Interactions between bumblebees and cyanobacterial blooms

Abstract: Today pollinators provide an important ecosystem service as they contribute to the pollination of 75 % of the world’s most important crop yields. Several bee species are threatened though due to different anthropogenic impacts and have declined in numbers. One overlooked cause of the decline might be the eutrophication of lakes and ponds in agricultural landscapes, which favour toxic algae blooms. Cyanotoxins like Microcystins have been proven to accumulate in higher animals, causing toxic events within the organisms sometime resulting in deaths. This study aimed to experimentally evaluate the interaction between toxic cyanobacterial blooms and pollinators. An experiment was hence conducted with six bumblebee colonies exposed to toxic cyanobacteria through their drinking water and with another six colonies used as controls. The bees were recorded by security cameras during the experiment to evaluate differences in drinking behaviour. The results did not show any significant differences in behaviour, colony status or concentration of Microcystins in the bees. Some tendencies were seen though and the method used for extraction of Microcystins from the bees is believed to need further development before obtaining reliable results. It is believed to be relevant to decide threshold concentration for the bees when evaluating to what extent toxic cyanobacterial blooms might affect pollinators. Further studies are motivated as the loss of pollinators as an ecosystem service would be both extremely hard and costly to replace with artificial pollination.