ideal burial environment to minimise decay. Unfortunately, when shipwrecks
are reburied there is little or no subsequent monitoring to determine effect-
iveness of such a technique. Before contemplating reburial as an alternative
storage technique, substantial work is required to establish whether wood is
susceptible to anaerobic decay. However, any decay by the anaerobic cellu-
lolytic flora in marine sediment is likely to occur slowly. A further consider-
ation when contemplating reburial is the speed at which the disturbed marine
sediment returns to fully anoxic conditions, since re-exposure of wood to aer-
obic seawater/sediment will result in the onset of decay by bacteria, fungi and
marine wood-borers. It is also necessary to monitor the burial environment
throughout the period of storage. Periodic inspection of buried timbers or
buried test wood samples, and monitoring of the sediment microcommunity
is also necessary. There are few international reburial projects being con-
ducted at the moment, which include on-site environmental monitoring and
safeguarding. These studies are all concentrated in the northern hemisphere
in marine environments.
The long-term survival of wood in marine sediments is dependent on the con-
ditions prevailing in the burial environment. Considerations include the Eh of
the sediment and pore water, the type and stability of the sediments, the chem-
ical composition of the pore water and seawater and the level of biological
activity in both seawater and sediment. Careful monitoring of the changes in
these important environmental parameters over time will ensure the success or
failure of reburial as a long-term storage method. Primarily reburial leads to
an initial increase in oxygen levels and water content allowing biodeteriora-
tion to continue for a short period until anoxic conditions are re-established.
This is due to the microbial processes within the sediments, which consume
the oxygen leading to the suppression of aerobic microbes.
The depth of burial is also important when considering reburial of archaeo-
logical wood. Studies have shown that shallow burial will not prevent long-
term deterioration of buried wood by microbes but at depths greater than
50 cm the extent of deterioration decreases significantly.
If reburial in anoxic marine sediments does prove to be successful as a pas-
sive storage method of waterlogged archaeological wood, it is likely to be
applicable only to long-term storage due to the expense and efforts in carry-
ing out reburial and site monitoring.
The natural degradation of wooden shipwrecks in-situcan be slowed down,
or even eliminated, by covering the site with a physical barrier such as poly-
ethylene or polypropylene textile (Figure 15). This method is very effective
because it uses the wrecked environment to create an overlying mound of
sediment, which becomes part of the site. It also physically prevents colon-
isation of any subsequently exposed wreck timbers by wood-boring animals,
like shipworm.
Conservation of Ancient Timbers from the Sea 295