Volume 44, Issue 1

The relative resistances among cultivated ( Porphyra yezoensis T-14) and wild Porphyra yezoensis strains collected from natural populations, and the non-cultivated species of Porphyra ( P. tenera , P . tenuipedalis , P. lacerata , P. suborbiculata , P . seriata , P. kanyakumariensis and P. pseudolinearis ) to infection by the microbial pathogen Pythium porphyrae was investigated. Resistance was assessed by exposing the isolates to equivalent amounts of infective material (zoospores) and measuring two parameters, supported fungal biomass and amount of disease produced. The cultivated and the wild strains of Porphyra yezoensis were highly susceptible to infections by Pythium porphyrae with relative infection levels of 1.00 and 0.88, respectively. The noncultivated species were relatively resistant and displayed fewer infection sites and infected thallus areas. Porphyra suborbiculata (0.13) and Porphyra tenuipedalis (0.19) were most resistant to infections by Pythium porphyrae . Minimal amount of fungal biomass was supported by resistant strains in terms of mycelial proliferation rate and oospore production. Initial steps of host-pathogen interactions observed with scanning and epifluorescence microscopy on a susceptible ( Porphyra yezoensis T-14) and relatively resistant ( P . tenuipedalis ) species revealed significant differences. Relatively high numbers of Pythium porphyrae zoospores attached and encysted on to the susceptible strains relative to other resistant strains. Only a transient relation between encystment rate and degree of resistance was observed among different Porphyra species. The encysted zoospores immediately germinated, formed appressoria and penetrated the algal cells near the site of encystment on the susceptible cultivar strains. On relatively resistant Porphyra tenuipedalis thallus surface, cysts with germ tubes growing on the thallus surface without attempting to penetrate the host were observed. Induction of appressoria, an essential prelude of penetration, following cyst germination, was not observed. Rarely very few long germ tubes penetrating the algal cells, with delayed appressoria formation was observed on Porphyra tenuipedalis thalli.

Potosynthetic performance in response to UV radiation was measured in the red alga Gelidium pulchellum Turner (Kützing) from northern Portugal in the laboratory. The experiments basically consisted of exposures to three different UV radiation conditions (PAR + UV-A + UV-B; PAR + UV-A and PAR alone) using artificial lamps and cut off foils followed by incubations at low irradiance of white light to determine the recovery capacity. The effects of two different PAR backgrounds (105 and 480 μmol photon m −2 s −1 ) and two growth temperatures (15 and 25 °C) as additional factors were also assessed. The optimal quantum yield of fluorescence (F v /F m ) decreased after 12 h exposure to PAR + UV (equivalent to a weighted UV dose closed to 150 kJ m −2 ; from photoinhibition of PSII electron transport action spectrum). The electron transport was also impaired by UV radiation. The PAR background was a key factor determining the UV responses in this species: thalli exposed to high PAR background (480 μmol m −2 s −1 ) exhibited a greater degree of photoinhibition and a slower recovery than plants irradiated by 105 μmol m −2 s −1 . On the other hand, an incubation temperature of 15 °C exacerbated the effect of UV radiation on photosynthesis (increased photoinhibition) followed by a slowing down in the recovery kinetic compared to samples incubated at 25 °C. These results suggest that repair processes may be stimulated with increasing growth temperature.

The marine green alga Caulerpa cupressoides was shown to contain a lectin which was purified by α-lactose-agarose affinity chromatography, followed by gel filtration on Bio Gel P-100. The lectin agglutinated trypsin-treated erythrocytes from humans and various animals, but was more active against human blood group A erythrocytes. The lectin was inhibited by lactose and some of its derivatives and was very strongly inhibited by the glycoprotein porcine stomach mucin. The molecular weight (MW) of Caulerpa cupressoides lectin, determined by gel filtration on a Bio-Gel P-100 column was 44,700, while by SDS-PAGE in the presence of 2-mercaptoethanol, the lectin exhibited a single protein band with a MW of 23,158, suggesting that the lectin is a dimeric protein. The lectin was heat stable losing part of its activity only at 80 °C and higher. The lectin showed high concentrations of glycine, acidic amino acids and serine and a low content of basic amino acids. The carbohydrate content of 11.05% suggested that the lectin is a glycoprotein.

The formation and the growth of regenerated fronds from cultivated barbs of Asparagopsis armata were investigated according to an experimental design methodology. A maximal ratio of 3.3 mm regeneration/mm barb was reached for two media constituted of seawater complemented with iron sulfate, EDTA and potassium bromide. The first optimal medium was composed of [FeSO 4 7H 2 O] = 0.20 mg L −1 , [Na 2 EDTA2H 2 O] = 2.9 mg L −1 , [KBr] = 12.0 mg L −1 and the second one of [FeSO 4 7H 2 O] = 0.2 mg L −1 , [Na 2 EDTA2H 2 O] = 4.6 mg L −1 , [KBr] = 28.7 mg L −1 . Barbs excised from adult thalli were placed for 4 weeks in seawater enriched with several chemical substances at different concentrations. The experimental procedure involved: 1) the screening of the influencing compounds with an Hadamard design and 2) the investigation of their optimal concentrations according to a Doehlert design of response surface methodology.

Sargassum muticum (Fucales: Sargassaceae) has been present in Scandinavia since 1984. In Limfjorden, a shallow Danish sound, it has invaded the habitat of the indigenous Halidrys siliquosa (Fucales: Cystoseiraceae). Studies have suggested a displacement of indigenous relatives by Sargassum muticum and that this could be due to differences in life history strategies. Our study is the first to document the phenology of S. muticum at the northern part of its European distribution range (Scandinavia) and the first to document the phenology of Halidrys siliquosa . Thallus height and weight, species cover and tissue carbon, nitrogen and phosphorus were measured. For Sargassum muticum a strong seasonality with midsummer maxima, similar to previously published results from other European sites, was found. Halidrys siliquosa only exhibited moderate seasonality, if any. Hence, the two species were found to be functionally different and have different life histories. Our results support the idea that the competitive success of Sargassum muticum is caused by its pseudo-perennial life history compared to the truly perennial life histories of many indigenous relatives. Conversion factors between commonly used biometric measures were derived from the phenological data.

A walled and biflagellate green organism assignable to the genus Chlamydomonas was isolated from seawater samples collected from the Red Sea, and unialgal cultures (YA-SH-1) were established. They were examined with light and electron microscopy and compared with both previously described marine or brackish water representatives of Chlamydomonas and related genera including Chlorococcum and Cystomonas . The alga was characterized by numerous spherical granules which were situated at the periphery of the cell and which covered the entire cell surface. Ultrastructurally, these granules were lipoidal globules projecting outward from the cell membrane. Based on this unique morphology as a major diagnostic feature, C. perigranulata sp. nov. was proposed.

Marine wood-degrading fungi are believed to contribute to the settlement and growth of wood-borers in the sea. However, little information is available on the association between species of these two groups of organisms. In view of this, we studied the occurrence of marine lignicolous fungi and wood-borers in mango ( Mangifera indica Linn.) panels submerged at three test sites along the Mandovi and Zuari estuarine systems in the coastal waters of Goa, India, during different seasons. A total of 33 fungi (20 Ascomycota, 1 Basidiomycota, 12 Mitosporic fungi) and 8 wood-borers (7 Teredinids and 1 Pholad) were recorded. A wide gamut of distribution patterns of fungi and wood-borers was found. A high frequency of occurrence (> 20 %) and a broad spatial distribution was noticed in the case of four fungi. Two woodborers, likewise, were prevalent at all three sites. Several other fungi were also very frequent, but were restricted in their site distribution. Twenty-three fungi were rare or found infrequently (< 8%). Four of the eight wood-borers recorded were also of sporadic occurrence. The fungi Periconia prolifica and Antennospora quadricornuta and the wood-borers Martesia striata and Lyrodus pedicellatus were present on the wood throughout the year. On the contrary, growth of most fungi and five species of woodborers was adversely affected during the low salinity monsoons. Two fungi and one wood-borer colonized wood preferentially during the monsoon season. Contrary to earlier observations, more fungi appeared as early colonizers on wood during the first month of submergence than later. Our study indicates that in Goa waters, Periconia prolifica and Antennospora quadricornuta and the wood-borers Martesia striata and Lyrodus pedicellatus are highly versatile in their occurrence and were present throughout the year, at all sites. The numerous variations in distributional patterns observed in this study highlight the need to examine the response of marine fungi to physico-chemical parameters at the individual species level.

The massive growth of the dinoflagellate alga Cochlodinium polykrikoides in Korean coastal waters was first observed in 1982. Thereafter the blooms associated with massive fish kills have been occurring annually, and C. polykrikoides is now regarded a harmful red tide organism in Korea. Recently, a new chain-forming Gyrodinium impudicum , usually occurring with Cochlodinium polykrikoides , was observed. Thus, we need to identify the toxic C . polykrikoides from the non-toxic Gyrodinium impudicum . Because of a similarity in morphology, it is difficult to distinguish the two species under the light microscope. In this study, comparisons were made using fine-scale features of transverse sections and biochemical analysis including rDNA sequencing targeted ITS regions. The observation of cellular arrangement and structure by transmission electron microscopy showed a similar distribution of the main components in both species, but location of the nucleus and distribution of the chloroplasts were different. Fatty acid composition showed that the long-chain polyunsaturated fatty acid docosahexanoic acid was not present in Cochlodinium polykrikoides . These data suggest that fatty acid composition may be a useful biochemical indicator to distinguish the microalgae. The amount of total carotenoids in Gyrodinium impudicum was approximately 10 times higher than in Cochlodinium polykrikoides . The nuclear DNA content in Cochlodinium polykrikoides was twice as high as that in Gyrodinium impudicum ( p < 0.06). Sequence analyses coding for the 5.8S rDNA and ITS regions showed quite different nucleotide alignments with only 55% similarity, the length of the ITS regions also differed. The genetic differences between the two microalgae will allow the development of species specific DNA probes for species differentiation.

A new dinoflagellate species, Karenia longicanalis sp. nov. is described from a bloom, which occurred in mid-May, 1998 in Victoria Harbour, Hong Kong and the southwestern coastal waters of Hong Kong Island. Live cells have up to 30 yellow-green, round chloroplasts, each containing a pyrenoid, and a spherical centrally located nucleus surrounded by a ‘nuclear capsule’. The cell is slightly dorso-ventrally flattened, 17.5–35.0 μm long and 13.75–32.5 μm wide. The epicone and hypocone are hemispherical. The cingulum is displaced about 22% of the body length. A straight apical groove is located to the right of the sulcal axis and extends over the apex and 2/3 down the dorsal side of the epicone. The sulcus extends from the cingulum to the antapex, where it makes an antapical indentation or concavity. No fish kills were observed during this bloom. Karenia longicanalis sp. nov. closely resembles morphologically Karenia digitata and Gymnodinium mikimotoi , and thus belongs to the ‘ mikimotoi -complex’.

Split wood blocks of Bruguiera gymnorrhiza and Rhizophora mucronata were submerged in the intertidal zone at five mangrove sites in Mauritius and 61 higher marine fungi were identified. Retrieval of the blocks over regular intervals revealed no distinct colonisation patterns that were common to all study sites or either of the hosts. A few taxa were dominant during particular stages of colonisation. Cumulospora marina was strictly an early coloniser. Cirrenalia pygmea and Lulworthia species were more common as early colonisers. Lignincola laevis was more common as an early to intermediate coloniser. Periconia prolifica occurred throughout the experimental period at three of the sites, while Dactylospora haliotrepha , and Coelomycete sp. 20 were late colonisers. A relatively high percentage of the fungi colonising the test blocks were mitosporic fungi.

Five species of the red algal order Rhodymeniales are reported from Malaysia for the first time and their characteristic features are described: Chamaebotrys boergesenii (Weber-van Bosse) Huisman (Rhodymeniaceae), Coelarthrum sp. (Rhodymeniaceae), two species of Champia (Champiaceae), C. compressa Harvey and C. vieillardii Kützing, and Lomentaria monochlamydea (J. Agardh) Kylin (Lomentariaceae). The alga with vegetative features similar to the Chamaebotrys/Coelarthrum group is new to science and is characterised by the presence of a conspicuously developed, solid, cartilaginous stipe. This alga seems to be more closely related to Coelarthrum on the basis of its upright habit rather than Chamaebotrys , which has decumbent or prostrate thalli. The production of slender branches in Champia vieillardii is an additional critical feature that distinguishes it from a closely related species, C. compressa .

The sporogenic tissue, motile zoospores and non-motile embryospores of Laminaria saccharina were exposed to the different levels of the ultraviolet-B radiation (UV-B) (0.1–1.2 W m −2 ) over 12–24 h. At an irradiance of 1.2 W m −2 spore release began after 4 h exposure of the sporogenic tissue to UV-B. There were also many non-motile spores and the fragments of damaged sporangia found in the media. The motile zoospores ceased their movement after their treatment with UV-B of 1.2 W m −2 for 8210 h, although they retained their viability. The embryospores did not survive after 24 h exposure at an irradiance of higher than 0.6 W m −2 . Tolerance to UV-B attenuated in the following sequence: spores within the sporogenic tissue—motile zoospores—embryospores. Our results strongly suggest that UV-B effectively controls spore release, germination and further development of the early ontogenic stages of Laminaria saccharina.