Role of Belostoma bakeri (Heteroptera) in the trophic ecology of a fishless desert spring

Abstract

We examined the foraging and production ecology of a top predator (Belostoma bakeri, Belostomatidae) in the fishless, thermally constant aquatic ecosystem of Montezuma Well, Arizona. Our results highlight the importance of prey behavior in energy flow in aquatic ecosystems. B. bakeri captured more amphipods (Hyalella montezuma) than damselfly nymphs (Telebasis salva) in laboratory experiments; H. montezuma spent significantly more time moving than damselfly nymphs did. Also, B. bakeri captured significantly more adult (≥ 3 mm) amphipods than juveniles (<3 mm) in the light but not in dark treatments. Production by B. bakeri was 2.8 g dw m−2 yr−1 (±2 SE = 0.3). Mean annual standing stock was 0.214 g m−2, annual P:B̄ ratio was 13.3, cohort P:B̄ was 4.7, and annual energy production was 5.88 × 104 J m−2 yr−1. Ecological efficiency was 13.2% between primary producers and amphipods in Montezuma Well, 5.1% between amphipods and damselfly nymphs, and 2.7% between lower levels and aquatic heteropterans. Production by B. bakeri made up 25% of the total energy incorporated in secondary consumer production and accounted for 72% of the production by the top predators in Montezuma Well.