The No. 2 Shipwreck Site on the northwestern continental slope (1488–1505 AD) is situated on the seabed between Hainan Island and the Xisha Islands in the South China Sea, at a depth of ~1500 m. Numerous wooden logs were discovered inside the shipwreck. This study assessed the degradation status of the waterlogged archaeological wood comprehensively. It also employed modern biotechnological methods to analyze the microbial communities within the wood and its surrounding environment. The results revealed that the waterlogged archaeological wood had experienced varying degrees of degradation. Even seemingly intact wood has undergone significant microstructural and chemical changes. Specifically, the secondary cell walls have been damaged, but the compound middle lamella remains relatively intact. Chemically, the degradation of hemicellulose and cellulose has resulted in a disordered arrangement of cellulose microfibrils, thereby weakening the mechanical properties of the wood cell walls. Additionally, a significant amount of iron salts was detected in some of the waterlogged archaeological wood. The microbial community within the wood was found to be predominantly composed of bacteria, with the Proteobacteria and Bacteroidetes phyla being the dominant groups. It is notable that the microbial community within the waterlogged archaeological wood exhibits a high degree of similarity with the microbial communities present in the surrounding seabed sediments and seawater. In conclusion, while some of the waterlogged archaeological wood has retained a relatively intact macroscopic appearance, its microstructure and chemical composition have undergone significant deterioration. Therefore, future conservation efforts should prioritise reinforcement and de-ironing to preserve the research value of these artifacts.

Nanhai No. 1, a shipwreck in the Southern Song Dynasty, China, has a history of more than 800 years. It was salvaged in 2007 and is now on display in the Guangdong Maritime Silk Road Museum. Due to the fact that the hull is a wooden cultural relic and exposed to the air, the biological corrosion and biodegradation caused by microorganisms are key problems of hull protection. At present, the antimicrobial agent Euxyl^® K100 (isothiazolinone) has a significant antimicrobial effect in the field, but it has a certain negative impact on the environment and archeologists. In order to reduce the use of chemical antimicrobial agents, we evaluated the inhibitory effects of cinnamaldehyde on the main destructive microorganisms of Nanhai No. 1. Cinnamaldehyde is the main active component of cinnamon, and has broad-spectrum antimicrobial properties. The paper diffusion method, gas diffusion method and minimum inhibitory concentration experiment were used to detect the inhibitory effects of cinnamaldehyde on the main microorganisms of Nanhai No. 1. We found that cinnamaldehyde had significant inhibitory effects on Bacillus tequilensis NK-NH5, Bacillus megaterium NK-NH10, Bacillus velezensis NK-NH11, Bacillus sp. NK-NH15, Bacillus sp. NK-NH16, Bacillus sp. NK-NH17, Fusariumsolani NK-NH1 and Scedosporiumapiospermum NK.W1-3. At the same time, cinnamaldehyde had more inhibitory effects on fungi than bacteria. Finally, we verified that cinnamaldehyde can effectively inhibit the growth of microorganisms in water, for storing the scattered wood blocks of the Nanhai No. 1 hull through laboratory simulation experiments. Cinnamaldehyde, as an environment-friendly antimicrobial agent, is of great significance to protecting water-saturated wooden relics from microbial corrosion and degradation in the future.

The Nanhai No. 1 was a wooden merchant ship of the Southern Song Dynasty, which wrecked and sank in the South China Sea, Yangjiang City, Guangdong Province, China. The Nanhai No. 1 shipwreck was salvaged as a whole in 2007 and began to be excavated in 2013. During the archaeology excavation, some of the hull wood fell off the hull. These waterlogged archaeological woods (WAW) were immersed in the buffer containing EDTA-2Na and isothiazolinone K100 for moisture stabilization, preliminary desalination, and microbial inhibition. We evaluated the properties of these WAW through testing the chemical components (including lignin, holocellulose, and ash content) of the wood, and monitoring the iron element content, anion and cation content in the buffer. At the same time, the microbial composition in the desalination buffer was also detected. The results showed that the holocellulose content in these WAW were much lower than in fresh wood. The ash content in these WAW decreased after desalination treatment. The iron element content, anion and cation content in the buffer were high and kept at a certain level after desalination treatment. At the same time, the problem of biodegradation in the buffer should be paid attention to. The comprehensive protection of WAW requires to combine wood properties and microbial problems. This study provides a reference for the protection of WAW from the Nanhai No. 1 shipwreck and other similar historical wood.

The wood of Wenzhou No.1 shipwreck exhibits significant degradation due to the intertidal burial environment. The shipwreck wood mainly consists of Chinese fir (Cunninghamia lanceolata) and Chinese cypress (Cupressus funebris), with different degradation characteristics. Chinese fir (BD: 0.19–0.33 g/cm³; MWC: 184.8–463.5%), used in load-bearing structures, displayed mild to severe degradation, while cypress (BD: 0.24–0.38 g/cm³; MWC: 171.7–280.6%) applied to joint components exhibited milder degradation. Both species showed substantial holocellulose loss (28–65% of sound wood). FTIR and XRD analyses revealed that both wood species had undergone hemicellulose degradation and cellulose crystallinity reduction, resulting in cell wall delamination and mechanical strength reduction, while residual lignin maintained structural stability, showing a polysaccharide degradation-lignin support pattern. EDS and XRD analyses revealed the presence of inorganic fillers (SiO₂, CaCO₃, and FeS₂) in wood, with iron content ranging from 0.1–13%. These findings provide valuable scientific references for the conservation of the Wenzhou No.1 shipwreck wood.

Purpose: Maritime cultural relics from the Nanhai No. 1 shipwreck were immersed in a buffer to maintain stability. To better monitor the changes in the composition of microorganisms in the buffer and, thus, prevent the damage to artifacts caused by harmful microorganisms. Methods: In September and November 2019, we conducted high-throughput sequencing of water samples from four types of maritime cultural relics (ironware, porcelain, axe, and hull wood) to reveal the composition and changes in microbial communities. In addition, we isolated culturable microorganisms and conducted biocide sensitivity tests and lignin and cellulose degradation tests. Results: Visible microbial colonization was observed in the water samples collected from the buffer solutions of ironware, porcelain, axe, and hull wood of the Nanhai No. 1 shipwreck; additionally, apparent differences in the composition of microorganisms in the water samples collected from different cultural relics and different collection times of the same cultural relics were noted. Few species of bacteria and fungi from the microbial community observed in the maritime cultural relics were cultured, and it was noted that various biocides had certain inhibitory effects on them. Some dominant strains had lignin and cellulose degradation abilities and could only grow under specific environmental conditions. Conclusion: We found apparent differences in the composition of microorganisms obtained from different cultural relics and different collection times of the same cultural relics. This study can provide data support for better protection of maritime cultural relics obtained from the Nanhai No. 1 shipwreck and provide a theoretical basis for the biological protection of other maritime cultural relics.

Understanding the corrosion mechanisms of ancient porcelains and the influence of marine-organism attachment is crucial for the conservation of underwater cultural heritage. In this study, we comprehensively analysed the chemical compositions and structures of the concretions and corrosion layers on the glaze surface of a bluish-white porcelain excavated from the Nanhai No. 1 shipwreck, with a particular focus on the morphological evolution of bubbles in the glaze during the corrosion process. The concretions contained a yellow porous structure that comprised a siliceous skeleton, while the main corrosion products were α-FeOOH and β-FeOOH. Furthermore, plausible hypotheses were formulated regarding the source of the concretions and the mutually beneficial relationship between silicon-rich marine organisms(sponges) and ancient silicate ceramics, providing a unique perspective for the conservation of waterlogged ancient ceramics.