Ulva Prolifera Research Articles

Influence of iron and carbon on the occurrence of Ulva prolifera (Ulvophyceae) in the Yellow Sea

Over the past decade, massive outbreaks of Ulva prolifera have occurred in the Yellow Sea, China, and caused negative effects to the coastal environments. In response, many scientific investigations have been conducted to ascertain the origins of and reasons for the algal bloom that has resulted in continuous green tides. In this work, we explored the influences of iron and dissolved inorganic carbon (DIC) on the occurrence of green algal blooms. The moderate-resolution imaging spectroradiometer (MODIS) data showed the blooming areas and movement of U. prolifera. Field observation showed that higher Fe(II) concentrations (average 0.145 mg L−1) can be correlated with large Ulva prolifera blooms. Furthermore, lower pH might enhance the accumulation of dissolved carbon into the green algae; a premise that was supported by higher concentrations of CO2(0.037 mmol L−1), HCO3− (2.58 mmol L−1) and the lowest pH value (7.69) being found together at site H11. The indoor iron- and bicarbonate-enrichment experiments further confirmed that higher concentrations of Fe(II) and HCO3− and a lower pH can increase the growth rate of U. prolifera. This study indicates that seawater chemical factors contribute to the long term, ongoing green tides in the Yellow Sea and provides new thoughts for the causes of U. prolifera blooms.

The seasonal dissipation of Ulva prolifera and its effects on environmental factors: based on remote sensing images and field monitoring data

Ulva prolifera blooms have occurred every summer in the South Yellow Sea since 2008. U. prolifera blooms appeared in the area near the Jiangsu shoal and then were driven to the Shandong Peninsula by the prevailing summer winds. The blooms covered a maximum area of more than 50000 km2 and had an aggregate estimated biomass of 3.64 × 105 tons. Large number of U. prolifera dissipation in the natural degradation and this cause a serious impact on the marine environment. We used MODIS, HJ-1A/B and GF-1 remote sensing image data to conduct large-scale monitoring of U. prolifera. Combined with sea surface monitoring station data from Haiyang city, Shandong province, we analyzed the impact of U. prolifera death on the coastal sea environment of Haiyang city from 2012 to 2016 using multiple regression analysis. It showed that chlorophyll-a concentration was related to sea surface temperature (SST), salinity, dissolved inorganic nitrogen (DIN) and phosphate (R2 = 0.50, P < 0.001). Among these, DIN and phosphate were important factors affecting chlorophyll-a concentration. There was a significant positive correlation between chlorophyll-a concentration and DIN, but a significant negative correlation between chlorophyll-a concentration and phosphate. The nutrients released by the decomposition of U. prolifera enhanced the growth of planktonic microalgae, and increased the mean chlorophyll-a concentration from 1.398 μmol/L to 2.819 μmol/L during May to August in the study area. This increased the Level of eutrophication in the coastal area and contributed to blooms of secondary algae such as red tides.

One-step green preparation of magnetic seaweed biochar/sulfidated Fe0 composite with strengthen adsorptive removal of tetrabromobisphenol A through in situ reduction

Rare information is available on the facile preparation of biochar/sulfidated Fe0 composite. A facile one-step green method was established for the synthesis of magnetic seaweed (Ulva prolifera) biochar/sulfidated Fe0 composite (S-Fe0/BC) to use excessive seaweed biomass. Removal efficiency of tetrabromobisphenol A (TBBPA) reached up to 88% in iron-sulfur treatment. Two major products were identified as bisphenol A and monobromobisphenol A, confirming the in-situ reductive debromination of TBBPA. Batch experiments showed that the removal of TBBPA was facilitated with S/Fe molar ratio of 0.2 and acidic conditions (pH = 3–7). The S-Fe0/BC composite had good stability and reusability based on the cycle experiments. The removal process of TBBPA by S-Fe0/BC composite might include chemical adsorption by S-Fe0/BC composite, reduction debromination by S-Fe0 and enhanced electron transfer. The environmentally-friendly S-Fe0/BC composite synthesized by one-step facile procedure showed novel potential applications in terms of pollution control of halogenated xenobiotic compounds such as TBBPA.

Hydro-biogeochemical modeling of the early-stage outbreak of green tide (Ulva prolifera) driven by land-based nutrient loads in the Jiangsu coast

The outbreak of a large-scale green tide (Ulva prolifera) will have a serious impact on marine environment, ecological functions, landscape, and coastal social economy. Eutrophication is generally considered to be the most important driving factor of this phenomenon. It is difficult to obtain the pressure-impact relationship between land-based loading and green tides by only surveying or monitoring, whereas modeling can perform this task easily. In this study, therefore, a hydro-biogeochemical model was established and verified by the measured hydrodynamic and water quality variables. In the initial outbreak area of Jiangsu coast, China, we studied the relationship between U. prolifera bloom and the driving factors of nutrient loads and structures by modeling different scenarios of land source inputs. It was found that the ratio of nitrogen to phosphorus could be affected significantly, which triggered the bloom of U. prolifera. When the land-based input doubled or halved, the dissolved inorganic nitrogen concentration increased 20.6% or decreased 9.5%, respectively, which might result in 14.5% increase or 46.3% decrease in the green tide, respectively. It was also found that the nutrient distribution and structure was affected by the land-based load, which caused the outbreak of U. prolifera. Moreover, the total nutrient load must be controlled to prevent the outbreak of green tide in the Jiangsu coast.

Agar extraction and purification of R-phycoerythrin from Gracilaria tenuistipitata, and subsequent wastewater treatment by Ulva prolifera

This study investigated the large-scale use of the red macroalga Gracilaria tenuistipitata to extract partially purified R-phycoerythrin in combination with the sequential extraction of agar. The main objective was to investigate the purification of R-PE, the extraction of agar and treatment of wastewater from the whole extraction process using the green macroalga Ulva prolifera. Results showed that the processing of 1 kg fresh biomass of G. tenuistipitata yielded a 30.34 μg/g R-phycoerythrin (purification ratio > 4) with 13.83% extraction efficiency. Initial phycobiliprotein extraction had no effect on the agar yield. The physicochemical properties of the agar had industrial applications. This method of extraction reduced the water volume and alkali requirement compared with that from direct extraction from algae. In addition, the removal rates (mean ± standard deviation) from wastewater of BOD, COD, total nitrogen, inorganic nitrogen, ammonia nitrogen, nitrate, nitrite, total phosphorus and inorganic phosphorus were 28.34 ± 0.10%, 23.50 ± 3.47%, 45.59 ± 6.31%, 63.82 ± 2.94%, 40.77 ± 0.95%, 74.06 ± 5.63%, 70.37 ± 2.59%, 65.26 ± 5.77%, and 72.40 ± 5.43% after the treatment with 2 days respectively. This extraction and subsequently eco-friendly wastewater treatment method could have practical application in the agar industry.

Extraction and identification of toxic organic substances from decaying green alga Ulva prolifera

In this study, the extraction, identification, and antialgal activity of toxic organic substances from decaying green alga Ulva prolifera, a disaster-causing alga on green tides in the Yellow Sea, were investigated. The toxic organic substances of U. prolifera were isolated by a sequence of procedures, namely, liquid-liquid extraction (LLE), silica gel chromatography column separation (SGCC), C18 solid phase extraction (C18 SPE), and acid-alkali separation (AAS) and their antialgal activities were tested against diatom Skeletonema costatum. The results showed that the 96h-EC50 value in each procedure was 57.00 mg•L−1, 12.14 mg•L−1, 11.70 mg•L−1, and 6.31 mg•L−1 in turn. Additionally, the initial (ethyl acetate extract in LLE) and final (Organic phase A in AAS) yield of toxic organics were 318 mg•kg−1 and 9 mg•kg−1 (the wet weight of U. prolifera). The final active fractions were preliminary identified as five 16- and 18-carbon fatty acids and four enols using GC–MS. The study may further evaluate the effect of bioactive substances on marine life after U. prolifera green tides bloom.

An anomalous bi-macroalgal bloom caused by Ulva and Sargassum seaweeds during spring to summer of 2017 in the western Yellow Sea, China

An unprecedented bi-macroalgal bloom caused by Ulva prolifera and Sargassum horneri occurred from spring to summer of 2017 in the western Yellow Sea (YS) of China, where annual large-scale green tides have prevailed for a decade. The distinct genesis and blooming dynamics of the two seaweed species were detected and described. Unlike the consistent raft-origin of the floating Ulva biomass, the massive pelagic S. horneri was derived from multiple sources (residual seaweeds from the previous winter bloom and those drifting from offshore water in the south). The scale of the green tide in 2017 was found smaller than the previous four years. We then discussed a number of hypotheses attributing to this reduction, including reduced epiphytic green algae from aquaculture rafts and the influences of the massive pelagic S. horneri. However, further research is needed to identify the origin of the pelagic S. horneri in the western YS and any affiliations with the benthic populations, and to elucidate the interactions of this species with the annual green tides and the ensuing consequences.

Absorptive process and biological activity of Ulva prolifera and algal bioremediation of coking effluent

The concentrates of coking effluents are toxic and technically challenging to treat. Environmental protection demands an efficient and cost-effective technique for coking wastewater treatment. The intertidal marine macro alga Ulva prolifera has a high tolerance to various environmental stresses. In this study, U. prolifera was collected from an intertidal field and tested in a laboratory-scale photobioreactor for potential bioremediation of coking effluent concentrate. Algal physiology and water quality were measured. During treatment, the quantum yield Fv/Fm and effective quantum yield Y(II) values showed 12% and 15% decreases in 24 h, respectively, and a complete recovery in 168 h. The algal physiological characteristics indicated that light irradiance provided in a sine pattern of enhanced algal growth by 53% in the coking concentrate. The removal efficiency for total nitrogen and total phosphorus was up to 26.1% and 68.5% in 24 h, respectively. It also showed high removal efficiencies for some heavy metals, chemical oxygen demand, biological oxygen demand, and nutrients within 24 h. The feasibility of using U. prolifera for coking concentrate treatment was also considered. This study provided a possible bioremediation technique for wastewater treatment, especially for concentrates of coking effluent, in the coking industry.

Spatio-temporal features of microplastics pollution in macroalgae growing in an important mariculture area, China

Macroalgae are being consumed by a growing number of people as functional food. Therefore, they are intensively cultivated to meet the rising demand. Mariculture is a potential source of microplastics (MPs). However, as a potential source of microplastics, little is known regarding the MPs pollution in macroalgae of open sea macriculture. Here we investigated the MPs characteristics in macroalgae in three sections of Haizhou Bay, an important mariculture area in China, during Pyropia culture (Pyropia yezoensis) and non-culture periods (Ulva prolifera, Sargassum horneri, Cladophora sp., Undaria pinnatifida, Ulva pertusa). It was found that P. yezoensis during the culture period had higher MPs abundance (0.17 ± 0.08 particles g−1fresh weight) than other macroalgae (0.12 ± 0.09 particles g−1 fresh weight) during the non-culture period, particularly for the nearshore sections. There were more fiber MPs in P. yezoensis (90.43%) in culture period compared to macroalgae (84.46%) in non-culture period. Highly similar spectrum of plastics in culture gears and macroalgae was verified. Pyropia culture gears released about 1, 037 tons plastics into the environment annually and the MPs abundances in seawater during the culture and non-culture periods were 1.04 ± 0.32 and 1.86 ± 0.49 particles L−1, respectively. The gap of MPs abundance between the two periods can be attributed to the tremendous trapping by massive biomass of P. yezoensis during the culture period and the continuous plastic release during the non-culture period. This study indicates that culture gears of macroalgae could be an important MPs source and the MPs can be transferred to human by edible macroalgae, and meanwhile macroalgae may be ideal biomonitors for MPs pollution in seawater due to their unbiased trapping and immovability.

Microbial ecology might serve as new indicator for the influence of green tide on the coastal water quality: Assessment the bioturbation of Ulva prolifera outbreak on bacterial community in coastal waters

Abstract The massive outbreak of Ulva prolifera had brought significant ecological impacts on marine coastal areas. In order to clarify the influence of outbreak of U. prolifera on marine microbial ecosystem, the microbial communities in different stages of blooming were analyzed by high-throughput sequencing. The sequences were clustered into 2979 operational taxonomic units (OTUs), and Shannon estimator varied from 3.241 to 4.892. The OTUs number and Shannon estimator demonstrated that both parameters were higher in samples HY_2–4, QD_2–4, RZ_2–4 than in HY_1, QD_1, RZ_1, indicating that the massive outbreak of U. prolifera caused the increase of microbial community diversity in coastal waters. The outbreak of U. prolifera led to increase in the abundance of some bacteria. According to the network analysis, the differences in hot bacteria in different stages indicated that the outbreak of U. prolifera caused the variation of microbial community. Based on Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis, the abundance of 41 metabolic pathways had changed due to the outbreak of U. prolifera. The microbial community could recover gradually after the disappearance of U. prolifera. The relative abundance of dominant genera Methylophaga, Polaribacter, Marinobacterium, Marivita, Tenacibaculum, Vibrio, Planktomarina, Crocinitomix, Draconibacterium, norank_f_Alteromonadaceae in stage 6 (after the outbreak of U. prolifera) kept the same level as stage 1 (before the outbreak of U. prolifera). These findings suggested that microbial ecology might serve as new indicator for the influence of green tide on the coastal water quality since marine microbial ecosystem could be temporarily bioturbated during the outbreak of the green tide.

High light might alleviate inhibitory effects of high temperature on growth and physiological parameters of Ulva prolifera

In order to explore the effects of high temperature (HT) and light on the physiological and biochemical aspects of macroalga Ulva prolifera, we cultured this species under two temperatures (20°C: low temperature, LT; 30°C: HT) and two light intensities (80 μmol m−2 s−1: low light, LL; 400 μmol m−2 s−1: high light, HL) for 5 days. It was found that (a) compared to 20°C, the chlorophyll a (Chl a) content was increased at 30°C under LL conditions, the relative growth rate (RGR) was significantly decreased at 30°C; (b) compared to LL treatment, HL significantly increased RGR but significantly decreased Chl a content; (c) LL-grown U. prolifera at 30°C showed the highest photosynthetic oxygen evolution rate; however, there were no significant effects of temperature and light on the relative electron transport rate; (d) superoxide dismutase activity was significantly decreased by HL, but no significant effects of temperature were observed; and (e) compared to LL, HL significantly increased the soluble sugar content at 20°C, but significantly reduced at 30°C. These results showed that the inhibitory effects of HT can be offset by HL intensity.

Changes in concentrations of biogenic sulfur compounds in coastal waters off Qingdao, China during an Ulva prolifera bloom

Distributions and variations of biogenic sulfur compounds including dimethylsulfide (DMS), dissolved and total dimethylsulfoniopropionate (DMSPd and DMSPt) and acrylic acid (AA) were investigated in coastal waters off Qingdao, China during the late-bloom and after-bloom periods of the Ulva prolifera bloom of 2015. DMSPd, DMS and AA concentrations after the bloom were significantly higher than during the late-bloom, but DMSPt concentrations in surface waters began to decrease. High concentrations of these compounds in the surface layer were associated with the bloom, with the exception of increased concentrations of DMSPt in the middle layer as decaying U. prolifera debris settled. The sea-to-air fluxes of DMS were estimated to be 18.08 and 24.24 μmol m−2 d−1 during the late-bloom and after-bloom, and about three times higher than the reported average fluxes of the Yellow Sea, which highlighted the impacts of U. prolifera blooms on DMS emissions.

The contribution of attached Ulva prolifera on Pyropia aquaculture rafts to green tides in the Yellow Sea

Green tides caused by the unusual accumulation of high floating Ulva prolifera have occurred regularly in the Yellow Sea since 2007. The primary source of the Yellow Sea green tides is the attached algae on the Pyropia aquaculture rafts in the Subei Shoal. Ulva prolifera and Blidingia (Italic) sp. are the main species observed on Pyropia aquaculture rafts in the Subei Shoal. We found that U. prolifera has strong buoyancy and a rapid growth rate, which may explain why it is the dominant species of green tides that occur in the China's sea area of the Yellow Sea. The growth rate of floating U. prolifera was about 20%–31% d–1, which was much higher than Blidingia (Italic) sp. There were about 1.7 × 104 t of attached algae on the Pyropia aquaculture rafts in May 2012. We found that 39% of attached algae could float when the tide rose in the Subei Shoal, and U. prolifera accounted for 63% of the floating algae. Our analysis estimated that about 4 000 t of attached U. prolifera floated into the surrounding waters of the Subei Shoal during the recycling period of aquaculture rafts. These results suggest that the initial floating biomass of large-scale green tides in the Yellow Sea is determined by the U. prolifera biomass attached to Pyropia aquaculture rafts, further impacting the scale of the green tide.

Efficient production of ulvan lyase from Ulva prolifera by Catenovulum sp. LP based on stage-controlled fermentation strategy

Ulvan lyase, specifically depolymerizing ulvan to unsaturated sulfated oligosaccharides with diverse biological activities, is becoming more and more popular. To provide an economical fermentative strategy, Catenovulum sp. LP cultured in low-cost medium that directly used Ulva prolifera as the main carbon source was used to produce ulvan lyase. The fermentation conditions were established in a shake flask containing 5% (w/v) U. prolifera powder, 0.2% K2HPO4, 0.4% NH4Cl, 0.5% NaCl, and 0.05% MgSO4. In a 5-L fermentor, series of strategies were used to systematically discuss the fermentation process. The enzyme with the best activity was obtained by the condition of a two-stage temperature (28–32 °C), initial pH 7.0, 1.5 vvm and two-stage agitation (200–400 rpm). The fermentation kinetic model of substrate consumption indicated that a shorter culture time may improve the ulvan lyase activity. Moreover, 10.09% improvement in enzyme activity was observed in a 30-L fermentor by shortening the fermentation time to 20 h. This fermentation method offers a promising prospect to enlarge the production of ulvan lyase and also provides a potential possibility to mildly prepare bioactive unsaturated oligosaccharides.

A light-limited growth model considering the nutrient effect for improved understanding and prevention of macroalgae bloom.

A useful growth process model for Ulva prolifera with light limitation considering the nutrient effect was proposed to better understand the development of macroalgae bloom. The interrelationship between light and nutrient limitation was demonstrated to obtain the mechanism. As a case study, thresholds of light and nutrients for different stages of Ulva prolifera growth were estimated using the proposed model. Limits of light intensity, nitrate, and phosphate concentration on the initial growth were found to be 40.0Wm-2, 6.5μmolL-1, and 0.27μmolL-1, respectively. The minimal light intensity for initial growth was found to increase monotonously with decrease in the nutrient concentration. It was also observed that the minimal light intensity for growth increases as the density of Ulva prolifera increases and the nutrient concentration decreases. Similarly, the minimal nutrient concentration for initial growth increases monotonously with decrease in the light intensity. In addition, the minimal nutrient concentration for growth increases with increase in the density of Ulva prolifera and decrease in the light intensity. It was demonstrated that the phosphate limitation on the initial growth of Ulva prolifera seedling can occur in most coastal waters of the southern Yellow Sea and a tendency of approaching the phosphate limitation on the growth of the floating thalli of Ulva prolifera exists. Evidence was provided to support the argument that the macroalgae thalli from aquaculture rafts, rather than that from seedlings or spores, can contribute to the original biomass of the floating green Ulva prolifera in the southern Yellow Sea. The model presented in this study can provide new insights into the interrelationship between the light and nutrient limitation, as well as into the growth mechanism of floating seaweeds. It can also provide a more accurate prediction of seaweed growth in light- and nutrient-limited environments.

Slow zeaxanthin accumulation and the enhancement of CP26 collectively contribute to an atypical non‐photochemical quenching in macroalga Ulva prolifera under high light

Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants, which dissipates excess energy and further protects the photosynthetic apparatus under high light stress. NPQ can be dissected into a number of components: qE, qZ, and qI. In general, NPQ is catalyzed by two independent mechanisms, with the faster-activated quenching catalyzed by the monomeric light-harvesting complex (LHCII) proteins and the slowly activated quenching catalyzed by LHCII trimers, both processes depending on zeaxanthin but to different extent. Here, we studied the NPQ of the intertidal green macroalga, Ulva prolifera, and found that the NPQ of U.prolifera lack the faster-activated quenching, and showed much greater sensitivity to dithiothreitol (DTT) than to dicyclohexylcarbodiimide (DCCD). Further results suggested that the monomeric LHC proteins in U.prolifera included only CP29 and CP26, but lacked CP24, unlike Arabidopsis thaliana and the moss Physcomitrella patens. Moreover, the expression levels of CP26 increased significantly following exposure to high light, but the concentrations of the two important photoprotective proteins (PsbS and light-harvesting complex stress-related [LhcSR]) did not change upon the same conditions. Analysis of the xanthophyll cycle pigments showed that, upon exposure to high light, zeaxanthin synthesis in U.prolifera was gradual and much slower than that in P.patens, and could effectively be inhibited by DTT. Based on these results, we speculate the enhancement of CP26 and slow zeaxanthin accumulation provide an atypical NPQ, making this green macroalga well adapted to the intertidal environments.

The complete mitochondrial genome sequence of Bryopsis plumosa

In 2015, a novel macroalgae began to bloom in Qinhuangdao on the coast of the Bohai Sea, Northern China. Bryopsis plumosa, a green macroalga, is one of the causal species of the macroalgae blooms, which have severely affected the environment and ecosystem on the coast of Qinhuangdao. In the present study, we sequenced the mitochondrial genome of B. plumosa for the first time (GenBank accession number MN853874). It was found that the ring-shaped genome was made up of 110,912 base pairs, including 29 protein-coding genes, 23 tRNAs, and 2 rRNAs. Phylogenetic analysis showed B. plumosa had close genetic relationships with algae Ulva prolifera, Ulva linza, and Ulva flexuosa. The present data will provide important information on the phylogenetics and molecular evolution of Bryopsis species.

Alleviation of Drought Stress in Wheat Using Exogenous Ulva prolifera Extract Produced by Enzymatic Hydrolysis

Drought is one of the major abiotic stresses that affect plant growth and reduce agricultural productivity. Use of algal extract as a biostimulant is gaining increased attention from researchers. This study aimed to investigate the potential of <i>Ulva prolifera</i> extract (UE) as a biostimulant when enzymatically extracted under conditions of water deficit. UE treatments (0.02%, 0.06%, and 0.1%) significantly improved the shoot length, root length, and dry weight of roots after 120 h of drought stress relative to that in treatment with the negative control. An increase in catalase (CAT) and peroxidase (POD) activity was also observed that resulted in improved antioxidant capacity. Application of 0.1% UE reduced the malondialdehyde (MDA) content by 30.06% compared with that in the negative control. In addition, the soluble sugar and protein content in wheat treated with 0.1% UE was increased by 23.10% and 93.51%, respectively, resulting in adjustment of the osmotic pressure. Results suggest that UE could significantly enhance the drought tolerance of wheat. This study provides a basis for increasing the value of UE as a biostimulant.

Growth characteristics of hybrids produced by closely related Ulva species

Comparative studies of closely related species from different habitats can potentially elucidate mechanisms of adaptation. Hybrids can act as valuable archives, enabling the evaluation of speciation. Brackish Ulva prolifera and marine Ulva linza show partial gamete compatibility and have been identified as closely related Ulva species based on molecular phylogenetic analysis. However, there are few reports on the biological characteristics of hybrids produced by brackish U. prolifera × marine U. linza. This study aimed to compare the morphological and growth characteristics of these two closely related Ulva species and their hybrids. The results showed that hybrid sporophytes had 1.0–3.6 branches per 1 cm of main stem, and the hybrid gametophytes had multiple branching characteristics, including the unbranched flat U. linza type, branched tubular U. prolifera type and branching types that were intermediate between the two. In addition, brackish U. prolifera, marine U. linza and their hybrid sporophytes exhibited high germination rates, approximately 6.6 times greater than hybrid gametophytes (12.7%). The highest daily growth rates of brackish U. prolifera and marine U. linza were 179.2% and 172.7%, respectively, which were significantly higher than those exhibited by hybrids (153.3%). These results demonstrated that the closely related brackish U. prolifera and marine U. linza have a greater capacity to adaptive to their environment than hybrids of the two species.

Acid treatment combined with high light leads to increased removal efficiency of Ulva prolifera

The attachment of Ulva prolifera to Pyropia rafts can cause severe economic losses during the cultivation of Pyropia because it can reduce the yield, harvest, and quality of the Pyropia. The existing methods for removing U. prolifera from the Pyropia raft have many limitations, such as low removal efficiency, Pyropia damage, and environmental pollution. In this study, we developed method that can effectively remove U. prolifera attached to the raft during Pyropia cultivation. After 3 h of citric acid (pH 4.0) and high light treatment (1200 μmol photons m2− s1−), followed by recovery in seawater for 24 h, the U. prolifera was completely dead, but the Pyropia was still active. We also studied the response mechanism of U. prolifera to acid and high light, and our results showed that under acidic and high light conditions, H+ may penetrate the interior of U. prolifera cells, causing obvious synergistic injury with high light to PSII in U. prolifera. The degradation of Cyt f in this process severely hindered electron transport and slightly reduced PSI activity. Acid also destroyed the U. prolifera photoprotective mechanism, as shown by the high non-photochemical quenching (NPQ) values and xanthophyll cycle pigment contents. This study provides a solid base for further research on optimizing the treatment of U. prolifera and improving its removal efficiency.