Dictyota Dichotoma Research Articles

Community gross primary production and respiration in epilithic macroalgae and Posidonia oceanica macrophytodetritus accumulation in the Bay of Revellata (Corsica)

We report estimates of community gross primary production (GPP), community respiration (CR), and net community production (NCP) based on the change of dissolved O2 during incubations over epilithic turf-forming macroalgae (Halopteris scoparia, Padina pavonica, and Dictyota dichotoma) on 7 occasions and in accumulations of Posidonia oceanica macrophytodetritus (i.e. litter) on 8 occasions in the Bay of Revellata (Corsica) from March 2009 to May 2011. In the epilithic macroalgae community, GPP ranged between 7.8 and 82.2 mmol O2 m−2 d−1, CR ranged between −108.5 and −13.6 mmol O2 m−2 d−1, and NCP ranged between −53.2 and −5.7 mmol O2 m−2 d−1. In the P. oceanica macrophytodetritus accumulation, GPP ranged between 5.7 and 91.6 mmol O2 m−2 d−1, CR ranged between −112.8 and −27.2 mmol O2 m−2 d−1, and NCP ranged between −46.8 and −9.9 mmol O2 m−2 d−1. GPP in both the epilithic macroalgae community and the P. oceanica macrophytodetritus accumulation peaked in summer and was lowest in fall, following the seasonal variation of incoming light. GPP correlated to macroalgal biomass but was unrelated to the biomass of living macroscopic plant material in the P. oceanica macrophytodetritus accumulation. The annual average of GPP was equivalent in the epilithic macroalgae and P. oceanica macrophytodetritus accumulation communities (17.6 and 19.4mol O2 m−2 yr−1). Both the epilithic macroalgae community and the P. oceanica macrophytodetritus accumulation were net heterotrophic with an annual average NCP of −6.1 and −8.8mol O2 m−2 yr−1, respectively. The NCP of the adjacent P. oceanica meadow at 10 m depth based on simultaneous measurements based on the open water O2 mass balance from moored O2 probes (optodes) was 28.9mol O2 m−2 yr−1. The potential export of dissolved organic carbon from the P. oceanica meadow could quantitatively meet the carbon demand to sustain the net heterotrophy of the adjacent epilithic macroalgae community in the Bay of Revellata. We also show the limitation and possibly over-estimation of extrapolating decay rates based on litter bag experiments with small quantities of material to “real” macrophytodetritus biomass densities.

Bioassays and virtual screening to identify potent natural antifouling compounds from the brown macroalga Dictyota dichotoma

Macroalgae are one of the potential natural sources for the isolation of novel eco-friendly antifouling compounds. In this study, the antifouling activity of an extract of the brown macroalga Dictyota dichotoma collected from the Red Sea was tested against bacteria isolated from the marine biofilm and larval forms of the barnacle. A maximum inhibition of barnacle larval settlement of 89.36% was observed in 25 µg ml-1 extract concentration at 24 h treatment. The secondary metabolite composition of the extract was analyzed by GC-MS and compounds were used as ligands for molecular docking with barnacle cement protein. The toxicity profile of secondary metabolites present in the extract was predicted through in silico analysis. The results indicate that the crude extract of the alga inhibited the biofilm formation by the bacteria and significantly reduced the settlement of the barnacle larvae. GC-MS analysis of the extract revealed the presence of five metabolites, including two fatty acids. All metabolites showed higher binding affinity with barnacle cement than the reference compound, copper. Among the secondary metabolites detected in the algal extract, the cholestane derivative exhibited maximum binding affinity (–14.2 kcal mol-1) with barnacle cement. The metabolites also showed positive for crustacean and fish toxicity in toxicity prediction using an in silico method.

Optimization and characterization of brown seaweed alginate for antioxidant, anticancer, antimicrobial, and antiviral properties

Alginate is a natural polysaccharide obtained from brown seaweeds and having advantageous health usefulness, was employed extensively in nutraceutical sectors and the pharmaceutical industry. This research was devoted for optimization of alginate extraction from different brown seaweeds. A Box-Behnken Design (BBD) was used for the optimization of alginate extraction from Padina pavonica by analyzing the influence of temperature (30, 40, and 50 °C), time (60, 120, and 180 min), and alkaline concentration (1 %, 2 %, and 3 %) on extraction yield and uronic acid content. The optimal conditions recorded to maximize the alginate yield and its uronic content were an alkali concentration of 2.5 % and a temperature of 39.95 °C for 102.5 min. The optimized parameters achieved from BBD were used to compare alginate extraction from P. pavonica, Sargassum cinereum, Turbinaria turbinata, and Dictyota dichotoma. FTIR, 1H NMR, and HPLC were used to characterize the extracted alginate. The bioactivity of alginate against free radicals, breast cancer cells (MCF-7), some pathogenic microbes, and SARS-CoV-2 viruses was tested. Under the optimized conditions, alginate was extracted from P. pavonica at a rate of 21.13 ± 2.47 % DW, S. cinereum at 24.08 ± 0.33 % DW g/L, T. turbinata at 17.47 ± 0.26 % DW, and D. dichotoma at a rate of 19.57 ± 3.60 % DW. The alginate extracted from D. dichotoma showed the highest antioxidant, anticancer, and antiviral activity.

Optimizing the fucoidan extraction using Box-Behnken Design and its potential bioactivity

Fucoidan is a sulfated polysaccharide that occurs naturally in the cell wall of brown seaweeds and has substantial biological efficacy. Optimizing the extraction of fucoidan from different brown seaweeds was the primary goal of this research. The optimization of fucoidan extraction was applied on the brown macroalga Turbinaria turbinata using a Box-Behnken Design (BBD) to inspect the impacts of different pH (3, 5, 7), temperature (70, 80, 90 °C) and extraction duration (60, 120, 180 min) on both the yield and sulfate content of fucoidan. The optimized parameters recorded to maximize the fucoidan yield and its sulfate content were a pH of 3.44 and a temperature of 82.26 °C for 60 min. The optimal conditions obtained from BBD were used for fucoidan extraction from T. turbinata, Sargassum cinereum, Padina pavonica, and Dictyota dichotoma. The highest average of fucoidan yield was derived from P. pavonica (40.76 ± 4.04 % DW). FTIR, 1H NMR, and HPLC were used to characterize extracted fucoidan. The extracted fucoidan's Physical characteristics, biochemical composition, antioxidant potential, antitumor effect against breast cancer cells (MCF-7), and antimicrobial and anticoagulant activity were assessed. The extracted fucoidan from D. dichotoma, followed by that extracted from S. cinereum, which had the highest sulphate content, depicted the highest antioxidant, anticancer, and anticoagulant activities. Fucoidan has demonstrated a strong antimicrobial action against some pathogenic microorganisms; Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia, and Candida albicans. The anticoagulant properties of fucoidan from D. dichotoma were stronger than those of fucoidan from S. cinereum, T. turbinata, and P. pavonica due to its higher sulphate content. These findings could be used for various biomedical applications to improve the pharmaceutical industry.

Assessment of Antibacterial Activity of Various Solvent Extracts of Dictyota Dichotoma Against Multidrug Resistant Bacterial Strain

Assessment of Antibacterial Activity of Various Solvent Extracts of Dictyota Dichotoma Against Multidrug Resistant Bacterial Strain

Exploring Bioactive Components and Assessing Antioxidant and Antibacterial Activities in Five Seaweed Extracts from the Northeastern Coast of Algeria.

The main goal of this study was to assess the bioactive and polysaccharide compositions, along with the antioxidant and antibacterial potentials, of five seaweeds collected from the northeastern coast of Algeria. Through Fourier transform infrared spectroscopy analysis and X-ray fluorescence spectroscopy, the study investigated the elemental composition of these seaweeds and their chemical structure. In addition, this study compared and identified the biochemical makeup of the collected seaweed by using cutting-edge methods like tandem mass spectrometry and ultra-high-performance liquid chromatography, and it searched for new sources of nutritionally valuable compounds. According to the study's findings, Sargassum muticum contains the highest levels of extractable bioactive compounds, showing a phenolic compound content of 235.67 ± 1.13 µg GAE·mg-1 and a total sugar content of 46.43 ± 0.12% DW. Both S. muticum and Dictyota dichotoma have high concentrations of good polyphenols, such as vanillin and chrysin. Another characteristic that sets brown algae apart is their composition. It showed that Cladophora laetevirens has an extracted bioactive compound content of 12.07% and a high capacity to scavenge ABTS+ radicals with a value of 78.65 ± 0.96 µg·mL-1, indicating high antioxidant activity. In terms of antibacterial activity, S. muticum seaweed showed excellent growth inhibition. In conclusion, all five species of seaweed under investigation exhibited unique strengths, highlighting the variety of advantageous characteristics of these seaweeds, especially S. muticum.

Comparative antioxidant potential, proximal biochemical composition, and pigment content of 11 brown seaweeds from the West of Ireland

The biorefinery and valorisation of sustainable bioresources such as seaweeds have increased in response to global circular economy initiatives. Several seaweed species are exploited worldwide in the biofertilizer, nutrition, bioenergy, cosmetics, or pharmaceutical sectors. Brown seaweeds are widespread, easily accessible, and abundant in northwest Europe regions, with some species being commercially harvested and processed.Here, both commercially exploited, and less studied brown seaweeds (n = 11) were collected from Irelands Atlantic coast and analysed for soluble carbohydrates, lipids, proteins, fatty acid, and pigment profiles as well as antioxidant potential. Soluble carbohydrates (62.7 µg glucose eq mg−1 DW) were highest in Saccharina latissima while lipids (148.2 mg L g−1 DW), fucoxanthin (1.35 mg g−1) and β-carotene (4.10 mg g−1) were greater in Dictyota dichotoma. The highest antioxidant activity (456.3 µmol Trolox eq mg−1 DW with TEAC assay) and soluble protein content (562.5 µg BSA eq mg−1 DW) were in Halidrys siliquosa extracts.Data matrix multivariate ordination indicated that some less studied brown seaweeds have further valorisation potential owing to their biochemical composition and bioactivity. The development of species-specific tailored cultivation strategies as part of integrated multi-trophic aquaculture systems has potential to contribute to environmental sustainability while introducing new natural bioactive products to markets.

Field survey of the phase and sex ratios of the brown alga Dictyota dichotoma (Dictyotales, Phaeophyceae) using sex‐specific molecular markers

SUMMARYDominance of one phase (i.e. diploid or haploid) has been reported in various isomorphic macroalgae; however, studies of the relative frequencies of the two phases are limited to a few taxa owing to the difficulty in identifying phases of sterile thalli. In Dictyota dichotoma, we have previously documented the dominance of fertile sporophytes. In the present study, the phase and sex ratios of sterile thalli of D. dichotoma were determined using newly developed sex‐specific markers. Differentially expressed genes were detected by transcriptome analyses of female and male gametophytic strains and a sporophytic strain aiming to identify candidate sex‐specific genes. These candidates were aligned with genome sequences on the sex chromosomes of Ectocarpus siliculosus and were identified as putative sex‐specific genes of D. dichotoma. Two primer sets were designed to discriminate phase and sex by the presence or absence of PCR products, and these markers were applied to examine the phase and sex ratios of D. dichotoma in various habitats and seasons. The proportion of sporophytes against 33–50 thalli examined in each of the five habitats at Ebisu Island, Shizuoka Prefecture was 88–100%, and the proportion of fertile sporophytes against total sporophytes (fertility proportion) varied among the habitats (0–54%). The fertile sporophytes were remarkably larger than the sterile sporophytes. At Tateyama, Chiba Prefecture, the dominance of sporophytes occurred in all seasons. The fertility proportion of sporophyte was relatively high from February (62.4%) to May (91.9%) and lower than 23% in other seasons. When artificial substrates were anchored in the middle of the D. dichotoma population, newly recruited thalli were all sporophytes, suggesting infrequent reproduction via tetraspores in nature. Based on these findings, we discuss potential fitness differences between the phases of D. dichotoma.

The distribution of radiotoxic 137Cs concentrations in seaweed and mussel species in the Mediterranean Sea

A study was conducted to determine the 137Cs activity concentrations in various seaweed and mussel samples from the North East Mediterranean Sea, including the brown algae (Dictyota dichotoma) and oarweed (Laminaria digitata), and mussel species (Haliotis asinina, Mytilus edulis and Mytilus galloprovinciali). The 137Cs activity concentration in seaweed species exhibited varying levels, ranging from 84.20 ± 1.82 to 236.05 ± 5.72 mBq kg−1 fresh weight (fw) for oarweed, and 106.29 ± 2.26 to 252.38 ± 6.04 mBq kg−1 fw for brown algae. The 137Cs value in mussel species were between 12.94 ± 0.51–101.84 ± 1.35 mBq kg−1 fw for M. galloprovincialis, 15.49 ± 0.58–71.52 ± 1.16 mBq kg−1 fw for M. edulis, and 10.36 ± 0.11–69.13 ± 1.34 mBq kg−1 fw for H. asinine. When comparing the 137Cs concentration in seaweed and mussel species, the average concentration in seaweeds was approximately four times higher than that in mussels. This significant difference in radioisotope concentration highlights the potential for higher bioaccumulation of 137Cs in seaweeds compared to mussels.

Chemical Composition, Antioxidant, and Antitumor Activity of Fucoidan from the Brown Alga Dictyota dichotoma.

Brown macroalgae are a rich source of fucoidans with many pharmacological uses. This research aimed to isolate and characterize fucoidan from Dictyota dichotoma var. dichotoma (Hudson) J.V. Lamouroux and evaluate in vitro its antioxidant and antitumor potential. The fucoidan yield was 0.057 g/g algal dry wt with a molecular weight of about 48.6 kDa. In terms of fucoidan composition, the sulfate, uronic acid, and protein contents were 83.3 ± 5.20 mg/g fucoidan, 22.5 ± 0.80 mg/g fucoidan, and 26.1 ± 1.70 mg/g fucoidan, respectively. Fucose was the primary sugar component, as were glucose, galactose, mannose, xylose, and glucuronic acid. Fucoidan exhibited strong antioxidant potential that increased by more than 3 times with the increase in concentration from 0.1 to 5.0 mg/mL. Moreover, different concentrations of fucoidan (0.05-1 mg/mL) showed their ability to decrease the viability of Ehrlich ascites carcinoma cells in a time-dependent manner. These findings provided a fast method to obtain an appreciable amount of natural fucoidan with established structural characteristics as a promising compound with pronounced antioxidant and anticancer activity.

Assessment of phytochemicals from marine algae Ulva fasciata and Dictyota dichotoma with antioxidant and antimicrobial potential

The marine ecosystem is a rich source of novel secondary metabolites with significant biomedical applications. Seaweeds are considered as the treasury of secondary metabolites with various biological activities. This study aims to analyze antioxidant and antimicrobial potential in green seaweed Ulva fasciata and brown seaweed Dictyota dichotoma. Extracts from four different solvents such as petroleum ether, chloroform, ethyl acetate and methanol using Soxhlet apparatus were tested for the qualitative analysis of phytochemicals. Secondary metabolites were analyzed quantitatively to correlate with the antioxidant (DPPH assay) and antimicrobial potential of seaweeds. Results showed a better antioxidant activity of U. fasciata in its methanolic extract (89.29%) and D. dichotoma manifested a maximum antioxidant activity (70.1%) for its ethyl acetate extract. Structural characteristics of seaweed derived bioactive material were investigated by Fourier transform infrared spectroscopy (FTIR) and manifested the presence of alcohol and phenolic compounds. The inhibition zone formed around the crude extract reveals the antimicrobial nature of bioactive substances of seaweed extract against the pathogens. High inhibition and antioxidant activity indicate an effective drug’s evolution from seaweeds against human pathogens.

The potential of seaweed extracts as a biostimulant for improving salt stress tolerance of Solanum lycopersicum L

The present investigation aimed to examine the effects of seaweed extracts (SWE) on tomato plants under saline conditions (50 mM of NaCl). The current findings have shown that the SWE obtained from Jania rubens (J. rubens) gave better results compared to those prepared from the other two seaweeds; Dictyota dichotoma (D. dichotoma) and Gelidium sesquipedale (G. sesquipedale). Indeed, under salt stress, the application of fresh seaweed at 2% significantly (p ≤ 0.05) increased the plant height (26.28 cm ± 0.95) compared with the non-treated stressed control (17.65 cm ± 1.04). Based on these results the effect of J. rubens on some biological and biochemical parameters of tomato plants was evaluated. In fact, increased contents of chlorophylls, total soluble sugars (TSS), and total free amino acids (TFAA) were observed in seaweed-treated plants compared to the control plants. Moreover, the treatment of stressed plants with SWE revealed a significant (p ≤ 0.05) improvement in antioxidant enzyme activities such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione S-transferase (GST). The extract also showed an increase in the enzyme activities of glutamate dehydrogenase (GDH) and phosphoenolpyruvate carboxylase (PEPC), which are implicated in the nitrogen and carbon metabolism, respectively. Furthermore, the analysis of the chemical composition of the liquid seaweed extracts (fresh and dried) has shown that they contain bioactive compounds such as polyphenols, flavonoids, soluble sugars, and amino acids, which can be responsible for the tomato's tolerance to salinity. Therefore, the SWE tested in the present study can be used as a biostimulant to enhance the salt stress tolerance of tomato plants.

Pyrolysis of brown macroalgae Dictyota dichotoma and its thermokinetic analysis

Pyrolysis of brown macroalgae Dictyota dichotoma and its thermokinetic analysis

İskenderun Körfezi'ndeki (Kuzeydoğu Akdeniz) Kahverengi ve Kırmızı Makroalglerin Temel Besin Maddesi ve Biyoaktif Bileşiklerindeki Mevsimsel Değişimler

Proximate and bioactive compounds (total phenolic, flavonoid, chlorophyll-a and total carotenoid contents) of three brown seaweeds (Dictyota dichotoma, Padina pavonica, Stypopodium schimperi) and a red seaweed (Jania rubens) from the north-eastern Mediterranean Sea (İskenderun Bay) were investigated seasonally at three sampling sites. Seasonal variations were found for all of the parameters studied. The highest ash content was in J. rubens (77.7%) in the spring. The results showed that J. rubens is a rich source with respect to mineral content. D. dichotoma had the highest crude protein content, whereas S. schimperi contained the most lipids. Phenolics ranged between 34.6 - 107.0 mg GAE/g dw. The highest total phenolics were found in S. schimperi in the summer, and the lowest in P. pavonica in the spring. The flavonoid contents (9.05-10.6 mg QE/g dw) were higher in brown seaweeds than that in the red seaweed. Moreover, chlorophyll-a and carotenoids levels were highest in D. dichotoma (4.53 and 2.83 mg/g, respectively) during the autumn. The results revealed that the biochemical composition of the examined seaweeds showed significant changes depending on the species, location and seasons.

Preparative three-dimensional GC and nuclear magnetic resonance for the isolation and identification of two sesquiterpene ethers from Dictyota Dichotoma.

Separation science plays a crucial role in the isolation of novel compounds contained in complex matrices. Yet their rationale employment needs preliminary structure elucidation, which usually requires sufficient aliquots of grade substances to characterize the molecule by nuclear magnetic resonance experiments. In this study, two peculiar oxa-tricycloundecane ethers were isolated by means of preparative multidimensional gas chromatography from the brown alga species Dictyota dichotoma (Huds.) Lam., aiming to assign their 3D structures. Density functional theory simulations were carried out to select the correct configurational species matching the experimental NMR data (in terms of enantiomeric couples). In this case, the theoretical approach was crucial as the protonic signal overlap and spectral overcrowding were preventing any other unambiguous structural information. Just after the identification through the density functional theory data matching of the correct relative configuration it was possible to verify an enhanced self-consistency with the experimental data, confirming the stereochemistry. The results obtained further pave the way toward structure elucidation of highly asymmetric molecules, whose configuration cannot be inferred by other means or strategies.

Chemical and Nutritional Profiling of the Seaweed Dictyota dichotoma and Evaluation of Its Antioxidant, Antimicrobial and Hypoglycemic Potentials.

Seaweed has been known to possess beneficial effects forhuman health due to the presence of functional bioactive components. The n-butanol and ethyl acetate extracts of Dictyota dichotoma showed ash (31.78%), crude fat (18.93%), crude protein (14.5%), and carbohydrate (12.35%) contents. About 19 compounds were identified in the n-butanol extract, primarily undecane, cetylic acid, hexadecenoic acid, Z-11-, lageracetal, dodecane, and tridecane, whereas 25 compounds were identified in the ethyl acetate extract, mainly tetradecanoic, hexadecenoic acid, Z-11-, undecane, and myristic acid. FT-IR spectroscopy confirmed the presence of carboxylic acid, phenols, aromatics, ethers, amides, sulfonates, and ketones. Moreover, total phenolic contents (TPC) and total flavonoid contents (TFC) in ethyl acetate extract were 2.56 and 2.51 mg GAE/g and in n-butanol extract were 2.11 and 2.25 mg QE/g, respectively. Ethyl acetate and n-butanol extracts at a high concentration of 100 mg mL-1 showed 66.64 and 56.56 % inhibition of DPPH, respectively. Antimicrobial activity revealed that Candida albicans was the most susceptible microorganism, followed by Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, whereas Pseudomonas aeruginosa showed the least inhibition at all concentrations. The in vivo hypoglycemic study revealed that both extracts exhibited concentration-dependent hypoglycemic activities. In conclusion, this macroalgae exhibited antioxidant, antimicrobial, and hypoglycemic potentials.

Ultrasound pretreatment to enhance the enzymatic hydrolysis of Dictyota dichotoma for sugars production

There is an increasing demand for natural resources for biorefining purposes. In this regard, the efficient use of seaweed seems promising as they represent a sustainable feedstock with advantageous characteristics, given their abundant concentration of carbohydrates and low lignin levels. However, in the context of sugar platform biorefineries, to make this activity sustainable, high availability of seaweed biomass is required. In this respect, beach-cast seaweed biomass represents an attractive alternative, reducing the negative impact associated with its accumulation and decomposition on the beaches, which affects the financial income of the region. In this study, Dictyota dichotoma deposited on the coasts of Cadiz (Spain) was collected at the end of the autumn season and used as raw material for the production of simple sugars in the frame of a biorefinery approach. The potential of ultrasound pretreatment was applied to two biomass concentrations (2.1 and 4.3 % w/v), at different amplitude percentages (20, 40 and 60 %) and pretreatment times (15, 40 and 60 min) to enhance algal biomass saccharification. The best condition for reducing sugars (RS) production was: 4.3 % w/v of algal suspension and 40 min pretreatment at 40 % amplitude. This condition supposes specific energy (Es) of 6.78 MJ/kg and leads to a total sugar concentration of 163.64 ± 0.93 mg RS/g dried biomass. A slight improvement in RS production could be attained by increasing the amplitude to 60 % (165.52 ± 3.89 mg/g) but requiring 50 % higher specific energy. Experimental data were fitted to simple first-order kinetics. The hydrolysis rate constant k was a function of the biomass concentration and practically independent of the energy applied. In addition, the average value of k was 8.6 times higher than that for non-pretreated seaweed.

Intra-Species Variations of Bioactive Compounds of Two Dictyota Species from the Adriatic Sea: Antioxidant, Antimicrobial, Dermatological, Dietary, and Neuroprotective Potential.

The marine environment has a significant impact on life on Earth. Organisms residing in it are vital for the ecosystem but also serve as an inexhaustible source of biologically active compounds. Herein, the biodiversity of two brown seaweeds, Dictyota dichotoma and Dictyota fasciola from the Adriatic Sea, was evaluated. The aim of the study was the determination of differences in compound composition while comparing their activities, including antioxidant, antimicrobial, and enzyme inhibition, in connection to human digestion, dermatology, and neurological disorders. Chemical analysis revealed several terpenoids and steroids as dominant molecules, while fucoxanthin was the main identified pigment in both algae. D. dichotoma had higher protein, carbohydrate, and pigment content. Omega-6 and omega-3 fatty acids were identified, with the highest amount of dihomo-γ-linolenic acid and α-linolenic acid in D. dichotoma. Antimicrobial testing revealed a dose-dependent inhibitory activity of methanolic fraction against Escherichia coli and Staphylococcus aureus. Moderate antioxidant activity was observed for both algae fractions, while the dietary potential was high, especially for the D. fasciola dichloromethane fraction, with inhibition percentages of around 92% for α-amylase and 57% for pancreatic lipase at 0.25 mg/mL. These results suggest that Dictyota species might be a potent source of naturally derived agents for obesity and diabetes.

Komposisi dan Kerapatan Jenis Alga di Taman Wisata Perairan Laut Banda di Kabupaten Maluku Tengah

The purpose of this study was to identify the type of algae, calculate the composition, density, diversity index, similarity index, and dominance index, and measure water quality parameters in the waters of the Banda Sea marine tourism park in central Maluku regency. The method used in this study is a line transect method and a quadrant frame measuring 1m x 1m. There are 3 stations used with 5 replications each. The results showed that there were three divisions of algae, namely Chlorophyta, Phaeophyta, and Rhodophyta, with details of the species obtained were Amphiroa fragilissima, Boodlea composita, Boergesenia forbesii, Cladophora, Chaetomorpha crassa., Dictyota dichotoma, Gracilaria edulispuntia, Halimeda macrophyopuntia. tuna, Padina australis, Ulva compressa, Ulva reticullata. and Valonia ventricosa. The Chorophyta division of 66% obtained the highest species composition value, the highest density was obtained by the Amphiroa fragilissima species of 0.205. In addition, the ecological index such as (1) the diversity index was in the medium category with a value range of 1.35-1.97, (2) the similarity index included in the high category with a value range of 0.72-0.86 which indicates that the ecosystem is in a stable condition and the dominance index of the three stations shows a value close to one, namely 0.87-1 which indicates that there is a tendency for one species to dominate. The measurements of water quality parameters such as temperature, salinity, and currents show that they are optimal for algae growth.

No bacterial-mediated alleviation of thermal stress in a brown seaweed suggests the absence of ecological bacterial rescue effects

While microbiome alterations are increasingly proposed as a rapid mechanism to buffer organisms under changing environmental conditions, studies of these processes in the marine realm are lagging far behind their terrestrial counterparts. Here, we used a controlled laboratory experiment to examine whether the thermal tolerance of the brown seaweed Dictyota dichotoma, a common species in European coastal ecosystems, could be enhanced by the repeated addition of bacteria from its natural environment. Juvenile algae from three genotypes were subjected for two weeks to a temperature gradient, spanning almost the entire thermal range that can be tolerated by the species (11–30 °C). At the start of the experiment and again in the middle of the experiment, the algae were inoculated with bacteria from their natural environment or left untouched as a control. Relative growth rate was measured over the two-week period, and we assessed bacterial community composition prior to and at the end of the experiment. Since the growth of D. dichotoma over the full thermal gradient was not affected by supplementing bacteria, our results indicate no scope for bacterial-mediated stress alleviation. The minimal changes in the bacterial communities linked to bacterial addition, particularly at temperatures above the thermal optimum (22–23 °C), suggest the existence of a barrier to bacterial recruitment. These findings indicate that ecological bacterial rescue is unlikely to play a role in mitigating the effects of ocean warming on this brown seaweed.