Hydrocarbon pollutants alter short-term recruitment in the barnacle Balanus eburneus

We examined barnacle recruitment to oil-treated clay tiles at two coastal and two protected sites along the Louisiana coast. Tiles exposed to crude oil and its water-soluble fraction (WSF) had diminished barnacle recruitment after 3 weeks, in comparison with non-treated tiles. Effects were most obvious at the exposed coastal sites. After a 6-week immersion, however, treatment effects were no longer consistent. In later experiments, Balanus eburneus recruitment was higher on weathered WSF tiles (exposed, and leached in seawater before immersion in the field) than on WSF tiles, but not different from control tiles. Hydrocarbons depress recruitment initially, but may be removed later by leaching or by hydrocarbon-degrading microbes, and the remaining biofilm may facilitate recruitment. While barnacle recruitment was generally higher at exposed sites, as expected from the literature, local factors caused significant variation in recruitment within exposure categories as well. Barnacles also grow to larger sizes at open-coast sites, probably because of increased water flow and planktonic food delivery. Naupliar abundances varied tremendously among sites and dates and were poor predictors of eventual recruitment.