Empirical model of the potential flux of aquatic productivity from lakes and streams onto land

Background/Question/Methods

There is increasing recognition of connections across traditionally-defined ecosystem boundaries. Although the flux of matter and energy across ecotones can have important implications for the recipient ecosystems, assessing these linkages has been challenging. Here, we generate an empirical model of the potential flux of aquatic productivity from lakes and streams to land. We developed empirical relationships between lake and stream variables and insect production, and scaled these up to the landscape level.

Results/Conclusions

Estimated annual aquatic insect emergence in the 11,214 lakes and 35,856 stream segments from the State of Wisconsin (USA) was similar (0.6 ± 0.2 gC•m^-2•yr•^-1). However, the smaller total benthic area of streams results in lower mean insect flux (4.0 ± 18.0 gC•m•yr•^-1) and lower mean deposition to land (0.04 ± 0.18 gC•m^-2•yr•^-1) compared with lakes (9.2 ± 20.3 gC•m•yr•^-1 and 0.06 ± 0.2 gC•m^-2•yr•^-1, respectively). There was higher total flux to land in north-central and north-western Wisconsin, which are areas with high density of small lakes. As a result of the relatively regular distribution of streams in WI, the distribution of lakes determined the main patterns of insect fluxes to land. Such hot spots of insect emergence could have diverse implications for terrestrial ecosystems, including support for terrestrial food webs surrounding the lakes, increased pollutant flux from lakes to land, or influencing bird migration pathways.