Multi metal assessment on biofilm formation in offshore environment

Eight metal and non-metal coupons were exposed to seawater in offshore platform laboratory on biofilm formation in seven days of every month interval time for one year period. Among metal coupons, the highest mean heterotrophic biofilm bacteria population (HBBP) ranges were observed in mild steel (MS) coupon (33.03 to 40.00 [×10⁴] CFUscm^-2) and lowest in copper (Cu) coupon (3.0 to 5.1 [×10⁴] CFUscm^-2). Non-metal coupons show, highest mean HBBP ranges in glass (GL) coupon (29.6 to 66.0 [×10⁴] CFUscm^-2) and lowest in polyvinyl chloride (PVC) coupon (34.4 to 52.5 [×10⁴] CFUscm^-2). Within the studied coupons, high HBBP level was witnessed in GL and simultaneously low in Cu due to its toxic leaching product of Cu₂O. Gram-positive bacterial deposit show dominated trend in all coupons with increasing order of Cu>SS>MS>PVC>GL>Cu-Ni 70/30>Cu-Ni 90/10>Br and Gram-negative show different in the order of Br>Cu-Ni 90/10>Cu-Ni 70/30>GL>PVC>MS>SS>Cu, respectively. The 16S rDNA sequence confirmed, heterotrophic biofilm Bacillus sp. (Gram-positive) were dominated in all coupons for all months.