<![CDATA[Graphical Abstract Highlight Research 1. 25 mg L⁻¹ AMPEP produced the highest cell density (55.96 ×10⁶ cells mL⁻¹) and growth rate (1.02 day⁻¹). 2. Low AMPEP concentration maximized biomass yield (7.13 g L⁻¹). 3. AMPEP increased total carotenoids while chlorophyll a remained unchanged. 4. Lipid accumulation peaked at 25 mg L⁻¹ AMPEP (14.81% w/w). Abstract Chlorella sorokiniana is widely investigated for biomass and biochemical production, yet its concentration-dependent responses to seaweed-derived biostimulants remain incompletely resolved. We evaluated Acadian Marine Plant Extract Powder (AMPEP) at 0, 25, 50, 100, and 150 mg L⁻¹ in BG-11 cultures maintained for 21 days, using three independent culture vessels per treatment. The 25 mg L⁻¹ treatment produced the highest observed cell density (55.96 ± 8.91 × 10⁶ cells mL⁻¹ versus 17.60 ± 4.84 × 10⁶ cells mL⁻¹ in the control), specific growth rate (1.02 ± 0.12 versus 0.66 ± 0.04 day⁻¹), culture dry weight (7.13 ± 0.96 versus 3.57 ± 0.26 g L⁻¹), and lipid content (14.81 ± 0.26 versus 6.28 ± 0.40% w/w). AMPEP-treated cultures also had larger cells than the control. Pigment responses were not uniformly enhanced: volumetric chlorophyll a did not differ among treatments, while carotenoid concentration and cellular pigment quotas showed contrasting patterns, with cellular chlorophyll a and carotenoid quotas highest in the control. AMPEP therefore produced concentration-dependent growth and biochemical responses in C. sorokiniana, with 25 mg L⁻¹ giving the strongest observed growth and lipid responses among the tested concentrations. These findings are restricted to the laboratory conditions evaluated and require confirmation with finalized longitudinal statistics and larger-scale cultivation.]]>
