Exposure to ultraviolet radiation delays photosynthetic recovery in Arctic kelp zoospores

Seasonal reproduction in some Arctic Laminariales coincides with increased UV-B radiation due to stratospheric ozone depletion and relatively high water temperatures during polar spring. To find out the capacity to cope with different spectral irradiance, the kinetics of photosynthetic recovery was investigated in zoospores of four Arctic species of the order Laminariales, the kelps Saccorhiza dermatodea, Alaria esculenta, Laminaria digitata, and Laminaria saccharina. The physiology of light harvesting, changes in photosynthetic efficiency and kinetics of photosynthetic recovery were measured by in vivo fluorescence changes of Photosystem II (PSII). Saturation irradiance of freshly released spores showed minimal I _k values (photon fluence rate where initial slope intersects horizontal asymptote of the curve) values ranging from 13 to 18 μmol photons m⁻² s⁻¹ among species collected at different depths, confirming that spores are low-light adapted. Exposure to different radiation spectra consisting of photosynthetically active radiation (PAR; 400–700 nm), PAR+UV-A radiation (UV-A; 320–400 nm), and PAR+ UV-A+UV-B radiation (UV-B; 280–320 nm) showed that the cumulative effects of increasing PAR fluence and the additional effect of UV-A and UV-B radiations on photoinhibition of photosynthesis are species specific. After long exposures, Laminaria saccharina was more sensitive to the different light treatments than the other three species investigated. Kinetics of recovery in zoospores showed a fast phase in S. dermatodea, which indicates a reduction of the photoprotective process while a slow phase in L. saccharina indicates recovery from severe photodamage. This first attempt to study photoinhibition and kinetics of recovery in zoospores showed that zoospores are the stage in the life history of seaweeds most susceptible to light stress and that ultraviolet radiation (UVR) effectively delays photosynthetic recovery. The viability of spores is important on the recruitment of the gametophytic and sporophytic life stages. The impact of UVR on the zoospores is related to the vertical depth distribution of the large sporophytes in the field.     

Wavelength-dependent induction of UV-absorbing mycosporine-like amino acids in the red alga Chondrus crispus under natural solar radiation

Polychromatic response spectra for the induction of UV absorbing mycosporine-like amino acids (MAAs) were calculated after exposing small thalli of the red alga Chondrus crispus under various cut-off filters to natural solar radiation on the North Sea island Helgoland, Germany. The laboratory-grown specimens typically contain only traces of palythine and synthesise five different MAAs rapidly and in high concentrations after being transplanted into shallow water. The resulting qualitative and quantitative patterns of MAA induction differed markedly with respect to spectral distribution. Furthermore, the wavebands effective for MAA induction vary within the MAA. UV-B radiation had a negative effect on the accumulation of the major MAAs shinorine (λ_max=334 nm) and palythine (λ_max=320 nm), while short wavelength UV-A exhibits the highest quantum efficiency on their synthesis. In contrast, the synthesis of asterina-330 (λ_max=330 nm), palythinol (λ_max=332 nm) and palythene (λ_max=360 nm) was mainly induced by UV-B radiation. Whether the synthesis of shinorine and palythine is induced by a photoreceptor with an absorption maximum in the short wavelength UV-A and whether a second photoreceptor absorbing UV-B radiation is responsible for the induction of asterina-330, palythinol and palythene remains to be studied.Our results show that C. crispus has a high capacity to adapt flexibly the qualitative and quantitative MAA concentration to the prevailing spectral distribution of irradiance. On one hand, this is regarded as an important aspect with respect to the acclimation of algae to increasing UV-B irradiance in the context of ongoing depletion of stratospheric ozone. On the other hand, the experiment demonstrates that UV-A irradiance is more important for the induction of the major MAAs shinorine and palythine than UV-B.     

Effects of native and invasive macroalgal canopies on composition and abundance of mobile benthic macrofauna and turf-forming algae

We examined the effects of native kelps, Laminaria longicruris de la Pylaie and L. digitata (Hudson) Lamouroux, and of the invasive alga, Codium fragile ssp. tomentosoides (Van Goor) Silva, on the composition and abundance of mobile benthic macrofauna and of turf algae by measuring the response of these assemblages to experimental removal of the respective macroalgal canopy. From June 2003 to November 2004, we censused macrofauna and measured canopy cover within 4 × 10 m strips of alternating Canopy Intact (control) and Canopy Removed treatments in both a Codium- and a Laminaria-dominated habitat in the rocky subtidal zone of a semi-protected embayment on the Atlantic coast of Nova Scotia, Canada. Macroalgal canopy cover fluctuated seasonally, peaking in September/October (69% cover in 2003; 55% cover in 2004) for Codium and in May 2004 (70% cover) for kelps, and with both canopy types reaching a winter minimum in January 2004 (22 and 28% cover, respectively). In both Codium and Laminaria habitats, significant effects of canopy removal on the overall macrofaunal assemblage were evident only during periods in which canopy cover in the Canopy Intact treatment was ≥ 50%. In the Codium habitat, 4 out of 11 characteristic taxa were more abundant in the Canopy Intact treatment, where taxonomic diversity also was higher. In contrast, 4 out of 11 characteristic taxa in the Laminaria habitat were more abundant in the Canopy Removed treatment and diversity was similar between treatments. Turf algae were sampled in November 2004 and, despite between-treatment differences in the light regime, there was no significant effect of canopy removal. Our results indicate that selection of algal habitats by mobile macrofauna is likely determined by the different shelter and foraging opportunities offered by these morphologically dissimilar ecosystem engineers.     

Altitudinal variation of UV-absorbing compounds in Plantago asiatica

UV-absorbing compounds such as flavonoids and phenolic acids are important for plants to protect their vegetative organs from harmful UV radiation at higher altitude. Two chemotypes, i.e., acteoside mainly-containing (AM) type and plantamajoside mainly-containing (PM) type were found by qualitative HPLC analysis of the phenolics in the leaves of Plantago asiatica in Mt. Norikura, Japan. Though AM type was not detected in low altitude populations, it occurred in high altitude populations. Acteoside has been reported to be more effective antioxidant than plantamajoside. On the other hand, higher accumulations of UV-absorbing substances were seen in higher altitude populations by quantitative analyses. Besides, B-ring ortho-dihydroxylated flavonoids notably increased than mono-hydroxylated flavonoids with increasing altitude. These results demonstrate that P. asiatica has chemically acclimated to high altitudes, in which severe environmental conditions such as higher UV radiation exist.     

Growth and annual production of the brown alga Laminaria japonica (Phaeophyta, Laminariales) introduced into the Uwa Sea in southern Japan

The brown alga Laminaria japonica is distributed from southern Hokkaido to the northeastern Honshu in Japan. Recently, aquaculture of L. japonica has expanded to the southern coast of Japan and to China along the East China Sea. In order to elucidate the growth, biomass and productivity of L. japonica in a subtropical area, we cultivated and examined it in the Uwa Sea, in southwestern Japan over a period of 2 years. The seawater temperature ranged from 13.8 to 26.8 °C in 2001/2002 and from 13.1 to 27.2 °C in 2002/2003. In 2001/2002, the maximum density, maximum mean length and maximum mean wet wt. of L. japonica were 59.7 ± 28.0 ind. 50 cm^− 1 (mean ± S.D.), 187.5 ± 82.7 cm (360 cm in the largest individual) and 130.1 ± 94.6 g wet wt., respectively. In 2002/2003, these values were 94.7 ± 22.2 ind. 50 cm^− 1, 159.3 ± 74.4 cm (300 cm in the largest individual) and 95.2 ± 69.5 g wet wt., respectively. Thus, the length and weight increased when the density was low (2001/2002), and the length and weight decreased when the density was high (2002/2003). The maximum biomass was estimated to be 7200 ± 3400 g wet wt. 50 cm^− 1 in 2001/2002 and 7300 ± 2000 g wet wt. 50 cm^− 1 in 2002/2003. Annual production was estimated to be 33.3 kg wet wt. m^− 1 year^− 1 in 2001/2002 and 34.0 kg wet wt. m^− 1 year^− 1 in 2002/2003. The present study indicates that the annual production of L. japonica per rope of 1 m at Uwajima Bay, the Uwa Sea corresponded to 1.1-2.2 m² of that of Hokkaido in their native area. Thus, the present study indicates that L. japonica is highly adaptable because it is able to keep a high level of productivity when grown in water with a high temperature.     

Thallus morphology and optical characteristics affect growth and DNA damage by UV radiation in juvenile Arctic Laminaria sporophytes

Growth of young sporophytes of the brown algae Laminaria digitata, L. saccharina and L. solidungula from Spitsbergen were measured in the laboratory after being exposed for 21 days to either photosynthetically active radiation (PAR=P) or to full light spectrum (PAR + UV-A + UV-B=PAB) using of cutoff glass filters. The plants were grown at 8±2°C and 16 h light : 8 h dark cycles with 6 h additional ultraviolet radiation (UVR) exposure in the middle of the light period. Growth was measured every 10 min using growth chambers with online video measuring technique. Tissue morphology and absorption spectra were measured in untreated young sporophytes while chlorophyll (Chl) a content and DNA damage were measured in treated thalli at the end of the experiment. In all species, growth rates were significantly higher in sporophytes exposed to P alone compared to sporophytes exposed to PAB. Tissue DNA damage is dependent on thallus thickness and absorption spectra characteristics of pigments and UV-absorbing compounds. In sporophytes exposed to UVR, energy demands for repair of DNA damage and synthesis of UV-absorbing compounds for protection effectively diverts photosynthate at the expense of growth. Photosynthetic pigment was not significantly different between treatments suggesting a capacity for acclimation to moderate UVR fluence. The general growth pattern in sporophytes exposed to P alone showed an increasing growth rate from the onset of light (0500–0900 hours) to a peak at the middle of the light phase (0900–1500 hours), a decline towards the end of the light phase (1500–2100 hours) and a minimum “low” growth in the dark (2100–0500 hours) relative to growth during the entire light phase. Under PAB, different growth patterns were observed such as growth compensation at night in L. digitata, delayed growth recovery in L. saccharina and minimal but continuous growth in L. solidungula. Growth as an integrative parameter of all physiological processes showed that the effect of UVR is correlated to the depth distribution of these species.     

The edible brown seaweed Alaria esculenta (Phaeophyceae, Laminariales): hybridization, growth and genetic comparisons of six Irish populations

Alaria esculenta populations from six differentgeographical locations on the Irish coast wereexamined for hybridization abilities, growth rates andgenetic make-up with a view towards identifying afast-growing strain suitable for aquaculture.Hybridization experiments under laboratory conditionswith the three most geographically dispersedpopulations showed that all cross combinations wereinterfertile, although differences were found insurvival, and in blade and hapteron morphology. Acomparison of relative growth rates showed significantdifferences amongst the self-crosses and hybrids. Thedata of the hybridization experiments and growth ratesunder laboratory conditions show that the bestpopulation for the purpose of seaweed aquaculture arethe Slea Head and Corbet Head self-crosses and theirhybrids. Genetic fingerprinting of the internaltranscribed spacer of the ribosomal DNA of five A. esculenta isolates from geographically separatedpopulations in Ireland revealed no restriction lengthpolymorphisms between the tested isolates and showthat the A. esculenta populations around theIrish coast are clearly genetically homogenous inrespect of the DNA region examined. The geneticanalysis, interfertility of the populations,morphology and growth rates are discussed with a viewto potential cultivation.     

Cladochytriales—a new order in Chytridiomycota

Recently, molecular and ultrastructural analyses have resulted in revised phylogenetic hypotheses in the phylum Chytridiomycota. The order Chytridiales, once considered monophyletic, has been subdivided into several new orders. However, the most recent analyses indicate that the emended Chytridiales is also polyphyletic. One monophyletic lineage in Chytridiales includes Cladochytrium, Nowakowskiella, and five other genera. Many of the chytrids in this clade have often been observed growing on decaying plant tissue and other cellulosic substrates from aquatic habitats and moist soils. In this study we analysed combined nu-rRNA gene sequences (partial SSU and LSU) of 30 isolates from North American aquatic and soil samples. Based on molecular monophyly and zoospore ultrastructure, we designate this clade as a new order, Cladochytriales, which includes four families: Cladochytriaceae, Nowakowskiellaceae, Septochytriaceae fam. nov., and Endochytriaceae.     

Glycoconjugates for the recognition of Bacillus spores

Carbohydrates act as ligands in many biological processes, including the folding and secretion of proteins, cell-cell recognition, adhesion, and sporulation in the Bacillus genus. Fluorescent-labeled disaccharide glycoconjugates have been applied to evaluate binding to bacterial spores assuming that the spore surface is covered with carbohydrates. This study has shown that specific recognition of bacterial spores is based on interactions between disaccharide glycoconjugates acting as ligands and monosaccharide units expressed on the exterior of bacterial spores. Using fluorophore-assisted carbohydrate electrophoresis (FACE), carbohydrates that are expressed on the exterior of the spores were enumerated. The findings have an impact on how to improve ligand selection, essential for sensor development. In addition, the findings provide new information for inhibition of bacterial spores, and in general, demonstrate how carbohydrates function as recognition signals in nature.     

Pathogenicity of intrathoracically administrated Bacillus thuringiensis spores in Blatta orientalis

The ability of Bacillus thuringiensis to produce septicaemia in Periplaneta americana and Blatta orientalis has been investigated. Spores and crystals from several wild-type strains as well as spores of a B. thuringiensis crystal-deficient mutant, were first orally administrated at high doses, and no significant mortality was recorded. Intrathoracic injection of spore suspensions in P. americana revealed that this species is not very susceptible to B. thuringiensis spores. B. orientalis, by contrast, was found to be very susceptible to B. thuringiensis, with a LD(50) of about 35,000 spores, that is similar to that reported on Lepidoptera challenged with parenterally injected B. thuringiensis.     

Effects of changes in ambient PAR and UV radiation on the nutritional quality of an Arctic diatom (Thalassiosira antarctica var. borealis)

Polyunsaturated fatty acids (PUFAs) are essential macromolecules that are synthesized by phytoplankton during spring bloom, and they play a key role in the Arctic food web. They are, however, considered to be sensitive to oxidation by UV radiation (280-400 nm). Changes in the food quality of primary producers may affect the transport of biomass and energy in the whole ecosystem. Using a common Arctic diatom, we looked at the effect of ambient and increased UV radiation on its nutritional quality, specifically, the fatty acid composition and elemental ratios. In May 2004, in the archipelago of Svalbard (79° N), a unialgal culture of Thalassiosira antarctica var. borealis was subjected to a 17-day experiment in outdoor aquaria. The diatoms were kept in semi-continuous culture (40 1) and exposed to three treatments with different levels of UV radiation: none (UV-shielded), ambient, and enhanced. Fatty acid composition, C:N:P ratios, photosynthetic pigment composition, optimum quantum yield of PSII, and cell numbers were analysed over the experimental period. An initial increase in PAR (photosynthetically active radiation, 400-700 nm) intensities profoundly affected the fatty acid composition and substantially inhibited the synthesis of PUFAs, but the relative amounts of PUFAs were not reduced by UV radiation. Enhanced UV radiation did, however, cause a significant reduction in optimum quantum yield of PSII and affected some fatty acids, mainly 18:0 and 16:1 n-7, during the first week of the experiment. Both ambient and enhanced UV radiation caused significantly lower C:P and N:P ratios. At the same time, these treatments elicited a higher relative content of the photoprotective pigments diadinoxanthin and diatoxanthin. After acclimation to the new light levels these effects faded off. Thus, brief periods with high light exposure may cause significant changes in photosynthetic activity and food quality, but the capacity for photo-acclimation seems high. The impact of UV radiation seems to be less important for food quality than that of PAR during a sudden rise in total light intensity.     

Induction of phenolic compounds in Hypericum perforatum L. cells by Colletotrichum gloeosporioides elicitation

Changes in phenolic metabolism after elicitation with Colletotrichum gloeosporioides (CG) has been studied in Hypericum perforatum L. (HP) cell suspension cultures. Soluble phenolics were analysed by HPLC-DAD and HPLC-DAD-MS/MS. HP cultures elicited with the CG elicitor showed a significant increase in xanthone accumulation. Xanthone accumulation increased twelve fold when the cells were primed with methyl-jasmonate (MeJ) or salicylic acid (SA), before elicitation. HP cultures exposed only to MeJ produced a set of flavonoids, the flavones which represent a substantial part (approx. 40%) of the total flavonoids accumulated in these cells. The possible importance of xanthones as a component of defence mechanism of HP against biotic stress is discussed.     

Morphogenetic responses from protoplasts and tissue culture of Laminaria digitata (Linnaeus) J. V. Lamouroux (Laminariales, Phaeophyta): callus and thalloid-like structures regeneration

The regeneration of meristematic tissues from sporophytes of Laminaria digitata was studied by protoplast and tissue culture. Sequential treatment of explants in sterile seawater with 1% Betadine for 5 min, 1% commercial bleach for 1–2 min and 2% antibiotic treatment supplemented with 1 μM GeO₂ overnight enabled viable explants as high as 55%. Different morphogenetic responses were observed from tissue culture on media supplemented with plant growth regulators alone or in combination, mainly filamentous calluses up to 50% according to the media. Dark green compact calluses were observed on two combinations: 4 μM Pi + 2 μM N-(2-chloro-4-pyridyl)-N’-phenylurea (CPPU) and 0.04 μM Pi + 0.44 μM 6-benzylaminopurine. Thalloid-like structures comparable to adventitious buds were regenerated on medium supplemented with 4 μM Pi + 0.45 μM zeatin but at low frequency suggesting a strong genotypic effect. Friable calluses were developed from protoplasts in enriched medium with polyamines and containing 0.40 μM CPPU + 0.45 μM 2,4-dichlorophenoxyacetic acid. In order to produce protoplasts, a one-step enzymatic protocol was developed and yields reached 22 × 10⁶ protoplasts per gram of fresh weight.     

UV radiation biomonitoring using cell compartmentation of UV-absorbing compounds in herbarium samples of a liverwort

Ultraviolet-absorbing compounds (UVACs) were analyzed in 90 herbarium samples of the liverwort Jungermannia exsertifolia subsp. cordifolia collected throughout Spain in the period 1913–2006, in order to evaluate their usefulness in UV radiation biomonitoring. This was assessed, for the first time in bryophytes, differentiating the soluble (mainly vacuolar) and insoluble (cell wall-bound) UVACs (respectively, SUVACs and IUVACs), which may represent different mechanisms to cope with UV radiation. The bulk levels of SUVACs and IUVACs, and the concentrations of seven individual compounds (five SUVACs and two IUVACs) were analyzed, and several environmental variables of the sampling points were obtained: longitude, latitude, altitude, ozone column, and modelled UV levels.Diverse positive relationships of UVAC variables with UV radiation levels were identified in both the temporal and spatial scales. The soluble compound p-coumaroylmalic acid showed significantly higher concentrations in the years after the onset of stratospheric ozone degradation (around 1975) with respect to the previous years. The bulk level and the concentrations of three individual SUVACs were higher in the Spanish samples analyzed in the present study than in the northern European samples analyzed in a previous study in which IUVACs were not considered. The bulk level of IUVACs was the biological variable best spatially correlated with the UV exposure of the samples and with important factors determining it, such as altitude and latitude. Furthermore, the bulk level of IUVACs was the biological variable selected by a stepwise multiple linear regression analysis to reconstruct the past levels of UV-B radiation. The reconstructed UV-B did not show a clear trend in the period 1913–2006, which was coincident with other climatic and biological UV reconstructions. Both SUVACs and IUVACs were significant loading factors differentiating summer and autumn samples in the Principal Components Analysis conducted using both UVACs and the environmental variables, but again the bulk level of IUVACs was the main loading factor differentiating the samples collected from the highest and most UV-exposed localities (Sierra Nevada). In general, these findings suggest that UVACs were stimulated by increased UV levels in time or space, and that IUVACs would be better UV protectants than SUVACs, probably due to their more efficient screening capacity.Overall, UVACs of J. exsertifolia subsp. cordifolia were good UV biomarkers, and their location in the soluble or cell wall-bound fractions determined their usefulness in the different aspects of UV biomonitoring, including the assessment of the UV-B increase associated to anthropogenic ozone degradation.     

The role of ammonium in photoprotection against high irradiance in the red alga Grateloupia lanceola

Combined and/or interactive effects of inorganic nitrogen (as ammonium) and irradiance on the accumulation of nitrogenous compounds, like UV-absorbing mycosporine-like amino acids (MAAs), chlorophyll a and phycobiliproteins, were examined in the red alga Grateloupia lanceola (J. Agardh) J. Agardh in a high irradiance laboratory exposure and a subsequent recovery period under low light. Also, photosynthetic activity as in vivo chlorophyll fluorescence of photosystem II, i.e. optimum quantum yield (F_v/F_m), electron transport rate (ETR) and quantum efficiency, were examined. Photosynthetic activity, phycobiliproteins and internal nitrogen content declined during the 3-day PAR (photosynthetically active radiation; 600 μmol s⁻¹ m⁻²) and PAR + UVR (ultraviolet radiation; UVB 280–315 nm 0.8 W m⁻², UVA 315–400 nm 16 W m⁻²) exposure. Ammonium supplied in the culture medium (0, 100 and 300 μM NH₄Cl) modified the responses of the alga to high irradiance exposures in a concentration dependent manner, mainly with respect to recovery, as the highest recovery during a 10-day low light period was produced under elevated concentration of ammonium (300 μM). The recovery of photosynthetic activity and phycobiliproteins was enhanced in the algae previously incubated under PAR + UVR as compared to exposure to only PAR, suggesting a beneficial effect of UVR on recovery or photoprotective processes under enriched nitrogen conditions. However, the content of MAAs did not follow the same pattern and thus it could not be concluded as the cause of observed enhanced recovery.     

Altitudinal variation of secondary metabolite profiles in flowering heads of Arnica montana cv. ARBO

The altitudinal variation on the contents of secondary metabolites in flowering heads of Arnica montana was assessed. Plants of A. montana cultivar ARBO were grown in nine experimental plots at altitudes between 590 and 2230m at Mount Patscherkofel near Innsbruck/Austria. The total contents of sesquiterpene lactones and flavonoids were not positively correlated with the altitude of the growing site. However, the proportion of flavonoids with vicinal free hydroxy groups in ring B to flavonoids lacking this feature significantly increased with elevation. Additionally, the level of caffeic acid derivatives also positively correlated with the altitude of the growing site. In particular amounts of 1-methoxyoxaloyl-3,5-dicaffeoylquinic acid significantly increased in higher sites and samples from the summit region contained 85% more of this compound than samples from valley sites. These results are discussed with regards to chemosystematic studies comparing samples collected in different altitudes as well as in the light of a UV-B protective and radical scavenging function of phenolics and their significance for plant life in environments with elevated UV-B radiation.     

Inter- and intraspecific variation in defensive compounds produced by five neotropical stink bug species (Hemiptera: Pentatomidae)

The differences in composition of defensive secretions between nymphs, adult males and adult females of Chinavia impicticornis (=Acrosternum impicticorne), Chinavia ubica (=Acrosternum ubicum), Euschistus heros, Dichelops melacanthus and Piezodorus guildinii (Hemiptera, Pentatomidae) were analysed within and between species using compositional log-ratio statistics and canonical variates analysis. Differences in composition between nymphs, males and females were found for all species, as well as when all species were pooled. In particular, tetradecanal appears to be a predominantly nymphal compound in D. melacanthus, E. heros and P. guildinii. In the two Chinavia species 4-oxo-(E)-2-hexenal and an unknown compound were more dominant in nymphs. The interspecific analysis revealed a good separation of defensive compounds according to their taxonomic relationship. Thus, the two Chinavia species grouped together, with (E)-2-decenal and (E)-2-hexenyl acetate, contributing to this separation. The other three species also differed from each other, with (E)-2-octenal associated to D. melacanthus, (E)-2-hexenal to P. guildinii and (E,E)-2,4-decadienal and tetradecanal to E. heros. The pooled analysis of stage ignoring species revealed tetradecanal and 4-oxo-(E)-2-decenal (tentative identification) strongly associated to nymphs. Thus, there are predictable differences between stages, and many of the differences are conserved between species. Consideration of these differences could prove to be important in understanding stink bug-natural enemy interactions, and in optimising biocontrol efforts.