Deterioration of Wood by Marine Borers in a Tropical Harbour: Influence of Environmental Parameters and Biotic Factors

Abstract

Wooden structures in marine conditions are subjected to biodeterioration mainly due to marine borers, which cause substantial economic losses. Biodeterioration is a worldwide problem and especially high in tropical countries like India. Hence, destruction rates of wood by marine borers were studied using wooden test panels submerged as short-term and long-term basis at three stations (Slipway Complex, Ore Berth and Marine Foreman Jetty) in Visakhapatnam harbour from February 2007 to January 2009. Data on environmental parameters (water temperature, salinity, pH and dissolved oxygen), fouling cover, and borer abundance were recorded. The deterioration level of panels deployed for short-term and long-term panels was highest at Ore Berth, slightly lower at Slipway Complex, and minimum at Marine Foreman Jetty. Wood deterioration was comparatively high during the months of lower water salinity than during the periods of higher water salinity. Spatial variations in degree of wood deterioration within the same harbour may be due to combined effect of environmental parameters particularly salinity and pollution, and intense biofouling. Water temperature barely affects wood deterioration in tropical waters. Borer activity and wood destruction are severe and significant in Visakhapatnam harbour and none of the measured environmental parameters is of any restrictive role in wood biodeterioration. Keywords Biodeterioration; Borers; Biofouling; Environmental parameters; Visakhapatnam harbour Background Of the various materials introduced by man into marine environment, wood is the only natural and renewable material with unceasing prospective as a construction material, especially in the light of growing environmental safety concerns (Cragg, 1996; Satyanarayana Rao, 2001). Wood is in wide use for harbour structures such as piles, piers, wharves, floating/static fenders, dock blocks, groynes, marinas, and fishing craft such as dinghies, canoes, catamarans, pontoons, boats and several vessels. Untreated timber used for these mentioned purposes is subjected to rapid deterioration mainly by marine wood boring