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Vibrio phages have emerged as a potential alternative to antibiotic therapy for treating Vibrio infections. In this study, a lytic Vibrio phage, vB_ValA_R15Z against Vibrio alginolyticus ATCC 17749T, was isolated from an aquatic water sample collected in Xiamen, China. The phage had an icosahedral head (diameter 69 ± 2 nm) and a short, non-contractile tail measuring 16 ± 2 nm. The genome of vB_ValA_R15Z was found to be a double-stranded DNA consisting of 43, 552 bp, containing 54 coding sequences (CDSs) associated with phage packaging, structure, DNA metabolism, lysis and additional functions. The BLASTN results indicated that vB_ValA_R15Z shared less than 90.18% similarity with known phages recorded in the NCBI GenBank database, suggesting that vB_ValA_R15Z was a novel Vibrio phage. Furthermore, phylogenetic analysis revealed that vB_ValA_R15Z belongs to the genus Kaohsiungvirus. In addition, a typical lytic mechanism (holin-endolysim) was found in the genome of vB_ValA_R15Z, while no antibiotic resistance- or virulence factor-related gene was detected. Overall, the study provides valuable insights into the isolation and characterization of vB_ValA_R15Z, highlighting its potential as an effective phage therapy option for combating Vibrio alginolyticus infections. [ABSTRACT FROM AUTHOR]

Macroalgal biomass blooms, including those causing the green and golden tides, have been rising along Chinese coasts, resulting in considerable social impacts and economic losses. To understand the links between the ongoing climate changes (ocean warming and acidification) and algal tide formation, the effects of temperature (20 and 24 °C), pCO2 concentration (Partial Pressure of Carbon Dioxide, 410 ppm and 1000 ppm) and their interaction on the growth of Ulva prolifera and Ulva lactuca (green tide forming species), as well as Sargassum horneri (golden tide forming species) were investigated. The results indicate that the concurrent rises in temperature and pCO2 level significantly boosted the growth and nutrient uptake rates of U. lactuca. For U. prolifera, the heightened growth and photosynthetic efficiency under higher CO2 conditions are likely due to the increased availability of inorganic carbon. In contrast, S. horneri exhibited negligible responsiveness to the individual and combined effects of the increased temperature and CO2 concentration. These outcomes indicate that the progressive climate changes, characterized by ocean warming and acidification, are likely to escalate the incidence of green tides caused by Ulva species, whereas they are not anticipated to precipitate golden tides. [ABSTRACT FROM AUTHOR]

Vibrio alginolyticus causes substantial economic losses in the aquaculture industry. With the rise of multidrug-resistant Vibrio strains, phages present a promising solution. Here, a novel lytic Vibrio phage, vB_ValC_RH2G (RH2G), that efficiently infects the pathogenic strain V. alginolyticus ATCC 17749T, was isolated from mixed wastewater from an aquatic market in Xiamen, China. Transmission electron microscopy revealed that RH2G has the morphology of Siphoviruses, featuring an icosahedral head (73 ± 2 nm diameter) and long noncontractile tail (142 ± 4 nm). A one-step growth experiment showed that RH2G had a short latent period (10 min) and a burst size of 48 phage particles per infected cell. Additionally, RH2G was highly species-specific and was relatively stable at 4–55 °C and pH 4–10. A genomic analysis showed that RH2G has a 116,749 bp double-stranded DNA genome with 43.76% GC content. The intergenomic similarity between the genome sequence of RH2G and other phages recorded in the GenBank database was below 38.8%, suggesting that RH2G represents a new genus. RH2G did not exhibit any virulence or resistance genes. Its rapid lysis capacity, lytic activity, environmental resilience, and genetic safety suggested that RH2G may be a safe candidate for phage therapy in combatting vibriosis in aquaculture settings. [ABSTRACT FROM AUTHOR]

Under global change scenarios, the sea surface temperature is increasing steadily along with other changes to oceanic environments. Consequently, marine diatoms are influenced by multiple ocean global change drivers. We hypothesized that temperature rise mediates the responses of polar and temperate diatoms to UV radiation (UVR) to different extents, and exposed the temperate centric diatoms, Thalassiosira weissflogii and Skeletonema costatum, and a polar pennate diatom Entomoneis sp., to warming (+5°C) for 10 days, then performed short‐term incubations under different radiation treatments with or without UVR. The effective quantum yields of the three diatoms were stable during exposure to PAR, but decreased when exposed to PAR + UVR, leading to significant UV‐induced inhibition, which was 3% and 9%, respectively, for T. weissflogii and S. costatum under ambient temperature but increased to 12% and 17%, respectively, in the cells acclimated to the warming treatment. In contrast, UVR induced much higher inhibition, by about 45%, in the polar diatom Entomoneis sp. at ambient temperature, and the warming treatment alleviated the UV‐induced inhibition, which dropped to 36%. The growth rates were significantly inhibited by UVR in S. costatum under the warming treatment and in Entomoneis sp. under ambient temperature, while there was no significant effect for T. weissflogii. Our results indicate that the polar diatom was more sensitive to UVR though warming could alleviate its impact, whereas the temperate diatoms were less sensitive to UVR but warming exacerbated its impacts, implying that diatoms living in different regions may exhibit differential responses to global changes. [ABSTRACT FROM AUTHOR]

Phytoplankton face numerous pressures resulting from chemical and physical stressors, primarily induced by human activities. This study focuses on investigating the interactive effects of widely used antifouling agent Irgarol 1051 and UV radiation on the photo-physiology of marine diatoms from diverse latitudes, within the context of global warming. Our findings clearly shown that both Irgarol and UV radiation have a significant inhibitory impact on the photochemical performance of the three diatoms examined, with Irgarol treatment exhibiting more pronounced effects. In the case of the two temperate zone diatoms, we observed a decrease in the inhibition induced by Irgarol 1051 and UVR as the temperature increased up to 25°C. Similarly, for the subarctic species, an increase in temperature resulted in a reduction in the inhibition caused by Irgarol and UVR. These results suggest that elevated temperatures can mitigate the short-term inhibitory effects of both Irgarol and UVR on diatoms. Furthermore, our data indicate that increased temperature could significantly interact with UVR or Irgarol for temperate diatoms, while this was not the case for cold water diatoms, indicating temperate and subarctic diatoms may respond differentially under global warming. [ABSTRACT FROM AUTHOR]

Blooms of microalgal red tides and macroalgae (e.g., green and golden tides caused by Ulva and Sargassum) have caused widespread problems around China in recent years, but there is uncertainty around what triggers these blooms and how they interact. Here, we use 30 years of monitoring data to help answer these questions, focusing on the four main species of microalgae Prorocentrum donghaiense, Karenia mikimotoi, Noctiluca scintillans, and Skeletonema costatum) associated with red tides in the region. The frequency of red tides increased from 1991 to 2003 and then decreased until 2020, with S. costatum red tides exhibiting the highest rate of decrease. Green tides started to occur around China in 1999 and the frequency of green tides has since been on the increase. Golden tides were first reported to occur around China in 2012. The frequency of macroalgal blooms has a negative linear relationship with the frequency and coverage of red tides around China, and a positive correlation with total nitrogen and phosphorus loads as well as with atmospheric CO2 and sea surface temperature (SST). Increased outbreaks of macroalgal blooms are very likely due to worsening levels of eutrophication, combined with rising CO2 and SST, which contribute to the reduced frequency of red tides. The increasing grazing rate of microzooplankton also results in the decline in areas affected by red tides. This study shows a clear shift of algal blooms from microalgae to macroalgae around China over the past 30 years driven by the combination of eutrophication, climate change, and grazing stress, indicating a fundamental change in coastal systems in the region. [ABSTRACT FROM AUTHOR]

The effects of ocean warming on phytoplankton have been extensively studied, but little has been documented on responses of differently sized diatoms to changes of temperature over wide ranges. We grew three diatom species, Thalassiosira pseudonana, Thalassiosira weissflogii, and Thalassiosira punctigera, with cell volumes of 199, 1805, and 13,599 μm3, respectively, at seven temperatures (5, 10, 15, 20, 25, 30, and 35°C) over 15 generations, and investigated their physiological responses. The optimum growth temperature (Topt), maximum growth rates (μmax), and thermal niche width (w) decreased by 16%, 48%, and 29% per order of magnitude in cell size increment, respectively. The cell volume of each species diminished significantly and linearly with increased temperatures, by 22% in T. punctigera, 17% in T. weissflogii, and 11% in T. pseudonana, respectively. However, the cellular biogenic silica (BSi) contents increased with rising temperature till the optimum growth temperature for growth, with the sensitivity of BSi to temperature changes (Q10BSi) ranging from 1.4 in the largest to 3.4 in the smallest diatom. The largest diatom T. punctigera showed the highest deactivation energy and succumbed to warmer conditions over its Topt, while the smallest was the most tolerant of warming. Although the moderate increase in growth temperature increased the diatoms' BSi levels, warming to temperatures higher than the optimum temperature for growth significantly reduced it. Our results suggest that diatoms acclimated to warmer conditions diminish their cell size but increase their mineralization of silica, which has profound significance in ocean carbon and silica biogeochemical cyclings. [ABSTRACT FROM AUTHOR]

Macroalgae, playing a crucial role in coastal marine ecosystems, are subject to multiple environmental challenges due to tidal and seasonal alterations. In this work, we investigated the physiological responses of Pyropia yezoensis to ocean acidification (ambient CO2 (AC: 400 μatm) and elevated CO2 (HC: 1000 μatm)) under changing salinity (20, 30 psu) and light intensities (50, 100 μmol photons m−2 s−1) by measuring the growth, pigment content, chlorophyll fluorescence, and soluble sugar content. The key results are the following: (1) P. yezoensis exhibited better growth under normal salinity (30 psu) compared to hyposaline conditions (20 psu). (2) Intermediate light intensity increased phycoerythrin content, ultimately enhancing thalli growth without significant changes to the contents of chlorophyll a and carotenoids. (3) Ocean acidification alleviated hyposaline stress by enhancing pigment production in P. yezoensis only at a salinity of 20 psu, highlighting the complex interplay of these environmental factors. These findings indicate that higher light intensities and elevated pCO2 levels could mitigate the stress caused by low salinity. [ABSTRACT FROM AUTHOR]

Many algae respond to the CO2 limitation in seawater by inducing a CO2 concentrating mechanism (CCM) to obtain sufficient inorganic carbon to meet their photosynthetic needs, and Ulva sp. is a model population suitable for studying the ecological adaptability of macroalgae. As the dominant species of green tide disaster, Ulva sp. often faces strong inorganic carbon restriction due to its rapid growth and high population density and must have evolved a variety of carbon acquisition strategies, such as CCM, to overcome these limitations. This paper briefly summarizes the position and function of the important components of CCM (inorganic carbon transporters, carbonic anhydrase, Rubisco, and pyrenoid) and introduces several indexes suitable for evaluating the relative function of CCMs in macroalgae from the aspects of affinity between photosynthesis and Rubisco for CO2, and carbonic anhydrase inhibitor. The methods of judging the carbon sequestration pathway of Ulva sp., the CCM responses of diversity under different carbon sources, and the related genes that may be involved in the operation of CCMs were summarized. This work could provide a reference for revealing the CCMs of macroalgae and lay a foundation for further research on the inorganic carbon utilization strategy of the Ulva sp. [ABSTRACT FROM AUTHOR]