Do correlations exist between chromatophore arrangement and photosynthetic activity in seaweeds?

In Dictyota dichotoma, as in many other plants, the chromatophores which at low intensities occupy the cell walls perpendicular to the light beam move to the side walls parallel to the light beam if exposed to high light intensities. The aim of this investigation was to find out whether or not the changes from low- to high-intensity arrangement and vice versa function as an active control mechanism to regulate photosynthetic activity in D. dichotoma under the respective light condition. Four different experimental approaches were made: (a) In white and blue light experiments the changes of the transmittance and of the rate of photosynthetic oxygen production in high- and low-intensity arrangement were compared. (b) The kinetics of the depression and recovery of the PS-rates, as well as of the transmittance changes, were determined during high- and low-intensity movement, respectively. (c) Transmittance and PS-rates of thalli under illumination with polarized and unpolarized light of the same intensity (1,000 1x) were compared. (d) PS-rates of thalli after darkening as well as after preirradiation with weak and strong red light, conditions under which the chromatophores occupy the same position in the cells, were measured. In all these experiments the photosynthetic activity was strongly influenced by pre-illumination, but was independent of the respective chromatophore arrangement. This finding was confirmed by experiments with two other algae: (1) In the brown alga Alaria esculenta which does not display light-induced chromatophore displacements and concomitant transmittance changes, pre-irradiation with high light intensities decreases the PS-rates. (2) In the green alga Ulva lactuca, which shows circadian chloroplast movements, the PS-rates depend on the pre-irradiation only, irrespective of the chloroplast position. Thus we may conclude that in these organisms the function of chromatophore displacements is not the regulation of photosynthetic activity. Other ecological functions are discussed.     

Circadian rhythms in the chromatophore movements of Dictyota dichotoma

In the brown alga Dictyota dichotoma Lamour the phaeoplasts move to the anticlinal walls (profile position) in strong light and to the periclinal walls (face position) in dim light. By these movements transmittance changes are caused. If the algae were grown in light:dark cycles of about natural daylengths, circadian oscillations of the amplitudes and the kinetics of these transmittance changes are initiated. The lengths of the free running periods vary between 24 and 29 h. In addition, light:dark grown thalli were transferred into continuous dim or strong light or darkness, in order to check whether or not the rhythms continued under these conditions. By taking photomicrographs of intact thalli and of isolated cortical cell layers, prepared by bisecting, it could be shown that the maxima and minima of circadian transmittance changes correspond well with the number of phaeoplasts at the periclinal cell walls. The ecological relevance of these phenomena is discussed.Presented in part by the first author at the XI. International Seaweed Symposium, Qingdao, People's Republic of China, 19 to 26 June, 1983     

Peculiarities of innervation in chromatophore muscle cells ofLoligo vulgaris

The contractile cortex in muscle cells of the large brown chromatophore organs inLoligo vulgaris features a small open slit in its proximal portion. The slit accommodates a nerve fiber, penetrating into the central core of the muscle cell. The functional properties of the fiber, in relation to the contraction of the muscle cell, are discussed.Supported by Deutsche Forschungsgemeinschaft.     

Prolonged reproductive consequences of short-term biomass loss in seaweeds

This study describes the reproductive collapse of a large giant-kelp forest (Macrocystis pyrifera; Point Loma, southern California, USA) and the dynamics of its subsequent recovery. High-frequency sampling within a 100-m² area, combined with a 3-year reproduction time-series from four other sites over a broad depth gradient, were used to (1) quantify temporal and spatial patterns of change in size and fertility of adult sporophytes, and (2) examine physical and biological factors that regulate such changes. Giant-kelp sporophytes have the potential for continuous reproduction, yet from March to November 1999, sporophytes at the high-frequency sampling site went from completely sloughing (actively releasing zoospores) to completely sterile, despite a relatively constant biomass of sporogenous tissues. This shift to sterility was rapid, with 65% of sporophytes ceasing to slough during late-June/early-July 1999, and did not co-occur with stressful physical conditions (i.e. high temperatures, low nutrients, or high wave intensity). Instead, the cessation of reproductive output corresponded to an episodic, sublethal amphipod-grazing event that stripped blade biomass from all sporophytes. Although the grazer infestation affected the entire kelp forest, peaks in grazer abundance were localized, moving through the population during late spring and summer, and causing patchiness in sporophyte size and fertility on a scale of meters. The reproductive collapse was size-dependent, since smaller sporophytes were the first to cease sloughing. The grazing event waned in the fall and sporophyte vegetative growth rapidly recovered lost biomass (within ~2 months). Such growth, however, occurred at the expense of the production of sporogenous tissue and caused a prolonged period (>4 months) of decreased reproductive output. These results suggest a trade-off between sporophyte growth and reproduction, allowing short-term disturbances to have lasting impacts on the reproductive output of giant-kelp populations.     

Effects of light quality on chlorophyll and biliprotein accumulation in seaweeds

The control of chlorophyll and biliprotein synthesis by different qualities of continuous light in four seaweeds, collected off the coast of Málaga (Spain) in the winter of 1986 and 1987, was investigated over the short term. In the green algaUlva rigida C. Aghardh, and in the red algaeCorallina elongata Ellis et Soland andPlocamium cartilagineum (L.), chlorophyll synthesis was induced by blue light. However, in the red algaPorphyra umbilicalis (L.), chlorophyll accumulation was primarily induced by red light. Phycoerythrin synthesis inCorallina elongata, Plocamium cartilagineum andPorphyra umbilicalis was stimulated primarily by green light, whilst phycocyanin synthesis was induced by red. The effect of light quality on the synthesis of photosynthethic pigments was rapid. The induction of chlorophyll synthesis of after 6 h in light was 11 to 20% higher than in the dark control. The induction of biliprotein synthesis was two times greater than that of chlorophyll. The results are discussed in terms of chromatic adaptation and as adaptative responses to the underwater light environment. The possible role of phytochrome, and of a blue-light photoreceptor, in the control of chlorophyll and biliprotein synthesis is discussed.Please address all correspondence and requests for reprint to Dr López-Figueroa at his present address: Botanisches Institut der Universität München, Menzingerstraße 67, D-8000 München 19, FRG     

Use of seaweeds for monitoring trace elements in coastal waters

Concentrations of a wide range of trace elements: arsenic, cadmium, cobalt, chromium, hafnium, nickel, thorium, uranium, zinc and the rare earth elements, cerium, europium, samarium, terbium and ytterbium were determined by instrumental neutron activation analysis in the brown alga,Fucus vesiculosus from Eckwarder Hörne, North Sea and from Rügen, Baltic Sea. Another brown alga,Sargassum filipendula from Sri Lanka, Indian ocean (representing an unpolluted control station) was similarly investigated. Cobalt, chromium and nickel concentrations were highest inF. vesiculosus from the North Sea while zinc was highest in samples from the Baltic Sea, reflecting high levels of these elements in coastal waters of the North and the Baltic sea. Cadmium, cobalt, nickel and zinc levels were lowest inS. filipendula from Sri Lanka, probably demonstrating lower levels of those elements in coastal waters. Concentration levels of hafnium, thorium, uranium, and the rare earth elements were highest inS. filipendula. Two years later in 1994,S. filipendula along withUlva sp. (green alga) was resampled from the same sampling site, and in addition to the above elements, six other trace elements (Ag, Ba, Br, Rb, Se and Sr) were determined.Sargassium filipendula showed a particular affinity for Ag, As, Br and Sr. For the other elements, marginal concentration differences were observed betweenS. filipendula andUlva sp., probably reflecting the regional background levels. Substantially higher concentrations of Hf, Th, U, and the rare earths were found again in the 1994Sargassum andUlva samples, reflecting the effect of a substrate rich in rare earth elements. The brown algae used in this study may be used to monitor trace elements in coastal waters.     

Changes in photosynthetic pigment concentration in seaweeds as a function of water depth

We conducted a study of the relationship between changes in photosynthetic pigment content and water depth in Great Harbor near Woods Hole, Massachusetts, USA, on the green algae Ulva lactuca and Codium fragile and the red algae Porphyra umbilicalis and Chondrus crispus. A calibrated underwater photometer equipped with spectral band filters measured light attenuation by the water column. The depth required for a 10-fold diminution of photon flux was 3.6, 5.3, 6.0 and 6.0 m for red, blue, yellow and green light, respectively. Seaweeds were attached to vertically buoyed lines and left to adapt for 7 days; then, with their positions reversed, they were allowed to readapt for 7 days. All species showed greater photosynthetic pigment content with increased depth. Further, the ratio of phycobiliproteins and chlorophyll b to chlorophyll a increased with depth. Changes in pigment content were reversible and occurred in the absence of cell division. There was a net loss of pigments near the surface (high irradiance), and subsequent synthesis when seaweeds were transferred to a position deep in the water column (low irradiance). In contrast, seaweeds which were found in intertidal habitats changed only their pigment concentration, and not pigment ratio, a phenomena analogous to higher plant sun and shade adaptation. Therefore, seaweeds modify their photon-gathering photosynthetic antennae to ambient light fields in the water column by both intensity adaptation and complementary chromatic adaptation.     

Concentration of polyvalent metals by seaweeds in Vostok Bay,Sea of Japan

Spectrophotometric methods were used to measure the contents of the polyvalent metals Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo and Zn in 16 species of red, brown, and green seaweeds and 2 species of higher water plants collected from the intertidal and sublittoral zones of Vostok Bay, Sea of Japan. Some of the species displayed a unique capability for increased accumulation of groups of several metals. We have termed this ability specific group concentration. Thus, Ptilota filicina concentrates Ti, V, Mn, Fe, Ni, Cu, Zn, and Mo; Polysiphonia japonica Ti, V, Mn, Fe, Zn, Mo, and Cr; Rhodomela larix Ti, V, Mn, Fe, Ni, Zn, and Cr; Agarum cribrosum Ti, V, Mn, Fe, Ni, Zn, and Cr; Ulvaria splendens Ti, V, Mn, Fe, Ni, and Cu; Ulva fenestrata Mn, Fe, Ni, and Cu; Enteromorpha prolifera Mn, Co, Zn, Mo, and Cr; codium yessoensis V, Mn, Fe, Ni, and Cr; Zostera asiatica Ti, Mn, Ni, and Mo; Phyllospadix iwatensis Ti, V, Mn, Fe, and Zn. Specific group concentration makes possible a new approach to the study of active transport of polyvalent metals, physiologically significant for live organisms, through cell membranes, and the study of the formation of complex metal compounds inside the cell, i.e., the study of the processes that determine the degree of element concentration. The contents of the metals studied in sea water and the accumulation coefficients were also determined. The variation range is extremely high both for the seaweed species and metals investigated. Maximum coefficients were noted for Mn: 1.8·10⁵; Ti: 4.4·10⁴; Fe: 2.4·10⁴; Cr: 1.2·10⁶.     

Comparative study of heavy metal distribution in some coastal seaweeds of Alexandria, Egypt

The distribution of Cd, Cu, Fe, Hg, Mn, Ni, Pb, and Zn concentration in five algae species (Enteromorpha intestinalis, Enteromorpha linza, Ulva lactuca, Corallina mediterranea, Pterocladia capillacea) collected from three areas having different types of metal contamination along Alexandria coastal waters (Egypt) were determined by Atomic Absorption Spectrometry. The recovery study was carried out using a Certified Reference Material TORT-2. The obtained heavy metal contents indicate that different species demonstrate various degree of metal accumulation. Enteromorpha intestinalis (green algae) recorded the highest levels of Fe and Mn while Corallina mediterranea (Calcareous red algae) recorded the highest concentration of Pb, Ni, and Cd in the three areas under study. According to the present study, filamentous algae (Enteromorpha intestinalis) showed the ability to concentrate greater amount of trace elements than the foliaceous ones (Enteromorpha linza). In each area, mercury concentration has nearly the same value for all species under study.     

Contents of heavy metals in marine seaweeds from the Egyptian coast of the Red Sea

Seaweeds belonging to 14 different genera of Chlorophyta, Phaeophyta, and Rhodophyta were analysed to determine the levels of heavy metals in two areas of the Egyptian Red Sea coast. Among the trace metals analysed, Mn and Zn showed the highest mass concentrations in the surface sea waters of the two studied areas. However, algae obtained from the Suez area had higher concentrations of the investigated heavy metals than those collect in the Mars Alam area. Nevertheless, a high variability of the metal levels occurs among the studied algae and also between the investigated areas. Moreover, Zn was the most abundant metal in the seaweeds of the Suez area, while Pb was predominant in the Mars Alam area in red and brown algae. Liagora spp. had the highest average concentration factor of Zn in Suez (29 161-fold), while the average concentration factor in Enteromorpha spp. at Mars Alam was 20 091-fold. The highest Metal Pollution Index (MPI) value was recorded in Liagora spp. (22.0) at Suez. This represents a 4.6-fold higher value than that recorded in Liagora spp. at Mars Alam. Among green, brown, and red algae in Suez, the highest values of MPI were recorded in Cladophora spp. and Halimeda spp. (18.2 and 18.3), Padina spp. (16.2), and Liagora spp. (22.1), respectively; while at Mars Alam, the highest values of MPI were recorded in Cladophora spp. (6.6), Padina spp. (3.4) and Liagora spp. (4.8), respectively.     

Survival and growth of the Norway lobster Nephrops norvegicus in relation to light-induced eye damage

 The long-term survival and growth of Norway lobsters, Nephrops norvegicus (L.), were examined in relation to light-induced retina breakdown. The incidence of eye damage was first assessed in tagged N. norvegicus released in Loch Torridon, on the west coast of Scotland between 1978 and 1983. Of 34 recaptures examined, all but four showed evidence of eye damage, varying in extent from 1 to 63% of the retina. Additional tagged N. norvegicus were released in Loch Torridon in 1984 and 1985 in order to compare recapture and growth rates in lobsters with and without eye damage. Three groups of N. norvegicus were released; normal sighted, partially sighted (median retina damage = 68%) and fully blinded (retina damage = 100%). From 1217 lobsters released, 235 were recovered by September 1992, when the experiment was concluded. The final proportions of N. norvegicus recaptured were found to be independent of eye-damage condition, and there was no evidence that growth rate was affected by eye damage. Combining all categories of releases, the overall proportion of females recaptured (0.244) was significantly greater than the proportion of males (0.145), suggesting better long-term survival in females than in males. At the time of release, ∼80% of the females were carrying recently spawned eggs. Although the proportion of berried females in the recaptures was slightly reduced in the two eye-damaged groups compared with the normal sighted group, the difference was not statistically significant. It is concluded that light-induced eye damage in N. norvegicus is irreversible, but such damage does not seem to influence their long-term survival, growth or reproduction. Received: 21 October 1998 / Accepted: 26 October 1999     

Abundance of Fucus spiralis and ephemeral seaweeds in a high eulittoral zone: effects of grazers,canopy and substratum type

According to a widely accepted view of intertidal community organization in the north-west Atlantic Ocean, the abundance of perennial seaweeds is regulated by the activities of herbivores (which control ephemeral algal competitors) and carnivores (which control populations of competing filterfeeders). This concept was examined in 1987–1988 in a eulittoral belt on the Atlantic shores of Nova Scotia, Canada, dominated by a closed canopy of Fucus spiralis. A factorial design was used to test the effects of (a) grazers (there were no carnivores present, (b) adult F. spiralis canopy, and (c) substratum type on the abundance of perennial and ephemeral seaweeds. Grazers had no significant (p>0.05) effect on the density or cover of juvenile F. spiralis, but significantly reduced canopy cover of adults through the winter. The presence of grazers significantly enhanced the cover of ephemeral algae in early spring. Barnacle presence enhanced the cover of juvenile F. spiralis, but reduced the canopy of adult plants through abrasion. The most important regulator of recruitment density in F. spiralis was the presence of a canopy of conspecific adults. Canopy greatly reduced juvenile development. There was no significant relationship between the covers of perennial F. spiralis and ephemeral seaweeds. This study demonstrates that the recruitment of the perennial rockweed population examined is not dependent on the activities consumer animals. The results contrast with work in the midshore intertidal of New England, where the activities of herbivores are thought to regulate the abundances of perennial seaweeds.     

Resource acquisition in two intertidal fucoid seaweeds, Fucus serratus and Himanthalia elongata : seasonal variation and effects of reproductive development

Seasonal variations and the effect of reproductive development on resource acquisition by two intertidal fucoid species, the iteroparous Fucus serratus L. and the semelparous Himanthalia elongata (L.) S. F. Gray were examined. The oxygen-exchange characteristics of vegetative apical tissue of both non-fertile and fertile plants and receptacle tissue were compared at monthly intervals throughout reproductive development. Respiratory rates in non-fertile F. serratus varied seasonally between 1.5 and 8.0 μmol g⁻¹ fresh wt h⁻¹; in fertile plants the receptacle had a significantly lower respiratory rate than the vegetative tissue. The respiratory rate of the vegetative button of fertile H. elongata displayed less seasonal variation and was lower than that of the receptacle, which varied from a maximum of 9.5 μmol g⁻¹ fresh wt h⁻¹ at receptacle initiation in October to a minimum of 2.0 μmol g⁻¹ fresh wt h⁻¹ in February. The maximum photosynthetic rate (P _max) of non-fertile plants of both species did not vary in a distinct seasonal manner (∼60 μmol g⁻¹ fresh wt h⁻¹ for F. serratus and ∼12 μmol g⁻¹ fresh wt h⁻¹ for H. elongata). In fertile plants, the P _max of the receptacle tissue was (∼50% lower in F. serratus, and at its peak three times higher in H. elongata, than that of vegetative tissue. The stable carbon-isotope ratio (δ¹³C) did not differ between different tissue types in F. serratus, but values did vary seasonally, being less negative in the summer than in the winter (−13.5‰ compared to −18‰). The receptacle tissue of H. elongata also displayed a distinct seasonal variation in δ¹³C values (−12‰ in summer, −16‰ in winter), whilst the δ¹³C of the vegetative button did not vary seasonally. The rate of uptake of inorganic nitrogen by the vegetative thallus was lower in H. elongata than in F. serratus. The receptacle tissue of F. serratus had lower uptake rates than the vegetative tissue, whilst the uptake rate by H. elongata receptacle tissue was higher than that of the vegetative button. Received: 14 March 1997 / Accepted: 22 April 1997     

Macro- and mesoherbivores prefer native seaweeds over the invasive brown seaweed <Emphasis Type="Italic">Sargassum muticum</Emphasis>: a potential regulating role on invasions

Herbivory has a strong impact on algal distribution, abundance and community structure and may influence the establishment and spread of introduced seaweed species. In this study, we assess the potential regulating role of herbivory on one of the most invasive brown seaweeds: Sargassum muticum. Multiple choice feeding experiments were conducted with 13 native seaweeds, S. muticum and 5 herbivore species from the Northwest, Southwest and South of Portugal. S. muticum was always the least or among the least preferred seaweeds and attained one of the highest growth rates of the tested seaweeds, with and without herbivores. The addition of herbivores increased the number of cases by 40% in which the invader had higher growth rates. Our results suggest that low grazing pressure on S. muticum by the recipient herbivore community may give the invader a competitive advantage over at least part of the native seaweed community, thereby contributing to the invasiveness of S. muticum along the Portuguese coast.     

宁夏贺兰石赋存特征及矿物成分分析

贺兰石是宁夏的五宝之一,具有极大的经济价值和人文含义.以银川市西部的贺兰山中段为研究区,调查分析贺兰石的赋存特征和矿物成分特征,结论认为(1)贺兰石含矿岩性段赋存于青白口系黄旗口组第一岩段下部,呈狭长的条带状分布,层位稳定连续,走向大致呈南北向,顺走向延伸长度约14 km.含矿层的厚度8～23 m;(2)矿石主要成分为粘土质矿物、绢云母和绿泥石,矿石的化学成分主要为SiO2、AI2O3、Fe2O3、K2O;(3)矿石吸水率均低于1%,矿石摩氏硬度为2～4,矿石体重平均为2.89 g/cm3,矿石抗压强度为58.17 MPa,抗拉强度7.1 MPa,抗剪强度19.16 MPa;(4)研究区贺兰石开采前景广阔,具有较大的工业价值.     

生物样品中氯苯类化合物的提取和测定

以水草和鱼样品为研究对象,采用超声波法提取生物样品中的氯苯类化合物(CBS)并用气相色谱进行定性和定量分析.结果表明:用超声波提取生物样品中CBS的最佳提取溶剂为正己烷,功率为25W,提取时间为20 min.植物和动物样品中CBS的提取方法稍有不同.在最佳提取条件下,鱼样中的平均加标回收率为75.2%～91.6%,水草中的平均加标回收率为88.2%～94.3%.另外,要根据污染物的检出限,确定生物样品中污染物提取的浓缩倍数.结论:用超声波法提取生物样品中的CBs的方法是可行的.     

The effects of sand movement on intertidal seaweeds and selected invertebrates at Bound Rock,New Hampshire,USA

A seasonal study of sand movement and the benthic intertidal organisms at Bound Rock, New Hampshire, USA was conducted between November, 1973 and February, 1975. The site is subjected to irregular sand fluctuations, as well as diurnal, neapspring and major summer sand intrusions. The abundance and distribution of intertidal species was interrelated with the historical sand fluctuations at the area. For example, the lower limits of Mytilus edulis, Balanus balanoides and Porphyra umbilicalis approximated the highest summer sand elevations. Highly abraded rock surfaces in the lower intertidal zone were dominated by opportunistic annuals (e.g. Enteromorpha spp.) and perennial psammophytic or sand-loving seaweeds (e.g. Ahnfeltia plicata and Sphacelaria radicans). Overall, the intertidal seaweed populations at Bound Rock showed a lower number of perennials and fewer species than adjacent rocky shores. The low species diversity of seaweeds at the study site is attributable to unstable environmental conditions and a limited number of habitats. Even so, several psammophytic microhabitats are evident at Bound Rock depending upon the extent of sand burial and abrasion. The morphological and reproductive adaptations of several psammophytic species are discussed.Published with the approval of the Director of the New Hampshire Agricultural Experiment Station as Scientific Contribution No. 812.Scientific Contribution No. 53 of the Jackson Estuarine Laboratory.