Volume 49, Issue 4

In vivo chlorophyll fluorescence measured by pulse amplitude modulated (PAM) fluorometry was used as an indicator of photosynthetic activity in tank-cultivated red algae [ Gracilaria cornea and Asparagopsis armata (tetrasporophyte phase, previously known as Falkenbergia rufolanosa )] using effluent seawater from sea bream fishponds (Sparus aurata ). Optimal quantum yield of indoor-grown G. cornea did not change during the period analysed (2 months). In contrast, optimal quantum yield decreased drastically in algae transferred from indoor to outdoor conditions. Maximal electron transport rate increased and photosynthetic pigments decreased in algae growing outdoors, indicating an acclimation to high irradiance. After 16 days, chlorophyll fluorescence decreased drastically and recovered partially when algae were transferred again from outdoor to indoor conditions. Falkenbergia rufolanosa was grown at three different biomass densities (4, 6 and 8 g l -1 ). The effects of three consecutive air compressor failure events on the photosynthetic activity were followed. An apparent degradation of the physiological conditions of the algae (resulting in their bleaching) was observed, concomitant with a strong decrease in the optimal quantum yield. This decrease was higher at algal biomass densities of 4 g l -1 than at 6 or 8 g l -1 . Three days after transfer to optimal conditions, i.e., normal aeration conditions, optimal quantum yield reached values around 0.50–0.55, close to the values before stress conditions. The results revealed that the use of chlorophyll fluorescence is a powerful means to rapidly detect different stress situations in integrated cultivation of seaweeds using fishpond effluents. In particular, the optimal quantum yield of algae can be monitored regularly as an early warning of the physiological stress in cultures.

Dwarf embedded Fucus populations in the Northwest Atlantic Ocean are restricted to the upper intertidal zone in sandy salt marsh environments; they lack holdfasts and are from attached parental populations of F. spiralis or F. spiralis × F. vesiculosus hybrids after breakage and entanglement with halophytic marsh grasses. Dwarf forms are dichotomously branched, flat, and have a mean overall length and width of 20.3 and 1.3 mm, respectively. Thus, they are longer than Irish (mean 9.3 mm) and Alaskan (mean 15.0 mm) populations identified as F. cottonii . Reciprocal transplants of different Fucus taxa in a Maine salt marsh confirm that F. spiralis can become transformed into dwarf embedded thalli within the high intertidal zone, while the latter can grow into F. s . ecad lutarius within the mid intertidal zone. Thus, vertical transplantation can modify fucoid morphology and result in varying ecads. Microsatellite markers indicate that attached F. spiralis and F. vesiculosus are genetically distinct, while dwarf forms may arise via hybridization between the two taxa. The ratio of intermediate to species-specific-genotypes decreased with larger thalli. Also, F. s. ecad lutarius consists of a mixture of intermediate and “pure” genotypes, while dwarf thalli show a greater frequency of hybrids.

The life cycle of the red alga, Furcellaria lumbricalis, is poorly known in the northern part of the brackish water Baltic Sea, even though it is one of the most common red algal species in the region. To study its life cycle and reproduction, monthly sampling (n=30/sampling site) was carried out for one year on the coast of Finland at four locations spanning 500 km along a salinity gradient (3.6–5.4 psu). In three of the populations studied, only tetrasporangia and spermatangia were produced. In the fourth population, at the lowest (3.6 psu) salinity, all algae examined were vegetative. Winter months were the main season for tetrasporangial production, when sori with masses of sporangia were present. Smaller sori with only a few tetrasporangia were observed during spring at higher salinities, and some sporangia were detected in the population at 5 psu salinity, even during the summer months. The timing and intensity of reproduction was regulated by a combination of factors including seawater salinity, along with seawater transparency, temperature and photoperiod. In conclusion, we hypothesise that three of the populations, living at salinities between 4.9–5.4 psu reproduce by thallus fragmentation and possibly by asexual tetraspore-to-tetraspore cycling without meiosis, and the fourth population, at a salinity of 3.6 psu, survives by thallus fragmentation and reattachment.

Reproductive morphology of the Mediterranean red alga Kallymenia patens is described for the first time, confirming its position in the genus. K. patens is characterized by a non-procarpic female reproductive apparatus, carpogonial branch systems consisting of supporting cells bearing both three-celled carpogonial branches and subsidiary cells that lack a hypogynous cell and carpogonium; fusion cells develop numerous connecting filaments, and tetrasporangia are scattered over the thallus and are probably cruciately divided. Old fertile spathulate specimens of K. patens are morphologically similar to K. spathulata, but they can be distinguished by the length of spathulated proliferations (up to 0.6 cm and 6 cm, respectively), the length of inner cortical cells (up to 70 and 30 μm, respectively), and the gonimoblast location (in proliferations from the perennial part of the blade and over all the thallus surface, respectively).

We compared epifaunal and epiphytic assemblages on the invasive alga, Codium fragile ssp. tomentosoides , with those on native kelps, Laminaria longicruris and L. digitata , at a moderately exposed site on the Atlantic coast of Nova Scotia. Thalli of each algal host ( Laminaria and/or Codium ) were sampled in two stands with monospecific canopy cover and one mixed canopy stand ( Laminaria and Codium ) in June and November 2004 and February 2005. Epifaunal assemblages on both fronds and holdfasts differed between algal species and among months, but no differences were detected between mixed and monospecific stands for each host type. Fronds of Laminaria supported greater densities of gastropods and asteroids, while amphipods, harpacticoid copepods, and a specialist herbivore ( Placida dendritica ) were more abundant on fronds of Codium . Holdfasts of Codium supported greater densities of nematodes and bivalves. Diversity of epifauna was greater on fronds of Codium than Laminaria and similar on holdfasts of both species. Codium supported a greater density of epiphytes than Laminaria . Total frond area of Laminaria and/or Codium and density of epifauna per m 2 of substratum did not differ between stands. Our results suggest that habitat selection by epibionts is likely determined by specific chemical, structural and morphological characteristics of the algal species, rather than the amount of habitable area available for colonization.

We performed an in situ experiment raising the concentration of organic matter in sediment relative to the natural concentration, and quantified biomass development of the invasive alga, Caulerpa taxifolia , and native C. prolifera . Our objective was to determine whether vegetative development of C. taxifolia is favored in sediments with a high content of organic matter. The number of stolon apices and fronds, and the total dry weight of C. taxifolia at the end of the experiment increased relative to initial values in the “natural” sediment, while those in the “organic matter-enriched” sediment did not change. As a result, the vegetative development of C. taxifolia in the “organic matter-enriched” sediment was marginally lower than that in the sediment with natural concentration of organic matter. The contention that the vegetative development of the invasive C. taxifolia is favored in sediments with a high content of organic matter is not sustained. Additionally, we wanted to evaluate whether the presence of an external source of dissolved organic carbon (DOC) would facilitate the survival of Caulerpa taxifolia and C. prolifera under conditions unfavorable for biomass development. To this end we performed two laboratory experiments (one under light-saturated and another under light-limited conditions) where we maintained fragments of C. taxifolia and C. prolifera in the presence of different low molecular weight DOC compounds and assessed the survival of the two species. Mortality of Caulerpa fragments occurred under light-limited conditions only and showed no relationship to the presence of any of the low molecular weight DOC compounds tested. Our results, therefore, do not provide support for the contention that the presence of low molecular weight DOC compounds could contribute to alleviating negative effects associated with light-limited conditions.

We examined the effects of varying light intensity on fatty acid composition in symbiotic dinoflagellates (SD) isolated from hermatypic corals Millepora intricata , Pocillopora damicornis , Seriatopora caliendrum , Seriatopora hystrix and Stylophora pistillata . The corals were subjected to 95%, 30%, 8% and 2% of incident photosynthetic active radiation (PAR). Irradiance had a significant effect on fatty acid composition of polar lipids and triacylglycerols. SD showed substantial changes in the proportion of 16:0 as a response to variation in PAR. During adaptation to high light, the percentage of 16:0 increased in polar lipids and triacylglycerols. Additionally, the percentage of 14:0, 16:1(n-7) increased in triacylglycerols. Thus, high light conditions lead to an increase in storage products. Polar lipids of SD adapted to low levels of PAR had greater concentrations of 18:4(n-3), 20:5(n-3), 18:5(n-3) and 22:5(n-6) which are commonly involved in the formation of thylakoid membranes. Conversely, the amounts of 20:4(n-6) and 22:6(n-3) increased with increasing irradiance, suggesting an association with photosynthesis. The elevation in percentages of 18:4(n-3), 20:5(n-3) and 18:5(n-3) during exposure to low light was accompanied by an increase in chlorophyll a content in the SD cells. Light-dependent changes in fatty acid composition are probably due to the correlation of activity of photosystems with processes of production and desaturation of fatty acids.

In a study of structural diversity in the total pool of phlorotannins in brown algae, we have shown, for the first time in any alga (by means of solvent partition and NMR experiments), that Fucus spiralis has simultaneous production of two types of polymeric phlorotannins of the fucol and fucophlorethol classes, respectively. These components exhibited a greater antioxidant activity than ascorbic acid and the monomer phloroglucinol, a constitutive of the polymeric phlorotannins. No significant differences in antioxidant activity were observed between fucol and fucophlorethol.

Callus-like filaments of Halymenia sinenis were induced from different-sized healthy thalli and overgrown discoid crusts. The plant hormones IAA and 6-BA did not affect induction of filaments in cultures maintained in sterilized seawater. Percentages of filament induction from the thalli and overgrown discoid crusts were about 80% and 90%, respectively. The filaments grew normally between 13 and 23°C (best at 18°C), and between 10 and 15 μmol m -2 s -1 photon fluence. Photon fluence over 50 μmol m -2 s -1 harmed growth. In continuous culture of filaments attached to the substratum, discoid crusts formed and developed into erect juvenile germlings.

Rhodoliths are unattached calcareous red algae that form extensive beds. Although rhodolith beds are widely distributed in temperate and tropical areas, a recent discovery in the North Pacific Ocean represents a significant northward extension of known rhodolith distribution. This bed, located in Prince William Sound, Alaska, is composed of one rhodolith species, Phymatolithon calcareum , with two reproductive states, tetrasporangial and gametangial. A characteristic feature of this bed is that cryptofaunal chitons were the most abundant associated invertebrate species. Comparisons with P. calcareum populations in other regions showed that Prince William Sound thalli are smaller in many measurable anatomical features.

This is the first report of a detailed characterization of energy reserve glucans from a representative of the microalgal class Rhaphidophyceae (Ochrophyta). The hot-water extractable glucans from Haramonas dimorpha were shown by chemical and spectroscopic methods to be predominantly 1,3-β-D-glucans, with an average degree of polymerization of 12–16 residues and a relatively low proportion of side-branching with glucosyl residues. Based on their structural similarity with diatom glucans, H. dimorpha glucans should be referred to as chrysolaminaran.