The importance of cellulose content and wood density for attack of waterlogged archaeological wood by the shipworm, Teredo navalis

Abstract Archaeological wooden remains are at risk of rapid degradation by the shipworm, Teredo navalis , when exposed to open seawater. An earlier study has shown a difference in the extent of attack based on the state of preservation of the wood. The current study aims to examine in more detail how shipworm attack correlates to the state of preservation, as measured by density, and the amount of residual cellulose, and if it is thereby possible to estimate when attacks will occur based on the level of deterioration. This knowledge would have practical implications for in situ preservation of wooden natural and cultural heritage underwater as it may be able to predict whether a wooden object is in danger of being attacked. The results confirm that there is a significant correlation between the extent of deterioration of the wood and the shipworm attacks. Samples with low density ( 3 ) and a low cellulose content (≤ 24% weight/dry weight) showed no attacks (rating 0). Attacks (rating 1–2) were first observed when the density of the wood was ≥ 134 kg/m 3 , with concomitant cellulose contents of ≥ 29%. Severe attack (rating 3–4) was observed on samples where the density was ≥ 292 kg/m 3 and cellulose contents of ≥ 48%.