Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrometry. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved.

We report the complete chloroplast genome of the MED1 strain of Nephroselmis pyriformis from the Eastern Mediterranean Sea. At 111,026 bp, this genome is smaller and more compact than those of Nephroselmis olivacea and Nephroselmis astigmatica , and in contrast to the latter taxa, its inverted repeat contains no complete protein-coding genes. It encodes 3 rRNAs, 33 tRNAs and 94 proteins. Maximum likelihood analysis of a concatenated set of chloroplast genes from green algae belonging to deep-diverging lineages positioned the three Nephroselmis species in a strongly supported clade in which N. pyriformis is sister to N. astigmatica .

Harvesting impacts the costs of microalgae production and affects the characteristics of the final product. Therefore, this study evaluated Moringa oleifera seed powder (MP) as a bioflocculant compared to two chemicals (Aluminium Sulphate—AS and Iron Chloride—IC) to harvest a mixed microalgae culture (Chlorella vulgaris and Desmodesmus sp.) grown on digestate. MP was the most stable flocculant but resulted in the lowest harvesting efficiency of 75%, compared to 94% for AS and 100% for IC. Process parameters such as pH, duration of mixing, grinding method for obtaining the powder, and granulometry had no significant effect on the harvesting efficiency of MP, reinforcing that this is a robust flocculant. The use of a water extraction step increased the harvesting efficiency of MP to 91%, albeit with the need for a higher dosage of flocculant. The algae harvested with MP complied with maximum tolerable levels for swine, cattle, and poultry regarding most trace elements. Nevertheless, all algae samples had Fe and Al contents above the recommended levels, possibly due to the entrapment of metal-rich digestate particles. Therefore, more attention should be paid to the final composition of algae when proposing flocculation as a harvesting method for feed production.