Wood boring species present in the Tagus Estuary and the severity of their attack on wooden piles exposed in the area: a case study
L M S Borges, L Nunes, A A Valente, P Palma
Wood exposed in the marine environment is subject to degradation by wood boring organisms. This is probably one of the reasons why wood has been substituted by concrete and steel in maritime structures in many European coastal areas. Wooden piles obtained from a wharf exposed in the Tagus Estuary, Porto Brandão (Almada, Portugal) provided an opportunity to understand the main
agents of biodeterioration of wood, as wooden structures in the area are rare.
The examination of the piles revealed severe deterioration by wood boring organisms. Major destruction caused by limnoriids was observed in the outer layers of the piles. The species was identified as Limnoria quadripunctata but a field survey in wooden structures nearby the area where the piles were obtained, revealed also the presence of Limnoria tripunctata. Thus, it is possible that this last species was also responsible for the degradation observed. The piles were also attacked by teredinids but the severity of their attack was less extensive than that by limnoriids. Two terenid species were identified, Lyrodus pedicellatus and Nototeredo norvagica. N. norvagica was previously reported from test panels exposed in the Tagus in the 1980’s. However, this was the first time L. pedicellatus was reported in this area. The increase in water temperature surface due to global warming might be responsible for the increased activity in southern European waters of
L. pedicellatus, a warm water species. The higher activity of limnoriids in the Tagus Estuary in later years might be related not only with warmer water temperatures but also with an increase in salinity in the area, as limnoriids appear to be restricted to waters with salinities close to that of seawater.
The development of adequate methods of wood protection requires accurate identification to define the borer hazard at various sites. In this study the Tagus Estuary is used as a case study. Species identification also assisted in the documentation of the activity of particularly damagin species, which enabled biodeterioration to be related with defined organisms.