Green Macroalgae Research Articles

Tolerance of three temperate macroalgal taxa to marine heatwaves of differing durations and intensities is not modulated by irradiance

ABSTRACTMarine heatwaves (MHWs) are recognized as principal drivers of ocean change. However, interactions with other important local and global drivers such as ocean acidification, eutrophication and sedimentation, and the physiological mechanisms via which MHWs act on species are poorly understood. Additionally, past studies have often focused on ecologically dominant taxa such as kelps, fucoids and coral, potentially leading to a lack of understanding of direct impacts on associated species. To this end, we examined the individual and interactive impacts of MHW duration (14 and 28 days) and intensity (20.5°C and 23°C) as well as irradiance (2.3 and 4.4 mol m–2 d–1) on standardized growth of Caulerpa brownii, Corallina berteroi and Phymatolithopsis complex, three temperate macroalgal taxa that are important spaceholders in their native ecosystem in Te Whanganui a Tara Wellington, Aotearoa New Zealand. All three taxa exhibited no declines in growth in response to the exposure to longer and more intense MHWs. We posit that the simulated MHW scenarios were tolerated due to large thermal safety margins which can be expected from the range centre/leading edge position of the sampled populations, even though some of these scenarios far exceeded the intensities encountered in this region previously. Interactions between intensity, duration and irradiance were limited to an antagonistic irradiance-duration interaction in the non-calcareous green macroalga Ca. brownii only. Together, the displayed tolerance of the study species to the simulated scenarios implies limited impacts of strong MHWs four weeks or shorter in duration on ecosystem functioning in New Zealand kelp forest systems if brown algal canopies remain intact.

The cards you have been dealt: How an intertidal green macroalga absorbs blue-green light

Light-harvesting complex II (LHCII) is vital for many photosynthetic organisms to harvest light and safely dissipate excess energy. The LHCII found in Bryopsis corticulans is uniquely adapted to absorb blue-green light. In this issue of Structure, Li etal. determine the structural bases of light absorbance by B.corticulans LHCII, providing insight into the diversity of light-harvesting strategies in nature.

Enzyme-Assisted Extraction of Ulvan from the Green Macroalgae Ulva fenestrata.

Ulvan is a sulfated polysaccharide extracted from green macroalgae with unique structural and compositional properties. Due to its biocompatibility, biodegradability, and film-forming properties, as well as high stability, ulvan has shown promising potential as an ingredient of biopolymer films such as sustainable and readily biodegradable biomaterials that could replace petroleum-based plastics in diverse applications such as packaging. This work investigates the potential of Ulva fenestrata as a source of ulvan. Enzyme-assisted extraction with commercial cellulases (Viscozyme L and Cellulysin) and proteases (Neutrase 0.8L and Flavourzyme) was used for cell wall disruption, and the effect of the extraction time (3, 6, 17, and 20 h) on the ulvan yield and its main characteristics (molecular weight, functional groups, purity, and antioxidant capacity) were investigated. Furthermore, a combined process based on enzymatic and ultrasound extraction was performed. Results showed that higher extraction times led to higher ulvan yields, reaching a maximum of 14.1% dw with Cellulysin after 20 h. The combination of enzymatic and ultrasound-assisted extraction resulted in the highest ulvan extraction (17.9% dw). The relatively high protein content in U. fenestrata (19.8% dw) makes the residual biomass, after ulvan extraction, a potential protein source in food and feed applications.

Fossils, pseudofossils and problematica from the Ura Formation: Ediacaran of the Patom Basin, Siberia

The pseudofossils, problematica and actual macrofossils from the Middle Ediacaran Ura Formation of the Patom Basin of Siberia are critically reviewed. Both the pseudofossils and problematica are flat-clasts of ooid grainstones that are interpreted as a product of submarine gravitational or storm-induced erosional episodic events. Some extremely flat batten-shaped ooid and cementstones 2D-clasts closely resemble shreds of ribbon-like macrophyte phytoleims randomly scattered on a bedding plane. They can potentially be considered as a cement-incrustation along the algae thalli buried within ooid sands or shales, however, there is no certainty in their taxonomic identification. At the same time, other abiotic or microbially induced formation mechanisms of these fragments cannot be excluded. The Ura macrofossils, similar in size to the 2D-clasts, are described from the same outcrop, approximately 60 m downsection. They are represented mainly by the ribbon-shaped carbonaceous compressions of Liulingjitaenia alloplecta that demonstrate the stratigraphically lowest appearance of the Miaohe-type fossils in mid-Ediacaran (pre-Shuram, 580–570 Ma) strata of Ura Formation in close association with Doushantuo-type acanthomorphic acritarchs. These fossils are present as a detrital component or as in situ buried large (decimeter scale) colonial clusters. The colonies covered significant surface areas of the soft muddy sea-floor beneath wave-base. L. alloplecta themselves, commonly attributed to green macroalgae, could also be considered as composite colonies of filamentous microalgae or cyanobacteria.

Fatty acids composition and profiling of nine abundant marine Macroalgae, Egypt

This study analyzed the fatty acids composition and their profile qualitatively and quantitatively of the nine abundant macroalgal specimens collecting from Egyptian coasts. GC mass analysis identified 23 types, including 13 of saturated fatty acids (SFA) and 10 of monounsaturated fatty acids (MUSFA). SFA dominated with 78%, while MUFAs had 22%, and UFAs were negligible at 0.01%. MUSFA oleic acid (omega-9) was present in all species except green macroalgae Galaxura rugosa and Ulva fasciata, replaced by MUSFA linoleic acid (omega-6). Oleic acid methyl ester (omega-9) was registered in all the studied species, except red Hypnea cornuta & Jania rubens, and brown Hormophysa cuneiformis. Chlorophyta registered 35% of the fatty acid composition, followed by Rhodophyta (33%) and Phaeophyta (32%). Major SFAs were palmitic acid glycidyl ester, oleic acid glycidyl ester and palmitic methyl ester, comprising over half of total fatty acids. Red and brown macroalgae were richer in palmitic and oleic glycidyl esters, while green macroalgae had more palmitic methyl ester. Linoleic acid, nonadecylic acid, elaidic acid methyl ester, linoleic acid methyl, behenic acid, pentacosylic acid, palmitic acid, and trans-palmitoleic acid were exclusively identified in Chlorophyta. Lacceroic acid was distinguished in Rhodophyta, whereas pelargonic acid just appeared in brown alga Turbinaria turbinata. The maximum values of fatty acids were recorded in the green macroalga Caulerpa racemosa while reed macroalga Hypnea cornuta.was the minimum one. The research sheds light on the fatty acid composition and its potential implications for human health and nutrition.

Distribution of Ulva prolifera, the dominant species in green tides along the Jiangsu Province coast in the Southern Yellow Sea, China

Green tides have long occurred in the Yellow Sea for 17 years, with 5S-II Ulva prolifera being the dominant species. Previous studies indicate the Neopyropia aquaculture area in Jiangsu to be the main source of green tides in the Southern Yellow Sea. Little is known regarding the occurrence of this species in coastal dykes in Jiangsu Province. We investigated the species composition, diversity, and biomass of green macroalgae in these dykes during 2022 using internal transcribed spacers and 5S rDNA and identified U. prolifera, Ulva linza, Blidingia spp., Ulva meridionalis, Ulva torta, Ulva flexuosa, Ulva compressa, Ulva aragoensis, Ulva australis, and Ulva simplex. Ulva prolifera occurred in every month of the survey. Species diversity was highest in October, and the Ulva spp. biomass was highest in February. Attached 5S-II U. prolifera occurred in the coastal dykes in February, April, and June 2022. Dyke characteristicsand elevations may affect the biomass and species of Ulva spp. observed. Green tide blooms in the Yellow Sea have enabled 5S-II U. prolifera to colonize the Jiangsu coast dykes.

Use of citric acid-activated chlorine dioxide to control Ulva prolifera

Since 2007, green tides have occurred almost every year in the Yellow Sea, and a method to prevent them and to control levels of attached Ulva prolifera is urgently needed. In this study, we measured the effects of different concentrations of citric acid-activated chlorine dioxide solution (0, 50, 100, 150, 200, and 250 mg/L of chlorine dioxide) on the morphology (macrostructure and microstructure), chlorophyll a content, chlorophyll b content, carotenoid content, and chlorophyll fluorescence parameters (Fv/Fm, Y (II), NPQ, and ETRmax) of U. prolifera. Micropropagules in the treatment filtrate were cultured to determine whether the solution reduced the number of micropropagules released during the treatment process. The results showed that citric acid-activated chlorine dioxide at the appropriate concentration can be applied to remove U. prolifera from Neopyropia cultivation rafts. Because U. prolifera and its micropropagules died in the 250 mg/L chlorine dioxide group, we recommend that the appropriate concentration of chlorine dioxide for removing green macroalgae is ≥250 mg/L. Our results provide a scientific basis for convenient collection of accurate data for the U. prolifera prevention trial organized by the Ministry of Natural Resources of the People's Republic of China.

The bactericidal effect of green macroalgae Cladophora sp. from freshwater toward Gram-negative and Gram-positive bacteria

The bactericidal effect of green macroalgae Cladophora sp. from freshwater toward Gram-negative and Gram-positive bacteria

Anti-inflammatory, remorin-like protein from green marine Macroalga Caulerpa sertularioides (S.G.Gmel.) M.Howe

The most prevalent natural source of hydrocolloids, cosmetics, medications, and nutraceuticals is marine seaweed (macroalgae). Numerous bioactivities, including antiviral, anticancer, anti-inflammatory, and immunomodulatory characteristics, have been found in bioactive substances such as polyphenols and sulfated and non-sulfated polysaccharides. As a result, new start-up projects and industries based on seaweed are emerging in all regions of the world with abundant marine biodiversity. In this current investigation, the anti-inflammatory activity of two different marine macroalgae Caulerpa racemosa (CR) and Caulerpa sertularioides (CS) was evaluated. Consequently, CS demonstrated more anti-inflammatory and antioxidant effects at a lower dose than CR. The IC50 value for DPPH inhibition was 456.1 μg/mL, and 180.9 μg/mL for CS and CR respectively. A similar result was obtained in the case of protein denaturation (PD), membrane stabilization (MS), and protease inhibition (PI) anti-inflammatory assays with 127.2 μg/mL, 135.5 μg/mL, and 71.88 μg/mL for CR, and 66.78 μg/mL, 88.96 μg/mL, and 59.54 μg/mL for CS respectively. Based on the SDS-PAGE, the molecular weight of lectin responsible for the anti-inflammatory activity was determined as 17 kDa. Protein mass fingerprinting was performed for the particular lectin by in-gel trypsin digestion, MALDI-MS analysis, and Mascot peptide mass fingerprinting. Because of this, the unidentified lectin protein was discovered to be a remorin-like protein that shared 65% of its sequence with the remorin-like protein of Aegilops tauschii subsp. tauschii. Therefore, it is the hitherto report on the presence of remorin-like protein from the green macroalga Caulerpa sertularioides.

Sustainable biorefining and bioprocessing of green seaweed (Ulva spp.) for the production of edible (ulvan) and non-edible (polyhydroxyalkanoate) biopolymeric films

A sustainable biorefining and bioprocessing strategy was developed to produce edible-ulvan films and non-edible polyhydroxybutyrate films. The preparation of edible-ulvan films by crosslinking and plasticisation of ulvan with citric acid and xylitol was investigated using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) analysis. The edible ulvan film was tested for its gut-friendliness using Lactobacillus and Bifidobacterium spp. (yoghurt) and was shown to improve these gut-friendly microbiome's growth and simultaneously retarding the activity of pathogens like Escherchia coli and Staphylococcus aureus. Green macroalgal biomass refused after the extraction of ulvan was biologically processed by dark fermentation to produce a maximum of 3.48 (± 0.14) g/L of volatile fatty acids (VFAs). Aerobic processing of these VFAs using Cupriavidus necator cells produced 1.59 (± 0.12) g/L of biomass with 18.2 wt% polyhydroxybutyrate. The present study demonstrated the possibility of producing edible and non-edible packaging films using green macroalgal biomass as the sustainable feedstock.Graphical

New records of rarely reported species in the Mediterranean Sea (July 2023)

This Collective Article presents new information about the occurrence of 23 marine taxa that belong to five Phyla: two Chlorophyta, one Annelida, six Mollusca, three Arthropoda, eleven Chordata (one Ascidiacea, one Elasmobranchii and nine Teleostei) and extending from the Western Mediterranean to the Levantine Sea. All these records were reported from nine countries from the western to the eastern Mediterranean Sea, with a broad biogeographical coverage as follows: Spain: first records of the sacoglossans Cyerce graeca and Placida tardyi for the Alboran Sea and first records of the nudibranch Marionia gemmii for the Mediterranean waters of Spain; first records of nudibranch Algarvia alba in the Mediterranean Sea. Italy: First report of the long-legged crab Paragalene longicrura, a further new Mediterranean record of the rare offshore rockfish Pontinus kuhlii, first documented record of the spiny butterfly ray Gymnura altavela in Sardinia (Tyrrhenian Sea), new record of the red‐spotted wrasse Lappanella fasciata from the Messina Strait, first documented record of the rarely observed brown moray Gymnothorax unicolor in the Ionian coast, first record of the colonial ascidian Botrylloides israeliensis, first record of the Morocco dentex Dentex maroccanus, first record of mottled shore crab Pachygrapsus maurus and of an adult specimen of barracudina Lestidiops sphyrenoides in the Adriatic Sea, and further new Mediterranean records of Ross worm Sabellaria spinulosa along the same coast. Tunisia: second record of smalleye squaretail Tetragonurus cuvieri from the African Mediterranean coast. Slovenia: first records of the sea slug Trapania graeffei and Melanochlamys wildpretii, with the last one also representing the northernmost finding of this species. Croatia: northernmost record of the endangered twaite shad Alosa fallax in the Adriatic coast. Albania: first records of the Mediterranean spearfish Tetrapturus belone. Türkiye: first record from the Aegean coasts for Türkiye of the green macroalgae Cladophora battersii and Valonia aegagropila. Israel: first record of the skeleton shrimp Caprella acanthifera in the Southeastern Mediterranean Sea. Syria: first record of the Smooth grenadier Nezumia aequalis from Syrian marine waters.

The Detection of Green Tide Biomass by Remote Sensing Images and In Situ Measurement in the Yellow Sea of China

The world’s largest macroalgae bloom (also known as green tide) has been reported since the 29th Olympic Games in 2008, which is verified as the fast reproduction of floating green macroalgae (Ulva prolifera). It is helpful to assess the biomass of macroalgae for the government of marine environment protection. In this study, the synchronization cruise experiment was firstly introduced, which aimed to investigate the biomass evaluation of Ulva prolifera in the Yellow Sea of China. The Floating Algae Index by Polarimetric SAR image (FAIPS) was then proposed. Finally, the floating algae biomass evaluation model was demonstrated and verified, which showed an exponential relationship between FAIPS and wet biomass per area (kg/m2) of macroalgae. The model proposed in this paper can be used in the biomass assessment of floating algae in the presence of polarimetric SAR images, regardless of daylight and cloud coverage over the sea surface.

Potential of Red, Brown, and Green Macroalgae from Dato Beach, Majene, Indonesia as Natural Food Preservative

Macroalgae is one of the natural resources present in Indonesian coastline areas – specifically in Dato Beach, Majene, South Sulawesi. The abundance of macroalgae found in Dato Beach can be utilized in various sectors – including health, cosmetics, and food. The aim of this study was to investigate the secondary metabolites of three types of macroalgae in Dato Beach and their potential to inhibit the growth of pathogenic bacteria in food. The three macroalgae utilized in this study were Turbinaria decurrens (brown algae), Galaxaura rugosa (red algae), and Halimeda opuntia (green algae) representing the three groups of macroalgae based on their dominant pigments. Four types of pathogenic bacteria – namely, Staphyloccus aureus and Bacillus cereus as Gram-positive bacteria plus Salmonella typhi and Escherichia coli as Gram-negative bacteria – were collected from the Biology Laboratory at Universitas Sulawesi Barat, as these bacteria are commonly responsible for food spoilage. The study began with a sampling of macroalgae, followed by cleaning and drying, and subsequently extraction using methanol as the solvent. Methanol was chosen as the universal solvent for its ability to extract both polar and nonpolar components. Phytochemical screening was carried out to test for the presence of flavonoids, steroids/terpenoids, and alkaloids, which represent the three groups of secondary metabolites. The antimicrobial test was carried out using the well diffusion method, as a control used 80 ppm of ampicillin. The results of the study indicated that T. decurrens contains flavonoids, steroids, and alkaloids, G. rugosa contains flavonoids, terpenoids, and alkaloids, whereas H. opuntia only contains terpenoids and alkaloids. Furthermore, G. rugosa was found to have the best ability to inhibit bacteria, with an inhibition zone ranging from 22–23 mm; in some treatments, the diameter of the inhibition zone was even larger than the positive control. T. decurrens was only effective in inhibiting the growth of S. aureus, whereas H. opuntia demonstrated the potential to inhibit the growth of S. aureus and E. coli, and for B. cereus and S. typhi, it could only be inhibited by 100% (1000 μL) extract of the H. opuntia extract.

Effects of Ulva intestinalis Linnaeus seaweed liquid extract on plant growth, photosynthetic performance and water status of two hydroponically grown Lamiaceae species: Peppermint (Mentha × piperita L.) and purple basil (Ocimum basilicum var. purpurascens Benth.)

Seaweed extracts are considered as marine biostimulants and have been successfully used in agriculture to improve the growth and tolerance to different environmental stress conditions of many crops. Therefore, the present study was carried out for the first time and aimed to determine the effects of a seaweed liquid extract on growth and photosynthetic performance as well as the water status of hydroponically-grown peppermint and purple basil plants. For this purpose, the experiment was conducted under greenhouse conditions and plants were cultivated in hydroponic systems according to the nutrient film technique. A seaweed liquid extract at 10% was prepared from the green marine macroalgae Ulva intestinalis and then added to the nutrient solution of the hydroponic system. Based on our experimental data, the main results have proven that Ulva intestinalis seaweed liquid extract could be successfully used as a biostimulant in the hydroponic cultivation of peppermint for its enhancing effect on some plant growth and photosynthetic as well as water status parameters. However, it is not recommended to add the seaweed liquid extract of Ulva intestinalis to the hydroponic culture of purple basil since most of the parameters analyzed were shown to be negatively affected by the seaweed liquid extract treatment. Furthermore, the results of this study could be practical for enhancing the production of medicinal and aromatic plants by adding the Ulva intestinalis seaweed liquid extract to the nutrient solution of the hydroponic system.

The Genetic Diversity of Macroalgae on The Ekas Coast of East Lombok Based on Chromatogram Data from PCR Ampification

Macroalgae are multicellular photosynthetic organisms that live in water. Some species of macroalgae are very difficult to identify based on their morphology alone because they have great similarities. Therefore, identification of macroalgae diversity based on its genotype is very important to do in order to enrich the genetic information of macroalgae found on one of the beaches on the island of Lombok. This study aimed to analyze the genetic diversity of macroalgae from Pantai Ekas Beach, Jeowaru District, East Lombok, NTB using 18S rRNA gene markers. The research was carried out in 4 stages, namely sampling, morphological analysis of samples, isolation of total macroalgae DNA, isolation of genes by PCR amplification, agarose gel electrophoresis. Sampling was carried out at certain coordinates at east longitude and south latitude using the Ekas Beach quadratic transect method. The morphological analysis of the samples was guided by an identification key. Total DNA, macroalgae were isolated based on the spin column I DNA kit easy method. Genes were isolated by means of PCR amplification. Total DNA isolates and gene amplicons were confirmed by agarose gel electrophoresis. The results obtained were based on their morphology, all samples obtained were grouped into 9 macroalgae samples which could be divided into brown macroalgae (3 samples), green macroalgae (2 samples) and red macroalgae (4 samples). All samples have successfully isolated total DNA and its 18S rRNA gene which was confirmed by agarose gel electrophoresis chromatogram.

Distribution and diversity of the sympatric macroalgae of the pelagic Sargassum horneri in the Yellow and East China seas

The massive pelagic Sargassum horneri (Turner) C. Agardh, 1820 has increasingly occurred in the Yellow Sea and East China Sea. Significant intrusion of floating S. horneri into the southwestern Yellow Sea, the major bloom region of the green tides, has aroused speculations on the blooming mechanism and confounded concurrent prevention practices of green tides. The floating S. horneri were surveyed and sampled throughout its distributional range to study the diversity and abundance of sympatric macroalgae, including the epiphytes and non-epiphytes. The study showed that both types of macroalgae commonly coexisted with the pelagic S. horneri and showed distinct distribution patterns. The non-epiphytic green macroalgae, primarily Ulva prolifera, were free floating with S. horneri. They were initiated from the nearshore water of Jiangsu in late April followed by a rapid accumulation and expansion as the green tide developed. The non-epiphytic green algae were mostly restricted in the western coast of southern YS with biomass decreasing evidently toward offshore. Four species in Phaeophyta were commonly detected epiphytic on the pelagic S. horneri in the survey region and Proselachista taeniiformis was dominant. Unlike the co-occurring green algae, the species composition and abundance of epiphytes have no significant variation in the distributional range of the pelagic S. horneri. High frequency (80%) and abundance (0.25 ± 0.17 gEpi/gSar) of epiphytes indicated significant biological interactions with their hosts and ecological functions of this pelagic system, which deserves further investigation.

Acrylic acid and DMSP lyases in the green algae Ulva

Green macroalgae of the genus Ulva contain dimethylsulfoniopropionate (DMSP) produced from methionine through a transamination pathway. DMSP is converted by DMSP lyase enzymes (DLs) into acrylic acid (AA), a high-value compound with a vast market as its esters have applications in the production of plastic additives, textiles, sealants, adhesives and surface coatings. The levels of AA produced by Ulva species, and the processes to extract it from this biomass, are currently poorly understood. In this study an analytical method was implemented for the simultaneous measurement of AA, DMSP and the pathway intermediates (4-methylthio-2-oxobutyrate, 4-methylthio-2-hydroxybutyrate, and 4-dimethylsulfonio-2-hydroxybutyrate) in Ulva biomass. The amounts of these compounds – with a focus on AA – were then quantified after processing the macroalgae with different chemical, thermal, and enzymatic treatments. AA was extracted in the range of 0.22–0.45 % of the algal dry weight. Sequential enzyme treatments showed no higher yields compared to individual enzymatic treatments or chemico-physical extractions, an encouraging result for the application of the treatments in industry. Codon-optimised synthetic genes for two candidate DLs from Ulva mutabilis were expressed and purified in E. coli with solubility tags, and the biochemical characteristics of these recombinant lyases were investigated. Both enzymes UM021_MBP and UM030_Halo7 had lower activity than their microalgal counterpart Alma1, with whom they share 33.9 % and 39.7 % similarity at amino acid level respectively. UM030_Halo7 appeared more active than UM021_MBP, with Km and Vm of 7.10 mM and 5.99 mM/min/mg protein respectively. UM030_Halo7 showed a preferred pH of 6.0, an optimal of temperature of 20 °C, was inhibited by NaCl concentration equal or higher than 0.5 M but not by H2O2 up to 50 μM. These results advance our understanding of AA biosynthesis in Ulva at the molecular level, and could be useful to implement processes for extracting AA from Ulva species within a biorefinery framework.

Combined effects of ocean deoxygenation, acidification, and phosphorus limitation on green tide macroalga, Ulva prolifera

Ocean deoxygenation, acidification, and decreased phosphorus availability are predicted to increase in coastal ecosystems under future climate change. However, little is known regarding the combined effects of such environmental variables on the green tide macroalga Ulva prolifera. Here, we provide quantitative and mechanistic understanding of the acclimation mechanisms of U. prolifera to ocean deoxygenation, acidification, and phosphorus limitation under both laboratory and semi-natural (mesocosms) conditions. We found that there were significant interactions between these global environmental conditions on algal physiological performance. Although algal growth rate and photosynthesis reduced when the nitrogen-to‑phosphorus (N/P) ratio increased from 16:1 to 35:1 under ambient CO2 and O2 condition, they remained constant with further increasing N/P ratios of 105:1, 350:1, and 1050:1. However, the increasing alkaline phosphatase activities at high N/P ratios suggests that U. prolifera could use organic P to support its growth under phosphorus limitation. Deoxygenation had no effect on specific growth rate (SGR) but decreased photosynthesis under low N/P ratios of 16:1, 35:1, and 105:1, with reduced activities of several enzymes involved in N assimilation pathway being observed. Elevated CO2 promoted algal growth and alleviated the negative effect of deoxygenation on algal photosynthesis. The patterns of responses to high CO2 and low O2 treatments in in situ experiments were generally consistent with those observed in laboratory experiments. Our results generally found that the strong physiological acclimation capacity to elevated CO2, low O2, and high N/P could contribute to its large-scale blooming in coastal ecosystem.

Attached Ulva meridionalis on nearshore dikes may pose a new ecological risk in the Yellow Sea

Green tides have been reported to occur in many sea areas worldwide. In China, most of them are caused by Ulva spp., such as Ulva prolifera and Ulva meridionalis. Green tide algae shed are frequently the initial biomass for the formation of green tide. Human activities and seawater eutrophication are the fundamental causes of the formation of the green tides in the Bohai Sea, Yellow Sea, and South China Sea, but other environmental factors may also have an impact on the shedding of green tide algae, such as typhoons and currents. Algae shedding is divided into artificial shedding and natural shedding. However, few studies have explored the relationship between algal natural shedding and environmental factors. pH, sea surface temperature, and salinity are critical environmental factors affecting the physiological state of algae. Therefore, based on field observations of the shedding of attached green macroalgae in Binhai Harbor, this study assessed the correlation between the shedding rate and environmental factors (pH, sea surface temperature, and salinity). The green algae that shed from Binhai Harbor in August 2022 were all identified as U. meridionalis. The shedding rate range was 0.88% ± 0.11% d−1 to 4.78% ± 1.76% d−1, and was not correlated with pH, sea surface temperature, or salinity; however, the environmental conditions were very suitable for the proliferation of U. meridionalis. This study provided a reference for the shedding mechanism of green tide algae and revealed that with the frequent human activities along the coast, U. meridionalis may pose a new ecological risk in the Yellow Sea.

AKTIVITAS ANTIOKSIDAN DAN KADAR TOTAL FENOL MAKROALGA PERAIRAN TANJUNG BENOA, BALI

Purpose : The purpose of this study was to determine antioxidant activity of macroalgae in Tanjung Benoa, Bali, Method : In this research, the antioxidant activity of macroalgae in Tanjung Benoa, Bali, will be tested using the DPPH method. Total phenolic test / TPC (Total Phenolic Content) test was also carried out on macroalgae samples using the Folin-Ciocalteau method. TPC value is expressed as the equivalent of mg gallic acid (GAE)/g dry weight of the sample. Result: Samples obtained at the time of sampling were 10 macroalgae samples consisting of 5 red macroalgae (rhodophyta), 4 green macroalgae (chlorophyta) and 1 brown macroalgae (phaeophyta). The results of the antioxidant analysis showed that the 4 macroalgae that had the greatest percentage of inhibition were the macroalgae Chondrus crispus, Sargassum sp., Gracilaria sp and Acrosorium sp.1. The results of total phenol analysis showed that the highest levels of total phenol were found in macroalgae Sargassum sp., Gracilaria sp. and Acrosorium sp. 1. Conclucion : Total phenolic content of most of the macroalgae samples had a positive correlation with antioxidant potential.Keywords: macroalgae, antioxidants, total phenols, DPPH, Tanjung Benoa