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International audience; Lithophyllum species in the Mediterranean Sea function as algal bioconstructors, contributing to the formation of biogenic habitats such as coralligenous concretions. In such habitats, thalli of Lithophyllum, consisting of crusts or lamellae with entire or lobed margins, have been variously referred to as either one species, L. stictiforme, or two species, L. stictiforme and L. cabiochiae, in the recent literature. We investigated species diversity and phylogenetic relationships in these algae by sequencing three markers (psbA and rbcL genes, cox2,3 spacer), in conjunction with methods for algorithmic delimitation of species (ABGD and GMYC). Mediterranean subtidal Lithophyllum belong to a well‐supported lineage, hereby called the L. stictiforme complex, which also includes two species described from the Atlantic, L. lobatum and L. searlesii. Our results indicate that the L. stictiforme complex consists of at least 13 species. Among the Mediterranean species, some are widely distributed and span most of the western and central Mediterranean, whereas others appear to be restricted to specific localities. These patterns are interpreted as possibly resulting from allopatric speciation events that took place during the Messinian Salinity Crisis and subsequent glacial periods. A partial rbcL sequence from the lectotype of L. stictiforme unambiguously indicates that this name applies to the most common subtidal Lithophyllum in the central Mediterranean. We agree with recent treatments that considered L. cabiochiae and L. stictiforme conspecific. The diversity of Lithophyllum in Mediterranean coralligenous habitats has been substantially underestimated, and future work on these and other Mediterranean corallines should use identifications based on DNA sequences.

Plastid-encoded rbcL and psbA sequences from branched, Caribbean Sea Lithophyllum specimens indicate that four species are present, not one. Short (263 base pairs) rbcL sequences from an isolectotype of L. kaiseri (Gulf of Suez) and the holotypes of L. congestum, L. daedaleum and L. platyphyllum (Caribbean Sea) show that L. congestum and L. daedaleum are conspecific with L. kaiseri, the last having nomenclatural priority. Lithophyllum platyphyllum, currently considered a synonym of L. congestum, is recognised as a valid species. Lithophyllum stictaeforme, originally described from the Mediterranean Sea, is not conspecific with L. kaiseri (as L. congestum) as previously suggested. Lithophyllum neocongestum sp. nov. and L. pseudoplatyphyllum sp. nov. are proposed. Together with L. platyphyllum, these three branched species are so far endemic to the Caribbean Sea. This is the first report, documented by DNA sequence data, of a coralline species (L. kaiseri) widespread through the tropical Indo-West Pacific Oceans, Red Sea and Caribbean Sea.

The feasibility of the green alga Desmodesmus communis for biomass production was investigated, firstly testing different nitrogen forms in the growth medium and the effect of CO2-enriched air supply, secondarily scaling up the cultivation system in 70 L photobioreactors (PBRs). Maximum nitrogen uptake rate obtained in the performed kinetic experiment was higher for ammonium than for nitrate (188.0 vs 11.7 μmol g−1 h−1); however, D. communis cultured in PBRs with only aeration grew faster with nitrate reaching a biomass yield (1.23 g L−1) and a productivity (0.036 g L−1 day−1) about twofold higher than with ammonium, which caused a pH decrease in the medium affecting the algal growth. CO2 supply allowed algal growth optimization, maintaining a high productivity with both nitrogen sources, slightly higher with nitrate (0.050 vs 0.038 g L−1 day−1). Additionally, nitrate-supplied cells showed higher lipids (19.0 vs 9.4%) and proteins (33.0 vs 27.2%) values than those grown with ammonium. The semi-continuous scaled-up cultivation performed for 5 months attests the potential utilization of this species for valuable algal biomass production exploitable in various industrial applications.

In the last decade Ostreopsis cf. ovata blooms have been among the most intense along the entire Mediterranean coast, leading to ecological and human health problems, that are associated with the toxins (palytoxin-like compounds) produced by these algal cells. These compounds are secondary metabolites, whose rates of synthesis depend on the metabolism of their precursors. In general, growth dynamics and toxicity of dinoflagellates reflect the physiological status of the organism. The aim of the present study was to investigate the cellular production of the main biochemical compounds likely involved in the growth and toxicity dynamics of O. cf. ovata during exponential to the late stationary phase in batch cultures of an Adriatic strain. Removal of major nutrients from the medium was monitored along with concentration, biovolume and production of the main cellular components (e.g. polysaccharides, proteins, lipids and toxins). Nutrient uptake, as well as toxin production rates were calculated in the different growth periods. Nutrients (N and P) were completely depleted when cells entered stationary phase and the greatest net toxin production rate (RTOX) occurred during the first days of growth. The various palytoxins reported a relative abundance quite stable during the different growth phases, while the total toxin cellular amount increased along the growth curve. Total and extracellular released polysaccharides, as well as the lipid content increased greatly during the stationary phase, while proteins were mainly produced by cells during the exponential phase. The continuous release of polysaccharides could facilitate cell aggregation and the formation of the benthic community during algal blooms. The trend of production of the main cellular compounds in O. cf. ovata and the growth dynamics of this species lead us to hypothesize that the fast growth of this dinoflagellate, associated with the rapid use of environmental resources (nutrients, and phosphates in particular), may be an ecological/ adaptive strategy which could favor this organism in competition with other species.

Dinoflagellates are prolific producers of polyketide secondary metabolites. Dinoflagellate polyketide synthases (PKSs) have sequence similarity to Type I PKSs, megasynthases that encode all catalytic domains on a single polypeptide. However, in dinoflagellate PKSs identified to date, each catalytic domain resides on a separate transcript, suggesting multiprotein complexes similar to Type II PKSs. Here, we provide evidence through coimmunoprecipitation that single-domain ketosynthase and ketoreductase proteins interact, suggesting a predicted multiprotein complex. In Karenia brevis (C.C. Davis) Gert Hansen & O. Moestrup, previously observed chloroplast localization of PKSs suggested that brevetoxin biosynthesis may take place in the chloroplast. Here, we report that PKSs are present in both cytosol and chloroplast. Furthermore, brevetoxin is not present in isolated chloroplasts, raising the question of what chloroplast-localized PKS enzymes might be doing. Antibodies to K. brevis PKSs recognize cytosolic and chloroplast proteins in Ostreopsis cf. ovata Fukuyo, and Coolia monotis Meunier, which produce different suites of polyketide toxins, suggesting that these PKSs may share common pathways. Since PKSs are closely related to fatty acid synthases (FAS), we sought to determine if fatty acid biosynthesis colocalizes with either chloroplast or cytosolic PKSs. [(3) H]acetate labeling showed fatty acids are synthesized in the cytosol, with little incorporation in chloroplasts, consistent with a Type I FAS system. However, although 29 sequences in a K. brevis expressed sequence tag database have similarity (BLASTx e-value

Lithophyllum byssoides is a comm on coralline alga in the intertidal zone of Mediterranean coasts, where it produces biogenic concretions housing a high algal and invertebrate biodiversity. This species is an ecosystem engineer and is considered a target for conservation efforts, but designing effective conservation strategies currently is impossible due to lack of information abo ut its population structure. The morphological and molecular variation of L. byssoides was investigated using morphoanatomy and DNA sequences (psbA and cox2,3) obtained from populations at 15 localities on the Italian and Croatian coasts. Lithophyllum byssoides exhibited a high number of haplotypes (31 psbA haplotypes and 24 cox2,3 haplotypes) in the central Mediterranean. The psbA and cox2,3 phylogenies were congruent and showed seven lineages. For most of these clades, the distribution was limited to one or a few localities, but one of them (clade 7) was widespread across the central Mediterranean, spanning the main biogeographic boundaries recognized in this area. The central Mediterranean populations formed a lineage separate from Atlantic samples; psbA pairwise divergences suggested that recognition of Atlantic and Mediterranean L. byssoides as different species may be appropriate. The central Mediterranean haplotype patterns of L. byssoides were interpreted as resulting from past climatic events in the hydrogeological history of the Mediterranean Sea. The high haplotype diversity and the restricted spatial distribution of the seven lineages suggest that individual populations should be managed as independent units.

Since the 1990s red-tide blooms of Fibrocapsa japonica have frequently been observed in European waters; despite their recurrence also in the Adriatic coastal areas, they have never been conclusively linked to ichthyotoxic events. Since the toxicity of F. japonica is still under debate and its effects differ among the strains, in this study all the compounds previously postulated as involved in the toxic mechanism, such as brevetoxins, fatty acids and ROS, were screened for Adriatic strains. Whole algal extracts were analyzed for brevetoxin PbTx-2, which was not found, and for a qualitative and quantitative analysis of fatty acids. The fatty acid profile evidenced the presence of PUFAs, with considerable amounts of 18:4n-3, 20:4n-6, and 20:5n-3, as already found in different strains, but with a lower amount of arachidonic acid (20:4n-6). None of the PUFAs was released in the extracellular medium. Different toxicological assays (Vibrio fischeri, Artemia sp., haemolysis of fish erythrocytes) were performed using algal cellular, extracellular or subcellular samples as well as fractions of the algal extract, in order to identify the toxic compounds. The tested cultures were found to inhibit V. fischeri bioluminescence, to affect Artemia nauplii viability and to have haemolytic effects comparable to those previously observed in different strains. The solid phase extraction (SPE) of the Adriatic F. japonica extracts resulted in a high concentration of PUFAs in two main fractions, which caused mortality in Artemia nauplii and inhibition of V. fischeri bioluminescence. Fish (Dicentrarchus labrax) assays were also performed, reporting mortality after long exposure times and the cause of fish death was investigated. A significant increase of H2O2 in the tanks where sea basses were exposed to F. japonica was obtained, indicating that the presence of fish stimulates H2O2 production by algal cells and leading to the hypothesis of H2O2 involvement in F. japonica toxicity. The presence of oxidative stress in the exposed fish was confirmed by the increased malondialdehyde concentration in their gills. Overall these results indicate that since F. japonica cells can easily cling to fish gills, due to their high polysaccharide production, it is presumable that high PUFA amounts are released in loco, as a result of cell breakage, and that exert their toxicity together with ROS. This study shows that the Adriatic strains of F. japonica can be harmful to higher level organisms. Nevertheless a high cell density and a long lasting bloom are necessary to cause severe damage to fish gills or death for crustaceans.

Blooms of the toxic dinoflagellate Ostreopsis cf. ovata are usually associated with shallow and calm coastal waters, characterized by low nutrient concentrations. The algal cells typically cover the benthic substrates, such as the macroalgal and invertebrate communities and rocks, forming a mucilaginous film. Data reported on O. cf. ovate toxin production observed under both field and culture conditions show high variability in terms of toxic profile and cellular content; little is known about the environmental and physiological aspects which regulate the toxin dynamics. In this study, O. cf. ovata physiology was investigated using batch cultures supplied with nutrient concentrations similar to those found in the Adriatic Sea during the recurrent blooms and the observed cellular dynamics were compared with those found in a culture grown under optimal conditions, used as a reference. Data on the cellular C, N and P content during the growth highlighted a possible important role of the cellular nutritional status in regulating the toxin production that resulted to be promoted under specific intervals of the C:N and C:P ratios. The variable toxicity found for 0. cf. ovata in various geographic areas could be related to the different in situ prevalent environmental conditions (e.g., nutrient concentrations) which affect the cellular elemental composition and carbon allocation. The obtained results strongly suggest that in the environment toxin production is steadily sustained by a low and constant nutrient supply, able to maintain appropriate cellular C:N (>12) or C:P (>170) ratios for a long period. These results explain to some extent the variability in toxicity and growth dynamics observed in blooms occurring in the different coastal areas. (C) 2016 Elsevier B.V. All rights reserved.

Fibrocapsa japonica resting cysts were detected in coastal sediments of the Marche region (northern Adriatic Sea, Italy), where summer blooms regularly occur. Sampling was carried out along 18 transects (2 stations each) during May–June 2007. The identification and counting of raphidophyte cysts were carried out under the inverted microscope and molecular analyses were applied to sediment samples to confirm species-specific identification. Raphidophyte cysts were recorded in almost all stations with maximum abundance of 9 ± 5 and 12 ± 3 cysts g−1 dw for cysts of F. japonica and undetermined Raphidophyceae, respectively. Cyst formation was induced in F. japonica monoclonal cultures under different conditions: shadow-optimal temperature and dark-low temperature treatment; both experiments were performed at two salinity values (30 and 35). Cyst formation (preliminary cysts) was observed in both experiments, although with different encystment rates. However, only a further permanence in the dark at 15 °C in microplates led to the formation of mature cysts, probably supported by the possibility to adhere to solid surfaces. Before pre-cyst formation, vegetative cells showed a cytoplasmatic “brown body”.