Volume 46, Issue 1

A third species of Chamaebotrys, C. erectus , is described from an upwelling region off Socotra Island, Yemen. The new species clearly displays one of the defining features of the genus, viz. terminal tetrasporangia in nemathecial sori. The nemathecia become diffuse when mature and produce secondary tetrasporangia. Tetraspores can apparently germinate in situ , resulting in compound thalli with tetrasporic and cystocarpic parts. Carpogonial branches are four-celled and cystocarps are protuberant, both of which features illustrate the affinities of Chamaebotrys with the closely related Coelarthrum .

Photosynthesis versus irradiance curves, and their photosynthetic parameters, as well as photosynthetic pigment contents and dry weight (DW):fresh weight (FW) ratios, were studied in gametophytes, young sporophytes and old sporophytes of the brown alga Ecklonia cava Kjellman. Gametophytes had the highest pigment concentrations [Chlorophyll (Chl) a , Chl c and carotenoids] when expressed on a FW basis, followed by young and old sporophytes. However, per area unit, old sporophytes showed higher pigment contents than young sporophytes. Dry weight:fresh weight ratios were twice as high in blades of old sporophytes as in those of young sporophytes, and old sporophytes had fifteen times higher DW per surface unit than young sporophytes. The maximum photosynthetic rate was significantly higher in gametophytes than in sporophytes when expressed on a FW basis, but when this parameter was expressed on Chl a and area basis, old sporophytes had the highest values. Dark respiration rates on a FW basis were significantly higher in gametophytes and young sporophytes than in old sporophytes. Photosynthetic efficiency (α) based on FW basis was higher in the early developmental stages, i.e., gametophytes and young sporophytes. In the sporophytic stage, when α was expressed on area basis, old sporophytes showed higher values than young sporophytes. Compensation light level (I c ) and light saturation parameter (I k ) were significantly lower in gametophytes and young sporophytes than in old sporophytes. These differences in photosynthetic performance among developmental stages may be related to thallus structure and light conditions at growth sites. The results of this study suggest that gametophytes and young sporophytes exhibit the characteristics of ‘shade-adapted’ plants, i.e., high pigment contents, high α, and low I c and I k , which serve to optimise photosynthetic performance under the canopy of adult sporophytes.

The tropical green seaweed, Caulerpa taxifolia has been invading the northwestern Mediterranean Sea since 1984, and has been discovered recently in California. This strain of C. taxifolia has proved an aggressive colonist, capable of vigorous growth on a variety of substrates. It can displace the native seagrasses and seaweeds, and its progress remains unchecked by grazers, which either avoid it or are poisoned by it. A variety of unsuccessful attempts have been made to curtail its spread. In this report we document the susceptibility of C. taxifolia to ionic aluminium. The exposure of whole fronds to 1 mM AlCl 3 causes complete inhibition of photosynthesis in less than 2 hours. The effect is irreversible. The ecologically important seagrass Posidonia oceanica is unaffected by this treatment. The unusually low internal pH of 4.0 found in Caulerpa taxifolia may explain its vulnerability to aluminium poisoning, since the highly toxic Al 3+ ion predominates at low pH. The results of this study provide the basis for the development of an environmentally sound means of selectively reducing the dominance of the aggressive strain of C. taxifolia in areas where it adversely affects the native plants and animals.

Three species of marine red algae are reported from Malaysia for the first time and their morphological features are described along with taxonomic comments. Hypnea charoides Lamouroux (Hypneaceae, Gigartinales) represents a geographic record intermediate between the Australian type locality and the Japanese islands in the Pacific Ocean. Hypnea flexicaulis Yamagishi et Masuda is reported for the first time outside Japan. Polysiphonia apiculata Hollenberg (Rhodomelaceae, Ceramiales) is transferred to Neosiphonia , as N. apiculata (Hollenberg) Masuda et Kogame, comb. nov. Furthermore, a minute-statured new species of Chondria (Rhodomelaceae), C. decidua Tani et Masuda, is described for an alga that is primarily distinguished from morphologically similar species by its production of small deciduous branchlets, which may function as propagules.

Interactive effects of settlement density, nutrient concentration and temperature on growth and survival of Sargassum muticum germlings were recorded over 45 days in laboratory cultures, using a factorial experimental design. Germling growth was stimulated by high temperature (17 °C compared to 7 °C) and nutrient enrichment (seawater enriched with 32 μmol nitrogen and 2 μmol phosphorus per litre), and negatively related to settlement density (in the range of 10–100 germlings cm −2 ). Survival was reduced when high settlement density was combined with high temperature and nutrient enrichment. After 45 days the size-distribution of germlings became positively skewed in some of the high-density stands, probably as a result of a few large individuals gaining dominance and suppressing many small plants. Intraspecific competition, defined as the relative reduction of germling growth and survival in high-density cultures compared with low-density cultures, increased during the course of the experiment, and depended on temperature and nutrient regime. As biomass accumulated in the stands competition increased more per biomass-unit at 7 °C than at 17 °C, which indicates a reduced tolerance to competition in germlings at the lower temperature. These results suggest the presence of intraspecific competition in stands of young S. muticum germlings, and a reduced growth and competition ability of germlings at low temperatures.

Alexandrium affine (Inoue et Fukuyo) Balech, isolated from Bahía Concepción (Gulf of California), was studied to determine the effect of environmental factors on cyst germination and vegetative growth. Alexandrium affine was homothallic and isogamous, and formed cysts in nutrient-deficient (N- or P-limiting) medium. The maturation period of newly formed cysts varied between two weeks and three months, depending on the storage temperature, with colder temperatures prolonging the process. The rate of germination increased with increasing temperature, and was not significantly influenced by light. Germination experiments suggest a broad temperature window for A. affine cysts, ranging from 5 to 25 °C. The optimal vegetative growth rates were 0.25 to 0.34 day −1 at 20–30 °C. No vegetative growth was observed below 15 °C or above 35 °C. With HPLC toxin analyses, we confirm that this species does not produce saxitoxins. These data on the dormancy, excystment, and growth characteristics seem to be regulated by the environmental constraints of this subtropical bay.

A checklist of Moroccan Ceramiales (Rhodophyceae), based on both literature records and some original data, is presented. The distribution of each taxon for this region (12 Mediterranean and 26 Atlantic localities) is given. Using present-day taxonomy, 161 species and infraspecific taxa of this order are accepted for the Moroccan coasts.

Differentiation of thermal traits (i.e. growth, survival and reproduction) was studied in the green macrophyte Valonia utricularis (Roth) C. Agardh, which has a world-wide tropical to warm-temperate distribution. Ecotypic differentiation between northeast Atlantic/Mediterranean and Indo-west Pacific isolates occurred with respect to all investigated temperature characteristics. The Atlantic/Mediterranean group is more eurythermal and cold-tolerant compared to the Indo-west Pacific group, which is stenothermal and cold-sensitive. Isolates of Atlantic/Mediterranean origin show clearly higher growth rates at low temperatures (lower temperature limit: 5–8 vs. 18–20 °C) and a much better tolerance to low temperatures than the Indo-west Pacific isolates (0–5 vs. 16 °C). Large shifts towards low temperatures are accompanied by parallel but smaller shifts at high temperatures. Differences in upper survival temperatures amounted on average to 4 °C (32–33 °C vs. 34–37 °C) and growth ceased in the Atlantic isolates at 30 °C, whereas the Indo-west Pacific isolates still reached significant growth at 33 °C. Additionally, temperature requirements for reproduction were shifted towards lower temperatures in the Atlantic/Mediterranean isolates [18–20 and 25 °C vs. 28–30(33) °C]. The cold-adapted Atlantic/Mediterranean ecotype retained a strong tropical imprint with high temperature tolerance and high growth rates at temperatures > 25 °C. The northern distribution limit in the northeastern Atlantic Ocean at 39 °N (at the 13 °C February and 17 °C August isotherms) is probably set by a growth and/or reproduction boundary. The northern distribution limit in the Pacific Ocean at 26 °N (at the 21 °C February and 29 °C August isotherms) is probably set by low lethal winter temperatures. The different latitudes of these boundaries must be attributed to the occurrence of more cold-adapted populations in the northeastern Atlantic Ocean compared to the northwestern Pacific Ocean. The development of cold-adaptation in the northeastern Atlantic Ocean and its absence in the northwestern Pacific Ocean has been related to different impacts of Pleistocene glaciations.

The Holocene diatom flora identified in three sediment cores from marine bays in the Windmill Islands (East Antarctica) is described and depicted for the first time. One hundred and twenty-four diatom taxa could be identified of which eighty-one taxa have a circum-Antarctic distribution. All taxa are listed in a table together with appropriate references and remarks on ecology and biogeography. The most diverse genera are Fragilariopsis , Navicula and Thalassiosira . Some taxa (e.g., Chaetoceros spp., Fragilariopsis curta, F. cylindrus , Navicula glaciei and Synedropsis spp.) have the potential to be used as indicator taxa for the reconstruction of palaeoceanographic conditions in the Windmill Islands.

The partial purification of UDP-glucose-4-epimerase was carried out on the red macroalga Solieria chordalis . A 60-fold purification factor was obtained by chromatography on DEAE Protein-Pack 8 HR and Superose 12. Gel-filtration fast protein liquid chromatography (FPLC) showed that the enzyme had an apparent molecular mass of 130 kDa. The UDP-glucose-4-epimerase from Solieria chordalis does not require complementary NAD addition for activity, unlike the enzyme from some other organisms. Moreover, the optimal pH was at 8.5 and the apparent K M values for UDP-glucose and UDP-galactose were 87 μM and 630 μM, respectively.