ASSESSING THE EFFECTS OF SALINITY AND ACIDIFICATION ON BARNACLE ADHESION, GROWTH AND BIOMINERALIZATION

Barnacles are dominant members of marine biofouling communities throughout much of the world's oceans. They tenaciously adhere to nearly any inert surface in the marine environment, including aquaculture facilities, ship hulls and other marine structures, resulting in a tremendous cost and performance burden for maritime industries. Barnacles adhere using a secreted proteinaceous cement, which rapidly forms adhesive bonds with surfaces and cures. Although we are beginning to understand the biochemical mechanisms involved in barnacle adhesion, relatively little is know about how the environment affects barnacle adhesion and subsequent mineralization. Here, we assess the impact of variations in salinity and pH on adhesion, growth and biomineralization in the barnacle Amphibalanus (= Balanus) amphitrite.

In two separate experiments, barnacle larvae were cultured from adults collected from the Beaufort Inlet, NC. In the first experiment, juvenile barnacles were gradually acclimated to eight target levels of salinity, ranging from 10 - 45 in steps of 5, while keeping pH and temperature as consistent as possible. In a second experiment, juvenile barnacles were exposed to three levels of pH (8.1, 7.8 & 7.5), while temperature and salinity were held constant. Barnacles were exposed for up to four months to these conditions. At the conclusion of the exposure period, barnacle adhesion strength was assessed in shear following ATSM standards. The effect of salinity on adhesion strength was significant, but non-linear (Fig. 1). Adhesion strength was significantly lower in barnacles held at 35 & 45 as compared to those at 15. The effect of pH on adhesion strength was not significant (Fig. 1). Growth (measured as the area of the barnacle base plate) was significantly affected by salinity, but not pH. Area of the base plate was significantly higher at 15 as compared to 40 and 45. Salinity did not significantly impact microhardness of the barnacle shell. Hardness testing of barnacles exposed to different levels of pH is currently underway.