Atmospheric pressure requirements of bumblebees (Bombus impatiens) as pollinators of Lunar or Martian greenhouse grown food
Long-term space exploration missions to the Moon or Mars will require food production facilities to sustain human life. Considering that the atmospheric pressure on the Moon and Mars is much less than that on Earth, scientists have been studying plant production in controlled environments with reduced pressures in order to better understand effects on growth and development. Some plants have been found to successfully grow in environments with pressures as low as 10 kPa. However, candidate species such as tomatoes, tomatillo, squash, pumpkins, melons, sunflower and canola are complicated by the requirement of insect pollinators for successful crop production. Here we show that bumblebees, Bombus impatiens, can function as efficient pollinators in environments with total atmospheric pressures as low as 50 kPa. We found that when bumblebees were exposed to an environment of 50 kPa or higher, they maintained foraging activity levels and a foraging efficiency similar to that exhibited under ambient conditions. However, their activity levels and efficiency were decreased when exposed to an environment lower than 50 kPa. In these experiments, the partial pressure of oxygen was reduced in proportion to the total pressure. When oxygen was returned to an ambient partial pressure of 20kPa at low total pressures, activity improved. Our results demonstrate that bumblebees can function well as pollinators in environments with total atmospheric pressure of 50 kPa or higher, and activity improves at lower levels as long as oxygen levels are adequate. This study is a first step in determining the atmospheric requirements for plant-pollinator interactions in a space station, Moon or Mars greenhouse, which may be essential for long-term space exploration.