To identify cryptic stages of marine brown macroalgae present in the “bank of microscopic forms”, we incubated natural substrata of different geographical origins and isolated emerging Phaeophyceae into clonal cultures. A total of 431 clones were subsequently identified by barcoding using 5′-COI. A proportion of 98% of the isolates belonged to the Ectocarpales. The distribution of pairwise genetic distances revealed a K2P divergence of 1.8% as species-level cut-off. Using this threshold, the samples were ascribed to 83 different species, 39 (47%) of which were identified through reference sequences or morphology. In the Ectocarpaceae, 16 lineages of Ectocarpus fulfilled the barcode criterion for different species, while three putative new species were detected. In the Chordariaceae, numerous microthalli were microstages of known macroscopic taxa. A separate cluster contained Hecatonema maculans and other microscopic species. Taxa traditionally classified in Acinetosporaceae were split in two species-rich groups containing Pylaiella and Hincksia in one and Acinetospora in the other. Feldmannia species were present in both clusters. The present study shows that the germling emergence method is suited to reveal the diversity of hidden life-history stages, albeit with a bias towards early successional species.

DNA barcodes and morphological observation were used to evaluate the number of species within the genus Corallina sensu lato in Atlantic Iberia and to identify a set of morphological characters that may discriminate them. Five species were detected: (i) C. officinalis, (ii) C. caespitosa, (iii) Ellisolandia elongata, (iv) Corallina sp. 1, and (v) Corallina sp. 2. The first three species were widespread whereas Corallina sp. 1 was only detected in southern Atlantic coasts of Iberia and Corallina sp. 2 occurred both in the Atlantic and the Mediterranean, nevertheless, with morphological and molecular differences. The widespread occurrence of the recently described C. caespitosa along Atlantic Iberia is substantiated with sequence data for the first time; it spans from the Bay of Biscay to Andalusia and the French Mediterranean. Molecular support is also provided for the presence of C. officinalis and E. elongata in Atlantic Iberia. Plants of C. officinalis were correctly identified attending to their external morphology, however two distinct species were detected under the two forms of C. elongata (“typical” and “elongated”) reported for Galicia in the literature (C. caespitosa and Ellisolandia elongata, respectively). Plant size, habit, branching, and shape of intergenicula seem the most informative morphological characters to discriminate among the various members of Corallina s.l. in Atlantic Iberia.

Padina distristromatica Ni-Ni-Win & H. Kawai and Padina pavonicoides Ni-Ni-Win & H. Kawai, two species recently described from the Mediterranean Sea, are reported for the first time from the coasts of the Iberian Peninsula, and the former also from the Balearic Islands. In this paper new data are provided for both species, especially cell dimensions. The indusium features, which are proposed as new taxonomical character for P. distristromatica, as well as the lack of stolon-like structures in this species, are considered useful features for distinguishing P. distristromatica from P. pavonica. A distribution map of both species in the Spanish coasts is also provided.

On the basis of literature data and new morphological and ecological studies, the reinstatement of species rank for the Black Sea endemic species Cystoseira bosphorica is proposed. Previously reduced to a simple form of the Mediterranean endemic species C. crinita, this member of the caespitose Cystoseira group without spinose-like appendages clearly differs from C. crinita by having the axes long with smooth and prominent apices, the branches with numerous and slightly prominent cryptostomates, the aerocysts frequent, large, oval to subconical-broader at the apex, with 2 or more apical outgrowths, and by the receptacles long, cylindrical-tuberculate, simple or bifid, with apices blunt bearing sometimes a short lateral sub-apical spine. The species that shares the greatest number of characters with C. bosphorica is not C. crinita but the Mediterranean endemic species C. barbatula; however, this latter species clearly differs from C. bosphorica by the constant absence of aerocysts, the filiform branches with prominent and spaced cryptostomates, and by the receptacles smaller, compact, simple, humpy and subulate with sometimes 1–2 long lateral spine-like appendages.

Cyanobacteria of the genus Nostoc and green algae in the Chlorophyceae are widespread in nature and may occur in symbiotic associations with lichen-forming ascomycetes or as free-living cyanobacteria. Recent findings for some groups of lichens suggest that special lichen-forming photobiont lineages may exist independent of the free-living lineages, but few comparisons on photobiont growth, pigment, and polysaccharide production have been made. The goal of this study was to isolate photobionts, confirm their identity, and characterize their growth, pigment and polysaccharide production relative to free-living lineages. Algal growth, pigment contents, and polysaccharide concentration was measured using standard methods. The identification of Nostoc species was determined using transfer RNA for Leucine (trnL) nucleotide sequences and green algae using the internal transcribed spacer 1 of ribosomal DNA (ITS rDNA) sequences. An additional heptanucleotide repeat was present in the trnL gene of the Nostoc strain that associates with Leptogium rivulare. The biomass of pigment and polysaccharide production was highest in the lichenized Diplosphaera chodatii but the specific growth rate was highest in the free-living green alga, Chlorella vulgaris. The specific growth of the free-living Nostoc was higher than the lichenized Nostoc but pigment production was similar and polysaccharide production was lower than some of the lichenized Nostoc isolates. It was further hypothesized that the rates of growth, polysaccharide and pigment production may be key factors in compatibility of lichen algae with the fungus.

The toxic epi-benthic dinoflagellate Ostreopsis is distributed worldwide in coral reef ecosystems and temperate regions. There are nine species described to date based on morphological features. Some of them have been proved to be producers of palytoxin-like compounds, representing a threat to coastal marine organisms and human health. The taxonomy of the genus is currently under revision due to morphological similarities among species. The present study aims to provide additional information on morphology, 5.8S and ITS data and toxin content from thirty three strains isolated along the west coast of Reunion Island, in the Indian Ocean. Two morphotypes, non overlapping in size, were distinguishable: the small morphotype (DV = 53.5 ± 6.9 µm; W = 37.7 ± 5.6 µm) with a typical tear-drop shape and the large morphotype (DV = 103.9 ± 5.1 µm; W = 85.3 ± 6.9 µm) with a rounded shape. Phylogenetic analysis revealed the presence of three genotypes. Within the small morphotype, two different species were identifided, O. cf. ovata and a cryptic species not previously characterized. The larger cells constituted a genetically homogeneous clade. Nucleotide divergence between this species and the one qualified by Sato et al., 2011 of Ostreopsis sp. 5 was relatively low (p < 0.088) and those two strains are likely to be the same species. Haemolytic analysis resulted in no palytoxin-like activity in any of the three species.