Insights into the harmful algal flora in northwestern Mediterranean coastal lagoons revealed by pyrosequencing metabarcodes of the 28S rRNA gene

This study investigated the genetic diversity of phytoplankton communities in six shallow lagoons located on the French coast of the northwestern Mediterranean Sea that represented a trophic gradient ranging from oligotrophic to hypereutrophic. The phytoplankton communities were sampled once a month from spring (May) to the beginning of autumn (September/early October) in 2012 and fractionated by size. Metabarcodes were generated from cDNAs by targeting the D1-D2 region of the 28S rRNA gene and pyrosequenced using Roche 454 technology. Examination of the annotated barcodes revealed harmful algal species not previously documented in these lagoons. Three ichthyotoxic species belonging to Pfiesteriaceae were detected: Luciella masanensis was relatively widespread and abundant in many samples, whereas Pfiesteria piscicida and Stoeckeria changwonensis were found as single barcode sequences. Furthermore, a phylogenetic analysis of barcodes annotated as belonging to Pfiesteriaceae suggested the existence of two previously undescribed clades. The other toxic or potentially harmful dinoflagellates detected through rare barcodes were Dinophysis acuminata, Vulcanodinium rugosum, Alexandrium andersonii and A. ostenfeldii. The two most abundant dinoflagellate taxa were Gymnodinium litoralis and Akashiwo sanguinea with respect to sequence numbers. Four diatom species from the genus Pseudo-nitzschia that potentially produce domoic acid were identified (P. galaxiae, P. delicatissima, P. brasiliana and P. calliantha). These observations are discussed in terms of the literature and monitoring records related to the identified taxa in this Mediterranean area.     

Striking convergence in the mouthpart evolution of stream-living algae grazers

This scanning-electron microscopic study demonstrates the convergent evolution of the mouthparts of various herbivorous stream animals (insects from different orders, an isopod, snails, fish, and a tadpole) feeding on epilithic algal pastures. This food source is rich but is often difficult to harvest. Nevertheless, a large number of species can live on it because they have evolved highly specialized mouthparts. There are four functional problems that an algae grazer has to solve: the algae must be removed from the stone, they have to be collected and crushed, and a current shield is needed to prevent the water flow sweeping away the food. Among the 30 algae grazers examined in this study, a limited number of morphological solutions have been found for each of these adaptational problems. There are multiple evolutionary pathways for mouthpart adaptation and even closely related species have often evolved different types of tools for the same function. This refects the existence of a certain amount of evolutionary scope. Such freedom of evolution is present, however, only at the beginning of the adaptiogenesis of an algae grazer. Once one of the evolutionary pathways is taken, further improvement of the mouthparts is possible only by the refinement of the ‘chosen’ type of tools. The consequence of this is that a large number of astonishing convergences have occurred in algae grazers that have independently trodden the same evolutionary pathway.     

The distribution of benthic marine algae in relation to the temperature regulation of their life histories

Mainly on the basis of the distribution patterns of 42 species of the recently revised genus Cladopkora (Chlorophyceae) in the north Atlantic Ocean, it appeared possible to distinguish 10 phytogeographic distribution groups of wide applicability. Experimentally determined critical temperatures limiting essential events in the life histories of 17 benthic algal species were used to infer possible phytogeographic boundaries; these appeared to fit closely the phytogeographic boundaries derived from field-distribution data. For a temperate species, at least six different boundaries can be postulated and should be checked in the northern hemisphere: (1) the ‘northern lethal boundary’ (corresponding to the lowest winter temperature which a species can survive); (2) the ‘northern growth boundary’ (corresponding to the lowest summer temperature which, over a period of several months, permits sufficient growth); (3) the ‘northern reproductive boundary’ (corresponding to the lowest summer temperature permitting reproduction over a period of several months); (4–6) the corresponding southern boundaries. Photoperiodic responses may influence the temperature responses. Many phytogeographic boundaries appear to be of a composite nature. For instance, the southern boundary of Laminaria digitata follows the European 10°C February isotherm (which corresponds to the highest winter temperature permitting fertility in the female gametophyte, i.e. to the ‘southern reproductive boundary’), and the American 19°C summer isotherm (corresponding to the ‘southern lethal boundary’). Thus, experimental evidence supports the validity of eight of the following 10 distribution groups (for distribution groups 2 and 6, such evidence could not be found): (1) the amphiatlantic tropical-to-warm temperate group, with a north-eastern extension (examples: Gracilaria foliifera and Centroceras clavulalum); (2) the amphiatlantic tropical-to-warm temperate group, with a north-western extension (example: Hypnea musciformis); (3) the amphiatlantic tropical-to-temperate group (example: Sphacelaria rigidula =furcigera); (4) the amphiatlantic temperate group: the Cladophora rupestris type (examples: Callithamnion hookeri, Dumontia contorta; Laminaria saccharina is transitional to type 10, I., digitata to types 5 and 10); (5) the amphiatlantic temperate group: the Cl. albida type (examples: Scytosiphon lomentaria, Petalonia fascia); (6) the tropical western Atlantic group; (7) the north-east American tropical-to-temperate group (example: Gracilaria tikvahiae); (8) the north-east American temperate group and the corresponding Japanese temperate group (examples: Campylaephora hypneoides and Sargassum muticum); (9) the warm-temperate Mediterranean-Atlantic group, and the corresponding warm-temperate Californian group (examples: Saccorhiza polyschides, Laminaria hyperborea, I., ockroleuca, Macrocystis pyrifera, Hedophyllum sessile); (10) the Arctic group (examples: Saccorhiza dermatodea and Sphacelaria arctica). Distribution groups 6, 9 and 10 have comparatively narrow temperature ranges with a span of 18 22°C between their lethal boundaries and of 5 12°C between their reproductive or growth boundaries. These narrow temperature ranges limit the species in these groups to the tropics; the temperate coasts on the eastern sides of the north Pacific and north Atlantic Oceans and in the southern hemisphere; and to the Arctic, respectively. The narrow temperature ranges of group 9 make the species in this group unfit for life on the western temperate coasts of the north Pacific and north Atlantic Oceans, where algae must cope with annual temperature fluctuations of more than 20°C. Conversely, algae in group 8 (containing the numerous Japanese endemic species) are characterized by wide temperature spans (e.g. 29°C between ‘lethal boundaries’, 12–19°C between ‘growth and/or reproductive boundaries’) and must be potentially capable of occupying wide latitudinal belts on temperate coasts along the east sides of the north Pacific and north Atlantic Oceans. Algae ‘escaped’ from Japan, such as Sargassum muticum, conform to this picture. Apparently Japanese algae do not have the capacity for long distance dispersal. The corresponding east American coasts (30–45 N) harbour very few endemic species, probably as a result of the adverse nature of these sediment coasts for benthic macroalgae and their functioning as a barrier to latitudinal displacements of the flora during glaciations. The remaining distribution groups (1,2,3,4,5,7) are characterized by wide temperature spans and wide distributions, often in both the Atlantic and Pacific Oceans and in both hemispheres. Six temperate species (in distribution groups 4, 5 and 9) with an amphiaequatorial distribution have similar winter-temperature maxima permitting reproduction and corresponding with winter isotherms of 15–17°C; their upper lethal temperatures are more dissimilar and correspond with summer isotherms of 20–30°C. Their amphiaequatorial distribution can be explained by assuming glacial temperature drops along east Pacific and east Atlantic equatorial coasts in narrow belts of intensified upwelling during the presumably intensified glacial circulation of the ocean gyres.     

COLONIZATION AND SUCCESSION OF ALGAE AND SOIL-ALGAL INTERACTIONS ASSOCIATED WITH DISTURBED AREAS1

The number and abundance of algal species were not significantly different between non-topsoiled areas and top-soiled areas. Successional trends were evident at both sites, since the number of species and their abundance increased over time. Soil-algal interactions were determined by regression analysis. A conceptual model was developed that illustrated the influence of soil chemical properties on algal abundance. Important factors affecting the soil algae were sodium, calcium, potassium, magnesium and certain trace elements. The possible influence of these factors on algal growth is discussed.     

Manganese-54 accumulation by Chlorella spp., Daphnia magna and yellow perch (Perca flavescens)

Concentration factor and biological half-life of ⁵⁴Mn were determined in three species representing an ecologically and economically important food chain. Green algae (Chlorella spp.), Daphnia magna and yellow perch (Perca flavescens) were exposed to ⁵⁴Mn in water and assayed for ⁵⁴Mn uptake. Steady state concentration factors computed from the laboratory data for algae, Daphnia and perch were 4230, 17 000 and 11, respectively. Respective biological half-lives were 1.6, 1.2 and 8.3 days.     

Vanadate-sensitive proton efflux by filamentous cyanobacteria

Abstract Light-induced proton efflux has been investigated with intact cells of Anabaena, Nostoc, Anacystis , and Aphanocapsa . The proton efflux by filamentous blue-green algae is biphasic, strongly inhibited by ortho -vanadate and insensitive to cyanide. These data are taken as evidence for a proton-pumping ATP-hydrolase present on the cytoplasmic membrane of Anabaena and Nostoc .     

Possible mechanisms for the inhibition of photosynthesis by ozone

Tropospheric ozone produced by industrial civilization is widespread. Although the levels are not clearly life threatening, they do have the potential to inhibit normal plant productivity, thought to be by an inhibition of photosynthesis. While the mechanism for this inhibition is not yet clear, there are several hypotheses for its cause. It is unlikely that ozone can penetrate the cell membrane unreacted; therefore, reactions at the plasma membrane either causing general ionic and metabolic disturbance within the cell or causing the production of unidentified toxic products must ultimately produce the alterations within the chloroplasts. While model systems, such as individual biochemicals, isolated chloroplasts, and algae, can give some understanding of possible reactions, they cannot provide the full story. One continuing controversy revolves about the role of stomata in the inhibition process-they play an important role, but the full interaction between stomatal closure and inhibition of photosynthesis has not yet emerged. In order to reach a political compromise on air quality standards, we need to have a good understanding of the fundamental mechanisms by which ozone causes any decline in plant productivity.     

Ichtyotoxic activity of extracts from Mexican marine macroalgae

Seventy-three species of macroalgae from the Mexican Pacific, Atlantic and Caribbean coast were screened for ichtyotoxic activity. Ethanolic, acetonic and aqueous extracts were prepared and tested against the fish Carassius auratus. The extracts were classified on the basis of their effects as: toxic if the fish died in two hours or less; moderately toxic, if the organism behaved abnormally but death did notoccur, and non-toxic if the fish did not display any change. 79% species were ichtyotoxic to some degree. Extracts of 39 species were toxic, with at least one extract with lethal effects, 19 were moderately toxic and 15 species were non-toxic. Only the extracts ofDictyota bartayresiana, Dictyota cervicornis,Lobophora variegata, Bryothamnion triquetrum and Laurencia obtusa were toxic in all three solvents. The acetone and ethanol extracts were more active, and therefore are more suitable for extraction of toxic substances. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of chlorophyll concentrations on the reliability of measurements with an oxygen electrode when studying photosynthetic efficiency in bioassays using microalgae

Euglena gracilis and Chlamydomonas reinhardtii were used as model organisms to establish the best conditions for studying photosynthetic efficiency using the Light Pipette – experimental system, which enables sensitive detection of changes in oxygen evolution/consumption and an easy collection and digitalisation of data. Chlorophyll concentrations of 0.005, 0.025, 0.050 and 0.075 mgmL^-1 were investigated using different light regimes. Cultures of E. gracilis at the same chlorophyll concentration absorbed more light(measured at 580 μmol m^-2 s^-1) than those of C. reinhardtii. Cell density had a considerable effect on the reliability of measurements. Chlorophyll concentrations between 0.025 mg_Chl ml^-1 and 0.050 mg_Chlml^-1 can be recommended when applying the Light Pipette system in bioassays using microalgae. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of seaweed preparations on murine immunocytes

During a screening programme for new medical agents, many aqueous extracts from 59 species of seaweed were found to possess bioactivity against murine immunocytes. Thirty-eight extracts (8 green, 12 brown, 18 red algae) showed suppressive effects on the mitogenic response. Furthermore, 16 extracts (2 green, 6 brown, 8 red algae) suppressed the production of Interleukin 1 (1L-1) from murine macrophage. Using the murine mixed lymphocyte reaction assay, suppressive effects were observed in 4 red algae, but none in green or brown algae. Nine seaweed extracts suppressed the production of secondary antibody (IgG, IgM). Extracts of 3 red algae suppressed strongly the proliferation of bone marrow cells, but 2 other red algae caused stimulation above 200%. This is apparently the first report showing immunosuppressive activity from marine algae.