Anadromous Sea Lamprey Influence Food Web Pathways in an Atlantic Coastal Stream

Anadromous Sea Lamprey Petromyzon marinus deliver a pulsed nutrient subsidy to Atlantic coastal waters during the spring.  The mechanisms by which recipient stream food web components respond to those nutrient subsidies are poorly characterized.  We conducted sea lamprey carcass addition experiments to quantify the autotrophic and heterotrophic responses of stream food webs.  We found increases in primary productivity immediately adjacent to carcasses but did not detect broader spatial changes in productivity downstream.  Among heterotrophs, we detected the assimilation of nutrients (via δ¹³C and δ¹⁵N) in several macroinvertebrate families and juvenile sea lamprey.  In contrast, we detected no increase in aquatic fungi biomass from carcass subsidies.  Canopy cover and flow disturbances were likely factors contributing to observed patterns.  We used our data and other published data to model Sea Lamprey spawning populations and corresponding nutrient influxes from adult carcasses.  We predicted enrichment of primary and secondary production from various levels of spawning escapement.  Our work underscores the importance of ongoing dam removal projects that restore connectivity between marine and freshwater habitats by allowing sea lamprey migration and spawning.