Volume 62, Issue 6

Algicidal bacteria can lyse phytoplankton cells, thereby contributing to algal bloom dynamics in the oceans. The target specificity of these bacteria determines their ecological impact. While species specificity of algicidal bacteria is documented, little is known about intra-species variability of their activity against phytoplankton. We describe variability in the Chaetoceros genus (Bacillariophyceae) to resist the lytic activity of the algicidal Flavobacterium Kordia algicida . This variability is evident between different Chaetoceros species, but even intra-specific variability of resistance is observed within one phytoplankton sample. This proves an ecological role of the individuality of diatom cells within a bloom.

The present work describes microalgal blooms that occurred in a eutrophic estuary (Golden Horn, Sea of Marmara, Turkey) between October 2013 and September 2014 following a remediation effort. The relationships between bloom-forming microalgal species and environmental factors were investigated during the study period. The changing environmental conditions (e.g. increasing water transparency and salinity) after seawater transfer to the Golden Horn Estuary stimulated phytoplankton growth with dense algal blooms. Annual average values of Secchi depth, salinity and dissolved oxygen increased in comparison with those in an earlier study in 2009–2010. Nine microalgal species, which consisted of four diatoms, two dinoflagellates, one cryptophycean, one raphidophycean and one euglenophycean, formed the blooms with water discolorations during spring and summer. The species that reached the highest bloom density were Plagioselmis prolonga (62.4 × 10 6 cells l −1 ) among crytophyceans, Heterocapsa triquetra (21.8 × 10 6 cells l −1 ) among dinoflagellates and Skeletonema marinoi (39 × 10 6 cells l −1 ) among diatoms. The abundance of dinoflagellates and phytoflagellates increased particularly in the upper estuary when compared to diatoms and their rapid growth and bloom formation revealed that they have a wide range of tolerance to changing environmental conditions and a strong ability to compete with other species in this study area.

Green tide algal blooms occur worldwide, especially in China’s Yellow Sea, and have caused serious damage to local ecological environments and economies. As a dominant agent of green tides, the green macroalga Ulva has caused widespread concern. In this study, phylogenetic clades were constructed among related Ulva species isolated from Pyropia rafts at six sites over 1.5 years based on internal transcribed spacer (ITS) and tufA sequences. In addition, traditional observation ploidy methods and flow cytometry methods were used to analyse continuous change in the biphase and sex ratios of Ulva species and to assess the changes in phase advantages over time. The results showed that the perennial Ulva populations on rafts mainly consisted of Ulva flexuosa and Ulva prolifera , and the biphasic dominance of the attached Ulva populations changed with the seasons: sporophytes were predominant mainly in winter and spring, and gametophytes were predominant mainly in summer and autumn. At the same time, there were some differences in gametophyte and sporophyte frequencies (mainly sporophyte biased) compared to the null model prediction of a √2:1 ratio, while the sex ratio of male and female gametophytes remained 1:1 throughout the year. Our results indicate the presence of both phases of bloom-forming species of Ulva in green tides year round, and that multiple generations coexist and grow continuously.

Hypnea is a monophyletic genus with a complex nomenclatural and taxonomic history, and is an important commercial source of carrageenan. Phylogenies of this genus have been accessed based primarily on Asian species; however, recent studies performed in South America revealed a great diversity of species, for which phylogenetic relationships need to be evaluated. Three infrageneric sections are recognized in the genus: Pulvinatae , Spinuligerae , and Virgatae ; however, morphological and molecular circumscriptions within each section lack clarity. In this study, we analyzed three distinct markers to establish phylogenetic relationships among Hypnea species. To assign each species to the correct section, morphological data were obtained from original descriptions, reference literature, and comparisons with type/topotype and herbaria specimens. Our analyses recovered robust phylogenies for the genus and provided new insights on the taxonomic status and relationships among and within Hypnea species. The combination of three genetic markers increased the resolution and support, resulting in the largest and best-resolved phylogeny of the genus to date. Single and combined analyses revealed that the three sections of the genus Hypnea are taxonomically irrelevant, as currently recognized. Morphological differences are not associated with monophyletic groups and similarities among clades could be better explained by convergent evolution in thallus habit.

Parts of the macroalgal flora of the eastern Mediterranean remain incompletely known. This applies in particular to the circalittoral communities. This study, based upon 2 cruises in the Ionian and Aegean Seas, surveyed benthic communities from 40 to 150 m depth by remotely-operated vehicle (ROV) with a special focus on detecting communities of the Mediterranean deep-water kelp Laminaria rodriguezii . These were complemented by shallow-water surveys on adjacent coastlines by snorkelling and scuba diving. While no kelp could be detected at any of the sites surveyed, ROV surveys of northern Euboia Island revealed the first east Mediterranean record of Sebdenia monnardiana (Sebdeniales, Rhodophyta). Snorkelling surveys on the coast of southeast Kefalonia yielded the first record of the alien alga Dictyota cyanoloma in Greece. This paper reports rbc L and SSU sequences for Sebdenia monnardiana , and COI for Dictyota cyanoloma.

Two rarely reported and one newly described species of benthic marine algae are herein recognized from deep-water habitats at Bonaire, representing the first Caribbean reports of each. Archestenogramma profundum is previously known only from its type collection in Bermuda at 17 m depth and the rarely reported Halymenia integra is known originally from its type locality at Cabo Frio, Brazil. Verdigellas discoidea is newly described on the basis of morphological and molecular evidence. It forms flat circular thalli to 6.5 cm in diameter, measuring to 390 μm thick. The disc-like algae are attached by several small holdfasts on the ventral surface, but the margins are mostly free from their substrata.

The minute red alga Crouania pumila (Callithamniaceae: Rhodophyta), recently described from the Caribbean Sea, is reported for the first time from the Red Sea, approximately 12,000 km from the type locality, based on microscope slide specimens collected 40 years ago by Dr. Yaacov Lipkin. These samples contribute new information regarding the reproduction of this algal species.

In the present paper, Dictyota hauckiana is reported for the first time from Vietnam. It was found growing with other marine macroalgae nearshore, at 1–2 m depth in Ninh Hai waters, Ninh Thuan province. Morphological observations and phylogenetic analysis based on the concatenated rbc L and psb A are presented. There are now 13 species of Dictyota known from Vietnamese waters.

The current industrial practice of using chemical bleach to achieve the pure white colour of agar is deleterious to both human and environmental health. This study evaluates the potential of solar irradiation as an alternative bleaching process for agar extracted from Gracilariopsis heteroclada in Iloilo, Philippines. The physico-chemical properties of agar obtained from alkaline-treated seaweed after exposure to different bleaching conditions (e.g. solar irradiation, hypochlorite solution, and ultraviolet and fluorescent lights) were examined and compared with commercial bacteriological agar. Photobleaching through solar irradiation produced agar with superior gel strength (1038.61 g cm −2 ), high 3,6-anhydrogalactose content (41.44%) and low total inorganic sulphate content (1.87%) without compromising agar yield (19.37%). Solar irradiation offers very promising results as a simple, low-cost, environmentally friendly alternative to the chlorine bleaching process for agar extraction.