To date, research on the toxicity and potential environmental impacts of nanomaterials has predominantly focused on relatively simple and single-component materials, whilst more complex nanomaterials are currently entering commercial stages. The current study aimed to assess the long-term and size-dependent (60 and 500 nm) toxicity of a novel core-shell nanostructure consisting of a SiC core and TiO 2 shell (SiC/TiO 2 , 5, 25, and 50 mg L -1 ) to the common model organism Daphnia magna . These novel core-shell nanostructures can be categorized as advanced materials. Experiments were conducted under environmentally realistic feeding rations and in the presence of a range of concentrations of humic acid (0.5, 2, 5, and 10 mg L -1 TOC). The findings show that although effect concentrations of SiC/TiO 2 were several orders of magnitude lower than the current reported environmental concentrations of more abundantly used nanomaterials, humic acid can exacerbate the toxicity of SiC/TiO 2 by reducing aggregation and sedimentation rates. The EC 50 values (mean ± standard error) based on nominal SiC/TiO 2 concentrations for the 60 nm particles were 28.0 ± 11.5 mg L -1 (TOC 0.5 mg L -1 ), 21.1 ± 3.7 mg L -1 (TOC 2 mg L -1 ), 18.3 ± 5.4 mg L -1 (TOC 5 mg L -1 ), and 17.8 ± 2.4 mg L -1 (TOC 10 mg L -1 ). For the 500 nm particles, the EC50 values were 34.9 ± 16.5 mg L -1 (TOC 0.5 mg L -1 ), 24.8 ± 5.6 mg L -1 (TOC 2 mg L -1 ), 28.0 ± 10.0 mg L -1 (TOC 5 mg L -1 ), and 23.2 ± 4.1 mg L -1 (TOC 10 mg L -1 ). We argue that fate-driven phenomena are often neglected in effect assessments, whilst environmental factors such as the presence of humic acid may significantly influence the toxicity of nanomaterials.