Volume 42, Issue 3

Species of Gracilaria in the western Pacific and the southeastern Asia are reviewed, giving 58 species and 4 varieties. A new subgenus, Hydropuntia is established and a list of the species and distribution in this region as well as a key to the species is provided.

Liagora tsengii sp. nov. (Liagoraceae, Rhodophyta) is described from St Kitts and Guadeloupe, Lesser Antilles, West Indies. Mature thalli are to 7–10 cm in height, pinkish grey, moderately to heavily calcified, mucilaginous, and dichotomously branched (often with numerous short proliferous lateral branches in older portions). Carpogonial branches are 4–5 celled and borne on the mid- or distal region of a mid-cortical supporting cell. Following presumed fertilization the zygote divides transversely and gonimoblast initials arise laterally from the distal daughter cell. A moderately diffuse gonimoblast is produced, although it does not intermingle with vegetative filaments. The lower gonimoblast cells and distal cells of the carpogonial branch coalesce and form a fusion cell. Post-fertilization sterile filaments arise from the basal cell of the carpogonial branch and occasionally from the supporting cell, and adjacent vegetative cells. Spermatangia are borne in clusters on spermatangial mother cells that arise from apical and subapical cells of assimilatory filaments. The new species differs from those previously included in the genus by its moderately diffuse gonimoblast and by the position of the post-fertilization sterile filaments. The former feature relates the new species to Liagora indica V. Krishn. et Sundararajan. Liagora tsengii differs from that species in the production of post-fertilization filaments from the carpogonial branch.

In order to verify the antiviral activity of extracts from Brazilian marine algae, aqueous cold extracts of eight species belonging to the classes Phaeophyceae, Rhodophyceae and Chlorophyceae were assayed for anti-herpes simplex virus (HSV-1) activity using an acyclovir-resistant strain. All extracts inhibited the propagation of HSV-1 in HEp-2 cells at non-toxic concentrations with Laminaria abyssalis the most potent species. These results suggest the Brazilian algae are promising sources of natural antiviral agents for the treatment of acyclovir resistant HSV-1 infections.

Photosynthetic performance, dark respiration, pigment concentration, tissue nutrient concentration and fresh : dry weight ratios were measured in juvenile and adult sporophytes of Undaria pinnatifida throughout the growing season from Port Phillip Bay. The photosynthetic rates (15 to 42 mg O 2 g −1 dw h −1 ) of Undaria pinnatifida sporophyte stages were higher on a dry weight basis in spring compared to summer coinciding with rapid growth of juvenile sporophytes in spring. Higher dw:fw ratios of adult Undaria sporophytes were found compared to young sporophytes. The seasonal trends in P max and α on a Chl a basis in juvenile plants are explained by higher pigment (Chl a , c , fucoxanthin) concentrations in spring than summer. Differences in pigment content and their ratios between sporophyte life stages may be indicative of light adaptation by juvenile plants. Lower saturated light requirement (I k ) and compensation points (I c ) were observed in spring compared to summer plants and lower I k values of juvenile sporophytes compared to adult sporophytes was also found during spring. Spring and summer compensation points in this study mostly ranged from 7.63 to 15.49 μmol m −2 s −1 . Low I k and I c , and high P max , α, and pigment content may enhance the capacity of juvenile Undaria to utilise low photon flux rates. No seasonal differences were found between respiration rates on a dry weight basis or between respiration in young and adult sporophytes. Respiration rates normalised to Chl a , were 2–3 times higher in summer in both young and adult stages. High C:N ratios (by atom) in juvenile (spring mean = 20.2; summer mean = 27.9) and adult sporophytes (spring mean = 11.32; summer mean = 18.6) indicate a higher accumulation of reserve carbohydrates by juvenile plants and N limitation in summer. Tissue C:N ratios increased in both stages from winter through to summer. Low N:P ratios in spring and summer for both stages (< 5) is also suggestive of N limitation. Overall the high N availability in Port Phillip Bay and the low light adapted physiological characteristics provide Undaria with a competitive advantage over other fast growing macroalgae.

Intertidal wood and decaying Rhizophora mucronata prop roots were collected from five mangrove stands in Mauritius. The higher marine fungi on the samples were identified and their percentage occurrence noted. Sixty-seven fungi were recorded from the intertidal wood samples. Lulworthia species were the dominant fungi on wood at all of the study sites. Forty-eight fungi were identified from dead parts of Rhizophora mucronata prop roots. The dominant fungus on the prop roots at each study site differed. The fungal communities on prop roots were slightly different from those on intertidal wood. The ascomycetes were the dominant group at all study sites. The diversity and occurrence of fungi at each of the study sites are compared and discussed in relation to the prevailing environmental conditions. Most of the taxa reported in this study are new records for Mauritius.

Historical records show that Chaetoceros furcillatus occurred sporadically in the Canadian Maritimes, but when abundant it grew in early spring for a few weeks following the decline of Thalassiosira nordenskioeldii and preceded the rise of C. debilis . Spores were present along with the vegetative cells even at early stages of the bloom, but they contributed most of the cell densities at the end of the maximum growth period. Spores sank out of the photic zone in a few days. Spore frequency correlated negatively to temperature and positively to salinity. Two spore morphotypes were found in our samples; paired, large cells with a fused (double) set of setae, and non-paired, small cells with a single (non-fused) set of setae. Non-paired spores are more frequently found in relatively less saline and somewhat warmer stations. Nevertheless, we interpret these two different spore types as a distinct morphological expression of the same species, perhaps at sub-specific level of a form. A nine year record shows a change in relative abundance of this species in Passamaquoddy Bay since 1991, and in the Outer Quoddy region since 1994. Chaetoceros furcillatus has become a consistent and a more abundant component of the local phytoplankton. Two alternative explanations for this increase are considered. Firstly, that the species demonstrates natural cyclicity of population dynamics. Secondly, it has responded to unidentified changes in the environment that result in increased abundance. We draw attention to the fact that this increase coincides with the growth of fish farming in this region. The mid-1980s marks the beginning of an explosive growth and the early-1990s mark economic commercialization of fish aquaculture industry. We also designate the lectotype of the species as a pair of spores on slide # 654 curated at the Farlow Herbarium Bailey Diatom Collection and restore the original epithet for this diatom.

Long-term sampling of the intertidal zone in southwestern Prince William Sound following the T/V Exxon Valdez oil spill provides the basis for a description of intertidal macroalgal community structure in the poorly studied protected waters of the northeast Pacific Ocean. Diagnostic species are described for three habitat types based on species abundances (cover and frequency). Mixed gravel/sand/silt (mixed-soft) sites are characterized by Fucus gardneri , mussels and barnacles in the mid-intertidal and by Cladophora sericea , Fucus , and Pilayella littoralis in the low intertidal zone; mussels and barnacles are common associates in the latter zone. Polysiphonia aff. tongatensis is found only at mixed-soft sites. Boulder-cobble sites are characterized by Acrosiphonia arcta , Fucus gardneri , and ‘ Ralfsia ’ sp. in the low zone; the mid-zone is mostly devoid of vegetation. Bedrock shores consist of a supralittoral Verrucaria fringe and a mid-intertidal Fucus -barnacle-mussel zone; the low intertidal is dominated by fleshy red algae at five of seven sites, with average cover exceeding 50%, although Fucus and a number of green algae are also diagnostic of these sites. Significant changes in species abundances over periods as short as 4 weeks are documented for a number of annual species, and interannual differences in species abundance and richness are also reported. Notable fluctuations of macroalgal species in time and space in southwestern Prince William Sound provide a challenge not just in characterizing community structure but also in ascribing changes to particular events.

In vitro carpospore release and germination experiments in Kappaphycus alvarezii (Doty) Doty farmed in Tawi-Tawi, Philippines, were conducted to develop new mariculture techniques for this carrageenophyte traditionally farmed for many years using cuttings. Carpospore release was assessed over 40 d. Maximum production was attained after fertile branches were exposed to air for a period of 0.5 to 1 h at 240 μmol photons m −2 s −1 and subsequently immersed in seawater at 200 μmol photons m −2 s −1 and at 30 and 35 ppt salinities. Highest average carpospore output from days 1 to 5 was 279,000 carpospore/g wet weight of thallus. Nutrient enrichment (F/2 medium) seems to have little effect on spore release. Carpospore settlement occurred 3–5 days after release. The first branch formed after 26 d in diluted F/2 (F/20) media at 35 ppt salinity and 160 μmol photons m −2 s −1 . Low irradiance (7 μmol photons m −2 s −1 ) and low or high salinities (25, 40 ppt) appeared to inhibit release and germling development. Higher levels of nutrients (F/2, F/20) enhanced growth of contaminants and reduced carpospore viability. Germling growth was highest in the more enriched medium (F/2) (10.57% growth d −1 ) when compared to F/20 medium (2.26 growth d −1 ).

The brown alga Sargassum muticum has been found attached in Sweden since 1987. This paper reports the distribution in Swedish waters based on 2 major surveys in 1993 and in 1996. Attached population were found along the entire eastern Skagerrak coast, and as far south as to the middle part of the eastern Kattegat coastline. The number of populations and population size decrease when going south, although the differences had dimished between 1993 and 1996. However, the number of new sites, as well as population numbers still increase. Areas with continuous populations can now be found along the NE Skagerrak coast, and isolated localities may also be found in the inner parts of the archipelagoes. No morphological differences were seen between plants from the more saline Skagerrak and the more brackish Kattegat. The maximum plant length recorded was 4.2 m. Sargassum muticum has definitely become a permanent member of the Swedish algal flora. Although the expansion into the Baltic is slow, it is most likely that, given time, the species will colonize suitable habitats in the entire Kattegat. The possibility of further expansion into the Baltic proper, with its low biodiversity, remains a subject for speculation.

In terms of widespread distribution and high population density Turbinaria ornata and Sargassum mangarevense are the most conspicuous organisms settled on the reefs in Tahiti and other high islands of French Polynesia. This study reports on quantitative investigations of the temporal and spatial patterns displayed by these two species. It was carried out at three different sites on Tahiti Island. Data dealing with density, maturity, size structure of the mature population, sex-distribution and fertility were collected over 16 months between November 1994 and February 1996. Turbinaria ornata and Sargassum mangarevense populations settle on the reef throughout the year with a peak in density during the cool season. A density gradient from the fringing reef to the outer biogenic ridge was evident. A peak in maturity and fertility was observed during the warm season. A dwarfism of thallus length was noticed in Turbinaria ornata on the outer biogenic ridge whereas it was not observed in Sargassum mangarevense . The populations of both species settled on the fringing reef and outer biogenic ridge, two physically and chemically unstable areas, exhibited a high sexual reproduction, whereas it was lower on the inner barrier reef. Whatever the area considered the period of reproduction of these two species extended throughout the whole year. The data collected during this study were used to explain the colonization of different habitats by these two species.

Random Amplified Polymorphic DNA (RAPD) markers were developed for genotyping in Laminaria digitata . Reproducible RAPD banding patterns were reliably obtained, using a quick micro-scale DNA extraction procedure. Intraspecific polymorphism was observed, allowing for unambiguous genotyping within sets of 3–4 sporophytes. A controlled crossing indicated that in this kelp RAPD markers are transmitted to the progeny in a Mendelian way. This approach was then applied to parentage analysis within a set of 30 anonymous sporophytes from a random cross experiment involving 4 parents. The parents of 26 offsprings were unambiguously identified, indicating that cross-fertilisation largely, if not totally, prevailed over self-fertilisation.