Resource competition across habitat boundaries asymmetric interactions between benthic and pelagic producers

In shallow aquatic systems benthic and pelagic primary producers typically compete for light and nutrients along opposing vertical supply axes pelagic algae shade the benthic habitat; conversely, benthic algae intercept the nutrient flux from the sediment to the pelagic habitat. We present a general framework for analyzing such spatially asymmetric resource competition across habitat boundaries using a mechanistic, dynamical model. We visualize the mechanisms determining the outcome of these cross-habitat interactions using zero-net-growth-isoclines, resource supply points, and resource consumption vectors. In extensive invasion analyses we characterize the abiotic and competitive persistence boundaries of pelagic and benthic primary producers, which are set by environmental factors determining nutrient and light supply and are modified by resource use by the competitor in the respective other habitat. We note several qualitative differences between cross-habitat and 'classical' within-...