Porphyra Umbilicalis Research Articles

Separation of floridoside and isofloridosides by HPLC and complete 1H and 13C NMR spectral assignments for d-isofloridoside

Isofloridosides (1- O-α- d-galactopyranosylglycerol) and floridoside (2- O-α- d-galactopyranosylglycerol) were extracted from the red alga Porphyra umbilicalis (Linné) Kützing (Bangiales, Rhodophyta). Their separation was achieved by HPLC (NH 2 P50 column) after successive purification of the crude extract by ion-exchange chromatography and HPLC (Sugar-Pak TM1 column). 1D and 2D NMR spectroscopy experiments allowed to completely assign the 1H and 13C spectra of d-isofloridoside.

New rhythmic changes in mitosis and growth in low differentiated green and red marine macroalgae

The cell division and vegetative growth of the thalli of simply differentiated macroalgae with a diffuse growth type—Ulva pseudocurvata (Chlorophyta) and Porphyra umbilicalis (Rhodophyta)-have been studied under natural and laboratory conditions. For this purpose the mitotic index and growth rate of algae were measured over 18 days. A diurnal rhythm of the mitotic index was revealed: the minimal mitotic index was registered in morning and daylight hours (for U. pseudocurvata 1–4%, for P. umbilicalis 0.5–2%), in the afternoon the index grew and reached its maximum 1 hour before dark (for U. pseudocurvata 12%, for P. umbilicalis 7%), then it slowly decreased during the night. In the studied algal species 2–3-and 6-day rhythms of mitotic index and growth rate were found for the first time both under natural and laboratory conditions. With constant white light these rhythms persisted for 9 days, this confirms the endogenous regulation of these rhythmic variations.

Seeding nets with neutral spores of the red alga Porphyra umbilicalis (L.) Kützing for use in integrated multi-trophic aquaculture (IMTA)

Nets in traditional Porphyra mariculture are seeded with conchospores derived from the conchocelis phase, and spend a nursery period in culture tanks or calm coastal waters until they reach several centimeters in length. Some species of Porphyra can regenerate the foliose phase directly through asexual reproduction, which suggests that the time, infrastructure, and costs associated with conchocelis culture might be avoided by seeding nets with asexual spores. Here, we present work from a short-term mariculture study using nets seeded with asexual spores (neutral spores) of a native Maine species of Porphyra. Porphyra umbilicalis (L.) Kützing was selected for this proof of concept research because of its reproductive biology, abundance across seasons in Maine, and evidence of its promise as a mariculture crop. We studied the maturation, release, and germination of the neutral spores to develop an appropriate seeding protocol for nets, followed by development of a nursery raceway to provide an easily manipulated environment for the seeded nets. Neutral spores were produced throughout the year on the central Maine coast; however, there was a temporal variability in the number and survival of released neutral spores, depending upon thallus position in the intertidal zone. Small thalli were strictly vegetative, but most thalli reproduced by neutral spores; sexual reproduction was absent. Neutral spores germinated quickly at 10 and 15 °C, but germination was delayed at 5 °C. Unlike some algal zygotes and spores, neutral spores of P. umbilicalis required light to germinate; however, irradiances of 25 and 100 μmol photons m − 2 s − 1 were equally sufficient for germination. Rafts of seeded nets were deployed in Cobscook Bay, Maine, at two distances from salmon aquaculture pens and at a control site on a nearby, fallow aquaculture site (no salmon). There was no difference in nitrogen content of harvested thalli; however, both the density and the surface area of harvested thalli were different among the sites. The possible causes of these differences are discussed in the context of potential use of P. umbilicalis in IMTA.

Effects of temperature and ammonium on growth, pigment production and nitrogen uptake by four species of Porphyra (Bangiales, Rhodophyta) native to the New England coast

Porphyra is one of the world’s most valued maricultured seaweeds and has been cultivated for several hundred years in Asia. The objective of this study was to produce critical information as a guide for the selection of an appropriate Porphyra species from coastal New England for the development of a land-based aquaculture system. Four Northwest Atlantic Porphyra species: P. leucosticta, P. amplissima, P. linearis and P. umbilicalis, were cultivated for 1 and 2 weeks at saturated light intensities (100–150 μmol photons m−2s−1) and six combinations of ammonium (25 and 250 μmoles L−1) and temperature (10, 15 and 20°C). Specific growth rate (SGR) increased with decreasing temperature in P. leucosticta, P. linearis and P. umbilicalis and increased with increasing temperature in P. amplissima. The SGR of all species was greater at the higher ammonium concentration. Porphyra linearis had the highest SGR, increasing in biomass by approximately 16% day−1. Phycoerythrin (PE) content was higher at 10°C and 250 μmoles L−1 in all species except P. amplissima. The PE content, measured as fresh weight (FW), of P. linearis (29 mg g−1 FW−1) and P. umbilicalis (26 mg g−1 FW−1) was significantly higher than the other two species. Tissue nitrogen content of all species measured in dry weight was on average 1.45% higher at 250 μmoles L−1 than at 25 μmoles L−1 ammonium concentration. Porphyra umbilicalis had the highest tissue nitrogen contents (6.76%) at 10°C and 250 μmoles L−1 ammonium. Based on these results, P. linearis and P. umbilicalis should be considered as potential candidates for bioremediation with finfish and shellfish mariculture.

Availability of ammonium influences photosynthesis and the accumulation of mycosporine-like amino acids in two Porphyra species (Bangiales, Rhodophyta)

The effect of ammonium concentration on photosynthetic activity estimated as in vivo chlorophyll fluorescence, i.e. maximal quantum yield (Fv/Fm) and electron transport rate (ETR) and on the accumulation of mycosporine-like amino acids (MAAs), chlorophyll a (chl a), biliproteins (BP) and soluble proteins (SP) in the red algae Porphyra leucosticta Thuret in Le Jolis collected from Lagos (Malaga, Spain) and Porphyra umbilicalis (Linnaeus) J. Agardh from Helgoland (Germany) was evaluated. Discs of both species were incubated with three ammonium concentrations (0, 100 and 300 µM) under artificial PAR and UV radiation for 7 days. Photosynthetic activity decreased under the culture conditions due to UV radiation and ammonium availability. The decrease of both Fv/Fm and maximal ETR was related to ammonium supply, i.e. the lowest decrease occurred in algae growing with the highest concentration of ammonium. In both species, after 7 days of culture, the content of chl a, BP and SP was higher under 300 µM than that under 0 and 100 µM ammonium. In both species, the content of MAAs was increased under 300 µM ammonium compared to the initial value, whereas a decrease under 0 and 100 µM ammonium was observed only in P. leucosticta. The content of MAAs in P. umbilicalis did not present significant differences compared to the initial value, probably because of the high initial content of MAAs. In both Porphyra species, four MAAs were identified: shinorine, porphyra-334, palythine and asterina-330. However, P. leucosticta modified its MAA pattern during the incubation time, reaching the same percentages found for P. umbilicalis, which did not show any change during the experimental period. P. leucosticta exhibited a decrease in BP/SP and BP/chl a ratios through the incubation time and an increase in MAAs/BP. The ratio MAAs/chl a did not show any variation with time or treatment, as was also true for all ratios in P. umbilicalis. In summary, ammonium supply diminished the decrease of Fv/Fm, increased the content of photosynthetic pigments (chlorophyll and biliprotein) and soluble protein, and stimulated of the accumulation of MAAs in the red algae P. leucosticta and P. umbilicalis.

Composition and spatio temporal variability of the epiphytic macroalgal assemblage of Fucus vesiculosus Linnaeus at Clare Island, Mayo, western Ireland

The composition and the patterns of spatial and temporal variability of the epiphytic assemblages of Fucus vesiculosus of Clare Island, on the western coast of Ireland, were investigated for an annual cycle. Specimens of Fucus were collected on seven sampling dates from three sites of the island (Portlea, Kinnacorra and Portnakilly). Data of cover of the most common epiphytic species were collected and analysed by multivariate and univariate techniques. Elachista fucicola, Polysiphonia lanosa, Porphyra umbilicalis, Spongonema tomentosum and Ulva compressa were the most common species. Spatial and temporal variation was detected both for the whole assemblage and for the most abundant species. In general, the assemblage was quantitatively more abundant and diverse in spring–summer than in autumn–winter. In spring–summer, there was a clear differentiation among the assemblage of Portnakilly and the assemblages of the other two sites. Individual species were also generally more abundant in spring–summer and their distribution at the three sites was often not consistent in time; P. lanosa was the only epiphyte for which a consistent effect of site was found. Spatial variation on a scale of meters to tens of meters was the most striking pattern of distribution of the epiphytic assemblage; significant effects related to this spatial scale were detected both for the whole assemblage and for individual species. Phenological patterns of the epiphytic species determining availability of propagules and limited dispersal, leading to aggregated patterns of distribution, are considered the main factors responsible of such patchiness. The importance of the incorporation of small spatial scales in sampling designs analysing the distributional patterns of epiphytic assemblages is discussed.

Limitations in the use of PAM fluorometry for measuring photosynthetic rates of macroalgae at high irradiances

Pulse amplitude modulated (PAM) fluorometry can be used for measuring photosynthetic electron transport rates (ETR) of marine angiosperms and macroalgae both in the laboratory and in situ. Regarding macroalgae, quantitative values and linear correlations between ETR and rates of photosynthetic O2 evolution have so far been shown only for a few species under low irradiances. As a logical continuation of such work, the aim of the present study was to (a) assess to what degree high irradiances would limit such measurements and (b) evaluate whether PAM fluorometry could be used quantitatively also for other marine macroalgae from different phyla. This was done by comparing ETR with rates of gross O2 evolution (net O2 exhcange corrected for dark respiration) at various irradiances for the green alga Ulva lactuca grown at two irradiances, the brown algae Fucus serratus and Laminaria saccharina and the red algae Palmaria palmata and Porphyra umbilicalis. At low irradiances, there was a clear positive correlation between O2 evolution and fluorescence-based ETR. At high irradiances, however, all algae featured an apparent decrease in ETR while O2 evolution remained relatively constant, and this resulted in markedly increasing O2/ETR ratios. This anomaly could be nicely illustrated in plots of O2/ETR as a function of the effective quantum yield of photosystem II (Y). Such plots showed that the O2/ETR ratio generally started to increase when Y reached a critical low value of c. 0.1. It was further found that the irradiance at which this value was reached varied with species and previous light histories. Thus, it is the Y value, rather than the irradiance per se

Water-soluble seaweed extracts modulate the respiratory burst activity of turbot phagocytes

In this study, we investigated the effects of water-soluble extracts (WSE) from seaweed species Ulva rigida C. Agardh, Enteromorpha sp., Codium tomentosum (Huds) Stackh., Fucus vesiculosus L., Pelvetia canaliculata (L.) Decne et Thur, Dictyota dichotoma (Huds) Lamour, Chondrus crispus Stackh and Porphyra umbilicalis (L.) J. Agardh, on the respiratory burst of turbot phagocytes, in search of biologically active substances with immunostimulating capacities. The stimulatory capacities of the extracts varied greatly, depending on their origin, the concentrations used and the time of incubation. The best responses were induced by the extracts obtained from U. rigida, Enteromorpha sp. and C. crispus. Pre-incubation of the phagocyte cells with U. rigida and C. crispus extracts and subsequent incubation with phorbol myristate acetate (PMA) showed that these cells responded to further stimulation by this substance and, at some concentrations, they showed higher respiratory burst activity than control cells stimulated by PMA alone, suggesting that the extracts had a priming effect. We also tested the effects of protein-free water-soluble extracts (PF-WSE) and of the polysaccharide fractions (PSF) obtained from the PF-WSE of U. rigida and C. crispus. These extracts induced an increase in the respiratory burst activity of turbot phagocytes, suggesting that most of the stimulatory capacity of the water-soluble extracts was associated with polysaccharides.

140 Ecophysiology of The Red Alga Porphyra Umbilicalis Kützing (Rhodophyta, Bangalies): Responses to Abiotic Stress

The effects of tidal elevation, emersion, sun exposure, and season on several antioxidant enzymes (ascorbate peroxidase, glutathione reductase, and catalase), pigments (phycoerythrin, phycocyanin, chlorophyll a and total carotene) and photosynthetic efficiency of photosystem II (Fv/Fm) in Porphyra umbilicalis were evaluated. Plants were collected monthly from sun‐exposed and shaded locations in the high, mid, and low intertidal following periods of tidal emersion ranging from 0–6 hours. Glutathione reductase activity was greatly affected by emersion during summer months, while ascorbate peroxidase and catalase activities showed no seasonal patterns. Differences in glutathione reductase and catalase levels occurred between sun‐exposed and shaded plants in the high and mid intertidal during summer. At all elevations, photosynthetic pigments showed a strong seasonal trend, with the effect of sun exposure being most apparent during summer. While total carotene increased with emersion during summer months, the combined effects of emersion and season were inconsistent for phycoerythrin, phycocyanin and chl a. Photosynthetic efficiency (Fv/Fm) decreased following emersion in summer and fall. During most months, sun exposed plants had lower Fv/Fm values compared to plants growing in the shade. This study emphasizes the importance of examining the effects of abiotic stresses simultaneously in order to reveal interactive relationships.

31 Effects of light and ammonium on growth, ammonium uptake and pigmentation of four porphyra (bangiales, rhodophyta) species native to the northwestern atlantic

The marketability and physiological characteristics of Porphyra (nori) make it a good candidate for integrated aquaculture. Four species were grown in separate three‐week greenhouse trials via tumble culture in small tanks (38L). Porphyra umbilicalis, P. linearis, P. leucosticta and P. amplissima were grown at 15, 8, 15 and 12 C, respectively. Plant growth, ammonium uptake, and pigment content were evaluated at three light levels (4%, 13%, and 58% of ambient sunlight), and two ammonium concentrations (25 and 250 ?M). The growth of Porphyra umbilicalis was higher at 250 ?M than at 25 ?M ammonium (P?0.002), while growth of the other three species were not affected by nitrogen concentration (P>0.05). With the exception of P. leucosticta, plant growth was greatest in high light (58% of ambient). Overall, average growth rates ranged from 31.8 (±2.8)%·day‐1 for P. amplissima to 8.8 (±1.2)%·day‐1 for P. leucosticta. Ammonium uptake rates were consistently higher in 250 than 25 ?M ammonium (P?0.05), except for P. amplissima (P>0.05). Uptake by P. umbilicalis was greatest at high light (P<0.005), but light did not affect uptake rates in the other three species (P>0.05). The phycoerythrin content of P. umbilicalis and P. leucosticta was greater at 250 ?M than 25 ?M ammonium, while it was not affected by nitrogen level in P. linearis and P. amplissima. The phycoerythrin content of all species decreased from low to high light (P<0.05); however, light affected the net phycoerythrin production only in P. leucosticta.

Species identification of red and brown seaweeds using ITS ribosomal DNA amplification and RFLP patterns

AbstractThe identity of five macroalgae used as sea vegetables or food ingredients has been determined by amplification of the ribosomal DNA ITS region and RFLP analysis. This allows the detection of specificity patterns for each species and provides an alternative method, when morphological or biochemical methods fail, for control of their use as food ingredients. Alga‐specific PCR primers have been used to determine the ITS rDNA sequences of DNAs extracted from dried and ground algae up to 5 years old. The seaweeds studied were the red algae Palmaria palmata (dulse), Porphyra umbilicalis (nori), and Chondrus crispus (pioca) and the brown algae Himanthalia elongata (sea spaghetti) and Laminaria sp (konbu). Total genomic DNA suitable for amplification was extracted from the alga powder following the CTAB method. This methodology allowed the sequencing of the amplified product and the drawing of theoretical restriction maps useful in the choice of restriction enzymes for RFLP analysis. Enzymes that appeared useful included Mbo I and Alu I. Cutting with a single enzyme was sufficient to obtain characteristic patterns for the red algae P palmata, P umbilicalis and C crispus. For the two brown algae H elongata and Laminaria sp the ITS rDNA sequence showed a lack of suitable restriction site, contrary to other species for which characteristic patterns were obtained.© 2003 Society of Chemical Industry

Species identification by SDS-PAGE of red algae used as seafood or a food ingredient

Abstract The identification, by SDS-PAGE, of four red algae used as sea vegetables or ingredients by the food industry, was performed. They were Palmaria palmata (Dulse), Chondrus crispus (Pioca) , Porphyra umbilicalis (Nori), Gracilaria verrucosa (Ogo-nori). For each species, variations in protein patterns were observed, according to the season. However, for all species, some protein bands were always present during the yearly cycle of the plant. The reference pattern of P. palmata was composed of six protein bands with apparent molecular weights between 59.6 and 15.2 kDa. The G. verrucosa pattern was constituted of eight permanent bands. Two pattern bands, with apparent molecular weights of 49.1 and 45.9 kDa,differentiated the G. verrucosa profile from other seaweed patterns. C. crispus could be identified by a reference pattern composed of seven bands; three, with close molecular weights (49.3; 46.2 and 43.2 kDa), were characteristic of this species. Finally, the P. umbilicalis pattern showed seven bands with molecular weights between 73.1 and 15.9 kDa. The presence of a band with a molecular weight above 70 kDa appeared to be specific to the Porphyra pattern. So the SDS-PAGE seemed able to identify the four red species used by the food industry, but this analytical method appeared to be applicable only to raw material dried in mild conditions.

CIRCADIAN GROWTH IN PORPHYRA UMBILICALIS (RHODOPHYTA): SPECTRAL SENSITIVITY OF THE CIRCADIAN SYSTEM

The circadian rhythm in growth of the red macroalga Porphyra umbilicalis (Linnaeus) J. Agardh was investigated under different spectral light conditions in laboratory‐grown thalli. A free‐running rhythm was observed in constant green or red light at irradiances of 2.5 to 20 μmol photons·m−2·s−1, whereas arhythmicity occurred in constant blue light at 6–20 μmol photons·m−2·s−1. The circadian oscillator controlling growth rhythmicity in Porphyra uses most of the visible sunlight spectrum and possibly multiple photoreceptors with a high sensitivity for blue light and a lower sensitivity for red light. This was inferred from three experimental results: (1) The free‐running period, τ, of the growth rhythm decreased with increasing irradiance, from approximately 25 h at 2.5 μmol photons·m−2·s−1 to 22 h at 20 μmol photons·m−2·s−1 in red or green light, (2) Dark pulses of 3 h duration, interrupting otherwise continuous green or red light, caused advances during the subjective day and delays during the subjective night; the circadian oscillator in Porphyra can discriminate darkness from green or red light, and (3) Low‐irradiance blue light pulses (2.5 μmol photons·m−2·s−1) shifted the growth rhythm in red light of higher irradiance (e.g. 10 μmol photons·m−2·s−1), and a strong, high amplitude, type 0 phase response curve was obtained that is usually observed with light pulses shifting a circadian rhythm in otherwise continuous darkness.

PRELIMINARY EVALUATION OF THE BIOREMEDIATION POTENTIAL OF PORPHYRA: PHOTOSYNTHETIC PRODUCTION BY BLADES AND CONCHOCELIS

Given their rapid growth and nutrient assimilation rates, Porphyra spp. are good candidates for bioremediation. The production potential of two northeast U.S. Porphyra species currently in culture (P. purpurea and P. umbilicalis) was evaluated by measuring rates of photosynthesis (as O2 evolution) of samples grown at 20° C. Gametophytes of P. umbilicalis photosynthesized at rates that were 80% higher than those of P. purpurea over 5–20° C at both sub‐saturating and saturating irradiances (37 and 289 μmol photons m−2 s−1). Porphyra umbilicalis was both more efficient at low irradiances (higher alpha) and had a higher Pmax than did P. purpurea (23.0 vs. 15.6 μmol O2 g−1 DW min−1), suggesting that P. umbilicalis is a better choice for mass culture where self‐shading may be severe. The photosynthesis‐irradiance relationship for the Conchocelis stage of P. purpurea was also examined. Tufts of filaments, grown at 10, 15, and 20° C, were assayed at growth temperatures at irradiances ranging from 0–315 μmol photons m−2 s−1. Tufts were slightly more productive at 15° than at 10° C, but only ca. 4–6% as productive as gametophytes. Maximum rates of net photosynthesis were reduced by 66–74% in tufts grown at 20° C (only about 2% of gametophytes). The Conchocelis stage, however, need not limit mariculture operations; once Conchocelis cultures are established, they can be maintained over the long‐term as ready sources of spores for net seeding.

Influence of ultraviolet radiation on the growth of the dominant macroalgae of the Barents Sea

Nine species of macroalgae collected on the East Murman coast of the Barents Sea were examined: Laminaria saccharina, Alaria esculenta, Saccorhiza dermatodea, Fucus distichus, Fucus serratus, Fucus vesiculosus (Phaeophyta), Palmaria palmata, Porphyra umbilicalis (Rhodophyta) and Ulvaria obscura (Chlorophyta). The samples were kept in three culturing tanks screened to sequester two wavelength ranges of UV radiation. There was a clear seasonal trend in the influence of UV-A, UV-B and of solar radiation without UV-A+B on the growth of the algae. The maximum growth rate was observed in tests with solar radiation excluding UV radiation. A prominent decrease in growth was induced by UV-B in all the species. Ulvaria obscura appeared to be the most sensitive to in situ levels of UV-B radiation, which reduced its growth rate to 54%. The least sensitivity was recorded in Fucus vesiculosus. There was found to be a critical period in May when the algae are affected most by ultraviolet radiation.

Seasonal variation in heteroside concentrations of field-collected Porphyra species (Rhodophyta) from different biogeographic regions.

Eight different species of the red algal genus Porphyra from different biogeographic regions in Europe, Africa, North America, Asia and Australia were collected over the course of the respective growth season and surveyed for the qualitative and quantitative occurrence of the low molecular weight carbohydrates, floridoside, D-isofloridoside and L-isofloridoside. Except for Porphyra saldanhae from South Africa, all species tested exhibited clear seasonal variations in their heteroside composition. Whereas Porphyra dioica and Porphyra umbilicalis from the North Sea showed highest carbohydrate concentrations in spring and summer, those of Porphyra leucosticta from Spain were highest in winter. The red algae studied exhibited highest concentrations of heteroside at different seasons, some in winter, others in spring or summer. The composition of the three compounds varied among the species studied. In P. columbina from Australia, L-isofloridoside was always quantitatively dominant, while floridoside was the major component in P. dioica. Usually D-isofloridoside was present in small concentrations, except in P. perforata from the Pacific coast of the USA where it occurred in equal concentrations with floridoside and L-isofloridoside. The results point to species-specific different enzymic activities of the underlying anabolic pathways. Correlations between the heteroside concentrations and various prevailing environmental parameters are detectable but do not reveal a general response of Porphyra. Data from the literature prove that numerous physical factors determine the growth patterns of various Porphyra species in different biogeographic regions. Of these, photoperiod, temperature and nutrients are the most important. Highest heteroside concentrations in the Porphyra species studied always coincided with enhanced growth, and this relationship determined that growth, though related to abiotic conditions, was also promoted by maximum carbohydrate content. The multiple physiological function of floridoside, D-isofloridoside and L-isofloridoside as osmolytes, compatible solutes and carbon reserves is discussed in relation to the environmental stresses that Porphyra species usually experience in their upper intertidal habitats.

Evaluation of in vivo thallus absorptance and chlorophyll fluorescence as biomarkers of UV-B exposure and effects in marine macroalgae from different tidal levels

A field survey and an outdoor experiment were conducted to evaluate the potential of chlorophyll fluorescence and in vivo absorptance spectra as biomarkers of short-term experimental and long-term solar UV radiation exposure in macroalgae. The eulittoral macroalga Porphyra umbilicalis (L.) (Rhodophyta) and the sublittoral macroalga Palmaria palmata (L.) (Rhodophyta) were collected at three different sites along a vertical transect on the beach and in the water column. Significant decreases in the absorptance spectra at 497 and 569 nm (consistent with the presence of R-phycoerythrin and/or carotenoids and phycoerythrobilin, respectively) occurred in P. palmata after exposure to elevated UV-B (2.7 Wm −2). Furthermore, depth-dependent decreases in thallus absorptance at specific wavelengths were found after all exposures, indicating that in vivo thallus absorptance may be a useful general indicator of UV exposure in conjunction with other biomarkers. Also, a depth-dependent decrease in F v F m was detected in P. palmata. A 60% decrease in thallus absorptance and lack of recovery in chlorophyll fluorescence F v F m ratio indicated irreversible damage to accessory pigments, chlorophyll a and photosystem II after exposure to elevated UV-B. Moreover, a depth-dependent increase in thallus absorptance between 290 and 325 nm was observed in P. palmata in response to short-term experimental elevated UV-B exposure and between 290 and 380 nm in response to long-term solar UV-B. In contrast, the eulittoral alga Porphyra umbilicalis exhibited a greater degree of tolerance of UV-B exposure. The results highlight the potentially damaging effects of high irradiances of photosynthetically active radiation and UV and the necessity of utilising several biomarkers when assessing the biological effects of UV-B irradiation associated with ozone depletion.

A preliminary comparison of the mariculture potential of Porphyra purpurea and Porphyra umbilicalis

Due to their rapid growth and nutrient assimilation,Porphyra spp. are good candidates for bioremediation and polyculture. The production potential of two strains of P. purpurea and P. umbilicalis from north-east USA was evaluated by measuring rates of photosynthesis (as O2evolution) of material grown at 20 °C. Photosynthetic rates of P. umbilicalis were 80%higher than P. purpurea over the temperature range 5–20 °C, at both sub-saturating andsaturating irradiances (37 and 289 μmol photonm-2 s-1). Porphyra umbilicalis was more efficient at low irradiances (higher α) and had a higher Pmax (23.0 vs 15.6 μmolO2 g-1 DW min-1) than P.purpurea, suggesting that P. umbilicalis is a better choice for mass culture, where self-shading maybe severe.

Influence of UV radiation and visible light on Porphyra umbilicalis: photoinhibition and MAA concentration.

Porphyra umbilicalis was cultured under constant light conditions but showed a diurnal pattern in chlorophyll fluorescence. Photoinhibition after light treatment was determined by PAM fluorescence measurements. Treatment with only UV irradiation caused a slow but steady decline in the effective photosynthetic quantum yield from which there was no recovery. Solar simulated irradiation led to a large decrease in quantum yield after short periods of irradiation; partial recovery occurred after shading the samples. No significant difference was found between samples exposed to PAR only or to PAR + UV-A and/or UV-B irradiation. Determination of mycosporine-like amino acids (MAAs)before and during exposure to solar simulated irradiation showed a high initial concentration of MAAs but no increase due to the irradiance treatment.

Effect of ultraviolet radiation on thallus absorption and photosynthetic pigments in the red alga Porphyra umbilicalis

The effect of ultraviolet (UV) radiation on thallus absorption, package effect, the concentration of photosynthetic pigments, photosynthetic oxygen production and effective quantum yield has been studied in the intertidal red macroalga Porphyra umbilicalis in the laboratory. High doses of UV-A and UV-B radiation result in a rapid decrease of thallus absorption and, after a 6 h exposure, total absorption is reduced to 25% of the initial value. Moreover, significant differences in the absorption peaks of the main pigments are found: while chlorophyll a (Chl a) and phycocyanin absorption peaks decrease by 65–67%, carotenoids and phycoerythrin (PE) peaks decrease by 75–82%. Uncoupling of the transfer of energy between PE and Chl a by UV is revealed by a gradual increase of fluorescence of PE up to 11 h of exposure, followed by a subsequent decrease of fluorescence of the PE, in parallel with the photobleaching of the pigments. Thalli with higher pigment concentration present a greater sensitivity to UV radiation, as revealed by a more pronounced decrease in total thallus absorption, oxygen production and effective quantum yield, and a less effective recovery under low irradiation. Exposure of the thalli to artificial UV radiation in an experimental chamber with spectra and doses more similar to those of the natural environment reveals that PAR + UV-A radiation promotes a gradual increase of the total absorption over 24 h; in contrast, PAR + UV-A + UV-B induces a significant decrease of the thallus absorption. However, the concentration in vitro of Chl a, carotenoids and biliproteins does not change in any of these light treatments. The spectrally averaged in vivo absorption cross section normalized to Chl a ( a *) increases after 24 h in PAR + UV-A, but it does not change in PAR and PAR + UV- A + UV-B, indicating that the degree of packing of the pigments in the membranes of the thylakoids (package effect) is decreased by PAR + UV-A, but that the reverse is induced by PAR + UV-A + UV-B. It is proposed that UV-A radiation induces an enhancement of the efficiency of light capture mediated by a relaxation of pigment packing in the light-harvesting antennae of this intertidal macroalga, while the reverse is promoted by UV-B radiation.