Combined effects of nanoplastics and tris (2-chloropropyl) phosphate on photosynthesis and antioxidant activity in Chlorella marina

Nanoplastics (NPs) and organophosphorus esters like tris (2-chloropropyl) phosphate (TCPP) are emerging pollutants of global concern in marine ecosystems. However, their combined ecotoxicological effects on primary producers remain poorly understood. We investigated the impacts of 100 nm NPs (10 ³ items·L⁻¹) and TCPP (0.5–50 μg·L⁻¹) on the marine microalga Chlorella (Chlorella marina) during 72-hour exposures. Physiological responses (e.g., chlorophyll a, Fv/Fm) and antioxidant activities (including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), malondialdehyde (MDA)) were quantified, complemented by scanning electron microscopy (SEM) to observe cellular interactions. We found the combined exposure significantly reduced chlorophyll a content (by 38–52 %) and photosynthetic efficiency (Fv/Fm by 30–45 %) compared to single exposures (p < 0.01). NPs adsorbed onto algal surfaces, exacerbating TCPP-induced oxidative stress: SOD and CAT activities increased 2.3–3.5-fold, while MDA levels rose by 60–80 %, indicating severe membrane damage. The synergistic effects were concentration-dependent, with high-dose TCPP (50 μg·L⁻¹) + NPs causing the most pronounced inhibition. NPs act as carriers to enhance TCPP toxicity in C. marina, disrupting photosynthesis and antioxidant systems. These findings highlight the need to evaluate combined pollutant risks in marine environments, particularly in urbanized coasts where NPs and OPEs co-occur.