Volume 64, Issue 4

Laboratory experiments have shown that light and temperature requirements are critical determining factors for thallus survival and growth of three Mediterranean Kallymeniaceae (Rhodophyta): Verlaquea lacerata , Croisettea requienii , and Meredithia microphylla , and explain their current bathymetric and habitat distribution. Verlaquea lacerata is annual and survived more than 1.5 years in culture, while C. requienii and M. microphylla are perennial and survived more than four and nine years in culture, respectively. The maximum survival was observed at 20–50 µmol photon m −2  s −1 and 10 and 12 °C within an 8:16 h light:dark regime for the three species, while a strong decrease in survival was observed at temperatures of 24 and 26 °C, indicating a weak tolerance to warming temperatures in the Mediterranean. The maximum value of the rate of daily marginal extension per initial surface area was similar in the three species: 0.017 day −1 for V. lacerata (10 °C/8:16 h light:dark regime/10 µmol photon m −2  s −1 ), 0.021 day −1 for C. requienii (18 °C/14:10 h light:dark regime/10 µmol photon m −2  s −1 ), and 0.017 day −1 for M. microphylla (12 °C/8:16 h light:dark regime/20 µmol photon m −2  s −1 ). The experiments permitted the establishment of culture conditions for the target species, and the successful culture of marginal fragments indicates the possibility of indefinitely maintaining the species in the laboratory for bioconservation purposes.

It is likely that the introduction of the brown macroalga Undaria pinnatfida from the Pacific into the North Atlantic will impact competitively on the native species Saccorhiza polyschides ; both are large kelps occupying the same subtidal zone with very similar life histories. The present study examines their tolerance to changes in salinity, under laboratory conditions, in order to provide a better understanding of their respective competitiveness in an estuarine environment. Experiments were carried out over a full range of salinity values, from 35 to 0, with respect to zoospore settlement and attachment, germination, post-germination progression to form gametophytes, gametophyte sex ratio, sporophyte production and blade length. Undaria zoospores settled and attached over the salinity range from 35 to 14 and germinated between 35 and 3.5. Post-germination progression occurred over the range from 35 to 14 whilst only small differences in the male/female ratio were recorded. Sporophyte blade production and development occurred over the range from 35 to 17.5 and peak production and longest blade length was recorded at 21. Saccorhiza zoospores settled and attached at and above 24.5 and germinated between 35 and 21. Sporophyte production and blade development occurred over the range from 35 to 24.5. In general, Undaria was shown to be much more tolerant of reductions in salinity compared to Saccorhiza and is more likely to penetrate further into estuarine environments.

During the spring of 2016, benthic blooms of Acinetospora crinita (Ectocarpales, Phaeophyceae) producing voluminous mucilaginous aggregates frequently occurred at surveyed locations of the west Istrian Coast (northern Adriatic Sea, Croatia). In mucilage-affected macroalgal assemblages, the concentration of ammonium ranged from 50 to 300 μM. To investigate whether ammonium has the potential to harm fucalean species, a selected taxon, Cystoseira compressa was exposed to increased ammonium concentrations in laboratory conditions. Experiments revealed that exposure to 50 μM ammonium severely damaged the thalli while exposure to 300 μM caused complete necrosis of thalli in 2 days. These findings suggest that benthic algal blooms, enhanced by climate change and eutrophication, can negatively affect the populations of fucalean species due to production of ammonium during the decay of mucilaginous aggregates, causing thallus necrosis.

Selenium water pollution is an increasing environmental problem that requires investigation of cellular responses of aquatic primary producer organisms, especially algae. Industrial wastewater with selenium contamination is often coupled with high salinity (60–70). In this study, the biochemical responses of two strains of the halotolerant alga ( Dunaliella salina Hoze-soltan and Dunaliella salina CCAP 19/18) to different selenium concentrations were evaluated. Although at high selenium concentrations both strains showed lipid peroxidation and cell number reduction, Dunaliella salina Hoze-soltan was less affected. Higher selenium tolerance in this strain might be attributed to the better activity of resistance responses like proline, total reducing sugar, superoxide dismutase (SOD) and peroxidase (POX), even at the high selenium concentrations. Catalase (CAT) had no significant role for protection against selenium toxicity as its activity declined in both strains with rising selenium concentration. Both strains accumulated selenium intracellularly, but the accumulation was about three-fold higher in Dunaliella salina Hoze-soltan than in the other strain. It can be concluded that Dunaliella salina Hoze-soltan may be a better candidate for selenium bioremediation of a high salinity environment. The data obtained from this study could be useful for improvement of algal ability for high efficiency selenium bioremediation in hypersaline environments.

Reports on fungi occurring on marine crabs have been mostly related to those causing infections/diseases. To better understand the potential role(s) of fungi associated with marine crabs, this study investigated the culturable diversity of fungi on carapace of the marine shallow-water hydrothermal vent crab Xenograpsus testudinatus collected at Kueishan Island, Taiwan. By sequencing the internal transcribed spacer regions (ITS), 18S and 28S of the rDNA for identification, 12 species of fungi were isolated from 46 individuals of X. testudinatus : Aspergillus penicillioides, Aspergillus versicolor, Candida parapsilosis, Cladosporium cladosporioides, Mycosphaerella sp ., Parengyodontium album, Penicillium citrinum, Penicillium paxili, Stachylidium bicolor, Zasmidium sp. (Ascomycota), Cystobasidium calyptogenae and Earliella scabrosa (Basidiomycota). With additional data from other published reports, a total of 26 species of fungi (23 Ascomycota, three Basidiomycota) have been recorded from X. testudinatus . Aspergillus is the most speciose genus on the crab, followed by Penicillium and Candida . All but one species ( Xylaria arbuscula ) had been previously isolated from substrates in the marine environment, although many are typical terrestrial taxa. None of the recorded fungi on X. testudinatus are reported pathogens of crabs, but some have caused diseases of other marine animals. Whether the crab X. testudinatus is a vehicle of marine fungal diseases requires further study.

This study aimed to survey algal model organisms, covering phylogenetically representative and ecologically relevant taxa. Reports about the occurrence of sulfonates (particularly sulfoquinovose, taurine, and isethionate) in marine algae are scarce, and their likely relevance in global biogeochemical cycles and ecosystem functioning is poorly known. Using both field-collected seaweeds from NW Scotland and cultured strains, a combination of enzyme assays, high-performance liquid chromatography and matrix-assisted laser-desorption ionization time-of-flight mass spectrometry was used to detect key sulfonates in algal extracts. This was complemented by bioinformatics, mining the publicly available genome sequences of algal models. The results confirm the widespread presence of sulfonates and their biosynthetic pathways in macro- and microalgae. However, it is also clear that catabolic pathways, if present, must be different from those documented from the bacterial systems since no complete cluster of gene homologues of key genes could be detected in algal genomes.

Seaweeds cover a wide range of applications, e.g. as food supplements, in animal feed, as biofuels or as sources of bioactive compounds. The Greek coast in the East Mediterranean is rich in various seaweeds that remain unexploited because their chemical and nutritional content has not yet been characterized. In the present study, eight seaweeds belonging to the Rhodophyta, Ochrophyta (class Phaeophyceae) and Chlorophyta were biochemically characterized and evaluated as potential food sources. Total polyphenol content, antioxidant activity, fatty acids and elemental composition were measured. Acanthophora nayadiformis, Ceramium sp. (Rhodophyta) , Codium fragile (Chlorophyta) , Cystoseira foeniculacea and Gongolaria barbata (formerly Cystoseira barbata ) (Ochrophyta, Phaeophyceae) had the highest phenolic content and strongest antioxidant activity. Both brown and red seaweeds were rich in minerals, with G. barbata, Dictyopteris polypodioides (formerly Dictyopteris membranacea ) (Chlorophyta, Phaeophyceae) and A. nayadiformis being the richest in macro- and microelements. The low Na/K ratio in most seaweeds (0.03–3.49) and the high iron content of red and brown algae (1.01–52.40 mg 100 g −1 of wet tissue) make algal consumption an attractive option. Chlorophyta and Phaeophyceae had the lowest n-6/n-3 PUFA ratios, with α-linolenic acid being the most abundant n-3 PUFA. The green algae Codium fragile and Ulva lactuca had the highest oleic and docosahexaenoic acid content, respectively. Finally, Rhodophyta were the highest producers of eicosapentaenoic acid. The findings confirmed the nutritional value of all seaweeds, highlighting brown seaweeds Cystoseira foeniculacea , G. barbata , and D. polypodioides as potential sources for food supplements and candidate species for seaweed cultivation in Mediterranean coastal waters.

Even though seaweeds have been considered a nutrient-rich dietary source of minerals in other parts of the world, there is little knowledge about trace element accumulation in seaweeds of the Arabian Gulf. The Arabian Gulf is of particular interest due to being an extreme environment, as it features some of the highest temperatures and salinities observed in any marine waters in the world. This study determined the minerals contents using inductively-coupled plasma-mass spectrometry (ICP-MS) in 10 of the most common seaweeds of this region ( Iyengaria stellata , Padina boergesenii , Chondria sp . , Feldmannia indica , Codium papillatum , Sargassum aquifolium , Ulva chaugulii , Ulva tepida and Ulva sp.) supported by morphological and molecular (DNA barcode)-based identification. The finding of U. chaugulii reported here is a new record for Kuwait. Most of the seaweeds were rich in essential minerals including Ca, Mg, Na, K, Fe and Zn and their contents were higher than those of other mineral-rich foods. Principal component analysis revealed species-specific distributions of minerals in seaweeds. U. tepida and I . stellata were found to be exceptionally rich in most of the macro- and trace elements along with low As and Se, and thus can be utilized for food and feed applications.