Rodrigo Almeda

In recent years, the Pacific brown macroalga Rugulopteryx okamurae has rapidly expanded across Mediterranean and Atlantic coasts, generating major ecological and socio‑economic impacts. In this study we examined the effects of exudates released by R. okamurae on the early developmental stages of two autochthonous sea urchin species, Paracentrotus lividus and Arbacia lixula , which are key benthic grazers in the invaded regions. Fertilized eggs were exposed for three days to different concentrations of R. okamurae exudates, and subsequent effects on survival, growth, and developmental abnormalities were determined for both sea urchin species. Acute exposure to 50 g L⁻ ¹ exudates caused about 90% embryonic mortality in both species. Lower concentrations significantly reduced larval growth and increased malformations. Median effect concentrations, expressed as equivalent R. okamurae biomass, for growth inhibition were 16 g L⁻ ¹ for P. lividus and 14 g L⁻ ¹ for A. lixula , indicating similar sensitivity. Malformations increased significantly at exudate concentrations equivalent to 0.5 g L⁻ ¹ of R . okamurae biomass in P. lividus and 5 g L⁻ ¹ in A. lixula . The HPLC–MS analysis of R. okamurae exudates confirmed the presence of several bioactive polyphenols, with vanillic acid exhibiting the highest concentration (1.73 ± 0.09 µg L ⁻¹ ). Overall, our results show that R. okamurae exudates strongly inhibit the early developmental stages of native sea urchins. The presence of high biomass of this invasive alga could contribute to reduced larval survival and recruitment, driving sustained declines in their benthic populations. As these key grazers play a central role in regulating macroalgal community dynamics, their reduction would weaken grazing pressure and create conditions that further facilitate the invasion and ecological impacts of R. okamurae in the invaded Atlantic and Mediterranean rocky shores.

In recent years, the Pacific brown macroalga Rugulopteryx okamurae has rapidly expanded across Mediterranean and Atlantic coasts, generating major ecological and socio‑economic impacts. In this study we examined the effects of exudates released by R. okamurae on the early developmental stages of two autochthonous sea urchin species, Paracentrotus lividus and Arbacia lixula, which are key benthic grazers in the invaded regions. Fertilized eggs were exposed for three days to different concentrations of R. okamurae exudates, and subsequent effects on survival, growth, and developmental abnormalities were determined for both sea urchin species. Acute exposure to 50 g L⁻¹ exudates caused about 90% embryonic mortality in both species. Lower concentrations significantly reduced larval growth and increased malformations. Median effect concentrations for growth inhibition were 16 g L⁻¹ for P. lividus and 14 g L⁻¹ for A. lixula, indicating similar sensitivity. Malformations increased significantly at concentrations of 0.5 g L⁻¹ in P. lividusand at 5 g L⁻¹ in A. lixula. The HPLC-MS analysis of R. okamurae exudates confirmed the presence of several bioactive polyphenols, with vanillic acid exhibiting the highest concentration (1.73 ± 0.09 µg L-1). Overall, our results show that R. okamurae exudates strongly inhibit the early development stages of native sea urchins. The presence of high biomass of this invasive alga is therefore likely to reduce larval survival and recruitment, driving sustained declines in their benthic populations. As these key grazers play a central role in regulating macroalgal community dynamics, their reduction would weaken grazing pressure and create conditions that further facilitate the invasion and ecological impacts of R. okamuraein the invaded Atlantic and Mediterranean rocky shores.

Highlights• The Toconao plastic-pellet spill was a major pollution incident in European waters.• The toxicity of spilled Toconao plastic pellets on marine plankton was assessed.• No or slightly effects were observed in microalgae, sea urchin larvae and fish larvae.• Leachates from Toconao pellets caused moderate mortality in copepod nauplii.• Micronization and weathering slightly increased the toxicity of leachates.• Low concentrations of additive UV622 were found in the pellet leachates.• The additive UV622 exhibited low toxicity to nauplii and echinoid larvae.• Overall, the spilled Toconao pellets showed low short-term aquatic toxicity.

Successful development and dispersal of meroplanktonic larvae are critical for recruitment and population dynamics of benthic invertebrates. With increasing anthropogenic stressors on marine ecosystems, it is essential to understand how combined pressures impact these sensitive early life stages. We investigated the effects of different types of chemical pollution in combination with a simulated marine heatwave (+5°C) on larval stages of the abalone Haliotis tuberculata coccinea, an endangered subspecies endemic to Macaronesia. Larvae were exposed for 48 h to crude oil, leachates of car tire particles, and leachates of beach-collected plastics. Two separate exposure experiments were conducted to examine (1) the effects on development and survival of early larvae and (2) the potential impacts on metamorphosis in late larvae. Early larvae were sensitive to all tested pollutants as shown by increased mortality. However, leachates of car tire particles induced the strongest effects with all surviving larvae being smaller than controls and showing signs of abnormal development. These responses were milder for the other pollutants. The heatwave treatment significantly reduced the survival of early and metamorphosis of late larvae. In contrast, metamorphosis was only slightly affected by the tested pollutants, though in different directions, indicating reduced as well as enhanced metamorphosis. Overall, our results demonstrate that abalone larval sensitivity is influenced both by developmental stage and the combination of stressors. The findings underscore that warming and chemical pollution pose a significant threat to the early life stages of H. tuberculata coccinea. This presents a considerable risk for these overexploited populations in Macaronesia.

Millions of tons of plastic enter the ocean annually, yet the effects of their leachates on the microbial loop are poorly understood. This study investigates how dissolved organic carbon released from field-collected plastics and a bioplastic influences the growth of the protozoan Oxyrrhis marina and its associated bacterial community. Plastics increased dissolved organic carbon concentrations in seawater by 5 to 34-fold, stimulating O. marina growth by up to an order of magnitude compared with the control. After exposure to conventional beach plastic leachates and bioplastic leachates, O. marina exhibited growth rates up to 0.3 and 0.4 d$^{-1}$, respectively, even in the absence of microalgal prey. We estimated that each gram of microplastics could lead to daily assimilation of up to 0.7 g of carbon per gram of protozoan, indicating that plastic-derived carbon enhances heterotrophic metabolism in the microbial loop through osmotrophy. Given that autotrophic prokaryotes are negatively impacted by plastic leachates and that plastic pollution is expected to triple in the coming decades, plastic leaching could alter the balance between microbial primary production and heterotrophy in the ocean.