Hive health and human presence

The western honey bee (Apis mellifera) is endangered by many of the physical stressors they experience in human-dependent areas, including poor nutrition, pesticides, and pathogens.

In an international study, the Applied Genomics and Bioinformatics group of the University of the Basque Country (UPV/EHU) has investigated the situation of bees in areas of intensive agriculture, in semi-natural areas and natural areas, taking the hive as the unit.

“For several years it has been evident that the mortality of bees has increased a lot; That is why about 6 years ago we began to investigate what factors influence the bee microbiota and what relationship this has with bee diseases or health”, explains Iratxe Zarraonaindia, Ikerbasque researcher at Applied Genomics and Bioinformatics. The researchers attribute great importance to the anthropization of the areas, that is, “to intensive agriculture, the chemical products used, etc.”

“In collaboration with three Croatian universities, we have had the opportunity to investigate some beehives located on the Croatian island of Unije, far from human influence. For ten years these hives have not received any treatment; its bees were known to survive for a long time despite the presence of the Varroa mite, which causes a disease that makes bees sick and die. We wanted to investigate how anthropization influences the microbiota or community of microorganisms of bees. To do this, we have compared the hives on the island of Unije with the microbiota of two hives located in rural areas”, explains Zarraonaindia.

In order for the two hives in the agricultural area to be comparable, “genetic sisters” have been used (hives made up of bees that contain the same genetic material as those in the agricultural area), one of which has been moved to a semi-natural area. “We have clearly seen that anthropization has a significant impact, since only 16 days later we detected that the microbial imbalance due to agricultural stress had been attenuated in the hive transferred to the semi-natural zone”, explains the doctor. This demonstrates that the honey bee microbiota has a high adaptive capacity. “We didn’t expect the composition of the microbiota to change so quickly,” she confesses.

The researchers have found a clear gradient related to the degree of anthropization and the microbial community of the hive: “The microbiota of the Unije island hive is more balanced, its proportion of beneficial microorganisms is higher and in a semi-natural environment the proportion is decreasing , while in the agricultural field the hive has a very unbalanced composition, there are more opportunistic bacteria and it is more sensitive to diseases”, explains Zarraonaindia. According to the researcher, “in agricultural areas stress factors are highly activated.”

Researchers from the Applied Genomics and Bioinformatics group Andone Estonba and Iratxe Zarraonaindia on the island of Unije, preparing the hives for the study, together with their Croatian colleagues (Photo: Marin Kovačić / University of Osijek)

apibiome research

These conclusions have allowed the research group to determine biomarkers that will provide information on the health of bees. For example, researchers have detected that a certain bacterium, Arsenophonus, is very abundant in agricultural areas, that it is less present in semi-natural areas, and that it hardly appears in natural areas.

They have studied the entire hive, not just the bees. This is one of the most important keys to this research: “This approach is innovative. We have studied the apibiome: the set of microorganisms in the niches present in the hive. We have studied the intestine of the bees, the entrance of the hive, the bee bread (the substance that the bees feed on) and the air inside the hive”. As previously mentioned, the Arsenophonus bacterium is the most frequent in the agricultural area, and it is a trend that has been found in all niches. Therefore, it is a very suitable biomarker to measure the impact of agriculture on hives and measure their health; In addition, “this method is not invasive, since it can be carried out by taking a sample from the entrance of the hive.”

The researchers have reported this study in the academic journal Scientific Reports. It is entitled “A short exposure to a seminatural habitat alleviates the honey bee hive microbial imbalance caused by agricultural stress”.

This research is the core of the thesis that doctoral student June Gorrochategui Ortega is carrying out in the Department of Genetics, Physical Anthropology and Animal Physiology, within the IKERTALENT program, financed by the Department of Economic Development, Sustainability and Environment of the Basque Government. The research has been carried out in collaboration with groups from the University of Osijek, the University of Zadar and the University of Zagreb, in Croatia.

The study is the fruit of a year of work. But work will continue in this line of research. “Now we have moved the hive from the semi-natural area to a natural area to see if its microbiota is balanced and becomes the same as that of the bees in the natural area. This will allow us to know the extent of both the genetic contribution and the environmental contribution.” (Source: UPV/EHU)