Algal Thalli Research Articles

The prevalence of the fish pathogen Yersinia ruckeri among representatives of the marine flora and fauna of the Sea of Okhotsk

This study investigates the spreading of the Gram-negative bacterium Yersinia ruckeri, pathogenic for fish, among representatives of the marine flora and fauna of the Sea of Okhotsk. The enzyme-linked immunosorbent assay (ELISA) revealed the presence of Y. ruckeri outer membrane antigens in 9 of the 29 samples obtained by washing the internal organs of fish, shellfish, crustaceans, and surfaces of algal thalli. Using lipopolysaccharide (LPS) containing a fluorescent label we detected LPS-binding proteins, which are a component of the innate immune system of invertebrates, in half of the samples studied. However, the simultaneous presence of Y. ruckeri and LPS-binding proteins was found only in brachiopods, scallops, and shrimps. It is assumed that this may be indicative of a particular response of the immune system of these animals to infection and/or manifestation of a toxic effect of Y. ruckeri.

The culturable mycobiota of Flabellia petiolata: First survey of marine fungi associated to a Mediterranean green alga.

Algae-inhabiting marine fungi represent a taxonomically and ecologically interesting group of microorganisms still largely neglected, especially in temperate regions. The aim of this study was to isolate and to identify the culturable mycobiota associated with Flabellia petiolata, a green alga frequently retrieved in the Mediterranean basin. Twenty algal thalli were collected from two different sampling sites in the Mediterranean Sea (Elba Island, Italy). A polyphasic approach showed the presence of a relevant alga-associated mycobiota with 64 taxa identified. The fungal isolates belonged mainly to Ascomycota (61 taxa), while only three Basidiomycota were detected. The phylogenetic position of sterile mycelia and cryptic taxa, inferred on the basis of LSU partial region, highlighted the presence of putative new phylogenetic lineages within Dothideomycetes and Sordariomycetes. This work represents the first quali-quantitative analysis of the culturable mycobiota associated to a green alga in the Mediterranean Sea.

Diffusion or advection? Mass transfer and complex boundary layer landscapes of the brown alga Fucus vesiculosus.

The role of hyaline hairs on the thallus of brown algae in the genus Fucus is long debated and several functions have been proposed. We used a novel motorized set-up for two-dimensional and three-dimensional mapping with O2 microsensors to investigate the spatial heterogeneity of the diffusive boundary layer (DBL) and O2 flux around single and multiple tufts of hyaline hairs on the thallus of Fucus vesiculosus. Flow was a major determinant of DBL thickness, where higher flow decreased DBL thickness and increased O2 flux between the algal thallus and the surrounding seawater. However, the topography of the DBL varied and did not directly follow the contour of the underlying thallus. Areas around single tufts of hyaline hairs exhibited a more complex mass-transfer boundary layer, showing both increased and decreased thickness when compared with areas over smooth thallus surfaces. Over thallus areas with several hyaline hair tufts, the overall effect was an apparent increase in the boundary layer thickness. We also found indications for advective O2 transport driven by pressure gradients or vortex shedding downstream from dense tufts of hyaline hairs that could alleviate local mass-transfer resistances. Mass-transfer dynamics around hyaline hair tufts are thus more complex than hitherto assumed and may have important implications for algal physiology and plant-microbe interactions.

Elemental variability in the coralline alga Lithophyllum yemenense as an archive of past climate in the Gulf of Aden (NW Indian Ocean).

This study presents the first algal thallus (skeleton) archive of Asian monsoon strength and Red Sea influence in the Gulf of Aden. Mg/Ca, Li/Ca, and Ba/Ca were measured in Lithophyllum yemenense from Balhaf (Gulf of Aden) using laserablation inductively coupled plasma mass spectrometry, and Mg/Ca ratio oscillation was used to reconstruct the chronology (34y). Oscillations of element rates corresponding to the algal growth between 1974 and 2008 were compared with recorded climate and oceanographic variability. During this period, sea surface temperatures (SST) in Balhaf recorded a warming trend of 0.55°C, corresponding to an increase in Mg and Li content in the algal thallus of 2.1mol-% and 1.87μmol-%, respectively. Lithophyllum yemenense recorded decadal SST variability by Li/Ca, and the influence of the Pacific El-Niño Southern Oscillation on the NWIndian Ocean climate system by Ba/Ca. Additionally, algal Mg/Ca, Li/Ca, and Ba/Ca showed strong and significant correlations with All Indian Rainfall in the decadal range indicating that these proxies can be useful for tracking variability in the Indian monsoon system, possibly due to changes of the surface wind system, with deep water upwelling in summer, and a distinct seasonality.

Fatty acid patterns of the kelps Saccharina latissima, Saccorhiza polyschides and Laminaria ochroleuca: Influence of changing environmental conditions

Kelps play a key role in coastal ecosystems and exhibit great potential as feedstock of valuable compounds with potential biotechnological applications. This study established the fatty acid patterns of Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl & G.W. Saunders, Saccorhiza polyschides (Lightfoot) Batters, and Laminaria ochroleuca Bachelot de la Pylaie, subjected to seasonal variations, from different sources (wild and aquaculture), and cultivated at different depths at sea. Stipes, blades and whole specimens were studied. S. latissima and S. polyschides specimens exhibited a higher total fatty acid content during the colder winter months and a general tendency of decreasing unsaturation towards the warmer ones. An inverse trend was found for L. ochroleuca samples. Total fatty acid content of S. latissima stipes and blades increased by over 21.5% and 31.4% with increasing depth, respectively. There were also distinct within-thallus variations, S. latissima blades exhibiting generally higher total fatty acid amounts and slightly more n-3 polyunsaturated fatty acids (PUFA) than stipes. The whole specimens of S. polyschides and L. ochroleuca grown in an integrated multi-trophic aquaculture (IMTA) system revealed no significant differences of fatty acid content compared to the ones collected at sea. Conversely, in S. latissima from IMTA the content of fatty acids per dry weight was nearly 60% higher than in the ones from natural wild stocks, registering a large increase in the amount of the most appreciated health beneficial PUFA, cis-5,8,11,14,17-eicosapentaenoic acid (C20:5n-3c), and a significant decline in the n-6/n-3 ratio, making these edible algal specimens potentially adequate for nutritional purposes. Altogether, our results reinforce the major contribution of surrounding environmental conditions, as well as of species-specific factors, in the chemical composition of algal material. Furthermore, it encourages the optimization of culture conditions and the careful selection of algal thallus sections to improve the recovery of natural valuable compounds.

Variation in oxidative stress indices of two green seaweeds growing under different heavy metal stresses.

Concentrations of nine heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) were determined in the green seaweed species Cladophora glomerata and Ulva compressa collected from El-Mex and Sidi Kirayr locations. The heavy metal concentrations in algal tissues were in direct correlation with their soluble concentrations in seawater with the descending order: Fe<Mn<Zn<Cu<Cr<Pb<Ni<Cd<Co. The bioaccumulation factor of iron and copper was higher in both tested species collected from El-Mex, while it was maximum for cadmium in Sidi Kirayr location. This metal contamination led to apparent alternation in algal thalli morphology. The results showed that C. glomerata had a superior adaptation to metal stress than U. compressa, due to its ability to produce non-enzymatic and enzymatic compounds for scavenging of the produced reactive oxygen species. The recorded contents of the oxidative stress indices (phenols, antioxidant activity, lipid peroxidation, hydrogen peroxide, and ascorbic acid) and the antioxidant enzymes (catalase, peroxidase, and superoxide dismutase) were higher in both tested seaweeds from El-Mex bay. Additionally, the estimated metal pollution index and pollution load index for the tested algae and seawaters ensured their ability as metal pollution bioindicators for monitoring marine environment quality and as biomarkers for oxidative damage assessment.

A new SIMS zircon U–Pb date from the Ediacaran Doushantuo Formation: age constraint on the Weng'an biota

AbstractAs a well-known phosphatized Lagerstätte, the Ediacaran Weng'an biota in central Guizhou Province of South China contains diverse acanthomorphic acritarchs, algal thalli, tubular microfossils as well as various spheroidal fossils. These fossils provide crucial palaeontological evidence for the radiation of multicellular eukaryotes after the termination of the Neoproterozoic global glaciation. While the Weng'an biota is generally considered as early Ediacaran in age on the basis of phosphorite Pb–Pb isochron ages ranging from 572 Ma to 599 Ma, the reliability and accuracy of these age data have been questioned and some geologists have proposed that the Weng'an biota may be younger than 580 Ma instead. Here we report a SIMS zircon U–Pb age of 609 ± 5 Ma for a tuffaceous bed immediately above the upper phosphorite unit in the Doushantuo Formation at Zhangcunping, Yichang, South China. Litho-, bio- and chemostratigraphic correlations suggest that the upper phosphorite unit at Zhangcunping can be well correlated with the upper phosphorite unit at Weng'an, which is the main horizon of the Weng'an biota. We therefore conclude that the Weng'an biota could be as old as 609 ± 5 Ma.

ALGAL LEAF SPOT OF LANSIUM PARASITICUM CAUSED BY CEPHALEUROS sp. IN THAILAND

Algal spot symptoms appeared on Lansium parasiticum (Osbeck) Sahni & Bennet leaves in late August, 2014 when rainy and warm weather favoured algal growth. The disease was found in 20% of surveyed L. parasiticum plants in Songkhla, Thailand, showing an orange to brown small, 1-4 mm circular scurf on the leaves. Thalli were sub-cuticular with sub- epidermal growth, and consequent necrosis of epidermal cells in the leaf tissue. Filamentous algal cells were short and cylindrical, 8-15×3-7 μm, with length/width ratio 1:1.1-4. Setae were short filaments with two to five cells, 100-180 × 3-7 μm. Sporangiophores, on the upper leaf surface, developed from the thalli of the algal colony. Sporangia were elliptical, 5-10×5- 8 μm. Gametangia were spherical to elliptical (8-15×3-7 μm), produced beneath the cuticle. Gametes were spheroidal (7-10×7-9 μm), zoospores were elliptical (5-10×5-8 μm). These morphometric traits were consistent with Cephaleuros sp. (Thompson and Wujek, 1997). The sequence of the 18S rDNA (GenBank accession No. LC086008), showed 94% identity to C. virescens (KM020142) and C. parasiticus (KM020146). In pathogenicity test, leaves of healthy L. parasiticum were wounded by rubbing with celite, inoculated by spraying with a suspension of algal thallus fragments (0.1 g/ml fresh thalli w/v) (Suto and Ohtani, 2011). Algal infection was evident after three months when small thalli (0.2 - 0.6 cm diameter) were observed. Reisolated algae were consistent with those originally isolated. To our knowledge, this the first report of algal leaf spot of L. parasiticum caused by Cephaleuros sp.

How algae influence sessile marine organisms: The tube worms case of study

Tube worms and phytobenthic assemblages in three infralittoral and shallow circalittoral Mediterranean benthic communities developed between 5 and 35 m depth at Punta del Lazzaretto (Giglio Island, Central Thyrrenian sea) were investigated. Despite being three algae-dominated habitats, these displayed different covering both in terms of algal layers and algal morphologies, reflecting different structural organizations. Twenty-eight serpulid taxa have been reported, increasing both diversity and density values from most photophilic to most sciaphilous habitats. Multivariate analyses showed how algal thalli and tube worm assemblages were strongly correlated; substrata are influenced both physically and biologically, providing different conditions for tube worm settlement.

Non-calcified macroalgae from the lower Famennian (Upper Devonian) of the Holy Cross Mountains, Poland

Non-calcified algal remains were collected from the lower Famennian deposits at the Kowala quarry in the Holy Cross Mountains, central Poland. Each specimen is represented solely by vegetative organs. On the basis of the material collected, a new algal genus and species has been formally erected. Vittella dixii nov. gen., nov. sp. (Order ?Bryopsidales) includes thalli consisting of long bundles of hair-like filament structures arranged in parallel fashion to the thallus length. Some other algal remains are regarded as Inocaulis-like forms. They possess long, flat blades with entire margins, and are ornamented with very dense, hair-like projections. The rest of the specimens found so far has been illustrated and tentatively classified as probably belonging to either Bryopsidales or Dasycladales algae. The exceptional preservation of the non-calcified algal thalli investigated suggests that special taphonomic conditions have prevailed during sedimentation of the lower part of the Famennian Kowala section. These may have involved rather rapid burial in oxygen-restricted (dysoxic and anoxic) sea-bottom environment, inhibiting the activities of scavengers and bioturbators, as well as oxidative degradation. The preservation of the algae, together with sedimentological and geochemical characteristics of the host rocks indicate that they rather represent parautochthonous assemblage, buried close to their natural habitat.

First record of the noncalcareous macroalga Perissothallus from shallow-water deposits (Pennsylvanian) in the Kladno-Rakovník Basin, Czech Republic

The fossil genus Perissothallus is used for adpression fossils of late Palaeozoic noncalcareous freshwater algae consisting of erect, cylindrical branches that radiate from a central holdfast and dichotomize repeatedly. The taxon currently includes P. versiformis from the Upper Pennsylvanian of North America and P. densus from the Lower Permian of Germany. In this paper we describe a third species, Perissothallus dekovensis nov. sp., from the Gzhelian (Stephanian B;Upper Pennsylvanian) of the Kladno-Rakovnik Basin, Czech Republic. The new species differs from the previously described forms with regard to thallus size and branching pattern of the erect parts. Sedimentological data and the fossils that co-occur with the algal thalli suggest that P. dekovensis lived in shallow-water areas of a lake or abandoned channel that was surrounded by tree ferns, cordaites (especially Poacordaites-type), and lycopsids.

Coralline algal physiology is more adversely affected by elevated temperature than reduced pH

In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification.

Nutrient exploitation and competition strategies of the invasive seaweed Caulerpa cylindracea

The aim of this study was to evaluate whether the success of invasive Caulerpa cylindracea (Caulerpa racemosa var. cylindracea) in Mediterranean habitats may be linked to particular nutritional requirements and/or nutrient accumulation/reallocation dynamics within the algal thallus. To this end, a manipulative field experiment was carried out transplanting C. cylindracea and supplying nutrients to subtidal rocky macroalgal assemblages. Morphological features of C. cylindracea were measured, while percentage cover and tissue nitrogen, carbon and phosphorus were determined for C. cylindracea and two co-occurring species (the introduced Laurencia chondrioides and native Flabellia petiolata) in nutrient-enriched and unenriched conditions. Growth of C. cylindracea was greater in the nutrient-enriched plots while no effect of nutrient enrichment was detected in co-occurring macroalgae. A particularly high requirement for nitrogen has been observed in C. cylindracea, but without severe N-limitation, while a general nutritional state of P-limitation was detected in both invasive and co-occurring macroalgae. The absence of inhibition in hypertrophic conditions and under high levels of ammonia together with a strong uptake and quick reallocation of nutrients within the coenocytic thallus probably represent the main advantages over the other co-occurring species which could explain part of the success of C. cylindracea in the Mediterranean Sea.

A computerized database (CorMol) on the molluscan fauna from the Mediterranean reef ecosystems: Part I, the coralligenous formations

In the Mediterranean Sea, infralittoral and circalittoral rocky bottoms (from 15 to 120 m) are characterized by a biogenic habitat, named “coralligenous”, formed by the concretion of calcareous organisms, mainly algal thalli, and to a lesser extent by animal skeletons. This complex habitat is inhabited by a rich fauna that belongs to different taxonomic groups. Sponges, bryozoans, cnidarians and ascidians are the most common sessile organisms that inhabit the area, while crustacea and molluscs are the most common mobile organisms. Little information on the diversity of the molluscs that thrive in the coralligenous habitat is known, though this information is highly important for biodiversity management purposes. A database for the molluscs of the coralligenous habitat was compiled and a method implemented for the management of this information. More than 511 species of molluscs have been recorded so far from the coralligenous formations, the majority of which belong to the class Gastropoda (357 sp.) followed by Bivalvia (137 sp.), Polyplacophora (14 sp.), Cephalopoda (2 sp.) and Scaphopoda (1 sp.). Among these, the gastropod Luria lurida (Linnaeus, 1758) and Charonia lampas (Linnaeus, 1758), the endemic bivalve Pinna nobilis (Linnaeus, 1758) and the endolithic bivalve Lithophaga lithophaga (Linnaeus, 1758), are protected by international conventions.

Removal of cypermethrin with seaweed Gracilaria lemaneiformis

The removal of cypermethrin with a red macroalga, Gracilaria lemaneiformis, was studied under laboratory conditions. Results showed that the residue contents with G. lemaneiformis were significantly lower than those corresponding groups without the algal thalli after 96 h treatment. The removal rates decreased with increasing concentrations, which were about 50% without G. lemaneiformis after 96 h exposure, and increased to 89%, 73%, and 66% in flasks with G. lemaneiformis at the concentrations of 10, 100, and 1000 µg L−1, respectively. The amount of biosorption (absorption and adsorption) by G. lemaneiformis increased with the increasing concentration and exposure time. Adsorption was the main process for the removal by G. lemaneiformis, which accounted for 75%–97% of the total biosorption. However, biosorption only contributed 0.5%–19.3% to the total losses of cypermethrin, which was more efficient under the low concentration. Natural losses contributed the largest portion of losses, which was over 65% in all treatments during the experiment. The unknown pathway of removal, which might be the bio-decomposed by microorganisms attaching the algal thalli, also contributed a lot to the total removal. The results suggested that cultivation of G. lemaneiformis could significantly remove cypermethrin, especially at low concentrations, and large-scale cultivation of G. lemaneiformis has considerable potential of biorestoration of eutrophic and cypermethrin-polluted coastal sea areas.

Variation of amphipod assemblage along the Sargassum stenophyllum (Phaeophyta, Fucales) thallus

The spatial distribution of fauna associated to marine macroalgae has mostly been investigated considering a horizontal plane. However, the macroalgal substrates can present a three-dimensional structure. In this sense, investigating how the associated fauna varies throughout a vertical plane can contribute to understanding the distribution of these organisms. The brown macroalga Sargassumpresents a vertical stratification along its thallus and harbors an amphipod fauna with a variety of feeding habits. In this work, we tested if the amphipod assemblage varies along different portions of the Sargassum thallus. We collected whole Sargassum stenophyllum thalli, as well as isolated basal and distal portions, from a rocky shore located on the north coast of Sao Paulo, in southeastern Brazil. The composition of amphipod families varied according to the Sargassum portion and the families Corophiidae, Caprellidae and Hyalidae accounted for most of the differences. Moreover, the basal portion of Sargassum had a higher diversity of amphipod families than the distal one, which may be related to differences regarding habitat complexity (herein, measured as algal biomass) between these portions. Detritivores (such as Corophiidae) were more associated to the basal portion and herbivores to the distal portion (Hyalidae) or along the whole Sargassum thallus (Ampithoidae). The variation of amphipod assemblage along Sargassum thallus seems to result from the interaction between the fauna natural history and the differences in conditions and physical structure along the algal thallus. In this sense, the vertical stratification of Sargassum can add another source of variation to the spatial distribution of associated fauna.

Brown barcoded as red but reality is green! How epiphytic green algae confuse phycologists?

Promises and perils of DNA barcoding are now well-known, but no studies have revealed the extent of taxonomic misidentification of algal specimens available in primary DNA sequence repositories. Our original objective was to assess the molecular identity of the ubiquitous brown alga Turbinaria ornata (Sargassaceae:, Fucales) from the southeast Indian coast. We extracted total genomic DNA from freshly collected algal thalli and sequenced the nuclear ribosomal DNA Internal Transcribed Spacer-1 (nrDNA ITS1) barcode locus. Following a BLASTn DNA sequence similarity search, the identity of our alga was Laurencia thyrsifera, a Pacific red alga that has never been reported in India, which came as a big surprise. Further analyses of BLAST hits using a robust phylogenetic framework of Bayesian Inference led to the conclusion that our sequence belonged to an epiphytic Ulvellacean green algal genus Ulvella, which might have been extracted and amplified with our universal ITS primers. This is the first report for Ulv...

气候变化对海藻龙须菜(Gracilaria lemaneiformis)生长与光合作用耐热特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化对海藻龙须菜生长与光合作用耐热特性的影响 DOI: 10.5846/stxb201307061846 作者: 作者单位: 华南理工大学环境与能源学院 广州 510006,华南理工大学环境与能源学院 广州 510006,华南理工大学环境与能源学院 广州 510006,华南理工大学环境与能源学院 广州 510006 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(41076094,41276148) Effect of climate change on the growth and photosynthetic thermal tolerance in the marine macroalga Gracilaria lemaneiformis Author: Affiliation: College of Environment and Energy,South China University of Technology,College of Environment and Energy,South China University of Technology,College of Environment and Energy,South China University of Technology,College of Environment and Energy,South China University of Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨大气CO2升高和温室效应对龙须菜生长及生理生化特性的影响,在4种条件下培养龙须菜:1)对照组(390 μL/L CO2 + 20 ℃),2)CO2升高组(700 μL/L CO2 + 20 ℃),3)温度升高组(390 μL/L CO2 + 24 ℃),4)温室效应组(700 μL/L CO2 + 24 ℃),测定藻体生长和生化组分以及高温胁迫下的最大光化学量子产量(Fv/Fm)和光能利用效率(α)、光合速率(Pn)和呼吸速率(Rd)。结果表明,CO2升高、温度升高以及温室效应均促进龙须菜的生长,温室效应下的促进作用更明显。温室效应使龙须菜具较高的Pn和Rd以及较低的可溶性蛋白(SP)和可溶性碳水化合物(SC)含量。高浓度CO2对叶绿素(Chl a)和类胡萝卜素(Car)含量没有显著影响,而高温使其上升;藻红蛋白(PE)和藻蓝蛋白(PC)含量不受CO2浓度和温度的影响。龙须菜Fv/Fm、α、Pn和Rd值,在32 ℃处理3 h后略有上升,在36 ℃处理3 h后下降,而在40 ℃处理20 min后降到极低水平。正常温度(20 ℃)生长的龙须菜最高耐受温度在32-36 ℃之间,而较高温(24 ℃)生长的龙须菜在36-40 ℃之间;生长温度对光合作用和呼吸作用耐热性能的影响比CO2浓度的影响更大;而温室效应生长条件下的龙须菜光合作用表现出更突出的耐热性能。 Abstract:It was predicted that the atmospheric CO2 concentrations in the end of this century would be twice as much as the present level, and as a consequence of this the mean global temperature would elevate 4-5 ℃. At present, there are many researches on seaweeds in response to elevated atmospheric CO2 concentrations or temperature alone. However, the investigations concerning the impacts of combined effects of elevated atmospheric CO2 concentrations and temperature on seaweeds is very limited. The marine red macroalga Gracilaria lemaneiformis has been cultivated on large scales in both the southern and the northern parts of China. It is essential to evaluate how the climate change (such as the elevated atmospheric CO2 concentrations and global warming) affect this economically important species. In this study, G. lemaneiformis was cultured under the following four different conditions: 1) ambient control (390 μL/L CO2 + 20 ℃); 2) elevated CO2 (700 μL/L CO2 + 20 ℃); 3) elevated temperature (390 μL/L CO2 + 24 ℃); and 4) greenhouse effect (700 μL/L CO2 + 24 ℃). After cultured for 10 d, the growth and biochemical compositions were examined. At the same time, the changes of maximum photochemical quantum yield (Fv/Fm), light use efficiencies (α), net photosynthetic rate (Pn) and dark respiratory rate (Rd) under high-temperature stresses (32 ℃, 36 ℃ and 40 ℃) were explored. The results showed that elevated CO2, elevated temperature, or greenhouse effect all enhanced the growth of G. lemaneiformis, with the highest relative growth rate occurring under the culture treatment with greenhouse effect. The growth condition treated with greenhouse effect increased the rates of Pn and Rd in situ, but decreased the contents of solution protein (SP) and soluble carbohydrate (SC) in algal thalli. Elevated CO2 in culture increased the rate of Pn in situ, but the growth condition treated with elevated temperature had hardly affected the Pn in situ. Both chlorophyll a (Chl a) and carotenoid (Car) were increased with elevated temperature in culture, but their contents were unaltered with high CO2. Elevated CO2 or elevated temperature alone had no significant effects on the contents of phycoerythrin (PE) and phycocyanin (PC) of the algal thalli. The changes of Fv/Fm and α of the algal thalli under high-temperature stresses displayed the same tendency, i.e: their values all increased slightly under 32 ℃-stress, but decreased under 36 ℃-stress, and declined fiercely under 40 ℃-stress. In the course of 6 h of 32 ℃-stress, the rates of Pn in elevated temperature-grown algae and greenhouse effect-grown algae were much higher than those in the algae grown under control condition. In the course of 6 h of 36 ℃-stress, the rates of Pn in greenhouse effect-grown algae displayed the highest levels relative to the algae grown with other three treatments. It was shown that the high-temperature tolerance limit of photosynthesis in 20 ℃ grown algae was between 32 ℃ and 36 ℃, while that of 24 ℃-grown algae was between 36 ℃ and 40 ℃. Taken together, our results suggested that growth of G. lemaneiformis would benefit from elevated CO2 and/or elevated temperature. Moreover, the greenhouse effect (combined with elevated CO2 and elevated temperature) would improve the photosynthetic thermal tolerance to high temperature for G. lemaneiformis. 参考文献 相似文献 引证文献

A new approach to macroalgal bloom control in eutrophic, shallow-water, coastal areas

In summer 2012, an experiment was conducted in a shallow eutrophic lagoon with poor water exchange to determine the consequences of harvesting algae on the algal mat itself, which was traversed and repeatedly disturbed by large harvester boats. Four areas with high macroalgal density, measuring half a hectare each, were selected. Two were subjected to frequent disturbance of the algal mat and sediment (12 two-hour operations over a 38-day period) and the other two were left undisturbed as control. The following variables were determined: 1) water column physical chemistry and nutrients; 2) redox potential, nutrients and organic load in sediments; 3) C, N and P content of algal thalli; 4) macroalgal biomass.In 2013, a further experiment was conducted on a larger scale. Biomass was estimated in a high-density mat measuring 235 ha, where macroalgae were harvested and stirred up by four harvesting boats, and in two high-density mats measuring 150 and 120 ha, left undisturbed as control (9.15, 9.92 and 3.68 kg/m2, respectively).In the first experiment, no significant changes were observed in the water column. In sediment the main variation was a significant reduction in labile organic matter in the disturbed areas and a significant increase mainly in refractory organic matter in the undisturbed areas. Biomass showed a significant drastic reduction in disturbed areas and substantial stability in undisturbed areas. In the large-scale experiment, the biomass of the disturbed mat declined by about 63%, only 6.5% of which was due to harvesting. On the other hand, the undisturbed mat with higher density underwent a natural decline in biomass of about 23% and the other increased by about 50%. These results demonstrate that disturbance of high-density mat in shallow water by boats can cause decay of the mat.

Recent (2008–2012) seaweed flora of Hainan Island, South China Sea

During the period from 2008 to 2012, algal samplings were conducted off Hainan Island (China) at seven localities. A total of 252 benthic macroalgal taxa were collected where 53% were reds, 31% greens and 16% browns. The largest numbers of species belonged to the families Rhodomelaceae, Ceramiaceae, Corallinaceae (Rhodophyta), Cladophoraceae, Ulvaceae, Caulerpaceae (Chlorophyta), Sargassaceae and Dictyotaceae (Heterokontophyta). The analysis of the floristic diversity and composition during 2008–2012 revealed similarity to that of other large islands in the tropical zone of the Indo-Pacific where coral reefs are the main ecosystem. As was shown by comparative analysis of algal species composition and form diversity between the periods of 1990/1992 and 2008–2012, maximum similarity boundary values between the floras amounted to 66% (Rh), 65% (Ch) and 55% (Phaeophyceae, Ph). These decadal changes resulted in the loss of long-living volumetric forms of macrophytic algae with an increase in the number of fine filamentous algal forms, with tubular and blade-like thalli, as seawater pollution and probably natural catastrophes occurred during the period between the 1990s and 2000s.