Ecosystem size reverses the effect of the spatial coupling between autotrophic and heterotrophic ecosystems

The flow of non‐living resources between autotrophic and heterotrophic ecosystems can impact their ecosystem function. However, ecosystem size is similarly known to influence ecological properties and it is uncertain how the size of coupled ecosystems mediates the effect of resource flows. Here, we used a protist experiment to examine how differences in relative ecosystem sizes mediated the effect of non‐living resource flows on the functioning of two‐patch, autotrophic‐heterotrophic meta‐ecosystems. We found that when the autotrophic patch was larger, resource flows between the patches led to an increase in the total biomass of the meta‐ecosystem. Conversely, when the heterotrophic patch was larger, resource flows decreased the total biomass of the meta‐ecosystem. Patch size also played a critical role in determining the effects of resource flows on biomass density within individual autotrophic and heterotrophic ecosystems. Our findings reveal that differences in relative ecosystem size can significantly influence cross‐ecosystem dynamics and their implications for ecosystem function.