Interactions between environmental variables on growth rate and carrageenan content of Solieria chordalis (Solieriaceae,Rhodophyceae) in culture

Using vegetative propagules (ramuli) of the iota carrageenan producing red seaweed Solieria chordalis, a maximum growth rate of 6.8% d⁻¹ was achieved when cultured at 20 °C and 100 μmol photon m⁻² s⁻¹ in seawater supplemented with 20 μM NO₃-N or 10 μM NO₃-N plus 10 μM NH₄-N. Ramuli grew less well when nitrogen was supplied solely as NH ₄ ⁺ . Maximum carrageenan content was observed at the same temperature, irradiance and salinity as growth, but at lower nitrogen concentrations. These findings are discussed in relation to results obtained from studies on other iota-carrageenan producing carrageenophytes.     

Seasonal variation in growth and carrageenan content ofCalliblepharis jubata (Rhodophyceae,Gigartinales) from the Normandy coast,France

Study of the seasonal variation in the quality and content of iota carrageenan inCalliblepharis jubata from the Normandy coast of France shows that seasonal fluctuation of the environment affects the growth and chemical composition of this red alga. Growth increases during winter, when there is little synthesis of carrageenan and floridean starch is accumulated. When inorganic nitrogen content decreases, growth also decreases and stops (May to August); with high light intensity, the metabolism is oriented towards a synthesis of parietal carrageenans to the detriment of the reserve products such as floridean starch.Author for correspondence     

Phylogenetic relationship of Kappaphycus Doty and Eucheuma J. Agardh (Solieriaceae, Rhodophyta) in Malaysia

The genera Kappaphycus Doty and Eucheuma J. Agardh are important sources of carrageenan in Malaysia, offering lucrative revenues to the carrageenan industry, economy, and the local community. The extensive range of morphotypes and the lack of distinct morphological characteristics led to the application of molecular systematics in elucidating this taxonomic confusion. Local varieties of Kappaphycus and Eucheuma, identified using putative external morphology, were analyzed using the mitochondrial cox2–3 spacer and plastid RuBisCO spacer molecular markers. Phylogenetic analysis of these and non-local specimens indicate that Kappaphycus and Eucheuma are genetically distinct. Three main genotypes of Kappaphycus alvarezii were identified, of which two are extant in Hawaii. Morphological and color variations are not supported by molecular data, indicating that most of the local names are not genetically based. Both the cox2–3 spacer and RuBisCO spacer generated phylogenetic trees with similar topology except in variation of nodal supports. The two markers showed clear separation between Kappaphycus and Eucheuma and the existence of three Malaysian Kappaphycus cultivars. Cox2–3 spacer data is more variable and provides better resolution than the RuBisCO spacer, showing that Kappaphycus is more diversified with a larger number of genotypes, strains, and species which are unique to Southeast Asia. Kappaphycus sp. “Aring-aring” appeared to be phenotypically and genotypically different from other Kappaphycus congeners, whereas Kappaphycus striatum exhibited two different genotypes. Our data indicate that Eucheuma denticulatum is the dominant species in Malaysian waters and also suggested paraphyly in Eucheuma which will require further studies. The application of molecular taxonomy on Malaysian Kappaphycus and Eucheuma proves useful, offering valuable insights into the taxonomy and distribution of these commercially important Rhodophytes.     

Genetic diversity of Kappaphycus Doty and Eucheuma J. Agardh (Solieriaceae,Rhodophyta) in Southeast Asia

The commercial importance of carrageenophytes Kappaphycus and Eucheuma is well known, with much interest in terms of cultivation, marketing, and research. Considering the many lucrative prospects, these red seaweeds were introduced into various parts of the world for farming, where merely a few were comprehensively documented. Despite being extensively cultivated throughout Southeast Asia, the genetic diversity of Kappaphycus and Eucheuma is poorly studied, where heavy reliance is placed on the use of local or commercial names for identifications. This study used the mitochondrial-encoded cox1 and cox2–3 spacer genetic markers to investigate the Kappaphycus and Eucheuma haplotypes, cultivated and wild, available throughout Southeast Asia. Concatenated cox1–cox2–3 spacer datasets were also analyzed. The near full-length cox1 gene is preferred at revealing the genetic diversity of Kappaphycus and Eucheuma, provided a larger reference database is available. Both molecular markers were capable of delineating common members of the genus Kappaphycus (i.e., Kappaphycus alvarezii, Kappaphycus striatus, and Kappaphycus cottonii) and Eucheuma denticulatum, and revealed interesting genotypes and new species which may be potential alternatives to the common cultivars as well as materials for research. The relative scarcity of Eucheuma species is discussed and future sites for sampling are recommended.     

Effect of ammonium on growth and carrageenan content in Kappaphycus alvarezii (Gigartinales,Rhodophyta)

Kappaphycus alvarezii, cultured in a region deficient in nitrogen with intermittent application of 10 mM ammonium at three-day intervals for 1 hour, attained a daily growth rate of 4.6%, which was considered to be the optimum growth rate. Under such conditions, the C/N ratio was 29 with a carrageenan content of 58% and gel strength of 45–70 g cm^–2. Gel strength of carrageenan was high when nitrogen content was high and vice versa.     

Effects of nitrogen and phosphorus availabilities on growth, pigment, and protein contents in Hypnea cervicornis J. Agardh (Gigartinales, Rhodophyta)

The selection of seaweed species for their use as biofilters should be based on the knowledge of their nutrient requirements and tolerance to wide variations of nutrient concentrations. Therefore, tolerance and the physiological capabilities of Hypnea cervicornis J. Agardh (Gigartinales, Rhodophyta) to growth under nitrate, ammonium, and phosphate variations and to assimilate them into soluble proteins and photosynthetic pigments were evaluated in laboratory conditions. Treatments were composed of sterilized seawater enriched with 25 % von Stosch solution (without nitrogen and phosphorus), and nitrate or ammonium and phosphate were added in combination of 100:1 and 10:1 nitrogen/phosphorus (N/P). Nitrate concentrations varied from 0 to 500 μM, and ammonium concentrations varied from 0 to 50 μM. Growth rates of H. cervicornis increased linearly with addition of ammonium, but with nitrate addition, growth varied following a saturation kinetic, and the highest growth rate (14.45 % d^?1) was observed in 200 μM of N/P ratio of 10:1. An excess of nutrients was accumulated as proteins and phycobiliproteins (mainly as allophycocyanin and phycoerythrin) at higher phosphate availability (N/P ratio of 10:1), and H. cervicornis tolerated the highest ammonium and nitrate concentrations (50 and 500 μM, respectively). These physiological responses suggest that this species could be used as biofilter for nutrient removal in eutrophicated seawater and could be cultivated in integrated multitrophic aquaculture systems.     

Effect of drying temperature on carrageenan yield and quality of Kappaphycus alvarezii (Rhodophyta,Solieriaceae) cultivated in Brazil

This study evaluates the effect of different drying temperatures on the properties of semi-refined (SR) and refined (R) carrageenan extracted from Kappaphycus alvarezii cultivated in Brazil. Drying kinetics was studied in seaweeds under the following treatments: sun drying (control) and drying at 40, 60, and 90 °C in convective air dryer. Drying was carried out until the moisture content of seaweeds reached values below of 30 % on wet basis. Significant reductions in drying time were observed with the increase of temperature. At 90 °C, 30 % moisture content was reached in 100 min, as compared with the 1,440 min required by the sun-drying treatment. SR yields showed no significant differences when compared to the control, varying from 40 to 44 %, while R had a significantly higher yield (30 %) at 90 °C in relation to control (26 %). Gel strength of SR was significantly higher in the sun-dried samples (1,685.1 g cm^?2) and 60 °C samples (1,727.2 g cm^?2), but no significant differences were observed in R gel strengths. Lowest syneresis was observed in both SR (9.8 %) and R (10.3 %) after the treatment at 90 °C. Significantly lower viscosity values were observed for SR at 60 °C (233 mPa s) and at 90 °C (175 mPa s), as for R, the lowest value was observed at 90 °C (205 mPa s). Based on these results, it was concluded that best results for both types of carrageenan are obtained drying at 60 °C.     

Evaluation of steam explosion as pretreatment in agar extraction fromGracilaria dura (C. Agardh) J. Agardh (Gracilariaceae,Rhodophyta)

Steam explosion was investigated as a pretreatment step in the isolation of agar from the macroalgaGracilaria dura. As compared to conventional procedures, the yield of agar obtained using this method on alkali (Na₂CO₃) conditioned algal material was higher. Extractions performed first at 95 °C and then at 121 °C showed that the major fraction of the agar was extracted at 95 °C, independently of the pretreatment. The efficiency of sulphate hydrolysis during steam explosion ofG. dura previously conditioned in Na₂CO₃, was similar to that of a NaOH based alkali pretreatment. Except for a lower nitrogen content of the sample obtained after NaOH based alkali pretreatment and a higher 6-O-methyl--d-galactose content in the agar after steam explosion, the chemical composition of the agars showed no significant difference. Agars extracted after steam explosion had melting temperature, gel strength and apparent modulus of elasticity lower than those of corresponding native and alkali (NaOH) pretreated samples, but comparable to those of a commercial sample.Author for correspondence     

Assessment of Four Molecular Markers as Potential DNA Barcodes for Red Algae Kappaphycus Doty and Eucheuma J. Agardh (Solieriaceae,Rhodophyta)

DNA barcoding has been a major advancement in the field of taxonomy, seeing much effort put into the barcoding of wide taxa of organisms, macro and microalgae included. The mitochondrial-encoded cox1 and plastid-encoded rbcL has been proposed as potential DNA barcodes for rhodophytes, but are yet to be tested on the commercially important carrageenophytes Kappaphycus and Eucheuma. This study gauges the effectiveness of four markers, namely the mitochondrial cox1, cox2, cox2-3 spacer and the plastid rbcL in DNA barcoding on selected Kappaphycus and Eucheuma from Southeast Asia. Marker assessments were performed using established distance and tree-based identification criteria from earlier studies. Barcoding patterns on a larger scale were simulated by empirically testing on the commonly used cox2-3 spacer. The phylogeny of these rhodophytes was also briefly described. In this study, the cox2 marker which satisfies the prerequisites of DNA barcodes was found to exhibit moderately high interspecific divergences with no intraspecific variations, thus a promising marker for the DNA barcoding of Kappaphycus and Eucheuma. However, the already extensively used cox2-3 spacer was deemed to be in overall more appropriate as a DNA barcode for these two genera. On a wider scale, cox1 and rbcL were still better DNA barcodes across the rhodophyte taxa when practicality and cost-efficiency were taken into account. The phylogeny of Kappaphycus and Eucheuma were generally similar to those earlier reported. Still, the application of DNA barcoding has demonstrated our relatively poor taxonomic comprehension of these seaweeds, thus suggesting more in-depth efforts in taxonomic restructuring as well as establishment.     

Growth ofEucheuma isiforme (C. Agardh) J. Agardh on experimental rafts off the coast of Yucatan State,Mexico

A field experiment was carried out at two sites off Yucatan State, Southeast Mexico, in order to determine the feasibility of culturing the red seaweedEucheuma isiforme; this was done during May–September 1989. At both sites (Uaymitun and Dzilam) the 25 days harvest and 14 algae per line plant density growth rates (2.21% day^–1 and 1.21% day^–1, respectively) were significantly higher (p<0.05) than those obtained with other combinations of the two factors tested (50, 75, 100 and 125 days harvest and 9 and 14 algae per line plant density). The mean carrageenan content of the cultured algae was 35.8% and 31.4% at Uaymitun and Dzilam, respectively.     

Effect of temperature on the growth rate of Griffithsia tenuis C. Agardh (rhodophyta: ceramiales)

Clonal cultures of Griffithsia tenuis were grown for 18 days (Erdschreiber solution, LD 12 : 12, 2200 lux) at 13, 18, 22 and 25°C. The optimum temperature for growth (increase in number of cells) under these conditions was 22°C.

     

Preliminary approach to the characterization and seasonal variation of carrageenans from four Rhodophyceae on the Normandy coast (France)

Carrageenans extracted under alkaline conditions were studied in some Rhodophyceae from the Normandy coast. Among these, four species yielding iota-carrageenan were studied throughout a whole year: Calliblepharis ciliata, Calliblepharis jubata, Cystoclonium purpureum and Gymnogongrus crenulatus. Carrageenan content varied with season, being maximal at the end of spring and minimal in autumn, and was positively correlated with the growth of these algae. A culture of Cystoclonium purpureum was initiated and, without trying to optimize growth conditions, yielded a mean production of 50 g fresh wt m^–2 d^–1 in 36 weeks of continuous tank culture.     

Studies on the ecology and host specificity of Balbiania investiens (Rhodophyceae)

Finds of the rare epiphytic rhodophyte Balbiania investiens (Acrochaetiales) from River Österdalälven in Dalecarlia, Sweden, are described. Its distribution, history and taxonomy are presented and discussed. Information on its host, represented by certain species of the genus Batrachospermum (Nemalionales), is given with particular reference to ecology and distribution in Sweden. The algal composition and water chemistry of one new Swedish location are presented and categorized according to Israelson's classification of Scandinavian running waters.     

Influence of light,water motion,and stocking density on the growth and pigment content of Halymenia durvillei (Rhodophyceae) under laboratory conditions

The tropical red seaweed Halymenia durvillei Bory de Saint Vincent is a potential source of the high-value pigments, r-phycoerythrin (RPE) and r-phycocyanin (RPC). The unique properties of these pigments find many applications—from food to cosmetics, pharmaceuticals, and biomedical research. This study aimed to improve the land-based culture technology of H. durvillei by determining the appropriate combination of light, water motion, and stocking density that would result in high growth performance and high RPE and RPC content. Combinations of two light levels (full light, 100% and reduced light, 67%), two water motion levels (low and moderate), and three stocking densities (50, 100, and 200 g) were studied using 64.5-L glass tanks with flow-through seawater and aeration systems at the outdoor land-based seaweed nursery in Bolinao, Pangasinan, Philippines. After 6 weeks of culture, growth performance (growth rate and productivity) of H. durvillei and phycobiliprotein content were best under a combination of full light (100%), moderate water motion, and 50-g stocking density. The generally low light regime during the experimental period, which coincided with the cold, dry season characterized by shorter days and overcast skies, may have influenced H. durvillei to maximize the use of available resources such as light and possible increased nutrient availability from water motion to promote growth and phycobiliprotein synthesis. Treatments with low stocking densities generally showed satisfactory growth and phycobiliprotein content. This study provides groundwork for future research into mechanisms by which these and other factors affect the growth and physiology of H. durvillei in culture.

     

Some effects of plant growth regulators on tissue cultures of the marine red alga Agardhiella subulata (Gigartinales,Rhodophyta)

We examined whether auxins and cytokinins, either singly or in combination, stimulate cell division in tissue cultures of a red seaweed. Our experimental model consisted of filamentous and callus-like growths that developed from cross-sectional discs cut from young branches of Agardhiella subulata. Plant growth regulators were added to the medium to give combinations of an auxin with a cytokinin over a range of concentrations (1 µg L^–1 –10 mg L^–1). Several mixtures of auxins and cytokinins, as well as some single auxins, cytokinins and phenolics, stimulated cell division and growth in the tissue cultures beyond that of controls. The treatments that were effective included: phenylacetic acid/zeatin; phenylacetic acid/6-benzylaminopurine; -naphthaleneacetic acid/zeatin; 2,4,5-trichlorophenoxyacetic acid/6-benzylaminopurine; and indoleacetic acid/kinetin. High concentrations of cytokinins (i.e. 10 mg L^–1) inhibited the regeneration of plants in some of the cell cultures. These results provide further evidence that growth regulators can be used for the tissue culture of seaweeds and for the study of developmental phenomena in these plants.     

Vegetation patterns and spontaneous regression of Caulerpa taxifolia (Vahl) C. Agardh in Malinska (Northern Adriatic,Croatia)

The green alga Caulerpa taxifolia was recorded at Malinska in 1994 and this actually represents the highest northern latitude (45°7′30″N) at which this invasive alga has been found in the world. The alga was widespread at four sites from which it was eradicated by suction pumps during 1996 and 1997. However, it immediately and intensively recolonized all but one site. Throughout 1998 and 1999 the renewed vegetation showed consistent seasonal patterns. The alga nearly disappeared in April and May while regenerating from over-wintering parts of the thalli in summer. The maximum development occurred in autumn and winter with values of biomass (around 200 g dry weight m⁻²) and frond number (around 2000 m⁻²) generally lower than those reported for the north-western Mediterranean. Values for the frond length (10–18 cm) were in the same range as those in the north-western basin. Throughout 1998 and 1999 the biomass was closely correlated to frond number and length (adjusted R² = 0.90). During the following years C. taxifolia entered a phase of regression. The total colonized area, which amounted to several thousands of square metres in 1998, spontaneously declined in 2000 and 2001 so that only several thalli were found in 2004 during a detailed survey of the settlement. No major changes in winter seawater temperatures, ranging from 9.5 to 10.5 °C, were observed in the area from 1994 to 2004. Thus, other unknown processes could likely play a role on specific vegetation patterns of C. taxifolia in Malinska. Accordingly, it is difficult to explain why the still surviving thalli did not proliferate during the favourable summer–autumn period.     

Genetic differentiation in wild Kappaphycus Doty and Eucheuma J. Agardh (Solieriaceae,Rhodophyta) from East Malaysia reveals high inter- and intraspecific diversity with strong biogeographic signal

Journal of Applied Phycology - The region of Eastern Sabah, Malaysia, harbours a rich diversity of eucheumatoid (i.e. Kappaphycus and Eucheuma spp.) algae. The global cultivation of this group of...     

In situ rates of nitrate uptake by giant kelp,Macrocystis Pyrifera (L.) C. Agardh: Tissue differences,environmental effects,and predictions of nitrogen-limited growth

NO⁻₃ uptake rates were measured in situ for seven types of tissue of adult sporophytes of Macrocystis pyrifera (L.) C. Agardh. Uptake by mature blades of canopy fronds followed saturation kinetics. At near-saturation concentrations, mean rates of uptake by different tissues ranged from 0.1 to 2.1 μg-at.· g wet wt⁻¹ · h⁻¹ (7–68 ng-at. · cm⁻²· h⁻¹). Different tissues incubated under similar environmental conditions took up NO⁻₃ at different rates, indicating physiological differences. Uptake rates showed no apparent relation to tissue age or nutritional history, but were influenced by certain environmental factors: uptake was 44–48% slower in dark than at ambient mid-day light levels, and dark uptake was 40% slower by blades incubated at 12m depth than by blades incubated at the surface. These physiological and environmental differences resulted in generally rapid uptake by tissues located at or just below the surface and slower uptake by tissues deeper in the water column.Daily NO⁻₃ uptake by M. pyrifera populations was predicted using a model based on in situ NO⁻₃ uptake rates. According to predictions of the model, NO⁻₃ concentrations of 1–2 μM throughout the water column are required to support kelp growth at the 4% · day⁻¹ (wet wt) rate typical of inshore populations. Vertical stratification, with high NO⁻₃ concentrations only at near-bottom depths, would result in severe nitrogen-limitation of growth. Seasonal changes in frond size distribution do not greatly affect nitrogen-limited growth rate. The model was also used to evaluate potential fertilizing methods and problems in management of offshore kelp farms.