Pyropia kinositae, a cold-water red algal species found in East Asian marine environments, thrives on aquaculture rafts and adapts to continuous submersion. Its robust growth and suitability for offshore and northern regions make P. kinositae ideal for evolving mariculture practices in China, aligning with the industry's shift towards these areas. This study extensively investigated the optimal cultivation conditions (temperature, light, salinity, and nutrient levels) for the gametophyte generation of P. kinositae, focusing on conchospore germination, conchosporeling growth, and thallus growth. Conchospore germination and conchosporeling growth were optimal at 17 °C and salinity of 25–30, with light intensity optimal at 40–70 μmol photons m−2 s−1 for conchospore germination and 100 μmol photons m−2 s−1 for conchosporeling growth. The thalli showed best growth at 2 mg L−1 nitrogen, particularly at 12 °C with light intensity between 30–90 μmol photons m−2 s−1, where the peak photosynthetic rate and Fv/Fm value were observed, indicating optimal photosynthetic efficiency. Biochemical analysis of the thalli revealed significant variations in pigments such as chlorophyll a and carotenoid, alongside soluble proteins, ATP, and enzymes involved in photosynthesis, respiration, antioxidation, and nitrogen assimilation. Notably, higher nitrogen concentrations led to increased contents of soluble proteins, ATP, chlorophyll a, and carotenoid, as well as elevated activities of phosphofructokinase (PFK), nitrate reductase (NR) and malate dehydrogenase (MDH), suggesting increased nutrient availability enhanced the metabolic activities of the thalli. At a lower nitrogen concentration (0.1 mg L−1), the highest SOD activity and H2O2 contents were observed, indicating increased ROS generation and scavenging under stress of nutrient levels. Activities of antioxidant enzymes, such as SOD and CAT, increased with temperature, peaking at 13 °C, highlighting the enhanced defense against oxidative stress at this temperature. Additionally, RuBisCO activity was the highest at a light intensity of 70 μmol photons m−2 s−1. The optimal environmental conditions for the growth of P. kinositae gametophyte generation were obtained based on the physiological and biochemical performance, offering crucial information for optimizing cultivation practices for this economically valuable macroalga.

Macrocystis pyrifera is a large perennial brown alga used as a raw material in the chemical, energy, and medicine industries. It is also a high-quality material for the construction of seaweed beds with extremely high economic and ecological value. In the 1980s, M. pyrifera was introduced to China, and many experiments on its seedling and cultivation technologies were undertaken. However, research on its ecological adaptability is relatively challenging, and the aquaculture industry has not yet developed due to bottleneck problems. In the present study, the MaxEnt model was used to predict the suitability and potential invasion risk of M. pyrifera in China to lay a foundation for M. pyrifera culture industry development and marine ecological construction. Parameter optimization showed that the predictive performance of the model was the best when the feature combination was product, quadratic, and hinge features and the regularization multiplier was 0.8. Considering the correlation between environmental attributes and their contribution to the model, six environmental factors were selected to construct a prediction model for the suitability of M. pyrifera. Among these, light intensity and temperature produced the greatest impact on the natural distribution of M. pyrifera. For high suitable growth probability, the optimal light intensity was > 2 μmol/(m2·s) and the optimum temperature range was 10.5~17℃. Combined with ArcGIS, the modeling results showed that the suitable habitats for M. pyrifera in China are mainly distributed in the Yellow Sea and Bohai Sea, accounting for approximately 13.17% of the sea area, with a marginal suitability of 5.46%, low suitability of 2.85%, moderate suitability of 1.20%, and high suitability of 3.66%. Furthermore, Liaodong Bay and Bohai Bay are suitable sea areas for the introduction and cultivation of M. pyrifera as well as the construction of M. pyrifera farms. Some areas in Liaodong Bay are highly suitable, indicating a certain risk of invasion. Therefore, ecological safety evaluations should be strengthened if M. pyrifera cultivation is promoted near this area.

Neopyropia yezoensis is a typical intertidal seaweed and an indispensable species for conservation of seaweed resources. As one of the most important marine vegetables, the cultivation area of N. yezoensis has been largely increasing in the past decade and ranked the second highest among all the farmed seaweeds in China. It remains unknown whether large-scale cultivation of N. yezoensis has a genetic impact on wild populations. In this study, SSR markers and 18S rDNA were applied for diversity and genetic structure analysis of 22 N . yezoensis populations from North China. Twenty-two haplotypes were generated from 352 18S rDNA sequences and only three haplotypes were shared by both cultivated and wild populations. Based on 11 polymorphic SSR markers developed, the average polymorphism of the cultivated N. yezoensis populations was higher than that of the wild populations, with the percentage of polymorphic loci being 90.91% in most cultivated populations. The cultivated populations were clustered separately from the wild ones based on the population phylogenetic tree. This indicates that cultivated N. yezoensis populations are diverse and divergent from wild populations in China. However, there were cultivated individuals mixed with the wild ones based on the individual phylogenetic tree and STRUCTURE analysis. The genetic differentiation between cultivated and wild populations decreased with increasing cultivation time, suggesting a possible long-term and slow process of genetic introgression between cultivated N. yezoensis and the wild resource. The wild populations were grouped into two distinct clades by SSRs, with one distributed around the intersection between the Yellow Sea and the Bohai Sea, where the populations were characterized by a specific 18S rDNA haplotype. These findings provide useful insights into germplasm conservation, genetic breeding and improvement of N. yezoensis farming practices.

Climate change is altering geographic and phylogeographic distribution of macroalgae, laying great impacts on their conservation and sustainable utilization. The potential distribution of two dominant cultured seaweeds-Neoporphyra haitanensis and Neopyropia yezoensis was predicted under present and three representative concentration pathways (RCP 2.6, 4.5, 8.5) for 2050 s using the maximum entropy model (MaxEnt). The area under the receiver operating characteristic curve (AUC) was 0.998 for N. haitanensis and 0.992 for N. yezoensis, indicating high modelling accuracy. Sea surface temperature contributed mainly to the models. In addition to the predominant distribution in their native habitats in Northwest Pacific, high suitability along the east coast of North America and trans-hemispheric distribution was predicted for both species. In 2050 s, high-latitudinal and offshore expansion was observed, increasing over the present distribution area by 10.75%∼26.13% for N. haitanensis and 18.97%∼26.48% for N. yezoensis. Current geographic distribution centroid of N. yezoensis was located in Seocheon and the centroid shifted northeastward to the Sea of Japan in 2050 s. The most specific haplotypes or high genetic variations (based on chloroplast rbcL sequences) were identified in both regions. Current and future centroids of N. haitanensis were located in East China Sea, where the highest genetic diversity was identified. The overall haplotype and nucleotide diversity of both species was at low levels while the haplotype distribution showed spacial heterogeneity, more diversified at the convergence zones of warm and cold ocean currents. The overlapping between N. yezoensis and N. haitanensis geographic distribution centers and species’ genetic diversity hotspots implied their ability to adapt to future climate change. These findings provided vital information for conservation and sustainable utilization of these important intertidal seaweeds to address the global climate challenges.

Bangia fuscopurpurea is a widespread intertidal seaweed that is commercially cultured in China. This seaweed is frequently exposed to hyposalinity stress, but little is known about the adaptation mechanisms. Ascorbate−glutathione (AsA−GSH) cycle plays important roles in many organisms under a variety of abiotic stress, including hyposaline stress. In this study, we investigated the response of key metabolites and enzymes involved in the AsA−GSH cycle of B. fuscopurpurea under hyposalinity, with the addition of exogenous GSH and Lbuthionine-sulfoximine (BSO). The quantification of BfAPX gene expression was assessed across varied treatment regimens. And the putative interaction proteins of BfAPX were screened by yeast two hybrid system. It was found that under hyposalinity (15 and/or 0 psu), the content of reduced glutathione (GSH), total glutathione (GSH+ oxidized glutathione, GSSG) and cysteine, the ratio of GSH/GSSG and ascorbic acid (AsA)/ dehydroascorbic acid (DHA), and the activity of ascorbic acid peroxidase (APX) and monodehydroascorbate reductase (MDHAR) was significantly up-regulated. The hyposality-promoted GSH/GSSG was weakened while the glutathione reductase (GR) activity was promoted by adding exogenous GSH and BSO. The hyposality-promoted AsA/DHA ratio was strengthened by exogenous GSH but weakened by BSO. The dehydroascorbate reductase (DHAR) activity had no significant changes either with or without exogenous GSH under all salinities, while DHAR activity together with DHA content was enhanced by BSO. The expression of APX gene markedly increased under hyposalinity+BSO treatment. Putative interacting proteins of APX, including glutamate dehydrogenase 1a and fructose diphosphate aldolase, were identified through screening. The results indicated that the AsA−GSH cycle was involved in response of B. fuscopurpurea to hyposalinity by means of increasing GSH/GSSG ratio (through promoting GSH biosynthesis pathway and GSH regeneration from GSSG by GR catalyzation) and AsA/DHA ratio (promoting AsA regeneration through MDHAR). These findings would contribute to improve the aquaculture of this promising economic species and unveil how intertidal seaweeds address the global climate challenges.

温度是影响藻类生长发育的关键因素之一.本研究探讨了 6～22℃下,多肋藻(Costaria costata)小孢子体的生长情况及抗氧化生理特性,以探明其适温机制,为多肋藻海区栽培提供支撑.结果发现,培养初期(5 d内),多肋藻小孢子体在18℃下具有最大的相对生长速率(RGR),22℃下藻体梢部严重穿孔溃烂;随着培养时间延长(10 d),10℃下藻体RGR最高.实验周期内,不同温度组间Fv/Fm无显著差异,6～14℃下藻体均具有较高的总光合速率(Pt)和最大表观光合速率(Pnmax),Pnmax随着培养时间的延长在10℃下最高.培养3 d时,6℃下呼吸速率(Rd)最高;22℃下,藻体Rd随着培养时间延长显著上升,表明增强呼吸作用是多肋藻小孢子体对低温和高温胁迫的共同响应.22℃高温胁迫下,胡萝卜素(Car)和岩藻黄素(Fucox)、可溶性蛋白的含量升高;6℃时,SOD酶活高于其他温度组.在6～18℃范围内,灰分、碳水化合物和粗纤维的积累与温度具有一定的正相关性.综上,多肋藻小孢子体可在6～18℃生长,其中以10℃左右为佳.

Laver is the most widely farmed seaweed with the largest culture area in China. The spatio-temporal variations in composition, diversity, and functional properties of bacteria in seawater as well as the environmental variables of seawater in a large-scale laver farm in China were studied. Both the community richness indices and Shannon index in the laver farming area remained at a relatively stable level during laver cultivation. Fifty-nine prokaryotic phyla were detected in all samples, however, only six of these phyla accounted for 98.84% of all sequences. Proteobacteria, Gammaproteobacteria, Rhodobacterales, Rhodobacteraceae, and Octadecabacter were the most predominant bacterial taxa at different levels of classification. The keystone bacterial taxa were Bacteroidetes, Pseudomonadales, Rhodobacterales, Flavobacteriales, Loktanella, and Pseudoruegeria based on network analysis. Members of representative bacterial biomarker taxa in November may be associated with degradation of algal cell wall polysaccharides. A significant increase in metabolic exchange and transformation nutrients occurred in the seawater during the early and late stage of laver cultivation, indicating that the laver reproductive activities (i.e. the formation/release activities of archeospores and zygotospores) probably drove the variation of metabolic functional diversity of bacterial communities. Based on Mantel test and redundancy analysis, we found the hydrographic parameters (e.g. salinity, temperature, DO, pH) as well as the key carbon (e.g. POC, DOC) and nitrogen parameters (e.g. nitrate, DIN, DON, TDN) were crucial environmental variables to shape the bacterial community composition in the surrounding seawater of laver farm. In a word, our results suggested that the microbial community structure and function significantly changed across the different succession stages during laver cultivation. This work provides new insights on the characteristics of bacterial communities in a large-scale laver farming system and solidifies the importance of laver farming in shaping seawater microbiomes.

在实验室条件下,研究了多肋藻(Costaria costata)孢子体在不同光强下的生长、光合作用、营养成分以及抗氧化能力,以期揭示多肋藻小孢子体对光强的适应性,为多肋藻海区栽培提供参考.结果发现,藻体在光照强度30～120 μmol/(m2·s)均具有较快的生长速率,其中60 μmol/(m2 s)下相对生长速率(RGR)和藻体PSⅡ最大光化学量子产量(Fv/Fm)均最高.总光合速率(Pt)和最大表观光合速率(Pnmax)在培养前期(5 d)随光强增加而上升,随着培养时间的延长(10 d)在60 μmol/(m2·s)下最高;在60 μmol/(m2·s)下,藻体呼吸速率(Rd)较低.叶绿素a(Chl a)、岩藻黄素(Fucox)和类胡萝卜素(Car)的含量为低光组稍高于高光组(P＞0.05).粗蛋白、脂肪和粗纤维的含量与光强具有一定的正相关性,而碳水化合物含量则与光强呈负相关.结果表明,60μmol/(m2·s)适宜多肋藻小孢子体的生长.在较低或较高光强下,藻体呼吸作用均显著增强;此外,高光下,可溶性蛋白含量显著上升,低光下,抗超氧阴离子自由基(ASAFR)、超氧化物歧化酶SOD)、抗坏血酸过氧化物酶(APX)比活力较高,过氧化氢酶(CAT)比活力则在低光和高光下均下降,这些生理响应对多肋藻小孢子体适应不同光强具有重要的调节作用.

The purpose of this study was to develop stable microsatellite markers and evaluate the genetic background of cultivated Sargassum fusiforme. Based on the transcriptome data obtained by high-throughput sequencing, eleven polymorphic microsatellite markers were developed using four S. fusiforme populations from China. One cultivated population was from Dongtou (DT) and three wild populations were from Muye Island (MY), Pingyu Island (PY) and Nanji Island (NJ). The cultivated S. fusiforme had the highest genetic diversity, with 90.91% polymorphic loci and Shannon's information index (I) of 0.606, which were much higher than those of the wild populations (I = 0.425). The four populations were divided into two groups through a structure analysis. DT, PY and NJ were clustered into a group, and MY was an almost completely separate group. Both the structure and principal coordinates analysis showed that DT and PY had the lowest genetic differentiation, suggesting that the parents of the breeding population in Dongtou partly come from Pingyu Island. The observed heterozygosity of NJ was much higher than expected, indicating that the NJ wild resource was greatly affected by the environment. These eleven microsatellite markers could provide additional markers for germplasm resource evaluations and facilitate genetic analyses of the S. fusiforme population.

Abstract Neopyropia yezoensis is a typical intertidal seaweed and a major mariculture crops in China. The culture area of N. yezoensis has been largely increasing in the past decade. Whether large-scale cultivation of N. yezoensis has a genetic impact on wild populations remains unknown. Here, eleven polymorphic microsatellite markers were developed and applied for the genetic structure analysis of 22 N. yezoensis populations from along the coast of China. The populations were divided into 4 groups based on the Bayesian model-based structure analysis. A significant genetic structure difference was present between the cultivated populations and the wild ones. The 13 wild populations were divided into two distinct groups, with no obvious correlation between the inter-population genetic variation and geographical distance within each group. The average polymorphism of 9 cultured N. yezoensis populations was higher than that of the wild populations, and the percentage of polymorphic loci of the most cultivated populations was at a high level (P=90.91%). It indicated that the germplasm of cultivated N. yezoensis in China are diversified. The genetic differentiation between the cultivated populations and the wild populations decreased with the increasing cultivation time. But the gene flow between the cultivated populations and the wild ones was asymmetric, exhibiting a trend from wild population to cultured population. The result indicated that even if there is a genetic impact of N. yezoensis aquaculture on wild resource, it is a long-term and slow process. This research provided useful insights for future germplasm resource evaluation and genetic breeding of N. yezoensis.

基于大型经济海藻的经济和生态价值,开发具有潜力的新栽培物种是海藻栽培产业健康多样化发展的保障.多肋藻(Costaria costata)是一种具有很高营养价值及经济价值的大型褐藻,但并非我国本土物种.本研究采用MaxEnt模型预测多肋藻在我国的适生情况,并探究不同因子对多肋藻孢子体生长的影响,旨在为开展多肋藻栽培提供支撑.结果 表明,当正则化参数为1,训练集与测试集比值为70:30时,模型预测性能最佳.基于环境因子的相关性和对模型的贡献率,筛选出8项用于多肋藻适生预测模型的构建,其中温度与光强对多肋藻自然分布的影响最大,在光强不低于4μmol/(m2·s),月均温度不低于7℃,多肋藻的适生概率较高.模型显示,多肋藻在我国的适生区主要分布于黄渤海,约占该海域面积的11.32％,其中8.08％为边缘适生区和低适生区,中适生区和高适生区分别占1.33％和1.91‰主要位于辽东湾.表明辽东湾、大连沿海以及山东半岛沿海是多肋藻引种栽培的适宜海域.但辽东湾部分区域的高适生性也预示高入侵风险性,若开展人工栽培,应加强生态安全性方面的评估.

以条斑紫菜(Pyropia yezoensis)丝状体为材料,研究温度(15℃、25℃和35℃)与光强[40、100和300 μmol/(m2·s)]对营养藻丝和孢子囊枝光合生理的影响.结果 显示,15℃和25℃实验组中,营养藻丝和孢子囊枝的PSⅡ原初光能转化效率(Fv/Fm)、总光合速率(Pg)和净光合速率(Pn)均随光强升高而降低.在300 μmol/(m2·s)下,营养藻丝的Fv/Fm和Pg趋于零,Pn为负值.在25℃、40 μmol/(m2.s)下,营养藻丝的呼吸耗氧速率(Rd)在实验周期内一直显著高于孢子囊枝;其他组则随胁迫时间延长,二者间Rd差距逐渐缩小.总体上,在相同条件下,所测孢子囊枝Fv/Fm、Pg和Pn均显著高于营养藻丝,而Rd与营养藻丝相当.35℃实验组在6h时,孢子囊枝的Fv/Fm显著高于营养藻丝,但随光强升高直线下降(P＜0.05),其他组Fv/Fm均趋于0.在40、100 μmol/(m2·s)下,6h时,孢子囊枝Pg和Rd高于营养藻丝或二者相当;在300 μmol/(m2·s)下,后期营养藻丝Pn和Rd高于孢子囊枝,但在整个实验周期,二者的Pn均为负值.总体上,营养藻丝和孢子囊枝的FvJFm、Pg和Pn均显著低于(多数趋于0或负值)15℃和25℃,而35℃的奶高于15℃和25℃;后期,2种藻丝均出现发绿变白,甚至死亡现象.研究表明,在条斑紫菜营养藻丝的光合作用被严重抑制的光强、温度条件下,孢子囊枝仍具备相对高的光合活力,说明在温度和光强升高到不利于营养藻丝生长的情况下,刺激藻丝转向了孢子囊枝发育阶段,后者具备适应更高温度和光照的能力.