Movement of nutrients among ecosystems is a key process that drives productivity and influences ecological dynamics. This dissertation explores two aspects of nutrient transfer among ecosystems: translocation by migratory species and landscape controls on terrestrial ecosystem losses. As migrants move among ecosystems they can transfer materials and energy that alter ecosystem dynamics and processes. Among fishes, salmon are well-known to transfer large quantities of nutrients from the ocean to their freshwater spawning grounds as they migrate and die en masse. Less is known about the role of fish that spawn multiple times over their life and thus do not leave large quantities of carcasses in their spawning grounds. Much of this dissertation explores the role of white and longnose suckers as nutrient vectors in Great Lakes tributaries. I documented the early life history of longnose suckers, pathways of nutrient contributions from sucker migrations, and ecosystem metabolic responses. I found that sucker eggs and excretion contribute large quantities of nutrients to their spawning streams. Because early life mortality is often >99% and larvae spend little time feeding in their spawning streams, most of these nutrients become available to stream biota. Sucker nutrient contributions were large relative to background availability, even in an agricultural watershed context, and they led to increased gross primary production but not ecosystem respiration. Landscape processes also exert important influence over the availability and transport of nutrients in streams. Human land use has transformed many stream ecosystems as agriculture and urban development supply nutrients and alter stream hydrology. In the Hawaiian archipelago, human land use overlays large gradients of substrate age, precipitation, and slope which are important determinants of nutrient availability in terrestrial ecosystems. I examined the relative importance of natural gradients and human land use in determining stream nutrient concentrations and found that weathering patterns remain the primary control over P availability across the landscape, but that human activities are more important for N.