The role of the seagrass ‘Posidonia oceanica’ in underwater archaeological site formation : a comparative study of objects from Salina and Mellieħa Bays (Malta)

Abstract

This research project explores the post-depositional alterations of late Roman ceramics recovered from two underwater archaeological sites in Malta: Salina Bay and the Mortar Wreck in Mellieħa Bay. The study documents significant degradation observed in ceramics, particularly changes in texture, coloration, and structural integrity, potentially linked to the environmental conditions created in part by Posidonia oceanica. Through a combination of non-destructive analytical methods, including hand specimen analysis, photography, microscopy, and Mohs hardness testing, this research investigated the chemical and microbial processes influencing ceramic preservation. Key findings suggest that certain ceramics from Salina Bay exhibit surface discoloration and loss of structural integrity, while those from Mellieħa Bay demonstrated more extensive degradation, including a widespread presence of chalky textures and loss of material integrity. The analysis proposes that microbial activity, fluctuating pH levels, and sulfate reduction in the environment may be responsible for the observed changes. This study highlighted the complex interplay between marine ecology and ceramic preservation, providing possible insights into the post-depositional effects of seagrass P. oceanica possibly have on submerged cultural heritage. This thesis also calls for further research into seagrass and microbial influences, geochemical interactions, and the development of conservation strategies to mitigate possible postdepositional alteration to submerged cultural heritage.