Does Environmental Warming Enhance the Toxic Effects of Phthalates on Marine Life?

Abstract

Marine heatwaves driven by climate change pose a significant threat to marine organisms, exacerbating biodiversity loss in synergy with other anthropogenic stressors, such as chemical contamination. This study investigated the effects of extreme thermal events and phthalic acid esters (PAEs) pollution, both independently and in combination, on the embryonic development of the sea urchins Arbacia lixula, which were collected from the Capo Gallo-Isola delle Femmine Marine Protected Area near Palermo, Italy. Additionally, it examines whether the species' optimal developmental temperature (24°C) enhances tolerance to PAEs compared to ambient conditions (18°C). Fertilization followed a previous methodology [1], achieving a success rate > 95%. Fertilized eggs (4000 eggs/mL) were distributed in glass Petri dishes and incubated at 18°C and 24°C with PAE concentrations ranging from 0 to 50 mg/L until reaching the pluteus stage (48 h). A standard solution containing six PAEs (2000 mg/L each) was initially diluted in hexane to prepare the different exposure concentrations. The solvent was then evaporated under a gentle nitrogen flow, and the residue was reconstituted in 40 μL of dimethyl sulfoxide (DMSO), i.e., 0.4% in 10 mL of filtered seawater. DMSO was selected as a carrier due to its minimal toxicity and biocompatibility [2]. The ecotoxicological assessment revealed that heatwave conditions significantly amplified PAEs-induced toxicity, leading to a 76% decrease in median effective concentration (EC50) values. Morphological analysis showed that the combined impact of elevated temperature and PAEs exposure resulted in an increase in developmental abnormalities and a reduction in skeletal growth. Biochemical analysis further indicated that temperature was the primary factor affecting the activity of stress response enzymes, including alkaline phosphatase, esterase, and peroxidase. Statistical analysis (ANOVA) confirmed that both temperature (p = 0.0045) and PAEs concentration (p < 0.0001) significantly affected development. These findings suggest that heatwaves and PAEs contamination jointly reduce A. lixula embryo tolerance. Furthermore, the study suggests that 24°C may not be the optimal developmental temperature for the southwestern Mediterranean population of A. lixula. The results underscore the necessity of integrative ecotoxicological assessments, as evaluations based on single stressors or biological levels may lead to misleading conclusions regarding marine organism health and thermal tolerance. With rising temperatures, endocrine-active substances may be released from polymers in which they are mixed (e.g., plastics) or biosynthesized by various organisms as secondary metabolites [3]. This could increase environmental exposure, leading to bioaccumulation in the food chain and potential human health risks. Further research is needed to assess long-term impacts. Acknowledgements The authors would like to thank the National Biodiversity Future Center – NBFC, Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4 - Call for tender No. 3138 of December 16, 2021, rectified by Decree n.3175 of December 18, 2021 of Italian Ministry of University and Research funded by the European Union – NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of June 17, 2022 adopted by the Italian Ministry of University and Research, CUP B73C22000790001, Project title “National Biodiversity Future Center - NBFC”. References [1] C. Martino, M. Byrne, M.C. Roccheri, R. Chiarelli. Interactive effects of increased temperature and gadolinium pollution in Paracentrotus lividus sea urchin embryos: A climate change perspective. Aquat. Toxicol. 2021. 232, 105750. [2] M. N. Semenova, T.S Kuptsova, V.V. Semenov. Toxicity of organic solvents and surfactants to the sea urchin embryos. Chemosphere 2024. 353, 1