Phycology

Microalgae are emerging as a key biological platform for the production of important metabolites, environmental monitoring, and water treatment. However, despite their significant potential for a variety of industrial applications, several challenges associated with the efficiency of their cultivation hinder their widespread use. Here, focus was placed on the freshwater organism, Micractinium inermum strain EE-M2, to study the growth and accumulation of pigments, proteins, lipids, and starch under various strategies of increased inorganic carbon supply and ammonium nutrition conditions. NaOH and NaHCO₃ were tested as pH control agents. Combinations of constant sparging with atmospheric air enriched with CO₂ (finally 2.0% CO₂, v/v) and NaHCO₃ addition showed a slight increase in algal biomass productivity, but the metabolic profiles were indistinguishable from those obtained with pH regulation using NaOH. Decreasing the CO₂ concentration from 2.0% to 0.5% significantly reduced the final biomass yield and productivity of this strain (in a batch process). Also, the present study showed the feasibility of continuous cultivation of M. inermum to produce marketable biomass and metabolites. Under two cultivation strategies, batch and continuous, the alga effectively accumulated pigments (up to 2.7% of dry weight), proteins (up to 37.3%), lipids (up to 23.3%), and starch (up to 22.5%), indicating its biotechnological value. Overall, the obtained results demonstrate that M. inermum strain EE-M2 is a robust and fast-growing microalgal strain suitable for both laboratory and industrial cultivation.

The mitigation of toxic cyanobacterial blooms is a much-researched and ongoing challenge. Seasonal influences, microbial diversity, and the wide range of cyanotoxins known to be associated with cyanobacterial blooms add layers of complexity to these environmental threats. Strategies to remediate blooms must avoid inducing widespread cell lysis and the release of cyanotoxins, which would compound rather than address the problem. Bacterial isolates have been found to be effective in bloom mitigation and can impact the diversity associated with the bloom. The present study reports on the exposure of non-axenic cultures of colonial Microcystis sp. and filamentous Oscillatoria sp. isolated from dams in South Africa to low ratios of four antagonistic bacterial isolates for 4 days. TEM was used to assess ultrastructural changes, HPLC to determine the relative concentrations of microcystin-LR and RR, and next-generation sequencing (NGS) to explore possible shifts in diversity from control samples as a result of exposure to the biological control bacterial isolates used. Ultrastructurally, Microcystis showed greater signs of stress than cells of Oscillatoria, with isolate 1 (Aeromonas lacus) having the least effect overall, whilst Isolate B (Lysinibacillus) and 3Y (Pseudomonas sp.) induced cell lysis in Microcystis. All isolates reduced the concentration of the toxic microcystin-LR, while the -RR variant often increased after 4 days. Minimal diversity shifts were noted in Microcystis-treated cultures, whilst those of Oscillatoria showed a greater diversity shift, indicating an increase in families containing isolates linked to bloom decline.

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.