Anadromous Sea Lamprey Influence Stream Food Webs in an Atlantic Coastal Stream

Historically, spawning migrations of adult anadromous fishes and subsequent seaward migrations of juveniles linked freshwater and marine systems.  Adults provided nutrients to oligotrophic freshwaters and subsidized stream and lake food webs, that is, until populations declined due to migration barriers, habitat loss, and overfishing.  The roles of anadromous Sea Lamprey Petromyzon marinus in delivering subsidies to Atlantic coastal systems are poorly understood.  Lamprey may provide nutrient pulses during spring, coupled with rising water temperatures and increased photoperiod, which stimulate primary productivity and help meet metabolic demand.  We conducted a Sea Lamprey carcass addition experiment in a 3^rd order tributary to the Penobscot River, Maine.  We examined the spatial and temporal dynamics of nutrients from carcasses and influences on primary productivity with nutrient diffusing substrates and by inferring assimilation by juvenile Sea Lamprey (ammocoetes), macroinvertebrates, and freshwater mussels with stable isotopes analysis (δ¹⁵N and δ¹³C).  Our results demonstrated patchy primary productivity responses from carcasses influenced by habitat heterogeneity.  Preliminary data from stable isotopes suggests nutrient assimilation in stream organisms.  Our findings provide quantitative results as to the ecological role of anadromous Sea Lamprey and underscore the importance of freshwater-marine connectivity to Atlantic coastal streams.