants: microplastics. Photograph by Oregon State University.

Here we are into February already after some variable weather in January here in the Scottish Highlands. We had a couple of weeks of hard frosts, and a bit of snow, then spring-like conditions one day brought the bees out like it was high season. I didn’t need to open the windows to hear them. The noise was terrific. All four colonies on the back lawn apiary were out in black clouds of activity milling about in the air near the hives. Not much forage available yet with only a few snowdrops, witch hazel, viburnum, mahonia, and sweet box in flower.

I rescue a worker trapped in a cobweb near the back door. The bee dangles in chilled immobility in the shade but quickly revives as I untangle it in the warm sitting room and soon hear it flying against the patio door which I open to release it skywards.

Might Microplastics Impact Queens?

Over the past few months, we have discussed some of the possible contributing factors to queen failure and why so many of us are experiencing problems with honey bee reproduction and colony success. This week we explore microplastics; how they affect honey bees, and if they might they impact queen health?

What Are They?

Long strands of microfibres. Photograph by Caitlin Wessel.

Let’s take a look first at what they actually are and where we can find them. Microplastics are everywhere and are pervasive pollutants of soil, water, and air. They mainly comprise polyethylene, polypropylene, and polyacrylamide polymers. Worryingly, humans consume as many as 52,000 particles a year and probably inhale as many as 74,000 in a year. The particles are divided into groups according to size. Primary microplastics include microscopic particles used in consumer products such as cosmetics, detergents, and cleaning agents. The latter includes blast cleaning products for cleaning ship hulls in dry dock. Microplastics measure 1-5 mm in diameter, while nanoplastics measure less than 1 mm. They come in different forms such as microbeads (nurdles), microfibres , and microfragments.

Secondary Microplastics.

Secondary microplastics (MPs) form from the degradation of plastics where they break down in the atmosphere and water by natural weathering from things like discarded plastic litter. Wear and tear of motor vehicle tyres sends MP fragments up into the atmosphere, and farmers spread MPs on their fields in slurry and manure. Nanoplastics can get into plant root systems and have been found in lettuces.

Local litter.

Researching this topic inspired me to get out my litter-picker on local walks again and today I collected a fair bit of rubbish and reduced the environmental risk ever so slightly. Most environmental MPs are secondary and found in waste water treatment plants, swamps, bogs, oceans, and shorelines. Sadly, they are found in nearly every corner of the world including pristine Arctic and Antarctic landscapes, Mongolia, and Patagonia. MPs were found in 12% of honey samples tested in Ecuador in 20131, and also in Danish honey samples. This is not a surprise given that honey bees interact with plants, air, soil, and water and everything they collect contains MPs. Research to date shows that the honey tested was still fit for human consumption but it is still thought provoking.

Effects on Animals and Birds.

We know that marine animals and birds are harmed by MPs and studies show how digestive tracts are blocked and the animals lose their appetites. Altered feeding behaviour reduces growth and impacts reproduction. It has been suggested that other chemicals may make PMs more harmful and research shows how MPs can adsorb (hold together gases, molecules, and liquids in a layer on its surface) pollutants thus becoming both a source of pollutants and a sink for them. MPs have a strong attraction for lipids and fats which is why adsorption is a problem. Scientists are currently studying the new hot topic of the role of MPs in spreading pathogens, diseases, and viruses so keep a look out for future research in that area.

Scientists have already carried out some research on honey bees and the impact of MPs. What we have learned is worrying. One lab study2 demonstrated that, after 14 days of exposure to MPs, there were no honey bee deaths from acute toxicity, but the gut flora was reduced with decreased microbe diversity which negatively affected the gut microbiome. The gut microbiome is important for bee health related to immunuty and detoxification. Bee weight was reduced, and the sublethal effects found were changes in gene expression relating to antioxidation, detoxification, and immunity. The honey bees in the experiment were unaware of ingesting MPs as observed when they neither preferred or avoided sugar syrup laced with them.  After 21 days their respiratory systems were negatively affected. Another recent study found that MPs reach the honey bee brain and interfere with learning and memory3.

Alma et at al4 fed honey bees for one month on MPs (the MPs ingested by bees were tiny and measured in micrometres (µm)) in a laboratory experiment and they found microfibres in the cuticle, digestive tract, larvae, honey, and wax. Given the lipophilic nature of MPs it is not a surprise to find them binding to wax. Honey is still considered safe as a food but one wonders about levels of MPs in the comb. It was interesting to discover that the same concentrations of MPs were found in experimental commercial hives in Argentina as were found in the lab experiments. This is an emerging area of concern and we can expect to read more about it in the scientific journals and beekeeping press, so keep a look out.

What conclusions can we draw to help us in beekeeping? Well we live in the age of plastics and MPs are everywhere so we can only take action to mitigate some of the risks of further pollution. That gene expression is altered and oxidative cell damage decreases immunity and detoxification is of concern and may contribute to queen failure, but clearly only more related research will provide the answers. We now know that wax attracts MPs, so, will changing comb be helpful, or will the new comb contain trapped microplastics? I think that perhaps this area of study generates more questions than answers until more research informs us, but I wanted to draw your attention to the topic. Look out for something completely different next week.






4 thoughts on “How Microplastics Impact Honey Bees.”

  1. What a great article Ann. Yes MPs are everywhere and interesting you talked about the microbiome being affected in bees this is a problem with humans as well and they are found in the brain too. there is some debate nano plastics in soil and water affect a specific protein found in the brain that is linked to Parkinson’s disease and other types of dementia. So I wonder if this could affect bees brains in the sense of their ability to find food sources etc.
    I so hope we all wake up and really take responsibility for what we are doing to the environment. We can all start with little things like what kind of washing powder we use to pesticides in our gardens to reading labels of what is actually in our cleaning products and trying to reuse as much as possible. It’s so easy to make your own and much cheaper! Also picking up rubbish when we see it. You have done this for many years Ann when you are out for your walks. Reporting dumped rubbish is one of my tasks next week and to clean up an area.

  2. Thank you, Ann. I had no idea that there is so much tiny plastic debris in the environment. We can pick up plastic litter, but not these plastic particles. I sure hope that the emerging findings about the effects of these plastic particles, on the bees and on us, are not bleak. This makes me reconsider the wisdom of polystyrene hives.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.