Originally, I planned on studying seabirds for my directed studies project. Due to the short time frame allotted for data collection, however, that idea was lost with the wind. Seabird data collection is time-consuming and weather-dependent; so, I reluctantly changed my mind. Let me tell you how my alternate idea arose. During our algae class with Dr. Patrick Martone, I learned that coralline algae, with the help of their bacteria, provide settlement cues for a variety of invertebrate larvae. As you may have read in my previous blogs, this is the case for northern abalone. Huggett et al. (2006) found that the bacterial community on the surface of coralline algae provides important settlement cues for a species of sea urchin, Heliocidaris erythrogramma. They tested this by autoclaving rocks and algae, and by treating coralline algae with antibiotics (Hugett et al., 2006). Coralline algae treated in this way had reduced settlement rates. In addition, they isolated 250 strains of bacteria from the coralline algae and exposed the larvae to these single-strain biofilms. Larval settlement on many of the strains were comparable to settlement induced by coralline algae itself (Hugett et al., 2006). I wanted to test the same hypothesis for northern abalone.
Due to financial constraints and ethical concerns, Blair and I decided to use an iodine bath, instead of antibiotics, as our anti-bacterial mechanism. During pilot testing, we made agar plates of bacteria found on coralline rocks treated with iodine, and coralline rocks with their bacteria intact. Rocks treated with iodine had significantly less bacterial growth (we are in the process of confirming this, with more cultures incubating). Thus, we decided the iodine bath would do the trick. For the second half of our experiment, the abalone are given a choice between coralline-encrusted rock and bare rock habitat, both of which have been treated in our iodine bath. We expected less of a preference for coralline algae this time around, assuming bacteria are the main attractant. Trials are running as we speak, but so far our observations are quite curious.
It appears that the affinity of abalone to the coralline-encrusted rocks is stronger than before, even though these rocks have “lost” their bacteria. Could this mean that bacteria are not the main attractant to coralline algae for adult abalone? While it is early in the game to tell, it appears this may be so. A plausible alternative is that our iodine bath was inefficient at removing the bacterial film. This would explain the remaining preference for coralline algae. It would be great to repeat this experiment using the same methodology as Hugget et al. (2006).
Another explanation is that adult abalone are not attracted by bacteria, but by the physical and chemical properties of the coralline algae, itself. The shells of adults are often coated in a coralline algae crust, which may make the abalone shells cryptic and serve as camouflage (Sloan and Breen, 1988). It is possible that the attraction mechanism to coralline algae differs with the abalone life stage, with larval settlement triggered by bacteria, and adult habitat preference influenced by the pigments of coralline algae. Understanding the role coralline algae play in the life of northern abalone is important for conservation efforts. Regardless of the attraction mechanism, the abalone of the BMSC lab are keen to be pretty in pink. This sounds like a project for a master’s student…
Huggett, M. J., Williamson, J. E., De Nys, R., Kjelleberg, S., and Steinberg, P. D. (2006). Larval settlement of the common Australian sea urchin Heliocidaris erythrogramma in response to bacteria from the surface of coralline algae. Oecologia, 149(4): 604-619.
Sloan, N. A. and Breen, P. A., 1988. Northern abalone, Haliotis kamtschatkana in British Columbia: fisheries and synopsis of life history information. Can. Spec. Publ. Fish. Aquat. Sci. 103:1-46.