Sustainable Biofuel Production from Brown and Green Macroalgae through the Pyrolysis

The escalating demand for energy coupled with environmental concerns necessitates exploring sustainable alternatives to fossil fuels.The study explores the viability of using large ocean-based seaweeds as a source of thirdgeneration biomass,specifically focusing on their conversion to biofuel via the process of pyrolysis.Sargassum plagiophyllum and Ulva lactuca represent prevalent forms of macroalgae,posing significant discharge challenges for coastal regions globally.However,the exploration of their potential for bio-oil generation via pyrolysis remains limited.This study investigates the pyrolysis process of S.plagiophyllum and U.lactuca for biofuel production,aiming to provide valuable insights into their utilization and optimization.Pyrolysis experiments were conducted within temperature ranges of 400°C to 600°C and durations of 10 to 50 min using a batch reactor.The chemical analysis of the synthesized bio-oil indicated it contains critical compounds such as organic acid derivatives,furans,nitrogenous aromatics,and aliphatic hydrocarbons.The effectiveness of converting the initial biomass into bio-oil is significantly influenced by the pace at which the biomass undergoes decomposition,underscoring the importance of comprehending the kinetic aspects of this conversion.By applying the Arrhenius formula,we calculated the activation energies and frequency factors,with the findings for S.plagiophyllum being 15.27 kJ/mol and 0.477 s^(-1),and for U.lactuca,the values were 43.17 kJ/mol and 0.351 s^(-1),correspondingly.These findings underscore the potential of brown and green macroalgae as sustainable sources for biofuel production via pyrolysis,offering insights for further optimization and valorization efforts in the quest for renewable energy solutions.

Interaction between macroalgae and microplastics:Caulerpa lentillifera and Gracilaria tenuistipitata as microplastic bio-elimination vectors

The pollution of microplastics(MPs)in the ocean has become a serious matter of concern.The farmed seaweeds(Caulerpa lentillifera and Gracilaria tenuistipitata)were selected to study their ability of adsorption with two typical classes of MPs(polyamides and polystyrene),thereby revealing the interaction between MPs and macroalgae and exploring novel methods of removing MPs from macroalgae.The results demonstrate that polyamides(PA)fibers had no effect on the various physiological parameters of both seaweeds(e.g.,relative growth rate,photosynthetic oxygen evolution rate,the contents of malondialdehyde and extracellular polymeric substances)after 7 days of exposure,except for the chlorophyll-a concentration.However,the effects of polystyrene(PS)particles on the algae were strongly associated with the concentration of MPs exposure.Exposed to the high concentration(100 mg/L)of PS particles,the relative growth rate of C.lentillifera and G.tenuistipitata decreased by 54.56% and 30.62%,respectively,compared to the control,while no significant(P>0.05)harmful effect of PS particles on seaweeds was observed in an environment with a low content of PS particles(25 mg/L).The PS particles in concentration of 100 mg/L significantly(P<0.05)inhibited photosynthetic oxygen evolution rate and extracellular polymeric substances(EPS)contents in both seaweeds,but increased malondialdehyde(MDA)contents.When exposed for 72 h,the MPs adhesion rate of G.tenuistipitata is higher than that of C.lentillifera,which might be due to the higher EPS content of G.tenuistipitata.The MPs desorption experiment indicated that the combination of dewatering and washing had the highest desorption rate of MPs which could reach to 91.45%and 87.23%for C.lentillifera and G.tenuistipitata,respectively.This research demonstrates the potential of macroalgae as a vector for MPs in aquatic environment and provides methodological insights into decontamination procedures for removing the MPs from macroalgae.

Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta) I. Nitrogen storage under nitrogen enrichment and starvation

This paper deals with the N storage of Gracilaria tenuistipitata var. liui and Ulva pertusa under ammonium enrichment and starvation. After 10 days of ammonium enrichment, ammonium NH4,+ free amino acid (FAA), protein (pro), chlorophyll (Chi), phycoerythrin (PE) and total dissolved nitrogen (TDN) of the two macroalgae increased significantly. Total nitrogen (TN) increased significantly from 3.65% to 5.78% dry weight of G. tenuistipitata var. liui and 2.82% to 5.07% dw of U. pertusa, respectively. Protein and FAA were the most important N storage pools in the macroalgae. During N-starvation period, individual N pools of the two species were depleted at exponential rates. Each N pool in U. pertusa decreased more rapidly than in G. tenuistipitata, var. liui and the latter was able to sustain fast growth for more time ( > 20 days) than U. pertusa. N demands for supporting growth were different between the two species, U. pertusa grew more rapidly and had higher N demands than G. tenuistipitata var. liui did.

Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta) II. Feedback controls of intracellular nitrogen pools on nitrogen uptake

The potential feedback by intracellular nitrogen pools on maximum N uptake (NH + 4) rate were determined for Gracilaria tenuistipitata var. liui and Ulva pertusa. The results of correlation matrix analyzing showed that the surge uptake of ammonium seemed related to rapid changes in small intracellular pools of inorganic nitrogen or small peptide and amino acids rather than to changes in TN content of the macroalgae. The assimilation rates of nitrogen of U. pertusa and G. tenuistipitata increased slowly during N starvation and were mainly regulated by amino acids and some incorporation of amino acids into macromolecules. From ecological point of view, the fast growing and uptaking nutrient U. pertusa is more suitable to improve water quality in integrated shrimp culture ponds in which external nutrient supplies are usually high and constant during the culture period, while G. tenuistipitata var. liui is more suitable to be polycultured in a waters with intermittence supply of nutrients.

The Distribution of Green Algal Micro-Propagules and Macroalgae at the Early Stage of Green Tide in the Coastal Area of South Jiangsu Province in 2014

An integrated investigation was carried out during late April to late May of 2014 in the coastal area of South Jiangsu Province to understand the early development of green tide in the Yellow Sea and discover the temporal and spatial distribution of green algal micro-propagules and macroalgae at the early stage of green tide. The results showed that green algal micro-propagules distributed in all stations from late April to late May, and micro-propagules of high density(> 300 ind. L^(-1)) concentrated in the adjacent Porphyra aquaculture area. Floating macroalgae were initially observed in the northern survey areas, and increased gradually. The dominant species was U. prolifera in the floating macroalgae, ranging between 90% and 100%. The seawater surface temperature and salinity in the above mentioned time period were suitable for the growth of macroalgae. This work can help government to strengthen management to reduce the blooms of macroalgae in the coastal area of South Jiangsu Province and also facilitate the decision-making for managers at the early stage of green tide.

Ecophysiological characteristics of four intertidal marine macroalgae during emersion along Shantou coast of China,with a special reference to the relationship of photosynthesis and CO_(2)

Intertidal marine macroalgae experience periodical exposures during low tide due to their zonational distribution. The duration of such emersion leads to different exposures of the plants to light and aerial CO2, which then affect the physiology of them to different extents. The ecophysiological responses to light and CO2 were investigated during emersion in two red algae Gloiopeltis furcata and Gigartina intermedia, and two brown algae Petalonia fascia and Sargassum hemiphyllum, growing along the Shantou coast of China. The light-saturated net photosynthesis in G. furcata and P. fascia showed an increase followed by slightly desiccation, whereas that in G. intermedia and S. hemiphyllumexhibited a continuous decrease with water loss. In addition, the upper-zonated G. furcata and P. fascia, exhibited higher photosynthetic tolerance to desiccation and required higher light level to saturate their photosynthesis than the lower-zonated G. intermedia and S. hemiphyllum. Desiccation had less effect on dark respiration in these four algae compared with photosynthesis. The light-saturated net photosynthesis increased with increased CO2 concentrations, being saturated at CO2 concentrations higher than the present atmospheric level in G. furcata, G. intermedia and S. hemiphyllum during emersion. It was evident that the relative enhancement of photosynthesis by elevated CO2 in those three algae increased, though the absolute values of photosynthetic enhancement owing to CO2 increase were reduced when the desiccation statuses became more severe. However, in the case of desiccated P. fascia (water loss being greater than 20 %), light saturated net photosynthesis was saturated with current ambient atmospheric CO2 level. It is proposed that increasing atmospheric CO2 will enhance the daily photosynthetic production in intertidal macroalgae by varied extents that were related to the species and zonation.

Seasonal and spatial variation in species diversity, abundance, and element accumulation capacities of macroalgae in mangrove forests of Zhanjiang, China

The objective of this study was to investigate whether there was distinctive seasonal and zonal variation in the species diversity, biomass, and element accumulation capacities of macroalgae in two major intertidal mangrove stand types （Avicennia marina assemblage andSonneratia apetala assemblage） in the Zhanjiang region of southern China. Over a year, 31 species in 15 genera were identified in both mangrove assem-blages, of which the dominant species wereCladophoropsis zollingeriand Enteromorpha clathrat.Macroal-gal species were significantly most abundant in spring （p〈0.05）, followed by summer, winter, and autumn. Variation in the zonal distribution of macroalgal species was conspicuous in both intertidal mangrove as-semblages, with the greatest abundance in the middle zone, and the least in the front zone. Patterns in the seasonal and zonal variation in macroalgal biomass in theS. apetalaassemblage were similar to those of macroalgal species diversity in both mangrove assemblages. The seasonal patterns in tissue concentrations of 15 analyzed elements were not uniform among the macroalgaeC. zollingeri,E. clathrata, andGracilaria salicornia in theA. marina assemblage. All three species exhibited variation in their responses to ambient concentrations of different elements, implying their differential ability to absorb and selectively accumulate certain elements.

Physiological performance of three calcifying green macroalgae Halimeda species in response to altered seawater temperatures

The effects of seawater temperature on the physiological performance of three Halimeda species were studied for a period of 28 d.Five treatments were established for Halimeda cylindracea,Halimeda opuntia and Halimeda lacunalis,in triplicate aquaria representing a factorial temperature with 24°C,28°C,32°C,34°C and 36°C,respectively.The average Fv/Fm of these species ranged from 0.732 to 0.756 between 24°C and 32°C but declined sharply between 34°C(0.457±0.035)and 36°C(0.122±0.014).Calcification was highest at 28°C,with net calcification rates(Gnet)of(20.082±2.482)mg/(g·d),(12.825±1.623)mg/(g·d)and(6.411±1.029)mg/(g·d)for H.cylindracea,H.opuntia and H.lacunalis,respectively.Between 24°C and 32°C,the specific growth rate(SGR)of H.lacunalis(0.079%–0.110%d–1)was lower than that of H.cylindracea(0.652%–1.644%d–1)and H.opuntia(0.360%–1.527%d–1).Three Halimeda species gradually bleached at 36°C during the study period.Malondialdehyde(MDA)and proline levels in tissues of the three Halimeda were higher in 34–36°C than those in 24–32°C.The results indicate that seawater temperature with range of 24–32°C could benefit the growth and calcification of these Halimeda species,however,extreme temperatures above 34°C have negative impacts.The measured physiological parameters also revealed that H.cylindracea and H.opuntia displayed broader temperature tolerance than H.lacunalis.

DNA Barcoding Assessment of Green Macroalgae in Coastal Zone Around Qingdao, China

An assessment with assistance of DNA barcoding was conducted on green macroalgae in coastal zone around Qingdao, China, during the period of April- December, 2011. Three markers were applied in molecular discrimination, including the plastid elongation factor tufA gene, the internal transcribed spacer(ITS) region of the ribosomal cistron and rubisco large subunit gene 3' regions(rbcL-3P). DNA barcoding discriminated 8 species, excluding species of genus Cladophora and Bryopsis due to failures in amplification. We ascertained and corrected 4 species identified by morphological methods for effectively assisting the classification. The gene tufA presented more advantages as an appropriate DNA marker with the strongest amplification success rate and species discrimination power than the other two genes. The poorest sequencing success largely handicapped the application of ITS. Samples identified by tufA and rbcL as Ulva flexuosa were clustered into the clade of U. prolifera by ITS in the neighbor-joining tree. Confusion with discrimination of the complex of U. linza, U. procera and U. prolifera(as the LPP complex) still existed for the three DNA markers. Based on our results, rbcL is recommended as a preferred marker for assisting tufA to discriminate green macroalgae. In distinguishing green-tide-forming Ulva species, the free-floating sample collected from the green tide in 2011 was proved to be identical with U. prolifera in Yellow Sea for ITS and rbcL genes. This study presents a preliminary survey of green macroalgae distributed in the coastal area around Qingdao, and proves that DNA barcoding is a powerful tool for taxonomy of green macroalgae.

A mini-review on the microbial continuum:consideration of a link between judicious consumption of a varied diet of macroalgae and human health and nutrition

As the primordial,prokaryotic inhabitants on Earth,microbial entities were responsible for significant influences on the pathways taken in the development of life as we know it.The manifestation of numerous pathologies in humans is considered to be intrinsically associated with microbial dysbiosis in the gut(i.e.a poorly balanced microbiota).Such adverse health conditions include obesity,chronic fatigue syndrome,cancer,cardiovascular issues,neurological disorders,colitis,irritable bowel syndrome(IBS),and rheumatoid arthritis.Endosymbiotic events at the single cell level took place billions of years ago,eventually leading to eukaryotes,photosynthesis,and multicellularity.Macroalgae(seaweeds)were amongst the first organisms to develop these characteristics.Microbes and macroalgae interacted in a pattern of co-evolution,a process that applies to most,if not all living organisms.It is recognized that the normal human microbiome consists of over a trillion microorganisms,including about 2000 commensal bacterial species typically stationed in the gut.Many of these live in the colon,where they function in the digestion of foods,releasing bio-available nutrients,bioactive molecules,and various metabolites.They mediate communication signals between the gut and the brain,and promote the normal development of immune function,metabolic activities,behaviour,and neurological stability.As very early humans foraged for food,some would have benefi tted from coastal diets,rich in seaweeds and associated microbes.Such diets would have consistently provided all the nutrients essential for survival and growth,and as such,could have conveyed competitive advantages and contributed to enhanced cognitive sophistication.This mini-review article highlights studies regarding the health benefits of dietary fibres and the production of short chain fatty acids(SCFA).Insights are off ered regarding the positive effects the inclusion of macroalgae into the standard,Western diet can deliver in terms of providing appropriate fodder for those microbial populations deemed beneficial to human health and wellness.

Screening of antibacterial activity in marine green, red and brown macroalgae from the western coast of Libya

Marine macroalgae are considered as an excellent source of bioactive compounds which has a broad range of biological activities including antibacterial and antioxidant. Crude methanolic and water extracts of 19 marine algal species (6 Chlorophyta, 8 Phaeophyta and 5 Rhodophyta) collected from the western coast of Libya were evaluated for antibacterial activity against pathogenic bacteria (4 Gram-positive, 4 Gram-nega- tive). The extracts showed a significant antibacterial activity against Gram positive (Staphylococcus aureus, Bacillus subtilis, Bacillus spp., and Staphylococcus epidermidis) as well as Gram negative bacteria (Escherichia coli, Salmonella typhi, Klebsiella spp., and Pseudomonas aerugi- nosa). The algal aqueous and methanolic extracts displayed different degrees of antimicrobial activities against different bacteria, in some cases methanolic extracts showed higher antibacterial activity than aqueous extracts. Among tested algae, Brown algae namely Cystoseira crinite exhibited the highest antibacterial activity among tested algal species.

Adverse Effect of TiO2 Nanoparticles on Antioxidant System and Antitumor Activities of Macroalgae Gracilaria lemaneiformis

Recently,the widespread use of TiO2 nanoparticles(nano-TiO2)has attracted the global concern regarding their adverse effects to aquatic organisms.Nanoparticles may get to the aquatic environments and harm the growth of algae.This paper presents the studies of nano-TiO2 concentrations influence on the photosynthetic characteristics,antioxidant system and antitumor activity of marine macroalgae Gracilaria lemaneiformis after exposed to 0,5,10,20 or 40 mg L^-1 of nano-TiO2.Results showed that the photosynthetic pigment content of G.lemaneiformis obviously decreased and the antioxidant defense system was significantly disturbed after exposure to nano-TiO2.Compared with control,the maximum level of malondialdehyde showed 3.3-fold increase for 15 days exposure to nano-TiO2.The activity of superoxide dismutase and catalase enhanced obviously by 1.10-2.24-fold.The aqueous extract of G.lemaneiformis(AEGL)possesses anticancer activity against HepG2 liver cancer cells proliferation and the 48 h-cell inhibition exceeds 35%.But the toxicity of nano-TiO2 would inhibit the anticancer activity of AEGL.When G.lemaneiformis was exposed to nano-TiO2,the effect of the aqueous extract of G.lemaneiformis on the cell inhibition,reactive oxygen species production,apoptosis,cycle arrest of HepG2 cells significantly lessened,and which were linearly associated with nano-TiO2 exposure concentration.Those results further confirmed that nano-TiO2 can inhibit the anticancer activity of G.lemaneiformis.The results in this work imply that macroalgae can be an effective biomarker of nano-TiO2 contaminant,and can be useful indicator to evaluate ecological effects of increasing pollutants in marine ecosystem.

The current situations of green macroalgae and micro-propagules in Pyropia aquaculture of the Subei Shoal in spring of 2013

To discover the distribution of green algal micro-propagules in the Subei Shoal and clarify the growth of green macroalgae attached on Pyropia aquaculture rafts,an integrated investigation in Pyropia aquaculture area and one cruise in the coastal area of the Subei Shoal were carried out from March to May in 2013.The results showed that green algal micro-propagules were discovered in seawater and sediment during March to May.The average quantity of micro-propagules was 267 ind./L in surface seawater and 43 ind./g in sediment.The biomass of attached green macroalgae increased in Pyropia aquaculture from March to May.Three species,including Ulva prolifera,Ulva linza and Blidingia sp.were found in Pyropia aquaculture rafts.The dominant specie was Blidingia sp.and the second was U.prolifera in spring.This study indicated that the micro-propagules and macroalgae were existed in the coastal area of the Subei Shoal at the early stage of green tide.This was the key point to the governance of green tide in China.

In vitro antimicrobial and synergistic effect of essential oil from the red macroalgae Centroceras clavulatum (C. Agardh) Montagne with conventional antibiotics

Objective:To study the chemical profile,antimicrobial properties,and synergistic effect with known antibiotics of essential oil extracted from the marine red macroalgae Centroceras clavulatum(C.Agardh)Montagne,collected in Morocco.Methods:The chemical composition of the oil was analyzed by gas chromatography-mass spectrometry.The oil was evaluated for antibacterial(Pseudomonas aeruginosa,Escherichia coli,Bacillus subtilis,Micrococcus luteus,Staphylococcus aureus,and Klebsiella pneumoniae),and antifungal activity(Candida albicans,Candida glabrata,Candida krusei,and Candida parapsilosis),by the disc diffusion method.The minimum inhibitory and minimum microbicidal concentrations of the oil were determined,as well as the synergistic effects of its application combined with the antibiotics ciprofloxacin and fluconazole,by the checkerboard method.Results:Thirty molecules were identified in the essential oil,comprising 96.27%of the total oil composition.Monoterpenes such as carvacrol(36.06%)were the most abundant compounds,followed by caryophyllene(14.67%),endo-borneol(9.04%),pyroterebic acid(3.23%)and caryophyllene oxide(3.13%).The oil exhibited a moderate antimicrobial activity with inhibition zone diameters ranging from 9.0 to 15.0 mm.The minimum inhibitory concentration values varied between 0.9 and 14.7 mg/mL,and Bacillus subtilis and Escherichia coli were the more sensitive bacteria with 0.9 and 1.9 mg/mL,respectively.The minimum microbicidal concentration values ranged from 0.4 to 14.7 mg/mL.A significant synergic action was observed when the oil was applied in combination with ciprofloxacin and fluconazole,with fractional inhibitory concentration index values ranging from 0.31 to 0.50.Synergy was found in 80%of the combinations and a 2 to 16-fold reduction of antibiotics MIC was observed.Conclusions:Our findings suggest that the essential oil of Centroceras clavulatum should be further appraised for its potential use in the management of multi-drug resistant microorganisms,with the purpose to restore the activity of standard antimicrobial drugs.

Fossil middle triassic “sea cows” – placodont reptiles as macroalgae feeders along the north-western Tethys coastline with Pangaea and in the Germanic basin

The descriptions of fossil Triassic marine pla- codonts as durophagous reptiles are revised through comparisons with the sirenia and basal proboscidean mammal and palaeoenvironment analyses. The jaws of placodonts are conver- gent with those of Halitherium/Dugong or Mo- eritherium in their general function. Whereas Halitherium possessed a horny oral pad and counterpart and a special rasp-like tongue to grind seagrass, as does the modern Dugong, placodonts had large teeth that covered their jaws to form a similar grinding pad. The sirenia also lost their anterior teeth during many Millions of years and built a horny pad instead and specialized tongue to fed mainly on seagrass, whereas placodonts had only macroalgae availa- ble. Indirect evidence for Triassic macroalgae is provided by benthic palaeocommunities from different layers and extended European regions in the Germanic Basin. Studies of tooth wear stages for Placodus indicate that anterior teeth may have been used in a similar manner to the procumbent front teeth of modern Dugong. Paraplacodus and Placodus seem to have used these teeth as spatulas to dig out seaplants. Cyamodus and other placodonts such as Placochelys had smaller or reduced anterior teeth. The scarcity of highly worn palatine or maxillary and lower jaw dentary Placodus or Cyamodus teeth (less then 0.5%) suggests that they had a relatively soft diet. The seaplants would only have been squeezed in a similar feeding strategy to that of modern Dugong feeding on seagrass without jaw rotation and grinding. The phylogenetic trend in tooth reduction within the placodonts Paraplacodus, Placodus, especially in Cyamodus but also Placochelys, and Henodus within 11 My appears to have been a result of this plant-feeding adaptation and may even explain the origin or at least close relationship of the earliest Upper Triassic turtles as toothless algae and jellyfish feeders, in terms of the long-term convergent development with the sirens.

Dominant Macroalgae in Bahía de Cochinos, Matanzas, Cuba

Spatial-temporal variations of macroalgae were analyzed in a study conducted in Cueva de Los Peces (CP) and Punta Perdiz (PP), two dive sites located on the eastern coast of Bahía de Cochinos. The most conspicuous species found from 3 to 20 m depths were present in the biotopes of ridges and shallow and deep terraces. Sampling was carried out in September 2014, and March and October 2016 by autonomous diving and direct methods. Qualitative visual censuses and quantitative analyzes were used to estimate the coverage (%) of the genera according to the AGRRA methodology with the use of the 10 m linear transect and quadrats as the sampling unit. The first list of macroalgae for the area is offered that includes 49 taxa of which 10 were Rhodophyta, 10 Ochrophyta (Phaeophyceae), and 29 Chlorophyta. The dominant genera during the study period were Halimeda, Dictyota, Lobophora, and Udotea. Spatial differences were found regarding the specific composition. Temporal variations were evidenced in terms of the relative abundance of the genera present, which reveals temporal changes in the qualitative structure, where some species replace others. The information obtained is pioneering and can serve as a comparative baseline for future monitoring of the area.

Comparison on Purification Effect of Two Macroalgae Species on Prawn Tailwater

[Objectives]This study was conducted to investigate the purification effects of two common large seaweeds on the tail water of prawn farming in greenhouses,and to determine the best culture density of seaweeds.[Methods]Two large seaweed species,Gracilaria lichevoides and Ulva lactuca,were selected to set four culture densities of 0.5,2,4 g/L and a blank control group,respectively.The seaweeds were cultured in 100 L white polyethylene buckets,each of which contained 50 L of tail water from prawn culture.[Results]After 5 d,the nutrient removal rates of the two seaweeds were directly proportional to the density.There was no significant difference in NH_(4)-N removal rate between G.lichevoides and U.lactuca(P>0.05)by two-way analysis of variance,and the NH_(4)-N removal rate of the latter was higher.The removal rates of NO_(3)-N,TN and TP by G.lichevoides were significantly higher than those by U.lactuca(P<0.05).The specific growth rates of seaweeds were negatively correlated with their culture densities.The specific growth rates of G.lichevoides were 5.73%,1.654%and 0.48%,respectively,and those of U.lactuca were 2.01%,1.187%and 0.138%,respectively,when the culture densities were 0.5,2.0 and 4.0 g/L.Two-factor analysis of variance showed that the former was significantly higher than the latter,when the culture density of the two species of seaweeds was 0.5 g/L(P<0.05).The two-way analysis of variance showed that when the culture density of the two kinds of seaweeds was 0.5 g/L,the specific growth rate of G.lichevoides was significantly higher than that of U.lactuca(P<0.05).Based on the above research,the two macroalgae could reduce the nutrients in the wastewater to a large extent,but the culture density determined the scale and economic benefits of seaweed cultivation and further affected the normal growth,metabolism and quality of the seaweeds.[Conclusions]This study provides some theoretical basis for large-scale seaweed farming and biological selection of in-situ ecological restoration of eutrophic seawater.

Unprecedent green macroalgae bloom:mechanism and implication to disaster prediction and prevention

Green macroalgae bloom(GMB),with the dominant species of Ulva prolifera,has regularly occurred since 2007 along the China coast.Although disaster prevention and control achieved favorable results in 2020,the satellite-observed GMB annual maximum coverage(AMC)rebounded sharply in 2021 to an unprecedented level.The reasons for this rebound and the significant interannual variability over past 15 years are still open questions.Here,by using long-term time-series(2007-2022)optical and Synthetic Aperture Radar satellite observations(1000+scenes),meteorological data and water quality statistics,the mechanism analysis was performed by exploring effects from natural factors and human activities.Two key determinants for AMC are successfully identified from numerous potential factors which are the macroalgae distribution in a key area(the Subei Shoal)during a critical period(from April to May 20)and the nutrient availability.Furthermore,by using these two parameters,a novel model for AMC prediction(R^(2)=0.87,p<0.01)is proposed and independently validated,which can reasonably explain the significant interannual variability(2014-2021)and agree well with the latest observation in 2022(percentage difference 12%).Finally,suggestions are proposed for future disaster prevention and alleviation.This work may aid future bloom prediction and management measure optimization.

Effect of Seasonality on Distribution of Macroalgae in a Stream System(Xin'an Spring) in Shanxi Province,North China

A survey of the seasonal distribution of macroalgae in a stream system in Shanxi Province, north China, was undertaken from July 2004 to April 2005. The relative abundance and percentage cover of macroalgae, and several environmental factors were monitored along a 20-m stretch at each of four sites, at intervals of approximately three months （one sampling per season）. Several stream conditions were relatively constant over the sampling period （pH, maximum width and maximum depth）, whereas others exhibited a distinct seasonal pattern （water temperature and specific conductance）, and some fluctuated with no discernable seasonal pattern （current velocity and dissolved oxygen）. Forty-two species of macroalgae were found, with a predominance of Chlorophyta （26 species, 61.9%）. Rhodophyts and Charophyta represented the smallest proportion （1 species each, 2.38%）. Six macroalgae species were the most widespread, occurring in all four sampling sites. Twelve species were found at only one site each. In terms of seasonality, eight species occurred throughout the year, whereas 16 species were found in only one season each. The macroalgal community at Xin＇an Spring was species rich relative to other streams. Species richness per sampling site was negatively correlated with pH. Principal component analysis revealed that no single variable had much influence on the macroalgal seasonal dynamics. We calculated Sorensen similarity indices to compare our study with other continent-wide surveys of stream macroalgae, but the similarity indices were all very low. This study also shows that macroalgae in different locations have significant reproductive isolation.

Arsenobetaine and thio-arsenic species in marine macroalgae and herbivorous animals: Accumulated through trophic transfer or produced in situ?

Arsenobetaine（AB） and thio-arsenoribosides were measured in common macroalgae species（8 phaeophyta, 4 rhodophyta and 2 chlorphyta）, along the Australian south east coast line. As well, arsenic species profiles were measured for two common marine herbivores, the sea urchin Centrostephanus rodgersii and the fish Odax cyanomelas that graze on these macroalgae to understand if trophic transfer of these species would account for their presence in marine herbivores. AB was found in seven of the fourteen macroalgae species investigated but does not contributed significantly to any of the macroalgae arsenic content（0.01-1.2 μg/g）. AB was found in only two of the brown macroalgae and all the red and green macroalgae（with the exception of Corallina officinalis）. Thio-arsenic species were found sporadically, but not in high concentrations in any of the macroalgae investigated.AB present in macroalgae is likely to be associated with epiphytic organisms while thio-arsenoribosides are likely to be produced by decaying parts of damaged macroalgae.A laboratory feeding experiment in which the herbivorous gastropod, Austrocochlea constricta, was fed macroalgae containing thio-arsenoribosides for a 24 hr period every three days showed that these are readily accumulated over a short period. Thio-arsenoribosides in herbivores are therefore probably obtained through trophic transfer. Some AB is also obtained through trophic transfer; however, the presence of trimethylated arsonioribosides,a hypothesized precursor of AB formation in herbivores, suggests that some AB is produced within herbivores from the transformation of arsenoribosides accumulated from their diet.