Dark respiration in the marine macroalga Chondrus crispus (Rhodophyceae)

Dark respiration in the red macroalga Chondrus crispus was studied under a variety of conditions. The components of respiration were examined using selective inhibitors in order to characterise pathways of respiration and examine regulation of respiration in marine macroalgae.In comparison to respiration rates generally reported for higher-plant leaves and roots, the steady-state rate of O₂ consumption by this alga, after 30 min dark pretreatment, was found to be quite low (three- to sixfold lower than in higher plants). The addition of uncoupler had only a slight effect on the basal respiration rate, indicating that in these conditions, substrate supply could be limiting respiration. The addition of KCN inhibited respiration by approx. 60%, indicating the presence of alternative oxidase activity. The coefficient of engagement of the alternative pathway (calculated from the data herein) showed that under normal conditions there was little participation of the alternative pathway in O₂ consumption. The response of respiration to O₂ tension was examined with and without inhibitors and the apparent K _m was 17 to 21 M. The addition of KCN plus salicylhydroxamic acid almost completely blocked respiration in C. crispus. The hypothesis that respiratory substrate limits respiration in this alga was investigated by measuring respiration rates immediately after periods of photosynthetic activity. It was found that the respiration rate was dependent on the duration of the light period and could increase up to twofold. This stimulated rate of respiration declined in a first-order fashion during the next 20 to 30 min, finally reaching the basal, zero-order rate measured before illumination. These results strongly indicate a change in the nature of the respiratory substrates during this period. No change in the contribution of the alternative pathway of respiration could be detected following light pretreatment.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - SHAM salicyl hydroxamic acid     

Ammonium uptake by Chondrus crispus Stackhouse (Gigartinales,Rhodophyta) in culture

Cultivated Chondrus crispus was used in N-NH₄ uptake experiments in the laboratory. An elevation of temperature increased the apparent rate of uptake, especially up to 11 °C. Uptake in the dark was found to be 83 % of that in the light. The apparent uptake decreased with increasing internal N pool; rates were 26.5, 22.2 and 20.2 µg N g dry wt^–1 min^–1 for internal N pools of 2.7, 3.5 and 4.6%, respectively. Apparent uptake increased with the substrate N concentration. The resulting curve has two components: an active uptake and a diffusion component at high (> 5000 µg N L^–1) external N levels. Ks and V _max were calculated by deducting the diffusion component from the uptake curve: these were of 497 µg N L ^–1 and 14.4 µg N g dry wt^–1 min^–1. respectively, and reflect a low substrate affinity. This could be the result of 10 years of continuous culture of C. crispus. Uptake was similarly followed in the culture tanks and showed comparable results; nighttime would be the most appropriate time to supply nutrients.     

Etiology of infectious diseases in cultivated Chondrus crispus (Gigartinales,Rhodophyta)

The appearance of cavities and holes in fronds of commercially cultivated Chondrus crispus is described. These ultimately arise from the ravages of a green spot or green rot disease system in which several biotic agents can participate. Nematodes capable of bacterial grazing were recovered from necrotic lesions and we suggest that the nematodes can facilitate wound healing in diseased tissues. Bacteria isolated from disease lesions and from the surfaces of healthy fronds were screened for pathogenic strains. A particularly virulent one, the DOR isolate, was purified from small dark orange colored colonies grown on dilution plates. It was present in necrotic tissue and also recovered from surface scrapings of old healthy fronds, but not from their apical regions. Growth of the DOR isolate appeared to be inhibited by other bacteria colonizing the algal surface. It was shown to be a facultative pathogen, the virulence of which depended on the availability of ammonium or constituents easily metabolized to ammonium. It induced green rot disease in healthy C. crispus and was recoverable in pathogenic form from experimentally infected frond apices. A wound, disease and recovery cycle is discussed to illustrate potential interrelationships involving animal grazers, algal endophytes, Petersenia pollagaster, bacteria and nematodes.     

Short-term variations of mycosporine-like amino acids in the carrageenan-producing red macroalga Mazzaella laminarioides (Gigartinales,Rhodophyta) are related to nitrate availability

Journal of Applied Phycology - The effect of solar UV radiation exposure and NO3– supply on mycosporine-like amino acids (MAAs) accumulation in the carrageenan-producing red macroalga...     

Life history,morphology and crossability of Chondrus ocellatus forma ocellatus and C. ocellatus forma crispoides (Gigartinales,Rhodophyta) from the north-western Pacific

The morphology, life histories and crossability in culture are described for the marine red algae Chondrus ocellatus Holmes forma ocellatus from Japan, China and Korea and C. ocellatus f. crispoides Mikami (Gigartinaceae, Rhodophyta) from Japan. In culture, all isolates of both formae showed a Polysiphonia-type life history typical of the family Gigartinaceae. Plants of C. ocellatus f. ocellatus from Korea and China and some strains from Japan formed gametangia under long-day conditions (LD) at 15°C; however, two other Japanese strains required short-day conditions (SD) at 15°C for gametogenesis, indicating a photoperiodic response. Plants of C. ocellatus f. crispoides did not require SD for gamete formation. In all strains, tetrasporophytes of both formae produced tetrasporangia under LD. Isolates of C. ocellatus f. ocellatus from Japan, China and Korea were found to be completely sexually compatible regardless of photoperiodic characteristics, and the responses to daylength shown by progeny of LD and SD strains suggested Mendelian inheritance of a daylength factor. Chondrus ocellatus f. ocellatus was sexually incompatible with C. nipponicus Yendo, a morphologically similar species from Japan, but C. ocellatus f. crispoides was partially interfertile with both C. ocellatus f. ocellatus and C. nipponicus, indicating that the three entities are closely related. In view of the apparently higher breeding compatibility between C. nipponicus and C. ocellatus f. crispoides, and the fact that these two entities are more similar morphologically and reproductively, it is proposed, provisionally, to refer C. ocellatus forma crispoides to C. nipponicus.     

Chondrus crispus (Gigartinaceae,Rhodophyta) tank cultivation: optimizing carbon input by a fixed pH and use of a salt water well

The injection of exogenous carbon into intensively cultivated algal tanks is necessary to insure a maximum growth rate by stabilizing the dissolved inorganic carbon (DIC) pool, but represents the major part of the cultivation cost (ca. 73%). This study was conducted in paddle-wheel tanks ranging in size from 260 m² to 1000 m². Additional carbon was provided by carbon dioxide mixed into the incoming sea water through a tubular reactor. Production vs pH was analysed on 120 growth measurements covering two years of continuous cultivation. Whereas production peaked at pH 8.0–8.2, the economic optimum for pH regulation was in the range 8.4–8.5, where CO₂ injection was greatly reduced (–29%) for only a slight decrease in production (–4%). Expressed as a function of pH level, the specific carbon injection (g c gdw^–1 of Chondrus produced) showed an inverse exponential relationship, whereas gross photoconversion ratio (gdw mol photons^–1) varied according to a second degree equation with a low amplitude. The photoconversion ratio was not improved when the culture was maintained at a DIC concentration higher than the natural equilibrium (0.64 ± 0.11 gdw mol photons^–1 at 2.35 mM and 0.65 ± 0.15 gdw mol photons^–1 at 3.19 MM).A complementary source of carbon was found in underground salt water with a high and stable DIC concentration (10.15 ± 0.25 mmole Cl^–1). The mixing of the well water with natural sea water allowed another economy of CO₂ (–20% at pH 8.5) and nutrients (–12%), the total unitary cost of production being cut by about 17%.     

Delineation of Chondrus (Gigartinales, Florideophyceae) in China and the origin of C. crispus inferred from molecular data

Complete nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) sequences were obtained for 18 Chondrus populations collected at 15 sites from eight countries worldwide. Pairwise comparisons with the multiple alignment revealed that intraspecific divergences of ITS sequences ranged from 0.3 to 1.8% in C. crispus Stackhouse (except for the entity SVLH from France) and from 0.0 to 0.6% in C. ocellatus Holmes, whereas interspecific divergences in Chondrus varied from 1.4 to 5.0%. Three phylogenetic methods (neighbour joining, maximum parsimony and maximum likelihood) confirmed three main lineages: the North Atlantic lineage containing entities of C. crispus from Canada, France, Germany, England, Portugal, Ireland and Wales; a second lineage comprising three species: C. sp. 1, C. armatus (Harvey) Yamada et Mikami, and C. pinnulatus (Harvey) Okamura from the Northern Pacific; and a third lineage containing just one species: C. ocellatus from the Northern Pacific. Chondrus yendoi Yamada et Mikami separated from other Chondrus species singly. nrDNA ITS data indicate that a previous assignment of C. sp. 2 to Mazzaella japonica (Mikami) Hommersand may be incorrect, and additional evidence is needed to resolve the generic placement of this entity. It is inferred from the nrDNA ITS data that three Chondrus species are presently known in China with two, C. ocellatus and C. nipponicus, in Qingdao and two, C. armatus and C. nipponicus, in Dalian. We hypothesize that the ancestor of North Atlantic C. crispus had a Pacific origin, and that the present distribution of C. crispus in the Atlantic Ocean correlates with a trans-Arctic dispersal and vicariance events associated with Pleistocene glaciation maxima.     

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.     

Life history and photoperiodic responses in Chondrus giganteus forma flabellatus (Gigartinaceae,Rhodophyta) from Japan

The life history and photoperiodic responses of the carrageenophyte Chondrus giganteus forma flabellatus (Rhodophyta) from Japan were investigated in culture. This entity has a Polysiphonia-type life history and the formation of both tetrasporangia and cystocarps is controlled by daylength. A night-break of 1 h in the middle of a 16 h night was effective in inhibiting reproduction, confirming the classical photoperiodic nature of the response. Tetrasporangia formed at daylengths of 12 h or less, whereas cystocarps only developed at daylengths of 10 h or less. The formation of spermatangia required daylengths of 12 h or less, but production was not inhibited by a night-break of 1 h in the middle of a 16 h night.     

Relationship between cover of Chondrus crispus (Gigartinales,Rhodophyta) and Phymatolithon (Corallinales,Rhodophyta) on friable rock substrata

Field observations in sublittoral Prince Edward Island, Canada, indicated that on a friable sandstone substratum Chondrus crispus was more commonly associated with Phymatolithon sp. than with bare rock. Thus, a substantial proportion of the population of Irish moss along the coast of Prince Edward Island occurs on this encrusting coralline. These observation may be explained on the basis of the relative stability of the substratum in contrast to other studies in which sloughing of epithallial cells by species of both Phymatolithon and Lithothamnium has been reported to limit epiphytism by fleshy macrophytes.Issued as NRCC 31426.     

The effect of ultraviolet radiation on photosynthesis and ultraviolet-absorbing substances in the endemic Arctic macroalga Devaleraea ramentacea (Rhodophyta)

In field studies conducted at the Kongsfjord (Spitsbergen), the effect of filtered natural radiation conditions (solar without ulraviolet [UV]-A+UV-B, solar without UV-B, solar) on photosynthesis and the metabolism of UV-absorbing mycosporine-like amino acids (MAAs) in the marine red alga Devaleraea ramentacea have been studied. While solar treatment without UV-A+UV-B did not affect photosynthesis during the course of a day, solar without UV-B and the full solar spectrum led to a strong inhibition. However, after offset of the various radiation conditions, all algae fully recovered. Isolates collected from different depths were exposed in the laboratory to artificial fluence rates of photosynthetic active radiation (PAR), PAR+UV-A, and PAR+UV-A+UV-B. The photosynthetic capacity was affected in accordance with the original sampling depth, i.e. shallow-water isolates were more resistant than algae from deeper waters, indicating that D. ramentacea is able to acclimate to changes in irradiance. Seven different UV-absorbing MAAs were detected in this alga, namely mycosporine-glycine, shinorine, porphyra-334, palythine, asterina-330, palythinol, and palythene. The total amount of MAAs continuously decreased with increasing collecting depth when sampled in mid June, and algae taken in late August from the same depths contained on average 30–45% higher MAA concentrations, indicating a seasonal effect as well. The presence of increasing MAA contents with decreasing depth correlated with a more insensitive photosynthetic capacity under both UV-A and UV-B treatments. Populations of D. ramentacea collected from 1 m depth, with one fully exposed to solar radiation and the other growing protected as understorey vegetation underneath the kelp Laminaria saccharina, exhibited quantitatively different MAA compositions in the apices. The exposed seaweeds contained 2.5-fold higher MAA values compared with the more shaded algae. Moreover, the exposed isolates showed a strong tissue gradient in MAAs, pigments, and proteins. The green apices contained 5-fold higher MAA contents than the red bases. Transplantation of D. ramentacea from 2 m depth to the surface induced the formation and accumulation of MAAs after 1 week exposure to the full solar spectrum. Control samples which were treated with the solar spectrum without UV-A+B or with solar without UV-B showed unchanged MAA contents, indicating a strong UV-B effect on MAA metabolism. All data well supported the suggested physiological function of MAAs as natural UV sunscreens in macroalgae.     

Persistence of gametophyte predominance in Chondrus crispus (Rhodophyta,Gigartinaceae) from Nova Scotia after 12 years

Gametophytes predominated clearly over tetrasporophytes in an intertidal population of Chondrus crispus at Tor Bay (Nova Scotia, Canada) in the summer of 1991. Since this species is perennial and the rocky substrate is stable at this site, we predicted that gametophyte predominance would persist after several years. We confirmed this hypothesis by re-sampling the same area in the summer of 2003. This is one of the first long-term studies of the relative abundance of life-history phases done unequivocally at the same site for the Gigartinaceae.     

Reproduction ofChondrus crispus Stackhouse (Rhodophyta,Gigartinales) in sublittoral Prince Edward Island,Canada

The influence of size (as biomass), morphology and depth on reproductive patterns was examined in populations ofChondrus crispus in the sublittoral zone of Prince Edward Island, Canada. Fronds of ≥ 10 mg wet wt were considered, and a minimum biomass could not be related to reproduction. However, as frond biomass increased, the frequency of reproductive structures also increased. Reproductive maturity was related to the number of dichotomies. Fronds with less than two dichotomies were only occasionally reproductive, while those with two or more dichotomies could bear sori. Depth in the Prince Edward Island environment had no apparent influence on reproductive maturity, and there was no apparent relationship between depth and the vertical distribution of cystocarpic or tetrasporic fronds.