Volume 42, Issue 2

A comparison of the taxonomic composition of the diatom and dinoflagellate assemblages has been carried out for the south-eastern Barents Sea (Pechora Sea) and the south-western Kara Sea. All available literature and original data have been used in making the floristic lists which have been corrected for synonymy. The number of microphytoplankton species found in the south-western Kara Sea is somewhat higher than in the south-eastern Barents Sea (221 vs. 184 species respectively). The difference is most significant for the dinoflagellates (88 vs. 67 species). Diatoms formed a major part of the communities, accounting for 60% of the taxonomic composition in the Kara Sea, and 63% in the Barents Sea. In both regions, about 60% of the diatom assemblages are represented by centric diatoms, most of them being typical planktonic chain-forming species. A high similarity between the two areas was characteristic for most phytogeographical and ecological groups of the pelagic microalgae, and therefore we suggest that the plankton communities form a floristic entity with the status of a phytogeographical province. We name it the Novaya Zemlya Phytogeographical Province. The major reason for considering these two areas a biogeographical unit, is the similarity in the microphytoplankton assemblages and the stable water exchange which exists between the areas.

Seasonal occurrence and colonization of intertidal wood and introduced teak wood panels by marine fungi was investigated in Mangalore Harbour (west coast of India). Of the 33 taxa encountered, 29 taxa were found on intertidal wood and 15 on teak. The most frequently collected species on intertidal wood were: Trichocladium sp., Torpedospora radiata , Zalerion varium , Arenariomyces trifurcatus and Trichocladium alopallonellum (percent frequency: 15.7–22.6). On teak panels Antennospora quadricornuta was most frequent (89.6%) followed by Torpedospora radiata (23.5%). A maximum of seven taxa occurred per intertidal wood sample, wheareas three taxa occurred on teak. The species richness was highest during the monsoon period on intertidal wood, while it was highest during the summer on teak wood. More arenicolous species occurred on intertidal wood (9 taxa) than on teak panels (3 taxa). Among them Arenariomyces trifurcatus was most frequent (15.7%). Arenariomyces majusculus , Didymosphaeria lignomaris and Nimbospora effusa are new records for the Indian coast. The significance of these observations with respect to the earlier results on marine fungi in subtropics and tropics are discussed.

We examined the pattern of epiphyte accrual along the life-span of Posidonia oceanica leaves, both for the total epiphyte community and the main epiphyte groups (i. e. red encrusting algae and brown erect algae). Moreover, we document the importance of this epiphyte accrual pattern for evaluating P. oceanica -epiphyte interactions by assessing the dependence of the quantity and quality of light absorbed by epiphytes on their accrual pattern. Epiphyte biomass increased with leaf age following a sigmoidal curve (r 2 = 0.90, P < 0.001), both for the epiphyte community and for the two main groups. Total epiphyte biomass increased with leaf age at a rate of about 0.03 day −1 to reach a constant maximum value of 2.60 mg DW cm −2 on leaves older than 200 days. Brown erect algae grew about an order of magnitude faster (0.120 day −1 ) than red encrusting ones (0.017 day −1 ). However, the former group of algae reached their maximum biomass (1 mg DW cm −2 ) on 150 days-old leaves, whereas red encrusting algae continued to grow along the whole leaf life-span to reach a maximum biomass of 1.70 mg DW cm −2 . The non-linear increase in epiphyte biomass with leaf age involved a non-linear increase in epiphyte light absorption with leaf age, which reached a maximum constant value of 30% of incident light on 250 days-old leaves. Moreover, because red encrusting algae contribute a higher fraction to total epiphyte biomass on older leaves, we observed a shift in absorbed light quality with increasing leaf-age. Our results indicate the importance of accounting for the pattern of epiphyte accrual with leaf age when assessing seagrass-epiphytes interactions, especially for long-lived seagrass species where epiphytes may differ much in growth and biomass between young and old leaves.

The Uruguayan coastline extends for about 700 km between Brazil in the east and Argentina in the west. The coastal environment is affected by the seasonal and episodic variations in outflow of the Río de la Plata and its interaction with the subtropical convergence of the Brazilian and the Malvinas/Falkland currents. The benthic marine algae of that region have been largely neglected in comparison with other areas in the American Atlantic, and earlier accounts are mainly lists based on scarce material. Here we report the benthic marine algae occurring in Uruguay based on extensive collections and herbaria surveys. Seventy two specific and intraspecific taxa were found, 32 being new records for the region. In our view, Uruguay has a poor and transitional marine flora that includes members of the subtropical Brazilian flora and of the warm temperate flora of Argentina, together with several cosmopolitan species.

It is suggested that the evolution of marine mesoherbivores is influenced by the effect that these animals have on the host algae, the extent of food limitation and the ultimate factors controlling diet and habitat selection. Two contrasting models are proposed to explain the evolution of mesoherbivores: coevolution and sequential evolution. From the analysis of the available information on the biology and ecology of mesoherbivores it is obvious that: (i) no generalization can be made on the impact of mesoherbivores on the host algae, (ii) food limitation in mesoherbivores may be a common event, operating through diffuse competition, (iii) mesoherbivores have the potentiality to locate and colonize any host alga present in the habitat and, (iv) host selection, and possibly diet, is subordinate to habitat selection. Considering these results altogether, it follows that we cannot support or reject either of the two proposed models. Some suggestions are made for future research that might fill in the gaps in our knowledge of the biology and ecology of mesoherbivores.

In this paper, the metal accumulation in different fractions of the marine phanerogams Posidonia oceanica , Cymodocea nodosa , Zostera noltii and Ruppia cirrhosa and of the Chlorophyceae Caulerpa prolifera is studied on the Mediterranean Spanish coast. The distribution of the metals among the different parts of the plants was different for the five species. In Posidonia oceanica , Cd and Zn were accumulated to a higher degree in the leaves, and Pb in the roots. In Cymodocea nodosa , the four metals were found in higher concentrations in the leaves. In Z. noltii and R. cirrhosa , the highest concentrations of Hg, Cd and Pb were found in the roots, whereas Zn was equally distributed between roots and leaves. The rhizomes of C. nodosa showed higher contents of Zn than the roots, suggesting a translocation of Zn towards this part. Also the uniform distribution of Zn among the anatomic fractions of R. cirrhosa suggests some transport of this element. In C. prolifera rhizoids + stolons and fronds showed similar metal concentrations, indicating an appreciable mobility of the metals, probably due to the absence of internal cell walls. The five species varied in their bioaccumulation capacities. Thus, P. oceanica , Z. noltii and R. cirrhosa had the highest concentrations of Hg and Cd. In addition, P. oceanica showed the highest concentrations of Zn. Lead concentrations were very similar in all five species. For the phanerogams the relative bioavailability of the metals from the sediment was: Cd > Hg = Zn > Pb. In the alga the four elements showed similar concentrations to those in the sediment

Eight southern African seaweeds (5 Phaeophyta, 2 Rhodophyta and 1 Chlorophyta), previously shown to exhibit antibacterial activity, were analysed to assess the distribution of antibacterial activity in extracts from selected portions of their thalli. Seaweeds were separated into meristem and thallus (stipe, meristem and blade in the case of members of the Laminariales), milled, extracted and tested for antibacterial activity against ten Gram positive and Gram negative food-associated bacteria by agar diffusion. Extracts of the intercalary meristem of Ecklonia radiata showed significantly greater (P < 0.1) antibacterial activity than corresponding blade and stipe extracts, whereas Laminaria pallida showed a uniform distribution of antimicrobial activity throughout its thallus against all test bacteria. For seaweeds showing apical growth, the antibacterial activity of meristem extracts was either significantly greater (P < 0.1) or equal to that of thallus extracts. Thallus extracts never exhibited greater antibacterial activity than meristem extracts.

The yield, physical, and chemical properties of agars from two Philippine red seaweeds, Gracilaria eucheumoides and Gelidiella acerosa , were investigated on a bimonthly basis. The yield of agar from Gracilaria eucheumoides was at a maximum during the early rainy season (May, 29%) and at a minimum during the summer month of March (20%). In Gelidiella acerosa , a peak in agar yield was also recorded in May (21%), with generally higher yields recorded during the rainy than in the dry season. Agar gel strengths fluctuated from 225 to 430 g cm −2 and from 160 to 820 g cm −2 for Gracilaria eucheumoides and Gelidiella acerosa , respectively, and both agars exhibited strongest gels in July. Significant seasonal variations were observed in the gelling and melting temperatures of agar from Gracilaria eucheumoides , but not from Gelidiella acerosa . Sulphate content only varied slightly in agar samples from Gracilaria eucheumoides , while a higher sulphate content was found in Gelidiella acerosa agar during the dry season. Moreover, the sulphate content in G. acerosa agar fluctuated inversely with the 3,6-anhydrogalactose content. A FT-IR analysis showed a fairly constant spectrum for temporal Gracilaria eucheumoides agar while peaks attributed to S–O vibrations intensified in Gelidiella acerosa samples which were recorded to contain high sulphate residues and possess low gel strengths. Diagnosis of the FT-IR spectra in the 1000–400 cm −1 frequency range was also conducted in comparison with agarose and Gracilaria chilensis agar.

A mixture of water-soluble sulfated polysaccharides from the red seaweed Rhodomela larix (Turner) C. Ag. was fractionated into two fractions, PS1 and PS2, in terms of differences in solubility of their cetylpyridinium salts in potassium chloride solution. The main fraction, PS2, consisted of D-galactose (Gal), 3,6-anhydro-L-galactose (L-AnGal), 2- O -methyl-L-AnGal, sulfate and small amounts of L-Gal, 2- O -methyl-L-Gal and D-xylose. Analysis of the methanol-soluble partial methanolysis product from PS2 led to identification of disaccharide derivatives arising from agaroid-type repeating units, [→3)β-D-Gal(1→4)L-AnGal(1→] and [→3)β-D-Gal(1→4)2- O -methyl-L-AnGal(1→]. Furthermore, occurrence of both agaroid- and carrageenan-type repeats, [→3)β-D-Gal(1→4)α-L-Gal(1→] and [→3)β-D-Gal(1→4)α-D-Gal(1→], was discovered by analyses of the methanol-insoluble material remaining after the partial methanolysis. Sulfate groups in PS2 appeared to be located at O-6 of the (1→4)-linked L- and 2- O -methyl-L-Gal residues, O-6 of the (1→3)-linked D-Gal residue, O-2 of the (1→4)-linked L-AnGal residue and O-3 of (1→4)-linked D-Gal residue.

The life history of a marine dinoflagellate Pyrophacus steinii (Schiller)Wall et Dale was investigated using clonal cultures isolated from Tokyo Bay. The asexual reproduction is binary fission of the eleutheroschisis type. All processes of asexual and sexual cell division occur inside the theca of the mother cells. Sexual reproduction is anisogamous and heterothallic.Male gametes differ from female gametes and vegetative cells in size, shape and plate tabulation. The female gametes can not be differentiated from the vegetative cells. Cell fusion between the male and female gametes occurs within a few hours to several days after inoculation of the male gametes into a culture of a non-male clone. Zygotes are similar to the vegetative cells in shape except possessing two longitudinal flagella. One to two days after plasmogamy, the zygotes become non-motile, and their protoplasts contract. Within 1 to 3 days, following the condensation of protoplast, they transform to hypnozygotes (resting cysts). The specific features of the life cycle can be summerized as: i) the asexual reproduction is eleutheroschisis, ii) sexual fusion occurs after inoculation of the small round thecate cells, which are equivalent to male gametes, into a culture of a non-male clone, iii) male gametes are distinctive from vegetative cells in their smaller size, round shape, fewer plate number and pale chloroplasts, iv) female gametes can not be differentiated from the vegetative cells, v) the sexual life cycle is anisogamous and heterothallic.

The red alga Laurencia similis Nam et Saito (Rhodomelaceae, Ceramiales) from Borneo, Malaysia, contains two polybrominated indoles, 1-methyl-2,3,5,6-tetrabromoindole and 2,3,5,6-tetrabromoindole, as halogenated secondary metabolites, which have been previously isolated from Laurencia brongniartii J. Agardh. The two species share a unique taxonomic feature, the production of a single tetrasporangium-bearing periaxial cell per fertile segment, in the subgenus Laurencia . This similarity is strongly supported by halogenated metabolite chemistry. The close affinity between L. similis with spirally branched, terete thalli (section Laurencia ) and L. brongniartii with distichously branched, complanate thalli (section Planae Saito et Womersley) suggests that section Planae should not receive taxonomic recognition.