Oxidative stress varies in bees depending on the landscape

Bees collected from roadsides showed higher levels of oxidative damage in lipids, while samples from organic areas recorded the lowest values. This information comes from a North American study that evaluated honeybees (Apis mellifera) and small carpenter bees (Ceratina calcarata) in three types of landscape in central Ohio: conventional farmland, organic farmland, and habitats near highways.

The study measured markers of oxidative stress in adults and larvae. Scientists also analyzed pesticide residues in pollen using gas chromatography and liquid chromatography coupled with mass spectrometry. The comparison indicated an association between the residue profile in the landscapes and different physiological responses in bees.

Honeybees

In adult honeybees, the average lipid damage reached 1,67 nmol/mg in roadside areas. This value was higher than those recorded in organic areas (1,17 nmol/mg) and conventional areas (0,96 nmol/mg). The difference was statistically significant. The same pattern appeared in Ceratina calcarata. In this species, the average lipid damage reached 1,84 nmol/mg on roadsides, compared to 1,20 nmol/mg in organic areas and 1,65 nmol/mg in conventional areas.

Apis mellifera larvae also responded to the landscape. Samples collected from roadsides had an average of 1,05 nmol/mg for lipid damage. In conventional areas, the value reached 0,85 nmol/mg. In organic areas, it dropped to 0,57 nmol/mg. The authors observed significant differences between the organic areas and the other two environments.

Protein carbonylation

The study also evaluated protein carbonylation, another indicator of oxidative damage. In adult honeybees, the average reached 20,49 nmol/mg in conventional landscapes, 18,48 nmol/mg on roadsides, and 15,12 nmol/mg in organic areas. The difference between conventional and organic crops was significant. In Ceratina calcarata the average values ​​were similar across the three landscapes, with no statistically significant difference.

Residue analysis showed higher total concentration and greater diversity of pesticides in pollen collected from conventional farms. Organic areas and roadside habitats showed lower concentrations.

The study also highlights the complexity of physiological responses in the field. Farm size, floral diversity, forage availability, pollen nutritional quality, microclimate, management intensity, and vehicular pollutants can all influence oxidative stress. The researchers treat the results as associations between landscape and physiological response, not as proof of direct causality.

Further information can be found at doi.org/10.1111/phen.70046