Abalone behaving badly

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 Imageexposed 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…

 

Works Cited:

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. Oecologia149(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.

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Speedy sea snails and the voracious sunflower star

After a few long days of hauling rocks across Bamfield Inlet and up mountains of stairs, sewing baskets with fishing line, and capturing and transferring abalone into our trial tanks, things are running smoothly. The first portion of our experiment is set up, and we are in the process of observing whether Northern abalone exhibit habitat preference for coralline algae-encrusted rocks over plain rocks. So far, the results look promising. It appears that abalone do prefer coralline-coated rocks. As for the road here, well, that’s the most entertaining part.

As I sit here writing this blog post, I cannot help but notice that my upper body is quite sore, especially my trapezoids. The first trip to Scott’s Bay involved lugging multiple buckets of rocks to the dock, boating them across the inlet, and dragging them up the stairs into the lab (Thanks, Tim and Dom). For the second trip, we boated a wheel barrow across the inlet.  I am not one to complain about exercise, so I consider the rock-hauling a bonus to the research. Running around after escapee abalone, however, is a different story.

Many hours of rock-scraping and basket-sewing later, our tanks were set up. The bottom of each basket was coated with half coralline-encrusted rocks and half bare rocks. When it came time to transfer the abalone into the baskets, I thought it would be a jiffy. That’s not how it panned out. First of all, the giant muscular foot of the abalone allows them to hold on tight to the substrate. Second, they are quite irritable. Their escape response is extensive. Upon contact with a predator, the agitated abalone responds by moving its epipodial tentacles. The shell is then elevated, thrusted in the direction of the predator, and twisted in alternate directions. This is followed by rapid locomotion away from the predator (Parsons and Macmillan, 1979), which Joel and others refer to as “galloping” (see Joel’s blog).  If you are lucky, you can sneak up on an unsuspecting abalone and grab it off the substrate. Once it senses you, it clamps down. In the case this misfortune, one must resort to the Pycnopodia technique.

Pycnopodia helianthoides, known as the sunflower star, is actually quite frightening. This sea star is reputably one of the most “active and voracious subtidal invertebrate predators”, ingesting most organisms found in its path along the sea floor (Brewer and Kondar, 2005). Prior to yesterday, I thought it was a silly thing to be scared of a sea star. After handling the massive, stinky beasts housed in the abalone lab, I changed my mind. The Pycnopodia technique involves touching a tentacle of the sea star to an abalone, or sucking up sea water in which the sea star is situated, and squirting it towards an abalone. This technique proved overly effective. We soon found ourselves scrambling to keep the abalone in the tanks, as they were frantically crawling up the mesh walls and clamping down in undesirable places, including our fingers. The speed at which these sea slugs move is impressive.

Eventually we were able to contain the stressed abalone. Now that the abalone have recovered from the Pycnopodia technique , they are happily housed in our tanks. Stay tuned for our final results!

Works Cited

Parsons, D. W., & Macmillan, D. L. (1979). The escape response of abalone (Mollusca, Prosobranchia, Haliotidae) to predatory gastropods. Marine Behaviour & Physiology, 6(1): 65-82.

Brewer, R., & Konar, B. (2005). Chemosensory responses and foraging behavior of the sea star Pycnopodia helianthoides. Marine Biology, 147(3): 789-795.Image

The peculiar story of the northern abalone, coralline algae, and bacteria

The next few posts are dedicated to my directed studies project at Bamfield Marine Sciences Centre. The question I and a fellow student intend to answer is: Do northern abalone display habitat preference for coralline algae encrusted rocks, and is this preference mediated by bacteria? First, let me introduce you to our study organism, the northern abalone (Haliotis kamtschatkana). The northern abalone is the only species of abalone found in BC waters, with over 90 species distributed across the globe. Throughout its range from Sitka Island, Alaska to Baja California, the northern abalone is suffering (Sloan and Breen, 1988).

In BC, the northern abalone is listed as endangered (facing imminent extirpation or extinction) (COSEWIC, 2011). Overharvesting is the culprit. In 1976 a market for Canadian abalone developed in Japan and annual take increased from less than 50 tonnes to 425 tonnes within two years (Emmett and Jamieson, 1989). Despite fishery closures in BC (1990), Alaska (1995), Washington (1994), and California (2000), poaching of abalone has maintained low numbers (Rogers-Bennett et al., 2011).  Conservationists and abalone farmers alike are intent on rebuilding populations of H. kamtschatkana. Habitat and food preference of abalone has undergone extensive research in Australia and Japan, where abalone farming is prevalent. The preferences of northern abalone, however, remain quite mysterious.

The beautiful shell of the abalone is no mystery. Cox (1962) speculated that the diet of adult northern abalone contains more coralline algae and diatoms than other species of Haliotis, based on the mottled shell colour. Abalone larvae are known to settle and graze on crustose coralline algae, acquiring bacteria that may perform a metabolic role in their undeveloped gut (Garland et al., 1985).  I began to wonder if epiphytic bacteria were responsible for larval recruitment.  Since it is difficult to induce spawning in abalone out of season, my partner and I decided to study the effects of coralline bacteria on adult abalone habitat preference.

In a choice-experiment set-up, we will test whether adult northern abalone prefer coralline-encrusted rocks with or without bacteria. To do this, half of our coralline-encrusted rocks will be treated with iodine to remove bacteria. We hypothesize that because abalone are quite sedentary (Sloan and Breen, 1988), adults will also exhibit preference for coralline algae, so that their offspring are in the appropriate habitat for acquisition of coralline-derived bacteria. The implications of this study are fascinating and may provide lessons for abalone aquaculture.

First of all, abalone farms often use antibiotics (Daume, 2006). If juvenile abalone obtain enzymes from bacteria that help in digestion, then this is a big problem. Second, most abalone farms and hatcheries do not offer crustose coralline algae as habitat or food, as it is difficult to propagate commercially (Daume, 2006). A major problem with abalone aquaculture today is the inability to provide enough food for mature individuals (Daume, 2006). I hypothesize that this is a direct response to the absence of crustose coralline algae: larvae fail to acquire enzymes from the bacteria, and as they grow, metabolism is sub-optimal, thus copious amounts of food is required for growth. The population of hatchery-reared abalone at Bamfield Marine Sciences Centre has decreased from 500 to 122 in only a few years. Perhaps coralline algae are a destined saviour…

Works Cited

COSEWIC. http://www.cosewic.gc.ca/eng/sct1/searchdetail_e.cfm. last updated: 2011.

Cox, K.W. 1962. California abalones, family Haliotidae. Fish Bulletin. 118: 1-133.

Daume, S. 2006. The roles of bacteria and micro and macro algae in abalone aquaculture: a review. J. Shel. Res. 25(11): 151-157.

Emmett, B. And Jamieson, G. S. 1988. An experimental transplant of northern abalone, Haliotis kamtschatkana, in Barkley Sound, British Columbia. Fishery Bulletin. 97: 95-104.

Garland, C.D., Cooke, S. L., Grant, J. F., McMeekin, T. A. 1985. Ingestion of the bacteria on and the cuticle of crustose (non-articulated) coralline algae by post-larval and juvenile abalone (Haliotis ruber Leach) from Tasmanian waters. J. Exp. Mar. Biol. Ecol. 91: 137-149.

Rogers-Bennett, L., Allen, B. L., Rothaus, D. P. 2011. Status and habitat associations of the threatened abalone: importance of kelp and coralline algae. Aquatic conserve: Mar. Freshw. Ecosyst. 21: 573-581.

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.

Amazing wildlife I’ve seen this year

This summer I studied song birds in the Peace River and Red Earth Creek back-country of Northern Alberta. Prior to this experience, I didn’t know a whole lot about flying animals. After learning to identify ~150 species by sight and sound, however, things changed. Birds are amazing-especially their songs. Once you get addicted to birding (and you will), the world becomes a much more musical place. To make matters better, there are many other things you may stumble across while hiking through the forest at 5am searching for songs. Wolves, black bears, and a lynx are a few of the creatures I encountered. Oh, the wonders of field work. So far, Bamfield has offered exceptional wildlife sightings as well. I must admit, I wasn’t expecting to see multiple humpback whales in the inlet and a giant pacific octopus within the first month! This year I’ve added quite a few lifers to my list. Oh yes, let’s not forget the algae.