Phycology

Macroalgae are essential components of marine ecosystems, supporting biodiversity, primary productivity, and the functioning of coastal habitats. In the northeast Atlantic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands, Cabo Verde), they hold significant ecological and economic value and have recently emerged as key indicators of environmental change. This oceanic region faces increasing pressure from multiple stressors, including climate change, invasive species, habitat degradation, and other anthropogenic impacts, driving shifts in coastal ecosystems and the simplification of structurally complex habitats such as marine forests. To assess the current state of knowledge on Macaronesian macroalgae and identify gaps relevant to conservation and management, we conducted a systematic literature review following PRISMA guidelines. Our results show strong but uneven foundational knowledge, with the Azores and Canary Islands accounting for roughly 80% of publications. Research is dominated by fundamental studies in ecology and taxonomy, while applied research (e.g., resource exploitation, aquaculture, toxicology, and climate-change impacts) remains limited. Red algae and a few dominant orders (Ceramiales, Fucales, Dictyotales) are well represented, whereas green algae and less conspicuous taxa are understudied. Future research should expand geographic coverage, broaden taxonomic scope using molecular tools, strengthen applied research, standardize monitoring frameworks, and align scientific output with management needs.

Efficient inorganic carbon supply is a common limitation in microalgal cultivation, particularly in waste-derived media such as anaerobic digestate. Carbonic anhydrase (CA) accelerates the interconversion of CO₂ and bicarbonate and may therefore enhance carbon utilisation under conditions where inorganic carbon is abundant but not readily available. In this study, crude CA-containing extracts (aCA) were prepared from Scenedesmus-dominated algal biomass, and CA activity was quantified using an esterase assay (EAA). Although EAA activities varied depending on biomass pretreatment (0.15–0.47 U g⁻¹ DW), the physiological response to extract addition was consistent. In batch cultures of Chlorella sorokiniana grown in diluted digestate, aCA supplementation increased the specific growth rate (SGR) by 21–82%. In contrast, stimulation in a mineral medium was minimal, indicating that the benefit of aCA addition is most apparent under reduced inorganic carbon availability. In semi-continuous cultivation, repeated extract addition sustained a higher biomass productivity over time (rather than a specific growth rate). These results demonstrate that crude microalgal extracts containing CA can improve growth performance in digestate-based cultures and may offer a simple, low-cost approach to enhancing inorganic carbon utilisation in waste-integrated algal production systems.

Light and antioxidant systems play a crucial role in the life activities of algal cells. This study investigates the algicidal efficacy of hydrogen peroxide (H₂O₂) against the harmful algal bloom (HAB)-forming dinoflagellate Prorocentrum donghaiense Lu, with a focus on the modulating roles of light conditions and iron ion environments. Within 180 min, dark-adapted cells showed 78% greater viability loss than light-exposed ones, and Fe₃O₄ nanoparticles synergistically enhanced H₂O₂ inhibition. Imaging and cytometry confirmed cell damage, including membrane rupture. Mechanistically, H₂O₂ penetrated cells, induced severe oxidative stress, suppressed photosynthesis, and compromised membrane integrity. Darkness likely exacerbated toxicity by depleting antioxidant reserves. This study elucidates an apoptosis-like pathway underlying H₂O₂-induced cell death and highlights the critical influence of ambient light on treatment efficiency. These findings reveal an apoptosis-like death pathway and highlight ambient light’s critical role, suggesting that optimized nighttime H₂O₂ application with nanomaterial synergists could improve HAB control strategies.