Anthropogenic influence on seasonal and spatial variation in bioelements and non-essential elements in honeybees and their hemolymph

Micronutrient Deficiency May Be Associated with the Onset of Chalkbrood Disease in Honey Bees

Chalkbrood is a disease of honey bee brood caused by the fungal parasite Ascosphaera apis. Many factors such as genetics, temperature, humidity and nutrition influence the appearance of clinical symptoms. Poor nutrition impairs the immune system, which favors the manifestation of symptoms of many honey bee diseases. However, a direct link between dietary ingredients and the symptoms of chalkbrood disease has not yet been established. We show here that the elemental composition of chalkbrood mummies and healthy larvae from the same infected hives differ, as well as that mummies differ from larvae from healthy hives. Chalkbrood mummies had the highest concentration of macroelements such as Na, Mg, P, S, K and Ca and some microelements such as Rb and Sn, and at the same time the lowest concentration of B, As, Sr, Ag, Cd, Sb, Ba and Pb. Larvae from infected hives contained less Pb, Ba, Cs, Sb, Cd, Sr, As, Zn, Cu, Ni, Co, Mn, Cr, V and Al in contrast to healthy larvae from a disease-free apiary. This is the first study to demonstrate such differences, suggesting that an infection alters the larval nutrition or that nutrition is a predisposition for the outbreak of a chalkbrood infection. Though, based on results obtained from a case study, rather than from a controlled experiment, our findings stress the differences in elements of healthy versus diseased honey bee larvae.

Revealing Changes in Ovarian and Hemolymphatic Metabolites Using Widely Targeted Metabolomics between Newly Emerged and Laying Queens of Honeybee (Apis mellifera)

The queen bee is a central and pivotal figure within the colony, serving as the sole fertile female responsible for its reproduction. The queen possesses an open circulatory system, with her ovaries immersed in hemolymph. A continuous and intricate transportation and interchange of substances exist between the ovaries and hemolymph of queen bees. To determine the characteristic metabolites in the hemolymph and ovary, as well as understand how their rapid metabolism contributes to the process of egg-laying by queens, we reared Apis mellifera queens from three different age groups: newly emerged queen (NEQ), newly laying queen (NLQ), and old laying queen (OLQ). Using widely targeted metabolomics, our study revealed that the laying queen (NLQ and OLQ) exhibited faster fatty acid metabolism, up-regulated expression of antioxidants, and significant depletion of amino acids compared to the NEQ. This study revealed that the levels of carnitine and antioxidants (GSH, 2-O-α-D-glucopyranosyl-L-ascorbic acid, L-ascorbic acid 2-phosphate, etc.) in the NLQ and OLQ were significantly higher compared to NEQ. However, most of the differentially expressed amino acids, such as L-tryptophan, L-tyrosine, L-aspartic acid, etc., detected in NLQ and OLQ were down-regulated compared to the NEQ. Following egg-laying, pathways in the queens change significantly, e.g., Tryptophan metabolism, Tyrosine metabolism, cAMP signaling pathway, etc. Our results suggest that carnitine and antioxidants work together to maintain the redox balance of the queen. Additionally, various amino acids are responsible for maintaining the queen's egg production.

Sex-specific element accumulation in honey bees (Apis mellifera)

Honey bees are social insects that show division of labor and sexual dimorphism. Female honey bees differentiate in two different castes, queens or worker bees, while males are called drones. Worker bees have different tasks in the hive including collection of food, its processing, caring for brood, protecting the hive, or producing wax. The drones' only role is to mate with a virgin queen. Many studies have dealt with differences in physiology, behavior, and morphology of workers and drones. This is the first study that demonstrates differences in element accumulation and composition between workers and drones honey bees. Using inductively coupled plasma mass spectrometry, we found that worker honey bees have higher concentrations of most elements analyzed. Drones had higher concentrations of elements essential to bees, Na, P, S, Zn, Cu, and especially Se (2.2 × higher), which is known to be important for sperm quality and fertility in many animals. Until now higher Se content was not observed in male insects. These differences can be attributed to different environmental exposure, reproductive role of drones, but mostly to the food workers and drones consume. Worker bees feed on bee bread, which is rich in minerals. Drones are fed food pre-processed by worker bees.

Foraging Activity of Honey Bees (Apis mellifera L., 1758) and Exposure to Cadmium: a Review

Honey bees are commonly exposed to a broad spectrum of xenobiotics, including heavy metals. Heavy metal toxicity is of concern in the context of global pollinator declines, especially since honey bees seem to be particularly susceptible to xenobiotics in general. Here we summarize current knowledge on the interplay between cadmium, one of the most toxic and mobile elements in the environment, and honey bees, the primary managed pollinator species worldwide. Overall, cadmium pollution has been shown to be ubiquitous, affecting industrial, urban and rural areas alike. Uptake of this heavy metal by plants serves as the primary route of exposure for bees (through pollen and nectar). Reported cadmium toxicity consists of lethal and sublethal effects (reduced development and growth) in both adult and larval stages, as well as various molecular responses related to detoxification and cellular antioxidant defence systems. Other effects of cadmium in honey bees include the disruption of synaptic signalling, calcium metabolism and muscle function.

Honey Bees and Associated Matrices as Biomonitors of Soil Trace Elements: Assessment of their Sensitivity in a Regional Rural Environment

Honey bees (Apis mellifera L.) represent a random biosampler integrating pollutants over space and time. An effective biomonitor for trace element (TE) pollution should provide a linear response to TE levels in the environment. However, uncertainties in detecting TEs originating in soil limit their use. To address this, nine experimental sites with multiple apiaries were established in the Upper Palatine Forest, Czech Republic. The soils surrounding the hives were characterized by estimations of the pseudototal and (bio)available pools of TEs. Our study aimed to (1) quantify the linear relationships between soil TE indices and TE contents in bees, bee bread, honey, and wax, and (2) verify the biobarrier function protecting honey from TE contamination. Lead (0.046-0.140 µg g-1 ) and nickel (0.12-4.30 µg g-1 ) contents in bees showed strong linear correlations with (bio)available Pb (0.012-0.254 µg g-1 ) and pseudototal Ni (17.1-36.4 µg g-1 ) in soil (Pearson's r = 0.95 and 0.88, p < 0.005), providing high spatial resolution. A weaker, insignificant correlation was observed for chromium (Cr; r = 0.65) and vanadium (V; 0.44), while no correlation was found for cadmium (Cd). However, the lack of associations for Cr, V, and Cd may result from the low soil TE levels in the region, negligible differences among the majority of sites, and temporal concerns related to different time scales of the biomonitors, impacting the linear model's sensitivity. Biochemical traits in bees, such as the biobarrier function, and different bioavailability of TEs from ingested matter may affect the matrix-to-matrix transfer of TEs in an element-dependent manner. Consequently, the linear response of bee-related biomonitors to TE levels in the environment may significantly deteriorate. Environ Toxicol Chem 2024;43:288-298. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Landfill fire impact on bee health: beneficial effect of dietary supplementation with medicinal plants and probiotics in reducing oxidative stress and metal accumulation

The honey bee is an important pollinator insect susceptible to environmental contaminants. We investigated the effects of a waste fire event on elemental content, oxidative stress, and metabolic response in bees fed different nutrients (probiotics, Quassia amara, and placebo). The level of the elements was also investigated in honey and beeswax. Our data show a general increase in elemental concentrations in all bee groups after the event; however, the administration of probiotics and Quassia amara help fight oxidative stress in bees. Significantly lower concentrations of Ni, S, and U for honey in the probiotic group and a general and significant decrease in elemental concentrations for beeswax in the probiotic group and Li in the Quassia amara group were observed after the fire waste event. The comparison of the metabolic profiles through pre- and post-event PCA analyses showed that bees treated with different feeds react differently to the environmental event. The greatest differences in metabolic profiles are observed between the placebo-fed bees compared to the others. This study can help to understand how some stress factors can affect the health of bees and to take measures to protect these precious insects.

Monitoring metal patterns from urban and agrarian sites using the bumblebee Bombus terrestris as a bioindicator

Honeybees are well-established bioindicators for different types of pollutants. This study aims to establish another species of the Apidae family as a bioindicator, with a distinct behaviour and life cycle. The bumblebee Bombus terrestris was used as a bioindicator for 12 metals. Bumblebee hives were placed at sampling sites in and around the city of Aachen, Germany, and metal concentrations were assessed using ICP-MS. Metal concentrations were compared to those found in honeybees described in the literature. Spatial differences in metal patterns were investigated by comparing two land-use types: urban and agrarian. Seasonal differences were compared by taking samples in spring and summer. All analysed metals were detected above the detection limit and within or even above the concentration range found in honeybees. Significant spatial differences were found for the metalloid B and the metal Cd with higher concentrations at the agrarian sites than the urban sites. Significant seasonal differences were found for 8 metals: Fe, Zn, Cu, Ni, Cd, and As concentrations were higher in summer than in spring, while B and V concentrations were higher in spring. To categorise the results, we applied the honeybee contamination index (HCI) and adapted it to bumblebee purposes. According to the HCI, only one agrarian site showed a high contamination level. This study shows that bumblebees are suitable bioindicators for metals. The obtained data can serve as a first baseline in the establishment of additional monitoring studies or risk assessments.

Elucidating the Role of Honey Bees as Biomonitors in Environmental Health Research

Recently, the One Health concept, which recognizes the interconnectedness of environmental, animal, and human health, has gained popularity. To collect data on environmental pollutants potentially harmful to human health over time, researchers often turn to natural organisms known as biomonitors. Honey bees, in particular, prove to be exceptionally valuable biomonitors due to their capacity to accumulate pollutants from the air, soil, and water within a specific radius during their foraging trips. This systematic literature review summarizes the previous application of the bee species Apis mellifera in pollutant monitoring in articles published during the period of 2010-2020. Nineteen studies were included in this systematic literature review. Of these studies, the majority (n = 15) focused on the detection of heavy metals in honey bees and beehive products, while 4 studies focused on air pollution by polycyclic aromatic hydrocarbons or particulate matter. The matrix most often applied was the whole honey bee. The included studies demonstrated that honey bees and hive products deliver quantitative and qualitative information about specific pollutants. In this regard, the whole honey bee was found to be the most reliable biomonitor. We found that the included studies differed in design and the methods used. Standardized studies could foster a more consistent interpretation of the levels detected in beehive matrices from an environmental health perspective.

Unravelling Heavy Metal Dynamics in Soil and Honey: A Case Study from Maramureș Region, Romania

The study examined soil and honey samples from the Maramureș region, assessing potentially toxic elements and their concentrations. The highest concentrations were found for (Cu), (Zn), (Pb), (Cr), (Ni), (Cd), (Co), and (As), while (Hg) remained below the detection limit. Samples near anthropogenic sources displayed elevated metal levels, with the Aurul settling pond and Herja mine being major contamination sources. Copper concentrations exceeded the legal limits in areas near these sources. Zinc concentrations were highest near mining areas, and Pb and Cd levels surpassed the legal limits near beehives producing acacia honey. Nickel and Co levels were generally within limits but elevated near the Herja mine. The study highlighted the role of anthropogenic activities in heavy metal pollution. In the second part, honey samples were analyzed for heavy metal concentrations, with variations across types and locations. Positive correlations were identified between certain elements in honey, influenced by factors like location and pollution sources. The research emphasized the need for pollution control measures to ensure honey safety. The bioaccumulation factor analysis indicated a sequential metal transfer from soil to honey. The study's comprehensive approach sheds light on toxic element contamination in honey, addressing pollution sources and pathways.

Imidacloprid Pesticide Causes Unexpectedly Severe Bioelement Deficiencies and Imbalance in Honey Bees Even at Sublethal Doses

Pesticides impair honeybee health in many ways. Imidacloprid (IMD) is a pesticide used worldwide. No information exists on how IMD impact the bees' body bioelement balance, which is essential for bee health. We hypothesized that IMD disturbs this balance and fed the bees (in field conditions) with diets containing 0 ppb (control), 5 ppb (sublethal considered field-relevant), and 200 ppb (adverse) doses of IMD. IMD severely reduced the levels of K, Na, Ca, and Mg (electrolytic) and of Fe, Mo, Mn, Co, Cu, Ni, Se, and Zn, while those of Sn, V, and Cr (enzymatic) were increased. Levels of P, S, Ti, Al, Li, and Sr were also decreased, while only the B content (physiologically essential) was increased. The increase in Tl, Pb, and As levels (toxic) was alarming. Generally, IMD, even in sublethal doses, unexpectedly led to severe bioelement malnutrition in 69% of bioelements and to a stoichiometric mismatch in the remaining ones. This points to the IMD-dependent bioelement disturbance as another, yet unaccounted for, essential metabolic element which can interfere with apian health. Consequently, there is a need for developing methods of bioelement supplementation of the honey bee diet for better preventing bee colony decline and protecting apian health status when faced with pesticides.

Metal and Pb isotope characterization of particulates encountered by foraging honeybees in Metro Vancouver

Honeybees and their products are useful biomonitors of metal distribution in urban centres. This study investigates particulate sources that foraging honeybees encounter in Metro Vancouver. Metal concentrations and lead (Pb) isotope compositions were measured in topsoil (top 2 cm, n = 14) colocated with existing research hives and in particulate matter ≤10 μm (PM₁₀, n = 27) collected throughout Metro Vancouver (British Columbia, Canada) during honeybee foraging hours over the course of one year (2018-2019). Topsoil served as a proxy for resuspended/coarse PM and, together with PM₁₀, covered the size range of particulates collected by foraging bees both actively (pollen) and passively (dusts). Particulate matter ≤ 2.5 μm (PM_2.5, n = 7) was collected on Whistler Mountain during two transpacific events (in spring 2014) to estimate the possible effect of transpacific particulate input on the Pb isotope composition of Western Canada aerosols. Metal concentrations and Pb isotopes in topsoil and PM from this study and bees and hive products from previous studies (collected in 2014-2019) reveal similar spatial trends: there were elevated amounts of some metals associated with anthropogenic activity (e.g., Pb, Zn, Sb) and less radiogenic Pb isotope compositions in most samples collected nearer to the city centre in comparison to samples collected in more suburban or rural areas. Bees and hive products have a smoothing effect on the spatiotemporal variability of the data; metal concentrations and Pb isotope compositions vary less in hive products than in PM, presumably because bees interact with multiple environmental domains while foraging. Wildfire smoke and transpacific input are phenomena that cause measurable shifts in Pb isotope compositions of PM, but not in hive matrices. The findings highlight important considerations to make (i.e., the smoothing effect) when linking public health data and decisions with environmental data from hive products in urban centres.

Honey bees as biomonitors - Variability in the elemental composition of individual bees

Homogenized or pooled samples of honey bees are already used for monitoring of metal pollution in the environment for a couple of decades. This is the first study that analyzed the elemental composition of individual honey bees. One apiary with 21 hives was used to test in-hive and between-hive differences at the same location. Highest in-hive variability was observed for Al (14.1x), Li (10.3x), V (10.3x), As (8.9x) and Cd (7.9x). For the elements Cu, K, Mg, Na, P, S and Zn the smallest both in-hive (2.3x, 1.8x, 2.0x, 2.2x, 1.9x, 1.7x, 2.4x respectively) as well as between-hive variability (1.5x, 1.4x, 1.4x, 1.6x, 1.4x, 1.4x and 1.5x respectively) was observed. Nonetheless, between-hive variability was statistically significant for all the analyzed elements. We proved that these differences significantly influence comparison of element concentrations in bees from different locations. One hive from Mesić apiary had significantly lower concentrations of Al (hive 18: 18.6 mg kg^-1) and U (hive 1: 0.0013 mg kg^-1), while at the same time a different hive from the same apiary showed higher concentration of these elements (Al, hive 14: 125 mg kg^-1; U, hive 13: 0.012 mg kg^-1) compared to another location (thermal power plant, Al: 97 mg kg^-1, U: 0.0044 mg kg^-1). Therefore, when using honey bees as biomonitors, we recommend a larger number of hives to be sampled at each location to provide an adequate dataset for reliable interpretation of results. Comparing individual bee elemental concentrations, for Na, Mg, P, S, K, Fe, Cu, and Zn negative correlations were found between dry mass of a bee and concentrations of these elements. These negative correlations could be a consequence of higher honey or nectar content in some of the sampled bees. However, this should also be considered when using honey bees as bioindicators.