Setting up an Oyster Garden | Getting My Genes Wet

Last week Katherine arrived at Manchester. Check out her recent post on her plans

An excerpt:

My project this summer is to raise oysters descended from three Puget Sound populations under common conditions in order to measure differences in fitness. This type of experimental design is commonly referred to as a “common garden”, and allows one to control environmental variables so that phenotypic disparities among individuals can be attributed to their genetic differences.

Improvements (Guest Post)

Over the next few weeks students from the University of Washington FISH310 course (Biology of Shellfishes) will be providing insight into some of their indpendent research projects and thoughts on Olympia oysters in Puget Sound.

Today we have a post by Karl Seitz as a follow up on yesterdays account of his experiment. Here he provides some great feedback.


The study could be improved in many ways to provide better and more applicable results. First, sample sizes could be increased to provide a better representation of the natural populations. Our sample size was only ten oysters from each population and of those only five were used in the qPCR work and only the smallest were able to be used in the oxygen consumption work. Second, a better more accurate system could be devised to monitor metabolic rate using a more representative sample of the population. The tubes we used could only accommodate the smallest sized oysters so our results only represent this portion of the population. Also the dissolved oxygen meters all read different levels and continuously dropped even in the control tube which decreases our accuracy. We could also only monitor one population at a time with the meters so the Oyster Bay readings were always taken about twenty minutes after the Dabob readings began. We could also extend the period of monitoring to gain more perspective on how the oysters deal with stress through full recovery. Finally, there was some discrepancy as to which samples were which when normalizing with actin expression so that some samples may not have been normalized correctly. This could easily be corrected with better laboratory note taking.

As a class component I believe that having a group quarter long project is a great idea and that this particular project was perfect for that task. However, I do feel that this particular project would have been more appropriate in a physiology or population ecology class rather than in a general shellfish biology course. Since we were not necessarily learning about the specifics of what we were studying such as, the action of HSPs, the use and function of qPCR, and general stress responses in organisms, the project was often confusing and seemed non-applicable to what we were learning in class. I think projects more directly concerned with basic shellfish biology and taxonomy would be better suited for this particular class.

Any significant differences among the remnant populations? (Guest Post)

Over the next few weeks students from the University of Washington FISH310 course (Biology of Shellfishes) will be providing insight into some of their independent research projects and thoughts on Olympia oysters in Puget Sound.

Today we have a post by Karl Seitz

The Project

In the Pacific Northwest, the native Olympia oyster (Ostrea lurida) has been subjected to a number of stressors such as, overharvesting, competition with introduced commercial species, and habitat degradation, which have resulted in much reduced population levels (White et al., 2009). Special reserves were set up and strict harvesting guidelines were established but, the populations have not recovered well on their own (White et al., 2009). Due to this lack of natural recovery many state, tribal, commercial, and nonprofit groups have begun to show interest in active restoration of the species (White et al., 2009). For proper restoration to occur it must first be determined if there are any significant differences among the remnant populations and if so which population(s) should be used in the reintroductions?

Here we attempted to answer whether or not there are significant differences between different populations of Olympia oysters in Puget Sound, WA. We examined individuals from two areas of Puget Sound, Dabob Bay in the northern section of Hood Canal and Oyster Bay in southern Puget Sound just west of Olympia, WA. In order to determine if the populations differed we exposed them both to a mechanical stress (salad spinner) and looked for differences in their response to that stress. We measured their rates of oxygen consumption as a proxy for metabolic rate and also performed qPCR on gill tissue samples to compare expression of heat shock proteins (HSPs). From previous studies of these and other populations (Heare, unpublished data) we suspected Dabob to be a heartier stock and hypothesized that those individuals would exhibit a higher metabolic rate and expression of HSPs after stress than the Oyster Bay individuals.

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Results

We saw that, after normalization using actin expression, the expression of HSP was higher in the Oyster Bay individuals which was opposite of what we hypothesized. This may be because the Dabob population is more accustomed to stress events and therefore has a lower expression due to acclimatization to a stressful environment. The Oyster Bay individuals, being from a less stressful environment, may overreact to stress events since they are not accustomed to dealing with harsh conditions.

We also saw that prior to stress the Dabob population had a higher rate of oxygen consumption but, that after stress showed markedly lower consumption than the Oyster Bay. This was also opposite of our original hypothesis but, may be attributed to the type of stress we subjected them to and that Dabob may be accustomed to stress events. Since we subjected them to mechanical stress it seems logical that the oysters would close up to protect their internal structures from damage and in the closed condition oysters will not be consuming much oxygen. If the Dabob population is accustomed to repeated stress events it may explain why their oxygen consumption rates dropped and stayed low because they may stay in the closed condition awaiting further stress. Oyster Bay on the other hand closed for a shorter period of time before re-opening and increasing their metabolism to recover from any damage incurred by the stress.

Though our hypotheses were wrong we did observe differences in the populations’ response to stress. Our preliminary results suggest that the populations may possess distinct phenotypic differences that may be important considerations when planning restoration activities. Further statistical analysis of our data will prove whether these differences are in fact significant and prompt further investigation into these and other populations.

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References

White, J.M., E.R. Buhle, J.L. Ruesink, and A.C. Trimble. 2009. Evaluation of Olympia oyster (Ostrea lurida Carpenter 1864) status and restoration techniques in Puget Sound, Washington, United States. Journal of Shellfish Research 28:107-112.

Stay tuned tomorrow as Karl tells us what he thinks can be improved!

Metabolic response to stress in Olympia oysters (Guest Post)

Over the next few weeks students from the University of Washington FISH310 course (Biology of Shellfishes) will be providing insight into some of their independent research projects and thoughts on Olympia oysters in Puget Sound.

Today we have a post by Jessica Knoth

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Contrary to popular belief, the large Pacific oysters (Crassostrea gigas) found throughout the Salish Sea are not native to the area. Instead, the smaller and isolated populations of Olympic oysters (Ostrea lurida) are. They live in the intertidal zone along rocky shorelines, and in the 1800’s European settlers started harvesting them. This continued until the population eventually collapsed. Currently, there several remnant populations of Olympia oysters in the Puget Sound. Oyster Bay and Dabob Bay appear to have lower oyster survival and growth rates than the other two locations. For this reason, we decided to study both populations’ metabolic responses to stress.

Olympia oysters are sensitive to salinity, temperature, toxins, and other stressors. Ocean acidification, for example, has been detrimental to population growth (Hettinger et al. 2012). Larvae in the experiment were raised under different pHs. Those in a pH of 7.8 had a 15% decrease in larval shell growth rate, and a 7% decrease in shell area at settlement, when compared to the control larvae. After settling, the ‘stressed’ juveniles had a 41% decrease in shell growth rate (Hettinger et al. 2012). Temperatures above 40°C or below 0°C are also associated with significant mortality.

Judging by the growth and survival rates, Dabob Bay and Oyster Bay are not ideal places for Olympic oysters to live. However, small populations have continued to persist there. Because of this, we could safely assume that the oysters surviving there were fairly hardy. Dabob Bay has harsher conditions than Oyster Bay, so we hypothesized that the Dabob population will have a less drastic response to stress than the Oyster Bay population. To measure this, we induced stress on the oysters, took tissue samples, and then ran qPCR to measure the amount of glutamine synthase (a stress response gene) expressed in the two populations. We could measure the amount of glutamine synthase expressed by counting the amount of qPCR cycles it took for it to show up. A higher cycle number means it took longer for the synthase primer to react, which means there was a lower concentration of the stress response. Whichever oyster population had a higher number of cycles is the hardier population. For the experiment, we spun the two populations of oysters in a salad spinner to induce stress. We then took tissue samples and ran qPCR to determine the levels of glutamine synthase expressed. The more cycles it took for the glutamine synthase to show up, the less of it was expressed by the oyster. After normalizing with Actin, we found that Oyster Bay oysters expressed more glutamine synthase than Dabob oysters. This means they were more stressed by the salad spinner, which confirmed our hypothesis that Dabob Bay oysters are ‘tougher’ than Oyster Bay oysters – or at least they react less to acute stress. This is probably because they live in a stressful environment and are used to it. Hopefully, better understanding of stress inducement in Olympia oysters will lead to improved management and conservation of their populations.

I went into this project with next to no knowledge about oysters. For one, I thought Pacific oysters were native to the Puget Sound. I also found it interesting to learn how qPCR cycles worked. I’ve run PCR before for biology classes, but I’ve never used it in a real situation. I appreciate that our data may have real research applications.

References:

Hettinger, A., Sanford, E., Hill, T.M., Russell, A.D., Sato, K.N.S., Hoey, J., Forsch, M., Page, H.N., Gaylord, B. (2012). Persistent carry-over effects of planktonic exposure to ocean acidification in the Olympia oyster. Ecology 93:2758-2768.

Cheng, B.S., Bible, J.M., Chang, A.L., Ferner, M.C., Wasson, K., Zabin, C.J., Latta, M., Deck, A., Todgham, A.E., Grosholz, E.D. (2015). Testing local and global stressor impacts on a coastal foundation species using an ecologically realistic framework. Global Change Biology.