Open Access Senior Thesis
Bachelor of Arts
© 2012 Jesse Osborn
The rocky intertidal zone, experiencing fully marine and fully terrestrial conditions, has become increasingly investigated as a model ecosystem for studying the future implications of climate change. The barnacle, Balanus glandula, a common rocky intertidal inhabitant, plays an important role as a key prey item for many organisms. Low tide can be particularly challenging for barnacles as they are marine organisms subjected to the abiotic conditions of a terrestrial environment. The most stressful of these are increased temperature and decreased oxygen availability. This study aimed to investigate how low tide impacts the energy budget, specifically the digestion, of B. glandula. Barnacles are unable to feed at low tide however, if they were able to digest at low tide, they could maximize their energy intake by emptying their stomach to prepare to feed at the next high tide. However, digestion is a metabolically costly activity, which could make it less energetically favorable to digest when there’s less oxygen available. To test for an effect of low tide on digestion, barnacles were fed, and the time to first fecal production measured as a ‘baseline’. This was repeated, but barnacles were exposed to either a 16ºC or 35 ºC low tide immediately after being fed. The change in digestion time was calculated by comparing these two times for each barnacle. It was found that regardless of temperature, barnacles delayed their digestion by about 50-60 minutes after exposure to a one hour low tide. To determine the energetic cost of digestion, the rate of oxygen consumption was compared between starved and digesting barnacles. I was unable to detect any evidence of elevated metabolic activity during digestion. Additional testing is needed to confirm these results as the barnacles may have not fed during the trial, thus had no food to digest. While it appears that increasing temperatures associated with climate change will have little impact on the digestion of barnacles at low tide, if climate change alters the duration of low tide, there could be an energetic impact to barnacles due to the slowing of their metabolism as indicated by the delay in their digestion.
Osborn, Jesse, "The Affect of Low Tide on the Digestion of Balanus glandula, the Acorn Barnacle." (2013). Scripps Senior Theses. 141.