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The Medieval Climate Anomaly (MCA) is a well-recognized climate perturbation in many parts of the world, with a core period of 1000–1200 CE. Here we are mapping the MCA across the Antarctic region based on the analysis of published palaeotemperature proxy data from 60 sites. In addition to the conventionally used ice core data, we are integrating temperature proxy records from marine and terrestrial sediment cores as well as radiocarbon ages of glacier moraines and elephant seal colonies. A generally warm MCA compared to the subsequent Little Ice Age (LIA) was found for the Subantarctic Islands south of the Antarctic Convergence, the Antarctic Peninsula, Victoria Land and central West Antarctica. A somewhat less clear MCA warm signal was detected for the majority of East Antarctica. MCA cooling occurred in the Ross Ice Shelf region, and probably in the Weddell Sea and on Filchner-Ronne Ice Shelf. Spatial distribution of MCA cooling and warming follows modern dipole patterns, as reflected by areas of opposing temperature trends. Main drivers of the multi-centennial scale climate variability appear to be the Southern Annular Mode (SAM) and El Nino-Southern Oscillation (ENSO) which are linked to solar activity changes by nonlinear dynamics.

Cytotoxic platinum(II) alkynyl complexes of the type [(COD)Pt(Me)(C≡CR)] and [(COD)Pt(C≡CR)2] were evaluated for their cellular uptake, thioredoxin reductase (TrxR) inhibition and toxicity against zebrafish embryos. Quantification of the cellular uptake confirmed lower accumulation levels for the mono-alkynyl derivatives [(COD)Pt(Me)(C≡CR)] in comparison to the bis-alkynyl complexes [(COD)Pt(C≡CR)2]. Importantly, the complexes were efficient inhibitors of TrxR in contrast to cisplatin, which was not active. Toxicity studies in zebrafish showed lower activity if compared with the cytotoxicity against tumor cells indicating a suitable therapeutic index for the complexes.

A field population of Ulva pseudocurvata Koeman et C. Hoek (hereafter termed Ulva) at Sylt Island (North Sea, Germany) exhibited biweekly peaks of gametophytic reproduction during the colder seasons and approximately weekly peaks during summer. The reproductive events lasted 1-5 d and were separated from each other by purely vegetative phases. Under constant conditions in the laboratory, a free-running rhythm was observed with reproductive peaks occurring approximately every 7 d. When artificial moonlight was provided every 4 weeks, fewer reproductive events occurred, and the reproductive rhythm became synchronized to the environmental artificial moonlight rhythm. In the laboratory, apical disks were entirely converted into reproductive tissue after 8 d cultivation, while almost all basal disks stayed vegetative, which prevented the entire loss of the vegetative thallus during reproductive events. Seasonal size reduction of the thallus occurred from late autumn onward and was determined to be controlled by a genuine photoperiodic response, since size reduction could be induced from May onward by experimental short-day (SD) treatment but was prevented in a long-day (LD) or night-break regime (NB). A daily fine-tuning occurred with gamete release early in the morning at the first sign of daylight, following an obligatory dark ("night") period of at least 1 h duration. No release took place if the overnight dark phase was replaced by continuous light. Blue, green, or red light all triggered gamete release after a dark phase at an irradiance of 0.1 mu mol photons . m(-2) .s(-1), while 0.001 mu mol photons . m(-2) . s(-1) was equivalent to a dark control.

The plan of a study concerning the effect of irradiation of spermatogonia during successive generations in a mouse population is presented. The results from the first generation have failed to show any deterioration in the irradiation series when compared with simultaneous controls. There was a lower rate of death before weaning in the irradiation series compared to the controls. This might be spurious and will be further studied in succeeding generations. (auth)

Luning, K. G. 1990. Genetics of inbred Drosophila melanoguster. XXIV. Effects on the strength of the M-type. —Hereditas 113: 261–270. Lund, Sweden. ISSN 0018–0661. Received August 13. 1990. Accepted September 21, 1990 Several branches with genome from either of two inbred lines of Drosophila melanogaster, introduced into various sources of cytoplasms, were used in tests of the strength of the M-type. In contrast to the conventional tests of dysgenesis, we examined primary non-disjunction and chromosome loss in successive broods from M/P hybrid females. In broods from the 2nd week of egg-laying, there were increased frequencies of X0-males and a strong depression of fertility. There were no indications of cytoplasmic influence on the M-type. In a third line with the same cytoplasm as in a couple of the above mentioned ones, there was a lower effect on chromosome loss and on fertility. Crosses between different genotypes, but with the same source of cytoplasm, suggested a delayed genic influence in maternal inheritance. Tests of recombination in the X-chromosome indicated a gradual depression from the mid part to the distal end. There seemed to be no genic effect on the depression of recombination. It is suggested that there are pleiotropic effects of the P-factors and that the response to the various processes could be under both genic and cytoplasmic control in the M-type females.

To examine the possible influence of various sources of cytoplasms on recombination in the major part of the X-chromosome in Drosophila melanogaster, tests were performed in intra- and inter-line crosses. Two to six sister lines of various types were included. It was shown that cytoplasms of various sources could have different effects in the distal y-cx region but not in the mid (cx-v) or the sub-proximal (v-f) regions in both intra- and inter-line crosses. There were no diversities between sister-lines that had been separated for over 100 generations. Tests of two sets of sister-lines with the same source of cytoplasm in which different genomes had been introduced confirmed the earlier finding that there is an interaction of chromosomal and cytoplasmic influences on recombination. It is shown that changes in one extrachromosomal element (R-elements) had no demonstrable consequences on the effect on recombination. The necessity to consider cytoplasmic-bound variability is stressed.

In tests of secondary non-disjunction in hybrids from two inbred lines (+w ++ H– K/y wa ex vf – 2IBS Yy+) the majority of exceptional females are phenotypically w/wa. 1252 such females were tested individually to reveal whether recombination had occurred or not. 30 of these females were recombinants, and 13 of them had recombined in the y-w region. A subdivision based on the brooding scheme indicated that in the 1–5th day broods the frequency of recombination in the y-w region was 0.49 % and in the 11–14th day broods 2.09 %. (The corresponding frequencies from XX mothers of the same inter-strain cross were 0.88 and 2.59 %, respectively.) It is concluded that these results are in accordance with a former analysis of phenotypic deviants among exceptionals, thereby indicating that recombination at the most distal end of the X-chromosome is very similar in XXY and XX females. The results also suggest near normal pairing in the most distal end of the X-chromosomes of XXY females prior to non-disjunction.

Although Bridges (1916, Genetics 1: 1–52 and 107–183) found recombinants among exceptional XXY females in tests of secondary non-disjunction, he misinterpreted their origin and claimed that true secondary non-disjunction resulted in XX eggs with non-crossover chromosomes. Preliminary tests of inter-strain crosses of inbred lines indicated different frequencies of recombinant exceptional females in reciprocal crosses. Large scale tests confirmed this observation. However, they indicated that, as judged by recombination in the most distal end (y-w interval), there was presumably nearly the same frequency of chromosome pairing in XX females as in exceptional females from XXY mothers. In the more proximal regions there was a decreasing proportion of recombinants among exceptional females as compared to regular females. The decrease was more pronounced in one direction of crosses than in the reciprocal indicating a maternal influence. The use of inbred lines made it possible to compare the frequencies of recombinant X-chromosomes in females of primary and secondary non-disjunctional origin in the same genetic and cytoplasmic background. It was shown that the absolute frequency of recombinants was much higher in secondary non-disjunction than in primary. Some complex phenodeviants among the exceptional females revealed that their recombination could occur between euchromatic parts of the X-chromosomes and between X and either Y-arm indicating trivalent formation, however, of type different from that suggested by Cooper (1948, Proc. Nat. Acad. Sci. 34,5: 179–187).

In two inbred lines of Drosophila melanogaster, marker genes had been induced (y, wa, ex, v and f in Oregon, code “2”; and w in Karsnas, code “K”). As well as the two original lines, two derived lines with mutual exchange of cytoplasm and genome were obtained by more than 40 generations of back-crossing of reciprocal hybrids to males from the paternal line. Both XX and XXBsYy + females were available from the four lines. Isogenic hybrids with mothers from the two original and the two derived lines were tested for recombination in the y-cx-v-f regions. Simultaneous comparisons were made between hybrids from XX mothers and both XX and XXY daughters of XXY mothers. There was no difference between the two groups of XX females. In the distal region, y-ex, there was in all tests an increasing frequency of recombination over successive broods with the pattern influenced by the maternal genotype, the origin of the cytoplasm and the presence of an extra Y-chromosome. The median region, cx-v, showed a tendency towards decreasing recombination, with some influence exerted by the cytoplasm. The sub-proximal region, v-f, showed a slight tendency towards decreasing frequencies, in early broods related to the maternal genotype. The XXY females had lower frequencies than XX females. – It was shown that the Y-chromosome in XXY hybrids had, in all four combinations, a tendency to be included in the same nucleus as the centromere of the “K”-line more often than randomly. The similarity in the increasing frequency of recombination in the distal region, y-ex, in regular and secondary non-disjunction exceptionals as well as the decreasing frequencies of both recombination in the v-f region in XXY females and secondary non-disjunction are discussed.

Luning., K. G., Lake, S. and Linde, M. 1984. Genetics of inbred Drosophila melanogaster XII. Effects of an X-chromosome inversion on primary and secondary non-disjunction.—-Hereditas 100: 247–257. Lund, Sweden. ISSN 0018–0661. Received August 1, 1983 In an inbred line of Drosophila melanogaster. Oregon (code 2), an inversion covering the proximal half of the X-chromosome was induced (symbol: In(l) Lu-l y wd cxvf-2). It has been shown that inversion homozygotes have low frequencies of primary nun-disjunction. in the same manner as equilinear females with regular gene order of the 2–line. Intra-strain structural heterozygotes gave an excess of XO exceptionals but also a 5–fold increase of true primary non-disjunction (XXY) as compared to structural hornozygotes. Inter-strain crosses with mothers from line “K” revealed an influence both by the maternal genome and by the origin of the cytoplasm. Tests of secondary non-disjunction in structural heterozygous XXY females from both intra- and inter-strain crosses indicated highly complicated relations. When the mothers were of “2” origin the first brood showed lower frequencies of XXY exceptionals than in successive broods. whereas when the mother was of “K” origin there was a decrease after the 3rd brood (7th day). The “K”-line showed a dominance effect which was manifested by higher frequencies of XXY exceptionals. In regular daughters the Y-chromosome followed preferentially the proximal part of the X-chromosome of “K”. origin. There was no preference in the Y-chromosome distribution in intra-strain hybrids. There was a pronounced low frequency of recombinants among exceptionals. This indicates that the high frequencies of exceptionals from inversion heterozygous XXY females occur by another mechanism than in equilinear XXY females with the same genetic background.

Luning, K. G. 1987. Genetics of inbred Drosophila melanoguster. XVIII. Genetic interaction on R- and I-reactivity. - Hereditas 106: 233–239. Lund, Sweden. ISSN 0018–0661. Received September 16, 1986 Among the sublines derived from the inbred “K-line (Karmas) we isolated both R-lines (w-K and yw-K) and two independently arisen I-lines of which wf-K and ywf-K carried the same 1-factor in the X-chromo-some. The second I-line (yKYw-K) was recently isolated from an R-line. Tests of all intra-strain combinations: R/I, R/R, I/I and I/R were performed as well as some inter-strain tests. It was shown that in R/I hybrids the yw-K females gave lower reactivity than the w-K females, while in the males those from yellow mothers showed stronger I-reaction than from y+ mothers (yellow-effect). Still after one generation, the yellow-effect remained. — There was no yellow-effect in WR females. — The two I-lines showed, in I/I females, diverging results. The wf-K line and even more evidently the ywf-K line gave lower frequencies of XXY and X0 exceptionals than in R/R females. The yKYw-K was similar to R/R. — I/R hybrids showed higher frequencies of exceptionals than in 111 females. Only the yKYw-K line gave an excess of X0 males as compared to WR. The yellow-effect in R/I hybrids is discussed and the possibilities for molecular genetic analysis of independent I-factors in the same genetic background are stressed.

Effet de l'intervalle de generation et de l'homozygotie du locus yellow sur la reactivite R, implication des elements R cytoplasmiques dans ces phenomenes

Luning, K. G. 1984. Genetics of inbred Drosophila melanogaster. XI. Further tests of the effects of cytoplasm and maternal genotype on primary non-disjunction and chromosome loss.—Hereditas 100: 243–246. Lund, Sweden. ISSN 0018–0661. Received August 1, 1983 Three inbred lines of Drosophila melanogaster (code: “2”, “12”, and “K”) have been used in former tests of primary non-disjunction and chromosome loss. By repeated back-crossing, genome from the “K” line was introduced into cytoplasm of line “2”. F1 and F2 generations of reciprocal hybrids between lines “12” and “K” were tested for primary non-disjunction and chromosome loss. K/12 hybrids from the “K” line with “2” cytoplasm were tested in F1. Both the maternal genotype and the cytoplasm had a considerable influence on both amplitude and brood pattern of primary non-disjunction and chromosome loss. Comparisons between former tests with K/2 hybrids revealed both similarities and differences in response.

Luning, K.G. 1987. Genetics of inbred Drosophila melanogaster. XVII. Changes in the cytoplasm related to the length of the generation interval. - Hereditas 106: 107–113. Lund, Sweden. ISSN 0018–0661. Received May 2, 1986 A common genome “Karsnas”, code “K”, was by back-crossing introduced into cytoplasm from seven different iso-female lines. Two or four sister-lines were started from each. They were propagated with 14-day generation intervals. After more than 20 generations of back-crossing, sublines were branched off and were propagated at 2May generation intervals by sampling offspring from the 15–17th day of egg-laying. Five of the seven sets of sublines had a changed norm of reaction as regards the frequency of X0 males in the two or four sister-lines. In one cytoplasm only had one of the two sublines changed after 14 generations and in another cytoplasm none had changed after nine generations. We have shown here that it was the change in the generation interval that caused the change of norm of reaction. By repeating the tests at the 27th and 22nd generation, respectively, we found that all sublines had changed more or less. From one suhline which had changed less we established 17 suh-suhlines from single females. These fell into two (possibly three) groups as regards the frequencies of X0 males. One group showed the original norm of reaction typical of a short generation interval. This result indicates that the change of reaction is discontinuous rather than gradual. Some consequences are discussed.

Melatonin, the chief secretory product of the vertebrate pineal gland is also known to occur in numerous photoautotrophic organisms. The indoleamine is suspected to act as a transducer of photoperiodic information and/or to participate in antioxidative protection. In higher plants and other photoautotrophic organisms, contradictory results for melatonin content for samples from the same species show that further improvement of methods for reliable quantification is required. In the present study, melatonin was quantified in tomatoes, ginger and the marine green macroalga, Ulva lactuca, after extraction with three different extraction methods based on ether, acetone or perchloric acid. Melatonin was determined by enzyme-linked immunosorbent assay (ELISA) in high-performance liquid chromatography (HPLC)-purified extracts. The same HPLC system used for purification of extracts was used for parallel quantifications after derivatization of melatonin under alkaline conditions in the presence of hydrogen peroxide (HPLC-PD). Both quantification methods gave similar results with a high correlation [f(x) = 0.99x + 3.01; R(2) = 0.99]. In ginger, the melatonin concentration was below 5 pg/g (fresh weight, f.w.), whereas in tomatoes about 1200 pg/g (f.w.) were found, and in the green alga, U. lactuca, approximately 12 pg/g (f.w.). Taking into account the recovery rates for synthetic melatonin added prior to extraction, no substantial differences were observed in melatonin quantification between different extraction methods. The demonstrated methods based on HPLC purification and subsequent quantification by ELISA and HPLC-PD allow highly sensitive melatonin determinations in diverse photoautotrophic organisms with a low risk of overestimations by false-positive results.

For the first time, plantlets were obtained from fragments and cell aggregates (CA) of apical meristem of the red alga Gelidium sp. After two months of cultivation, an initial weight of 100 mg of fragments and CA from fresh meristem produced 3 g of plantlets without rhizoids. During the same period of cultivation, 100 mg of meristem fragments and CA isolated from thalli by the freezing-thawing procedure produced more than 20 g of plantlets with rhizoids. It is assumed that our methods for obtaining plantlets from fragments and CA of fresh and frozen-thawed meristem could be used to generate mass planting material for cultivation of algae (plantlets with rhizoids) in the sea and for tank-bubbling cultivation (plantlets without rhizoids). We speculate that meristem cells of frozen-thawed algae might be natural “seedstock” in the Arctic and Antarctic seas.

Field-collected tetrasporophytes of Palmaria palmata were tumbled in 300-L outdoor tanks from January to August at ambient daylength or in a constant short-day (SD) regime (8 h light per day), both at 10 or 15 degrees C. Tetrasporangia were massively induced after 2.5 months under SD conditions at 10 degrees C and completely lacking at 15 degrees C, both under SD or ambient daylength conditions, with a few tetrasporangia present at 10 degrees C and ambient daylength. Elongation rates of tagged tetrasporophytic thalli peaked from March to April in all four conditions, when the biomass densities in the outdoor tanks were close to 2.5 kg fresh weight m(-2). Under all four conditions, juvenile proliferations started to appear in June from the margins of the old fronds, and attained approximately 1 cm in length by the end of July. Approximately 80% of the tetraspores were released during the first three dark phases in a light/dark regime, and the remaining 20% during the light phases. A minimum of 10 min darkness was observed to trigger spore release. White light inhibited tetraspore release, while a similar number of spores were released in continuous red light or in the light/dark regime, although with no significant differences of spore release during subjective days and nights. Sporelings were successfully derived from the released tetraspores for mass propagation of the male gametophyte in 2000-L outdoor tanks in a greenhouse. Mass production of male gametophytic sporelings of P. palmata was completed two times by SD induction of tetrasporangia at 10 degrees C, release of spores in darkness and culturing the sporelings until they were ready to be propagated vegetatively in greenhouse tanks. One experiment lasted from January to October 2001, with spore release in June, and the second from September to April 2003, with spore release in January. These results may support the development of sustainable, year-round Palmaria farming. (c) 2005 Elsevier B.V. All rights reserved.

Many biological processes are under the control of an endogenous circadian clock, a prominent example within the plant kingdom being photosynthesis. Here we report a robust circadian rhythm of photosynthetic oxygen evolution in the marine red macroalga Grateloupia turuturu. The rhythm was obvious in continuous white light at irradiances ranging from 50 to 500 μmol photons m−2s−1. To assess whether this physiological rhythm was correlated with changes at the level of gene transcription in G. turuturu, abundance of the transcripts encoding the phycoerythrin α and β subunits and the ribulose 1,5 bisphosphate carboxylase/oxygenase (Rubisco) subunits was analysed under light-dark cycles (LD) and continuous illumination (LL). Abundance of both transcripts exhibited diurnal and circadian changes in G. turuturu. In LD conditions, abundance of the phycoerythrin transcript peaked between midday and late afternoon. This pattern was maintained under constant conditions (LL) for up to three cycles. For the Rubisco tra...

Various processes in the output pathway of the circadian clock are thought to act as important clock targets resulting in the circadian rhythms of photosynthesis observed in various algae. Examples of such processes are synchronization of the cell cycle, pigmentation, and light or dark reaction of photosynthesis. The newly detected, robust photosynthetic circadian rhythm in the red macroalga Kappaphycus alvarezii was investigated in more detail with respect to rhythmically changing components within the photosynthetic apparatus. The following major results were obtained; (1) The growing tips of Kappaphycus (0–2 cm) were found to exhibit a diurnal and circadian rhythm of nuclear division like many other algal species, (2) The circadian photosynthetic rhythm was apparent in the actively growing and dividing tip portions (0–;2 cm) as well as in older portions (2–4 cm) with little remaining mitotic activity. The Kappaphycus rhythm seems therefore to be independent of the cell cycle, at least in the older port...

Year-round induction of sporogenesis of Laminaria saccharina was performed by mechanically blocking the transport of the putative sporulation inhibitors produced by the blade meristem and culturing the plants in constant short days. Sporogenesis was successfully induced by removal of the blade meristem, either by cultivating distal blade fragments or by performing a transverse cut in the frond. The earliest sorus formation after artificial induction was 10 days. The age of the sporophytes used for induction was 6-11 months or 2 years in tank-grown or field-collected sporophytes, respectively. Zoospores were successfully released in all cases. Thus, by year-round artificial induction of sporogenesis, (1) sporeling production of L. saccharina and thereafter sporophyte cultivation could be achieved without seasonal limitation, and (2) the life cycle of L. saccharina (from spore to spore) could be completed within 8 months under controlled conditions. (C) 2004 Elsevier B.V. All rights reserved.

Tank cultivation of marine macroalgaeinvolves air-agitation of the algal biomassand intermittent light conditions,i.e.periodic, short light exposure of thethalli in the range of 10 s at the watersurface followed by plunging to low lightor darkness at the tank bottom andrecirculation back to the surface in therange of 1–2 min. Open questions relate toeffects of surface irradiance on growthrate and yield in such tumble cultures andthe possibility of chronic photoinhibitionin full sunlight. A specially constructedshallow-depth tank combined with a darktank allowed fast circulation times ofapproximately 5 s, at a density of 4.2 kgfresh weight (FW) m-2s-1. Growthrate and yield of the red alga Palmaria palmata increased over a widerange of irradiances, with no signs ofchronic photoinhibition, up to agrowth-saturating irradiance ofapproximately 1600 μmol m-2s-1 in yellowish light supplied by asodium high pressure lamp at 16 h light perday. Maximum growth rate ranged at 12% FWd-1, and maximum yield at 609 gFW m-2 d-1. This shows that highgrowth rates of individual thalli may bereached in a dense tumble culture, if highsurface irradiances and short circulationtimes are supplied. Another aspect ofintermittent light relates to possiblechanges of basic growth kinetics, ascompared to continuous light. For thispurpose on-line measurements of growth ratewere performed with a daily light reductionby 50% in light-dark cycles of 1, 2 or 3min duration during the daily light period.Growth rates at 10 °C and 50 μmolphoton m-2 s-1 dropped in allthree intermittent light regimes duringboth the main light and dark periods andreached with all three periodicitiesapproximately 50% of the control , with noapparent changes in basic growth kinetics,as compared to continuous light.

Two photoperiodic responses, the development of sporophylls and hairs, have been quantified in sporophytes of the brown alga Undaria pinnatifida. In a final experiment, the algae were cultivated in outdoor, 2000-L seawater tanks in a greenhouse for up to 12 weeks, and daylength was regulated by automatic blinds mounted on top of the tanks. Vegetative young sporophytes were treated under short-day (SD; 8 h light per day) or long-day conditions (LD; 16 h light per day), at 12 h light per day or in a night-break regime (NB; 8 h light per day, 7.5 h dark, 1 h light, 7.5 h dark). The earliest sporophyll development was observed 6, 7 or 9 weeks under LD, NB or SD conditions, respectively. After 12 weeks the sporophylls were significantly longer and wider under LD or NB conditions than in the SD regime, and only half of the experimental algae had formed sporophylls under SD conditions, but all algae under LD or NB conditions. In a foregoing 7-week culture experiment performed in 300-L indoor tanks, enhanced sporophyll formation had also been observed under LD and not under SD conditions (NB omitted). In both experiments, blade elongation rates remained high until the end of the experiments in SD, but declined during sporophyll initiation in LD, NB or at 12 h light per day. Another difference caused by photoperiod was observed in regard to the development of surface hair spots which occurred in both experiments on the blades in LD, NB or at 12 h light per day with identical densities, but were completely lacking under SD conditions. It is concluded that U. pinnatifida is a facultatative long-day plant in regard to reproduction forming vigorously sporophylls in long days, and an obligate long-day plant in regard to hair formation.

Anoxic conditions were widespread in NW Africa during the early Frasnian (Late Devonian) that resulted in deposition of organic-rich shales and limestones with total organic carbon (TOC) values of up to 14%. Organic richness and thickness of these sediments vary laterally, and organic-rich vs. organic-poor facies boundaries are likely to have been diachronous. A precise temporal–spatial reconstruction of this anoxic phase in NW Africa is complicated because the organic matter in outcrops is largely oxidised and biostratigraphic resolution in boreholes is generally low due to the lack of recoverable conodonts. This contribution is based on eight outcrop sections at the margin of the central Algerian Ahnet Basin, where detailed spectral gammaray measurements were carried out using a handheld instrument. The pre-weathering organic richness in Frasnian outcrop sections is approximated using the characteristic uranium enrichment in the anoxic facies that, based on well studies, is positively correlated with the total organic carbon content. Conodont biostratigraphic results from these sections suggest that the uraniumenriched interval (the anoxic interval) at the basin margin is most common in the basal Frasnian conodont Biozones 1–2, confirming previous results from the Anti Atlas in Morocco. In three of the eight localities studied the basal Frasnian has not been deposited and the Frasnian here commences with distinctly younger uranium-enriched intervals, including Zones 4–11. Well data from the eastern Algerian Berkine Basin is interpreted to indicate a significantly longer anoxic phase there. Million-yearscale diachroneities of the Frasnian anoxia, therefore, clearly exist across the North Africa shelf. It is assumed that the palaeorelief might have been a major factor in controlling the onset, duration, and intensity of anoxia in the region. D 2003 Elsevier B.V. All rights reserved.

Circadian regulation of transcriptional gene expression has been shown for a variety of taxa throughout the eukaryotic kingdom and for prokaryotic cyanobacteria but not previously for macroalgae. We reported earlier a strong circadian rhythm of photosynthetic capacity in the red macroalga Kappaphycus alvarezii (Doty) Doty. To determine whether this rhythm is correlated with circadian regulation of steady-state transcript abundance, we analyzed transcripts of genes whose protein products are involved in photosynthesis. Transcript levels of two plastid-encoded operons, one for phycoerythrin α and β subunits and another for RUBISCO large and small subunits, were analyzed under light:dark cycles (LD) and under constant illumination (LL) for several days. Both transcripts exhibited diurnal regulation under LD conditions with maximum transcript abundance during early daytime to midday. Under LL conditions, circadian oscillations of steady-state mRNA abundance were detected for up to three cycles; thus, the analyzed transcripts exhibited diurnal and circadian regulation. Interestingly, peak abundance of the RUBISCO transcript shifted to subjective night under LL. To our knowledge, this is the first report demonstrating that circadian control of steady-state transcript abundance occurs in a macroalga.

A word-wide overview is presented of the current state of mass cultivation of seaweeds. In comparison with a total annual commercial production of fish, crustaceans and molluscs of about 120 × 106t, of which one-third is produced by aquaculture, the production of seaweeds is about 10 × 106t wet weight; the majoirty of this comes from culture-based systems. The Top Ten Species List is headed by the kelp Laminaria japonica with 4.2 × 106t fresh weight cultivated mainly in China. The productivity of a well-developed, multi-layered, perennial seaweed vegetation is as high as dense terrestrial vegetation, and even higher annual values for productivity have been reported for tank cultures of macroalgae. Epiphytes provide a major problem for the seaweed cultivator, but can be controlled by growing plants at high densities in rope cultures in the sea, or, more easily, in seaweed tank cultures on land. The main environmental problem of animal (fed) aquaculture is the discharge of nutrient loads into coastal waters, e.g., 35 kg N and 7 kg P t−1 aquacultured fish. Integration of fish and seaweed farming may help to solve this problem, since seaweeds can remove up to 90% of the nutrient discharge from an intensive fish farm. Mass culture of commercially valuable seaweed species is likely to play an increasingly important role as a nutrient-removal system to alleviate eutrophication problems due to fed aquaculture.

The Lower Palaeozoic deposits in North Africa are dominated by sandstones and shales which often lack biostratigraphically useful body fossils. Trilobite burrows (Cruziana) partly fill this gap and provide the basis for medium-resolution stratigraphic interpretations. Several Ordovician-Silurian ichnostratigraphically significant Cruziana forms have been found and studied in the Kufra Basin (SE Libya), including C. goldfussi and C. furcifera from the Lower Ordovician Hawaz Fm. and a new ichnospecies, C. kufraensis, occurring in transgressive sandstones at the base of the Lower Silurian Tanezzuft Fm. The upper Tanezzuft Fm. and Akakus Fm. typically contain C. acacensis, a form that is characteristic of the Lower Silurian of Northern Gondwana.

The rate of oxygen evolution of the tropical red alga Kappaphycus alvarezii was measured for 6 days in the laboratory using a computer-aided method for long-term recording. In cool white light Kappaphacus exhibited a robust circadian rhythm of O2 evolution in the irradiance range of 100 to 1000 µmol m-2 s-1. With increasing irradiance the period of the free-running rhythm, tau, decreased in blue and increased in red light, but did not change significantly in green light. The accelerating or slowing action of blue or red light, respectively, points to two photoreceptors used in the light transduction pathway of the circadian oscillator controlling oxygen evolution or the light reactions of photosynthesis in Kappaphycus. No significant changes of tau were observed with increasing irradiance in cool white light, possibly due to the additive, opposing responses caused by blue and red light.

Previous laboratory studies in species of the Laminariales have revealed that both the onset of growth in early winter and the summer drop in growth rate are controlled by the annual course of daylength synchronizing endogenous, circannual clocks within the thallus. Moreover, it is known for some laminarian species that cultivation in the laboratory in constant short days (SD) leads to arhythmic, continuous growth activity of the blade throughout the year. Such a prolonged SD treatment has now been performed for the first time in outdoor-cultivated Laminaria digitata. Field-grown sporophytes were collected in May from the sea near Helgoland (North Sea) and cultivated on the island of Sylt (North Sea) in temperature-controlled outdoor tanks (300 l) at 10°C for 1·5 years either in a constant 8 h of light per day, controlled by an automatic blind on top of the tank, or in ambient daylengths. In constant SD, the growth rate remained at a steady-state level of approximately 0·4 cm day−1 from the end of June un...

Field-collected specimens of three species of Laminaria and three species of subtidal red algae (Delesseria sanguinea, Plocamium cartilagineum and Phyllophora pseudoceranoides) were exposed to natural summer sunlight on Helgoland (southern North Sea) for up to 4 h at 15 °C. Dark-adapted variable fluorescence (F, : F m ) was measured immediately after these treatments, and following 6, 24 and 48 h of recovery in moderate irradiances of white light. The response of plants to the full spectrum of natural sunlight was compared with that to PAR alone, UV-A + visible, UV-A + UV-B, or UV-A alone. The F, : F m values of all species were reduced to minimal values after 4 h in all of these treatments, but those of the more resistant species (Laminaria spp. and P. pseudoceranoides) were higher after shorter exposures to UV radiation alone than to PAR with or without UV. The recovery of F, : F m in all species was also more rapid in the two treatments that contained UV radiation alone than in those that included PAR. These results suggest that it is the high irradiances of PAR in natural sunlight which are responsible for the photoinhibition of photosynthesis of subtidal seaweeds and that the current ambient irradiances of UV radiation (either UV-B or UV-A) in northern temperate latitudes would not contribute significantly to this photoinhibition.

The sublittoral red alga Delesseria sanguinea was pre-cultivated in the laboratory in a predominantly green light field at 10 µmol m-2s-1 (10°C), with an approximately 0.5% daily increase in blade area. Such pre-cultivated blades were exposed horizontally in flow-through chambers for 5-6 days in April or May to solar radiation reduced to 11 or 19% by neutral density screens. In all three experiments conducted, the full solar spectrum (UVB+UVA+PAR) reduced growth rate significantly to 0-50% of values obtained in PAR alone, while this occurred with UVA+PAR only in one experiment. The growth rate of a Delesseria blade may thus be used as a sensitive and reliable biological indicator of UVB in natural solar radiation at a pre-chosen, neutral reduction level. Rapid measurements of growth rate of apical parts of Delesseria blades during and after UVB+UVA pulses of 2, 3 or 6 h duration were performed in the laboratory by measuring thallus area every 2 min by use of a CCD camera coupled to an on-line, computer-aided image analysis system. A single pulse of 2 or 3 h duration administered during the light phase caused a temporary drop in growth rate during and after the pulse, with recovery starting 2.5 h after the end of the pulse and completed by the end of the light phase. A single 6-h pulse at a biologically effective UVB dose (BEDDNA300nm) weighted according to Setlow (1974) of only 0.5 kJ m-2 reduced growth rate by 55% if administered around noon, or halted growth almost completely, if supplied at night, when no photoreactivation was possible. The UVB-sensitive behaviour of Delesseria compares well with the highly sensitive phytoplankton alga Emiliana huxleyi whose growth was reported to be halted at a daily, weighted BEDDNA300nm of 0.4 kJ m-2 administered during 4 days for 3 h in the middle of the light period.

The pathway from the intercalary frond meristem to distal frond portions was blocked in experimental sporophytes of Laminaria digitata in January by cutting 2 or 3 holes (15-25 mm diameter) 5 cm from the base of the frond. This procedure resulted in the formation of sori within 5-10 weeks adjacent to the distal edge of the holes. Frond portions that were cut at least 20 cm away from the stipe-frond transition readily formed sori within 5-7 weeks after isolation from the rest of the thallus. These findings suggest that the basal, actively dividing and expanding part of the laminarian frond is the source of inhibitors of sporangium formation which move in a distal direction and keep the young frond free of sori during the season of rapid growth, i.e. during the first part of the year. The natural occurrence of sori during the season of slow growth, i.e. the second part of the year in the Northern hemisphere, may be due to reduced synthesis and export of inhibitors of sporangium formation from the more or less resting basal meristem.