  We study a supersymmetric model in curved background spacetime. We calculate
the effective action and the vacuum expectation value of the energy momentum
tensor using a covariant regularization procedure. A soft supersymmetry
breaking induces a nonzero contribution to the vacuum energy density and
pressure. Assuming the presence of a cosmic fluid in addition to the vacuum
fluctuations of the supersymmetric field an effective equation of state is
derived in a self-consistent approach at one loop order. The net effect of the
vacuum fluctuations of the supersymmetric fields in the leading adiabatic order
is a renormalization of the Newton and cosmological constants.
