Suspended particulate organic matter (i.e., seston) is an important resource for stream biota that varies in both quality and quantity over time and space. We investigated the relationship between the elemental composition of stream seston and watershed properties (e.g., geomorphology and land cover) by sampling streams from the Upper Peninsula of Michigan. We found wide variation in elemental ratios (C:N, N:P, and C:P) among streams on each of ten sampling dates and within streams through time, with greater variation in C:P and N:P than in C:N. Watershed characteristics, such as agriculture (negative relationship) and wetlands (positive relationship), were strongly correlated to seston C:P. Links between land cover and the seston in draining streams may be related to nutrient limitation within terrestrial ecosystems. For example, wetlands tended to produce seston with a high C:P ratio perhaps in part because of strongly P-limited species. Further, strong correlation between elemental constraints in terrestrial and stream ecosystems appears regulated by precipitation, due to its role in material transport. We feel treating terrestrial ecosystems as cohesive processing units may be an effective strategy for modeling the effect of land cover on nutrient limitation in streams.