Deposition and decomposition of periodical cicadas (Homoptera: Cicadidae:Magicicada) in woodland aquatic ecosystems

Abstract

Many freshwater ecosystems receive allochthonous resource subsidies from adjacent terrestrial environments. In eastern North American forests, geographic broods of periodical cicadas emerge every 13 to 17 y to breed, and local abundances can sometimes be >300 individuals/m2. Most individuals avoid predation, senesce after breeding, and become a resource pulse for forest ecosystems; some cicada carcasses enter freshwater ecosystems where they represent a detrital resource pulse. Here, we present a 2-part study in which we examined the deposition of cicada detritus into woodland ponds and low-order streams in southwestern Ohio during the emergence of Brood X periodical cicadas. We compared the deposition of nutrients associated with periodical cicada detritus and terrestrial leaf litter into small woodland ponds and low-order streams. We used a laboratory experiment to compare patterns of decomposition and nutrient release of adult periodical cicada carcasses and sycamore leaf litter. Input of periodical cicada detritus to woodland streams and ponds was a function of local cicada emergence densities. Organic C loading to woodland aquatic ecosystems from cicada detritus was substantially less than that from terrestrial leaf litter; however, the higher mass-specific N and P content of cicada material made cicada detritus a relatively important nutrient input. N and P deposited in cicada detritus represented 0.2 to 61% of the N and 0.3 to 50% of the P deposited into woodland aquatic ecosystems via terrestrial leaf litter. Decomposition experiments indicated that cicada detritus was of much higher quality than was sycamore leaf litter; female and male cicada carcasses lost mass at significantly faster rates than sycamore leaves (female k = −0.05/d, male k = −0.04/d, sycamore leaf k = −0.002/d). Release rates of C, N, and P from cicada carcasses were 4, 39, and 150× greater, respectively, than release rates from sycamore leaves. Our study indicates that periodical cicada detritus can represent a substantial allochthonous resource pulse to forested aquatic ecosystems and that cicada detritus is of substantially higher quality than is terrestrial leaf litter. These results suggest that deposition and decomposition of periodical cicada detritus can affect the productivity and dynamics of woodland aquatic ecosystems and that the role of animal-derived resource pulses to ecosystems requires further exploration.