  We study the entanglement between two domains of a spin-1 AKLT chain subject
to open boundary conditions. In this case the ground-state manifold is
four-fold degenerate. We summarize known results and present additional exact
analytical results for the von Neumann entanglement entropy, as a function of
both the size of the domains and the total system size for {\it all} four
degenerate ground-states. In the large $l,L$ limit the entanglement entropy
approaches $\ln(2)$ and $2\ln(2)$ for the $S^z_T=\pm 1$ and $S^z_T=0$ states,
respectively. In all cases, it is found that this constant is approached
exponentially fast defining a length scale $\xi=1/\ln(3)$ equal to the known
bulk correlation length.
