  We introduce the concept of spatio-temporal steering (STS), which reduces, in
special cases, to Einstein-Podolsky-Rosen steering and the recently-introduced
temporal steering. We describe two measures of this effect referred to as the
STS weight and robustness. We suggest that these STS measures enable a new way
to assess nonclassical correlations in an open quantum network, such as quantum
transport through nano-structures or excitation transfer in a complex
biological system. As one of our examples, we apply STS to check nonclassical
correlations among sites in a photosynthetic pigment-protein complex in the
Fenna-Matthews-Olson model.
