Nitrogen and phosphorus uptake by the Brazilian kelp Laminaria abyssalis (Phaeophyta) in culture

The uptake of ammonium, nitrate and phosphate by laboratory-grown young sporophytes of Laminaria abyssalis was measured in a perturbed system (batch mode) at 18 °C and 35 ± 5 µE m^–2 s^–1 photon flux density. Uptake of all appeared to follow saturation-type nutrient uptake kinetics. The NO _inf3 ^sup– (K _s = 14.0 µM, V _max = 5.0 µmol h^–1 g^–1 dry wt) and NH _inf4 ^sup+ (K _s = 4.6 µM, V _max= 2.0 µmol h^–1 g^–1 dry wt) were taken up simultaneously, although NH _inf4 ^sup+ was taken up more rapidly. Values of K ₃ and V _max for phosphate were, respectively, 2.21 µM and 0.83 µmol h^–1 g^–1 dry wt. Nitrate and phosphate were both consumed in similar rates (V _max /Ks 0.37) at low concentrations. NH _inf4 ^sup+ , thus, might be a more efficient form of N fertilizer if artificial enrichment of seawater is used.     

Restriction enzyme analysis of variation and taxonomy in the kelp genus Laminaria (Laminariales,Phaeophyta)

High levels of phenotypic variation in kelp species necessitate the use of taxonomic markers that are independent of morphology. Restriction fragment length polymorphism (RFLP) analysis of nuclear DNA can provide such markers. In this paper we present the results of an RFLP analysis of cytoplasmic ribosomal DNA (rDNA) in three Laminaria species (L. agardhii, L. digitata, L. groenlandica). Comparison of the restriction maps of the nontranscribed spacer (NTS) in the rDNAs suggests that this method should be useful for the differentiation of these taxa. These results are discussed, as are the applications of RFLP mapping to the identification of field-collected, morphologically variable plants.     

Abundance changes in Laminaria setchellii and Pterygophora californica (Laminariales,Phaeophyta) near the Diablo Canyon Power Plant

Abundances of Laminaria setchellii and Pterygophora californica were determined three times per year for two years before startup of the Diablo Canyon Power Plant (DCPP) and thereafter for three years during which time the plant was in operation. The test site was situated at 3 m depth and was exposed almost continuously to heated effluent during plant operation. A control population was established about 60 m away from the test site and at an 8 m depth (i.e. lying below the heated plume). Abundances at both sites were relatively stable during the preoperational period. Abundances of Laminaria and Pterygophora declined, mortality increased, and recruitment ceased at the test site following plant operation and the discharge of heated effluent. In contrast, Laminaria abundance remained stable at the control site and a strong recruitment episode markedly increased Pterygophora densities during 1987, the final year of our study. Complete losses of Laminaria and Pterygophora were also observed in nearby shallow portions of Diablo Cove exposed to the thermal plume. Laminaria was more sensitive to heated effluent than Pterygophora. Adults of both species were more sensitive than juveniles.     

Growth and reproductive responses of Laminaria longicruris (Laminariales,Phaeophyta) to nutrient enrichment

A series of comparative culture experiments were conducted in order to determine responses of Laminaria longicruris male and female gametophytes and juvenile sporophytes to several temperatures (5, 10, 15, 20 °C), light levels (10, 35, 75 µmol m^–2 s^–1) and media nitrogen concentrations (0, 20, 100 µM ammonium-nitrogen). Responses were measured as numbers of male and female gametophytes producing gametangia and number of sporophytes produced following fertilization. Both male and female gametogenesis was reduced at 5 and 20 °C versus 10 and 15 °C. At 20 °C gametogenesis inhibition was greater with higher levels of ammonium-nitrogen concentration (100 µM). Sporophyte production was more sensitive to light, temperature and nitrogen concentration than gametogenesis. Production of sporophytes was inhibited completely at 20 °C. At lower temperatures, increasingly higher nutrient concentrations produced greater inhibition of production of sporophytes.     

A comparative analysis of wild and laboratory grown Laminaria abyssalis (Phaeophyta) using modulated fluorescence

Laminaria abyssalis fronds were either collected at the Brazilian costal area - 40 meters below sea level - or grown in the laboratory. The photochemical yield as defined by the Fv/Fm and the Fo - the dark fluorescence level when all PSII centers are open - varied with the distance from the stipe to the tip of the blade in wild grown fronds while it stayed constant in the laboratory grown plants. The chlorophyll a/c ratio levels decreased in the wild fronds from 12 (near the stipe) to 6 near the top. The chlorophyll c content increased from 0.8 to near 1.7 mg cm^–2 in the wild fronds. The laboratory fronds did not show variations in their chlorophyll contents. The wild fronds pattern changed after 2 months kept in the laboratory, producing similar results to those grown in the laboratory. The results indicate that the levels of the antenna complex in the wild fronds increase from the stipe to the top of the blade, in a fashion similar of the sun/shade leaves. Also, results show, that this alga is able to adapt itself to new light conditions, possibly increasing its level of antenna complex and photosynthetic units.Abbreviations PSII Photosystem II - Fo Chlorophyll fluorescence when all PSII are opened - Fm Chlorophyll Fluorescence when all PSII are closed - Fv Variable Fluorescence (Fm-Fo) - Fv/Fm Quantum Yield for Photochemistry     

Streblonema (Ectocarpales,Phaeophyceae) infection in the kelp Laminaria saccharina (Laminariales,Phaeophyceae) in the western Baltic

The brown alga Laminaria saccharina is the dominant subtidal macroalga in Kiel Bay, western Baltic. It is infected by the microscopic brown alga, Streblonema aecidioides. Infected thalli may show symptoms of Streblonema disease, i.e. alterations of blade and stipe, ranging from dark spots to heavy deformations and completely crippled thalli. Samples taken from a single locality all year round show that (i) the host population is infected at a high rate of 87±13% (SD), but that (ii) a considerable proportion of thalli containing Streblonema does not show disease symptoms, and that (iii) juvenile hosts, which mainly appear in autumn, are infected at almost the same rate. Thus the infection seems to occur early in the host's life. Juveniles in nature show fewer symptoms of the disease than adults. Two months after infection, oxygen production and growth in laboratory-raised experimentally infected juvenile hosts was not different from uninfected controls. Experimental thalli showed more severe morphological alterations than uninfected controls only four months after infection. Both field and laboratory observations indicate that a lag phase exists between infection and outbreak of the disease.     

Regeneration from callus of Undaria pinnatifida (Harvey) Suringar (Laminariales,Phaeophyta)

Calli were formed on the explants of midrib, meristem and immature stipe parts from freshly collected Undaria pinnatifida sporophytes. Each part was sterilized by Betadine and ethanol, and was cut into explants. The explants were incubated on an agar medium at 10 hours light and 14 hours dark photoperiod under a photon flux density of 80 µmol m^–2 s^–1. Callus was formed best on the explants of meristem parts at a temperature of 13 °C on PESI medium. Calli were cut off from the explants and were transferred into a sterile liquid PESI medium in flasks. Callus was dark brown in colour and was composed of well-pigmented cells. The cells were loosely bound and were separated by low power sonication, and were easy to attach to vinylon strings. From the calli formed on the explants of meristem parts, entire fronds were regenerated, but from the calli formed on the explants of midrib parts, only thin layered laminae were regenerated. The calli formed on the explants of immature stipe parts did not exhibit any regeneration at all.     

Surveys of Undaria pinnatifida (Laminariales,Phaeophyta) in Golfo Nuevo,Argentina

In December 1992, some sporophytes of the Asian kelp Undaria pinnatiftda were found growing subtidally at 6 m depth below A. Storni Port, Puerto Madryn, Argentina. During the winter of 1994, the species expanded significantly from its original location. Sporelings appear in early autumn and attain their maximum size (1.65 ± 0.10 m) during winter and early spring, when most of them become fertile. The fronds are lost in summer, with only some holdfasts and sporophylls surviving, and these disappear by the end of summer. The occurrence of U. pinnatida in Golfo Nuevo is reportedly due to an accidental introduction by cargo ships or fishing vessels arriving from Asian ports.     

Cultivation of Macrocystis integrifolia (Laminariales,Phaeophyta) in southeastern Alaskan waters

The artificial culture of Macrocystis integrifolia in southeastern Alaskan waters has been initiated as a first step in a project to augment the existing herring roe-on-kelp fishery in the state. The growing of Macrocystis in Prince William Sound has the potential of considerably enhancing this fishery by eliminating the costly importation of this kelp from southeast Alaska. In an ongoing feasibility study, Macrocystis has been cultured under laboratory conditions through the embryonic sporophyte stage and outplanted in waters near Sitka, Alaska (57° N). Growth of the outplanted kelps has been monitored as a function of the time and depth of the outplanting. Preliminary results suggest that light is limiting for growth in winter and that the optimal depth for outplanting will vary with the season.     

Callus formation in Ecklonia cava Kjellman (Laminariales,Phaeophyta)

Explants from stipes and meristems of Ecklonia cava were incubated on six media under several culture conditions. Both stipe and meristem explants developed calluses three to six weeks after inoculation onto all media except AS PC-1. Calluses developed on stipe explants but did not develop on meristem explants at a temperature of 23 °C. Temperatures from 8 to 13 °C were favorable for callus development. Callus development on meristem explants required light but callus development on stipe explants did not.     

Undaria pinnatifida (Laminariales,Phaeophyta) 12 years after its introduction into the Atlantic Ocean

Since its first introduction into the Atlantic for farming purposes in 1983, the brown alga Undaria pinnatifida has been found at several sites along the European coasts. The present study deals with an ecological experiment that was performed at the island of Ushant (Brittany, France) in order to check the ability of Undaria to recruit to a rocky substratum in situ. On the one hand, the authors were unsuccessful in getting Undaria to colonize a previously denuded area of shore, which was subsequently colonized by other native species, a result that may speak for a competition between Undaria and the local kelps. On the other hand, evidence is presented that Undaria pinnatifida has become a member of the Atlantic flora for good. The sporophytes can be found growing from low water mark of neap tide (+1.5 m) down to at least –15 m below lower water mark of spring tide. Its propagation is thought to occur in at least two ways: either step by step from cultivation sites along the coasts, or from the hulls of ships sailing from harbour to harbour. The preference of Undaria for settlement is on artificial structures.     

Culture and growth of Lessonia trabeculata (Phaeophyta,Laminariales) juvenile sporophytes in La Herradura de Guayacan Bay,northern Chile

Lessonia trabeculata is one of the major kelps found along the northern coast of Chile. In addition to its ecological and economic importance, L. trabeculata may be severely affected by environmental disturbances such as El Níño, which during 1982–1983 cleared wide areas along the coast of Peru and Chile. The main goal of this work was to mass culture L. trabeculata and to observe the growth of sporophytes obtained in the laboratory and cultured in the sea. Juvenile sporophytes obtained in the laboratory were attached between 1 and 6 m in depth. The linear growth rate, as blade elongation, was recorded weekly for seven months. No significant differences (p < 0.05) were found in sporophyte blade linear growth at different depths. The best elongation growth rate was 7.5 ± 1.6 mm d^–1 at 3 m during March. This preliminary work suggests that L. trabeculata follows an annual growth cycle similar to that of other Laminariales with a high rate of blade elongation during the summer and decreasing towards autumn. This species can be considered a potential candidate for aquaculture to increase the availability of raw material and aid in repopulation of overexploited areas.     

Comparative photosynthetic studies of Ecklonia cava (Laminariales,Phaeophyta) bladelets with and without zoosporangial sori

Photosynthetic rates were compared between Ecklonia cava bladelets with and without zoosporangial sori sampled from the subtidal zone (about 5 m deep) in Nabeta Bay, Shimoda, Japan. Photosynthetic rates of bladelets were lower in the sorus portion than in the non-sorus portion on the basis of area, dry weight and chlorophyll a. Respiration rates were higher in the sorus portion than in the non-sorus portion on the basis of area and chlorophyll a, whereas they were almost the same on a dry weight basis. The differences were mainly due to a large difference in dry weight per unit bladelet area between the sorus and the non-sorus portion. Light compensation points were higher in the sorus portion than in the non-sorus portion.     

Effect of a cationic cellulosic polymer on gametophytes of Laminaria digitata (Laminariaceae, Phaeophyta): Improvement of dispersed `free-living' cultures

As filament aggregation is responsible for heterogeneity of Laminariales gametophyte cultures, a project was conducted to obtain stable homogeneous `free-living' cultures of Laminaria digitatagametophytes. The alga was cultivated at 15 ^° Cunder low light and in the presence of a cationic cellulosic polymer, JR125. With 0.1%polymer in the culture medium, the filaments were dispersed and did not adhere to the culture vessel. The absence of any effect of the closely related, but uncharged, polymer LR-250 Natrasol on filament aggregation indicated that the cationic nature of the JR125 molecule was involved in gametophyte dissociation. In the presence of JR125, the gametophytes showed active vegetative growth; the doubling time, measured as chlorophyll concentration, was 5 days. The outer surface of the cell wall was clearly modified by the polymer treatment, as observed by transmission electron microscopy, while neither the inner cell wall or cell organelles were affected. Physiological studies indicated that JR125 treatment did not disturb cell physiology, there being no effecton respiration, photosynthetic activity, sensitivity to high-light stress or modification of pigment or fluorescence characteristics. We have therefore established the conditions for maintaining a stable culture of mixed male and female Laminaria digitata gametophytes in active vegetative growth. The presence of JR 125 in the medium yields a homogeneous culture without cell physiology becoming modified. This revised version was published online in August 2006 with corrections to the Cover Date.     

Micropopulation differentiation in phenol content and susceptibility to herbivory in the Chilean kelp Lessonia nigrescenss (Phaeophyta,Laminariales)

Micropopulation differences in phenol content between intertidal and subtidal individuals of the kelp Lessonia nigrescens were found. Subtidal plants showed: (1) significantly higher phenol content than intertidal individuals, in vegetative and reproductive tissues, (2) intra-plant differences, with higher content in apical frond tissues, (3) higher resistance to consumption by herbivorous fishes. The microscopic progeny of subtidal plants showed the same trend as adult plants: (1) haploid spores from subtidal plants had higher phenol content than spores from intertidal individuals, and (2) the microscopic sporophytes derived from subtidal spores and gametophytes were less consumed by herbivorous snails (Tegula tridentata) than those derived from intertidal plant propagules. No increase in phenol content was detected after mechanical injury to experimental fronds, or after transplantation to the subtidal environment.In addition to the absence of inducible responses, the different phenol content between intertidal and subtidal individuals, in adult diploid plants and also in the haploid progeny, suggests that both environments differ someway enough to fix the mentioned features on the plants of Lessonia nigrescens. It is likely that the differences in herbivory between the two distributional extremes contributed to the observed pattern.     

Relation between size and age of holdfasts of Ecklonia stolonifera Okamura (Laminariales,Phaeophyta) in northern Honshu,Japan

Ecklonia stolonifera is distributed along the coast facing the Sea of Japan. The size of various parts of the shoot (blade length and width and stipe length and diameter) and the age were determined at Ooma, Aomori Prefecture. The smaller the holdfast, the higher the percentage of one-year-old shoots. Holdfasts 10 cm in diameter seemed to be three years old, whereas holdfasts 40 cm in diameter seemed to be five or more years old. Zoosporangial sori were observed on blades three or more years old. Ecklonia stolonifera holdfast diameter expands only vegetatively by stoloniferous rhizoids. Zoospores, formed on shoots three or more years old, serve for the formation of new populations.     

Allocation of blade surface to reproduction in Laminaria longicruris of Long Island Sound (USA)

Sorus formation in the kelp Laminaria longicruris de la Pylaie (Phaeophyta) was quantified for a biennial population in Long Island Sound (Connecticut, USA), at the southern limit of its biogeographical range in the Western Atlantic Ocean. The allocation of blade surface to reproduction was measured monthly during two years, with additional samples taken at times of peak growth and reproduction. Sporophytes produced sori year-round, with the highest percentages of fertile plants (75 to 95 percent) occurring from October to December. The mean percentage of sorus area to blade ranged from 1 to 37 percent, remaining low and fairly constant during the spring and summer, but reaching much higher levels in the fall (when growth is minimal) and early winter. The comparatively low mean annual allocation of blade surface to reproduction (5 percent), was postulated to be due to temperature stress on these plants at the southern limit of distribution, but may instead be typical of the species. Such a small allocation of resources to reproduction nevertheless results in billions of spores per m² of substrate, making a major contribution of material potentially available to grazing food webs.     

Taxonomy of the southwestern Atlantic endemic kelp: Laminaria abyssalis and Laminaria brasiliensis (Phaeophyceae,Laminariales) are not different species

Two endemic species of Laminaria, Laminaria abyssalis Joly & Oliveira Filho and L. brasiliensis Joly & Oliveira Filho, from the tropical southwestern Atlantic coast have been described. The aim of this work was to determine the conspecificity of these species based on morphological and molecular analyses (ribulose 1,5‐bisphosphate carboxylase/oxgenase, large subunit (rbcL), internal transcribed spacer (ITS) and cytochrome c oxidase subunit I (coxI)). We found an overlap between the morphological characters that are considered taxonomically important for distinguishing these two species; these characters included a differing pattern of blade splitting. In the three molecular analyses, the Brazilian Laminaria specimens were grouped into one clade with maximum support. These data support the hypothesis that the individuals analyzed represent only one species, L. abyssalis. The molecular analysis also showed L. abyssalis to be sister group to L. digitata.     

Ecological effects of harvesting Lessonia (Laminariales,Phaeophyta) in central Chile

Lessonia nigrescens and L. trabeculata are economically important canopy-forming kelps in Chile. Experimental harvesting of stipes above the first dichotomy reduces stipe movement and inter-stipe friction, allowing the development of a heavy epiphytic load and increased grazing. Complete stipe removal leads to holdfast death as neither species is able to simultaneously regenerate all stipes. The invertebrate fauna inside the holdfast does not respond to upper canopy changes, but mortality does occur in partial or complete plant removals. Kelp removal also affects inter-plant distances, results in increased access of grazers to the outside and inside of kelp holdfasts, reduces recruitment of other algal species, and modifies the morphology of L. trabeculata such that the plants become more susceptible to removal by water movement.