We study the dynamical spin and nematic correlations in the bilinear-biquadratic spin-1 chain in the critical phase hosting deconfined spinons. We demonstrate how spinon interactions can be directly probed in the presence of a magnetic field or a single-ion anisotropy. Using a hydrodynamic treatment of the low-energy SU(3)_1 Wess-Zumino-Witten theory, we derive the long-wavelength dynamical susceptibilities, incorporating both the SU(3)-symmetric backscattering and SU(3)-breaking pairing interactions. Our analytical predictions are supported by numerical matrix-product-state (MPS) simulations of the underlying microscopic model.