| Popis: |
This research programme was instigated in response to concerns regarding the potential impact of sewage contamination from a long sea-outfall commissioned in 1991 in Portsmouth, Hampshire, on the long-term quality of local, historic wreck timbers. Information pertaining to the quality of seawater and the degradation of sacrificial wood samples, with particular emphasis on the action of the wood-boring crustacean, Limnoria spp, was collected and is presented in this thesis. The data was collected from three wreck sites in the Solent and surrounding waters: the Mary Rose (1509 - 1545), HMS Invincible (1744 - 1758) and HMS Hazardous (1698 - 1706). Both the Mary Rose and HMS Invincible sites are situated in an area of the Solent that was contaminated by sewage discharge. The site of HMS Hazardous is in cleaner water at Bracklesham Bay and was therefore designated as the control. Limnoriid activity was found to be higher at the HMS Invincible site than at the Mary Rose site - the HMS Invincible site also recorded the highest levels of sewage contamination. However, limnoriid activity was greater still at the "clean" control site of HMS Hazardous, thereby ruling out a conclusive link with sewage contamination. Water quality analyses showed the existence of vertical layering in the water column for many of the parameters determined. L. quadripunctata dominated the limnoriid population at the three sites but there was a significant presence of L. lignorum at the deeper Mary Rose site. On one occasion (winter 93/94), L. lignorum dominated the limnoriid population at the Mary Rose site. At the same time, the affinity for Scots pine wood observed during the rest of the study was not apparent. Faecal indicator bacteria were isolated from the biofouling layer of the wood blocks at both the Mary Rose and HMS Invincible sites and microbiological activity appeared to be greatest at the Mary Rose site. Fouling barnacles on the wood samples appeared to offer some protection from limnoriid activity in the short-term but had no long-term protective effect. |
