Tidal elevation affects the survival, growth, and performance of intertidal organisms because it regulates their exposure to heat, waves, food availability, and a variety of other abiotic factors. While previous research has explored the relationship between temperature and the performance of the barnacle Balanus glandula, there are unanswered questions about how tidal elevation affects B. glandula performance and growth. I compared the growth of B. glandula at three tidal elevations in Friday Harbor, Washington, and estimated the metabolic cost of emersion at each tidal elevation using a cost equation gained from thermal performance curves and average daily maximum temperatures. I also modeled climate change by adding 2°C to the average daily maximum temperatures at each shore height. I hypothesized that growth would decrease as tidal elevation increased as a result of increased heat stress. I also hypothesized that performance would decrease as tidal elevation increased, and that an increase in average daily maximum temperatures would most greatly affect high tidal elevations. I found that low tidal elevations had the highest growth. Energetic cost and aerial temperature were the highest at mid and high tidal elevations. Under the 2°C increase in temperature, energetic cost decreased with tidal elevation. These results are consistent with previous findings showing that B. glandula at higher tidal elevations had higher energetic demand. Further research is necessary to determine how growth and performance are correlated in B. glandula and how other factors such as food availability, optimal size, and reproduction affect their success
