Volume 48, Issue 4

Red algae of the order Bonnemaisoniales produce secondary metabolites that may be used as preservatives for industrial applications. Whereas species of Asparagopsis are cultured on a large scale for this purpose, no similar applications have been attempted for Bonnemaisonia species, despite evidence suggesting a similar potential for production of valuable natural products. Optimal conditions for growth of the Trailliella phase of Bonnemaisonia hamifera were assessed experimentally under controlled conditions. Several factors (temperature, photon irradiance, daylength, aeration, culture medium, concentration of nutrients) were tested. Optimal conditions for biomass production in Trailliella are represented by a combination of temperatures of 15–20°C, photon irradiances of 20–30 μmol photons m -2  s -1 and long daylenghts (16:8 h L:D). Quarter-strength von Stosch medium proved to be the best of those tested; aeration contributed also to a higher biomass production. Any attempts of large-scale cultivation should be performed therefore under similar conditions. The growth responses indicate that strains maintained in long-term culture collections can be successfully used for large-scale production.

Seasonal variations in vegetative growth and production of two seagrass species, Zostera asiatica and Z. marina , were investigated in Akkeshi Bay, northern Japan. Z. asiatica , a threatened species in Japan, was dominant, occurring from the intertidal zone to the deepest edge of the seagrass bed (5 m deep), whereas Z. marina was restricted to the shallower edge of the bed (<2 m). Above ground biomass and above ground net production per shoot were greater for Z. asiatica than for Z. marina . In contrast, shoot density was 3- to 4-fold higher for Z. marina . Biomass and production were minimum in winter to early spring (January to March), and maximum in summer (June to July) for both species. Annual production per unit area of Z. asiatica was larger than that of Z. marina (2033 and 1354 g DW m -2 y -1 , respectively). Our findings reveal contrasting growth patterns for the two species: Z. asiatica allocates more resources to enlarging shoot size, whereas Z. marina allocates more to increasing shoot density by clonal propagation of rhizomes. Seagrass beds consisting of Z. asiatica contributed importantly to coastal ecosystems in Akkeshi Bay area because of high productivity.

Intertidal irradiance, temperature, and aerial exposure were measured for two years in intertidal Zostera marina beds located in Yaquina Bay (Newport, OR, USA). These physical data were correlated with plant growth and other metrics measured at intervals during the study. Photosynthesis vs. irradiance (P vs. I) curves were determined by PAM fluorometry on plants along an intertidal gradient, and were used to estimate saturating irradiance (I k ) and daily hours of saturating irradiance (H sat ). Mean I k values were ∼64 μmol photons m -2  s -1 and H sat increased with increasing tidal position. Measurements taken during the second winter showed that H sat values in the low intertidal zone were within a critical range requiring eelgrass to use rhizome reserves to maintain carbon balance. However, plants continued to grow. Temperature differences across tidal gradients were not found to be physiologically important. These results suggested that temperature and irradiance were not limiting factors for intertidal Z. marina growth. High intertidal eelgrass, exposed to aerial conditions more frequently and for longer durations, exhibited signs of desiccation damage and appeared to have faster blade turn-over rates in spring and summer than their low intertidal neighbors. Thus, we concluded that the major factor limiting Z. marina in the upper intertidal zone was desiccation stress, which was acute and episodic rather than chronic.

Thecal morphology was studied, with an emphasis on sulcal plates, in 17 mainly tropical-boreal and tropical Protoperidinium species from the southeastern Mexican Pacific Ocean: P. brochii , P. claudicans , P. conicum , P. crassipes , P. depressum , P. divergens , P. elegans , P. excentricum , P. grande , P. latispinum , P. minutum , P. obtusum , P. oviforme , P. pentagonum , P. punctulatum , P. venustum and P. vulgare . These data were compared with those in published literature on the morphology of sulcal plates. Records of the species in the study region were compiled, and maps of global distribution for 11 are presented. The range of intraspecific variability in the morphology of sulcal plates still remains largely unknown, and accumulated relevant data need to be evaluated properly.

The membrane dye FM1-43 was used to visualise membrane internalisation in living cells of the marine centric diatoms Coscinodiscus wailesii and Thalassiosira punctigera . The results revealed dynamic and selective membrane trafficking and several cellular structures which have not been described in light microscopical studies. Intimate and regular contacts were found between the plasma membrane and the labiate processes and the inner face of the frustule in C. wailesii . The central cytoplasmic region close to the tonoplast and growing parts of the silica deposition vesicles became labelled, indicating that they were involved in membrane recycling. We never observed labelling of chloroplasts, nucleus or the vacuolar contents. These studies also revealed a novel perinuclear region that appeared not to show significant membrane turnover. When the cytoplasm was impaled with a micropipette, membranous material rapidly accumulated at the tip of the micropipette, presumably expelling it from the protoplast. This could be an effective defence mechanism against certain invasive pathogens, and further illustrates the highly dynamic nature of the endomembrane system.

Three new fungi are described from the halophyte, Juncus roemerianus , an endemic species in saltmarshes of the United States east coast. Pseudohalonectria halophila sp. nov. is an obligate marine fungus, whereas Phaeosphaeria anchiala sp. nov. is facultative, and Kolletes undulatus gen. et sp. nov. a terrestrial, but halotolerant hyphomycete. The taxonomic classification of P. anchiala in Phaeosphaeria is supported by phylogenetic analysis of the SSU and ITS region of the rDNA.

Crude extracts of Antarctic macroalgae were examined for toxicity to model strains of sympatric diatoms that could potentially foul them in nature. This is an initial step in determining the potential for ecologically relevant macroalgal defenses against fouling. Extracts of two species collected from McMurdo Sound were toxic to diatoms at or below concentrations originally present in the macroalgal thalli (the “natural concentration”). At least one extract type of all 22 western Antarctic Peninsula macroalgae was toxic at three-times the natural concentration and at least one extract type in 15 of these species was toxic at the natural concentration.

Various halophilic black yeasts were isolated from hypersaline water in solar salterns. Yeast population dynamics at different water salinities suggested the presence of several microhabitats. Sampling of wood immersed in hypersaline water containing up to 32% NaCl revealed frequent colonization with the black yeast species Trimmatostroma salinum and Hortaea werneckii . Growth on wood was determined by light- and scanning electron microscopy. Isolates of both species showed xylanolytic and lignolytic activity under hypersaline and non-saline conditions; T. salinum displayed cellulolytic activity as well. These results suggest an active lignicolous saprobic role of halophilic fungi in hypersaline water environments.