Phycology

Microalgae are increasingly recognized as promising biostimulants for sustainable agriculture, yet their potential remains underexplored due to the complexity of biostimulant activity and the vast diversity of species. Efficient standardized screening approaches are therefore needed. In this study, a high-throughput screening platform assessed the biostimulant activity of five microalgal species (Limnospira platensis, Chlorella vulgaris, Dunaliella salina, Microchloropsis gaditana, and Isochrysis galbana) in Arabidopsis thaliana. The system enabled full life-cycle assessment of A. thaliana under optimal and drought stress conditions, incorporating three application methods (soil amendment, irrigation, foliar spray) and a wide concentration range of 0.01–0.5 g/L. Biostimulant efficacy depended strongly on concentration and application method. Irrigation-based applications generally enhanced drought tolerance but delayed bolting and flowering. The highest concentration inhibited germination and root elongation, likely due to bioactive compound toxicity rather than salinity or pH. L. platensis exhibited broad activity across environmental conditions, while I. galbana likewise showed wide-ranging effects, including enhanced generative growth. In contrast, D. salina and M. gaditana primarily improved drought tolerance, and C. vulgaris acted mainly under optimal conditions. These findings highlight the value of A. thaliana to accommodate rapid biostimulant screening and identify both novel and established microalgae for further validation in crops.

Alaska’s kelp farming industry is expanding, with Alaria marginata (ribbon kelp) emerging as a promising crop. This species is valued for its food-grade applications, yet little is known about its cultivation performance. We tested the effects of five line-spacing treatments (0.31–1.83 m) on blade phenotype and yield under farmed conditions. Wider spacings produced longer, wider, and thicker blades. Sporophytes at 1.23 m and 1.83 m spacings were most likely to exceed 200 cm in length, while most blades were half that length for treatments closely spaced. Yield per meter was lowest at 0.31 m spacing (~2 kg m⁻¹) but exceeded 3 kg m⁻¹ in all wider treatments, with 1.23 m and 1.83 m spacings showing a probability of producing 6 kg or more. Results aligned with those of other kelp studies assessing line spacing on kelp performance. This work highlights the importance of aligning cultivation practices with market demands for either biomass or blade quality. The study was limited to one site and one growing season. Nonetheless, findings provide an initial framework for optimizing A. marginata cultivation in Alaska.

This study describes the results of integrative analysis of cyanobacterial communities in waterbodies of Moscow, Russia. 16S rRNA V3–V4 metabarcoding and light microscopy are implemented to investigate the diversity, abundance, and distribution of cyanobacteria, including the representatives of potentially toxigenic taxa—Anabaena, Aphanizomenon, Dolichospermum, Microcystis, and Planktothrix. High convergence is observed between microscopy and metabarcoding data for dominant genera, including Microcystis and Planktothrix. Sequence verification reveals total (100%) similarity between previously isolated toxigenic strains (e.g., Microcystis aeruginosa CBMC403m and CBMC523m) and corresponding highly abundant ASVs. In addition, current study ascertains the efficiency of metabarcoding for detection of rare cyanobacterial taxa missed by microscopy. We hereby acknowledge the limitations of V3–V4 16S rRNA-based metabarcoding approach for region species-level resolution and distinguishing potentially toxigenic taxa of cyanobacteria. At the same time, our findings validate metabarcoding as a rapid and reliable tool for monitoring of CyanoHABs in urban water ecosystems.