Correlation between bacterial decay and chemical changes in waterlogged archaeological wood analysed by light microscopy and Py-GC/MS

Holzforschung | Ahead of Print Correlation between bacterial decay and chemical changes in waterlogged archaeological wood analysed by light microscopy and Py-GC/MS Nanna Bjerregaard PedersenORCID iD: https://orcid.org/0000-0002-5744-939X , Jeannette Jacqueline ŁucejkoORCID iD: https://orcid.org/0000-0002-7717-4039 , Francesca ModugnoORCID iD: https://orcid.org/0000-0002-0446-668X and Charlotte Björdal DOI: https://doi.org/10.1515/hf-2020-0153 | Published online: 20 Nov 2020 PDF view on new site Abstract Full Text PDF References Recommendations Abstract Erosion bacteria are the main degraders of archaeological wood excavated from waterlogged environments. Light microscopy and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) were exploited to study waterlogged archaeological wood (Pinus sylvestris L.) at different stages of bacterial decay. The research explored the biochemical changes related to erosion bacteria degradation of the secondary cell wall in the wood cells and the chemical changes related to abiotic processes induced by the long-term waterlogged burial environment. Erosion bacteria were demonstrated by chemical analysis to cause significant holocellulose depletion. Detailed analysis of the holocellulose and lignin pyrolysis products revealed only minor chemical changes in the residual structure even after heavy erosion bacteria decay. Chemical changes in the lignin polymer is associated to enzymatic unlocking of the lignocellulose to gain access to the holocellulose fraction of the cell wall. Chemical changes in the holocellulose fraction are suggested to stem from depolymerisation and from alterations in the polymer matrix of the residual wood cell wall structure. Interestingly, a difference was observed between the sound reference wood and the waterlogged archaeological wood without erosion bacteria decay, indicating that long-term exposure in waterlogged environments results in partial decay of the holocellulose even in absence of bacterial activity

Study of the influence of physical, chemical and biological conditions that influence the deterioration and protection of Underwater Cultural Heritage

Two wrecks related to the Battle of Trafalgar (1805) were studied. Following the guidelines of the UNESCO-2001 Convention for the Protection of the Underwater Cultural Heritage, a holistic and interdisciplinary approach based on the development of four of the thirty-six Rules of this international agreement was applied. A non-destructive survey technique was developed to obtain information from the scattered cannons and anchors without altering their condition (Rule 4). The work performed provided information about the origin of both wrecks, the Fougueux and the Bucentaure, two ships of the line of the French Navy, and allowed to characterize the state of conservation at each site without jeopardizing their future conservation in the marine environment. In addition, measurements of the main physical, chemical and biological variables allowed correlating the conservation status at each site with the marine environmental conditions (Rule 15). Thus, in Fougueux shipwreck large iron objects are corroding at a higher rate (between 0.180 and 0.246 mmpy) due to high sediment remobilization and transport induced by waves at this site, causing damage by direct mechanical effect on metallic material and by removing the layer of corrosion products developed on the artefacts. Meanwhile artillery on Bucentaure site, covered with thick layers of biological concretion, is well preserved, with lower corrosion rates (0.073 to 0.126 mmpy), and archaeological information is guaranteed. Finally, the effectiveness of the cathodic protection as a temporary measure for in situ conservation (Rule 1) was evaluated on a cannon. The use of a sacrificial anode after 9 months reduced the average corrosion rate (from 0.103 to 0.064 mmpy) and the percent of corrosion rate in 37.9%. These results are very useful for developing a decision making system of the Site Management Program, based on predictive models of artefacts permanence and risk factors in the marine environment (Rule 25)

Oceans without history? Marine Cultural Heritage and the sustainable development agenda

This paper aims to set out the role Marine Cultural Heritage (MCH) can play in informing responses to global challenges and enhancing the sustainable development of coastal zones. This requires recognition of the importance of MCH as a knowledge base amongst marine ocean scientists, policy makers and marine stakeholders on the one hand and a greater effort by marine heritage specialists to engage with the 2030 Agenda on the other. The forthcoming UN Decade of Ocean Science for Sustainable Development (2021–2030) provides an opportunity to engage with the sea more widely but it is argued that the cultural element provided by considering past human action is currently lacking. The importance of understanding human interaction with the sea in terms of gaining a more complete picture of human history is briefly presented and a definition of MCH as all past action in the human zone is given. The article then sets out how MCH can enhance sustainable development in the marine zone with particular reference to SDG14 considering heritage tourism, coastal development and infrastructure, development aid policy, climate change, coastal management, fisheries and the offshore industry. The article highlights that the knowledge and data from MCH should be seen as crucial in evidence-based decision making across the coastal and marine sectors. The paper concludes that the inclusion of MCH approaches in initiatives aiming at coastal and ocean sustainability is not just advisable—it is essentia

Genomic analysis of a lignocellulose degrading strain from the underexplored genus Meridianimaribacter

The genus Meridianimaribacter is one of the least-studied genera within Cytophaga-Flavobacteria. To date, no genomic analysis of Meridianimaribacter has beenreported. In this study, Meridianimaribacter sp. strain CL38, a lignocellulosedegrading halophile was isolated from mangrove soil. The genome of strain CL38was sequenced and analyzed. The assembled genome contains 17 contigs with 3.33Mbp, a GC content of 33.13% and a total of 2982 genes predicted. Lignocellulosedegrading enzymes such as cellulases (GH3, 5, 9, 16, 74 and 144), xylanases (GH43and CE4) and mannanases (GH5, 26, 27 and 130) are encoded in the genome.Furthermore, strain CL38 demonstrated its ability to decompose empty fruit bunch, alignocellulosic waste residue arising from palm oil industry. The genome informationcoupled with experimental studies confirmed the ability of strain CL38 to degradelignocellulosic biomass. Therefore, Meridianimaribacter sp. strain CL38, with itshalotolerance, could be useful for seawater based lignocellulosic biorefining

A comparison of biodegradation caused by Teredinidae (Mollusca:Bivalvia), Limnoriidae (Crustacea:Isopoda), and C. terebans (Crustacea:Amphipoda) across 4 shipwreck sites in the English Channel

The need to protect underwater cultural heritage from biodegradation is paramount, however with many sites needing funding and support, it is hard to prioritise, thus the ability to identify high risk sites is crucial to ensure resources are best placed. In doing so a clear understanding of environmental conditions acting upon a site and abundance and composition of species present is essential to this identification. Therefore, the aim of this study was to assess the rate of biodegradation on four underwater cultural heritage sites in different marine environments by placing a series of wooden test panels in direct contact with the exposed structure on the sites. Upon recovery, test panels were photographed, X-rayed, and wood boring and sessile fouling species were identified and counted. The damage attributed to each species was recorded with CAD software. Results indicated a significant difference between sites, with HMS Invincible having the highest abundance of marine wood borers and the highest rate of surface area and volume degradation; whilst vestigial evidence of marine wood borers was found on the London, it would appear the environmental conditions had significantly impeded their survival. The study indicated further factors such as sediment type and coverage, availability of wood and the proximity of other colonised sites were also determining factors controlling the abundance of marine wood borers and the rate of biodegradation

Waterlogged archaeological wood : biodegradation and its implications for conservation

Although archaeological wood found in waterlogged environments is often described as well preserved, microbial degradation has taken place. Microscopic investigations revealed that despite different types of soil, water, sediment, pH, wood species, and age, archaeological wood was mainly degraded by erosion bacteria, even though soft rot and tunnelling bacteria decay was also occasionally observed. Erosion bacteria seem to be the only wood degrading micro-organisms active in near anaerobic environments. A weak skeleton consisting of the lignin rich compound middle lamella remains after decay and maintains the form and integrity of the historical wood, as long as it is kept waterlogged. Erosion bacteria and their attack of wood cell walls are described and illustrated in detail. Presence of active erosion bacteria in 1200 year old Viking poles, suggests that degradation is generally a slow process, that proceeds until all cellulose rich parts of the wood cell wall are utilised. The results indicate that depth of deposition in historic times as well as in reburial situations today, is an important factor for successful preservation in nature. In laboratory experiments, it was found that both clay and sandy soils had an equal protective potential, and were significantly less aggressive to wood than top soil. However, 20 cm depth of burial in waterlogged soil did not prevent significant attack by soft rot fungi, but different cover sheets had some positive effect Long term effects of soil and cover protections are still unknown. From observations on aerobic decay patterns in archaeological materials, valuable information can be obtained about the history of these objects before waterlogging. In active conservation situations, polyethylene glycol (PEG) in impregnation baths give rise to microbial growth at the liquid/air interface during immersion. However results indicate that the microbes present are not degrading the wood during treatment and therefore do not represent a threat for historical objects. Knowledge on microbial degradation in wood, particularly waterlogged archaeological wood, is important for the development of passive and active conservation strategies in future in the interdisciplinary areas of conservation and archaeology

From Declarative Models to Local Search

A solver is a general-purpose software for solving optimisation problems. It takes as input a description of a problem, called a model, and uses a collection of algorithms, called its solving technology, to ideally produce an optimal solution as output. Most solvers have a modelling language that cannot be processed by other solvers. This means that there is a risk of making an early commitment to a solver and its technology when writing a model. To address this risk, and to increase the accessibility of solvers, there has been a push for technology-independent modelling languages, a notable one being MiniZinc. A model written in MiniZinc is transformed by the MiniZinc toolchain in order to suit a targeted solver and its technology. However, for a solver to process a MiniZinc model, it also requires what is called a backend for MiniZinc. A backend translates the transformed MiniZinc model into the solver’s own modelling language and synthesises any components not in a MiniZinc model that the solver (or its technology) requires. The solving technology called constraint-based local search (CBLS) is based on the popular algorithm design methodology called local search, which often quickly produces near-optimal solutions, even to large problems. So, with the advent of CBLS solvers, there is a need for CBLS backends to modelling languages like MiniZinc. This thesis contributes to three research topics. First, it shows for the first time how to create a CBLS backend for a technology-independent modelling language, namely MiniZinc, and it shows that CBLS via MiniZinc can be competitive for solving optimisation problems. Second, it extends MiniZinc with concepts from local search, and shows that these concepts can be used even by other technologies towards designing new types of solvers. Third, it extends the utilisation of another technology, namely constraint programming, inside local-search solvers and backends. These contributions make local search accessible to all users of modelling languages like MiniZinc, and allow some optimisation problems to be solved more efficiently via such languages

The First Constraint-Based Local Search Backend for MiniZinc

MiniZinc is a modelling language used to model combinatorial optimisation and satisfaction problems, which can then be solved in a backend solver. There are many different backend solvers based on different technologies such as constraint programming, mathematical programming, or Boolean satisfiability solving. However, there is currently no constraint-based local search (CBLS) backend. This thesis gives an overview of the design of the first CBLS backend for MiniZinc. Experimental results show that for some relevant MiiZinc models, the CBLS backend is able to give high-quality results

String Variables for Constraint-Based Local Search

String variables occur as a natural part of many computationally challenging problems. Usually, such problems are solved using problem-specific algorithms implemented from first principles, which can be a time-consuming and error-prone task. A constraint solver is a framework that can be used to solve computationally challenging problems by first declaratively defining the problem and then solving it using specialised off-the-shelf algorithms, which can cut down development time significantly and result in faster solution times and higher solution quality. There are many constraint solving technologies, one of which is constraint-based local search (CBLS). However, very few constraint solvers have native support for solving problems with string variables. The goal of this thesis is to add string variables as a native type to the CBLS solver OscaR/CBLS. The implementation was experimentally evaluated on the Closest String Problem and the Word Equation System problem. The evaluation shows that string variables for CBLS can be a viable option for solving string problems. However, further work is required to obtain even more competitive performance