Significant contamination of bumblebee pupae by the metal aluminum which has links with Alzheimer's-like dysfunction may be a possible reason for the decline in bee population, reveals a study published online in the journal PLoS ONE.
Prof Chris Exley of Keele University in UK and his colleagues - suggest that it could be a factor in pollinator decline. The scientists measured the content of aluminum in pupae taken from 20 colonies of naturally foraging buff-tailed bumblebees (Bombus terrestris ssp.audax).
The pupae were found to be heavily contaminated with aluminium, with individual contents ranging from 13 to nearly 200 ppm while a content of 3ppm is toxic to human brain tissue. Smaller pupae had significantly higher contents of aluminum.
According to the authors, the excess aluminum has a variety of origins. "Human activities such as the burning of fossil fuels resulting in 'acid rain,' intensive agriculture producing acid sulphate soils and the mining of aluminum ores to make aluminum metal and salts have all contributed to the burgeoning biological availability of this non-essential metal."
Data have shown the significant accumulation of aluminum in at least one stage of the bumblebee life cycle and suggest the possibility of another risk factor contributing to the decline in its numbers.
"It is widely accepted that a number of interacting factors are likely to be involved in the decline of bees and other pollinators - lack of flowers, attacks by parasites, and exposure to pesticide cocktails, for example," said Prof Exley.