August 2009 Archives

Institut des Sciences de la Mer de Rimouski

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The crew of the Seascape Modeling Lab has just returned from a mission to Rimouski, Quebec (or "Remote-ski" as some say).  We visited the Institut des Sciences de la Mer de Rimouski and the Institut Maurice-Lamontagne, where there is some interesting work on the Gulf of St. Lawrence.  For those of us working in the Gulf of Maine, this is a good place to build collaborations.  There is a lot to compare and contrast between the two gulfs.  The two systems are so close to each other--even linked by currents--but can be as different as the Labrador Sea and the Norwegian Sea.

We were hosted by Frederic Maps--an oceanographer who is working in our lab this year.  He showed us some classic Quebec sights, such as a blue whale (see photo), some great Northern Lights, and poutine.  I thought I'd share a couple of Pete's pictures of this excellent trip.  I look forward to another visit hopefully soon.

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Blue whale (Balaenoptera musculus) - everyone aboard spontaneously cheered as the fluke came up and the whale dove.


Calanus finmarchicus diapause

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Did you ever wonder, attentive reader, why our model results only span the late winter / spring season? Well, first most of the modeling effort developed in the EML aims at a better understanding of the timing of arrival of right whales in the Gulf of Maine area, and this occurs around spring. Second, our beloved copepod Calanus finmarchicus (the most delicious meal for the right whales!) disappears for most of the year from the surface waters. They escape and survive unfavorable environmental conditions (which is between fall and winter, everybody in New England will acknowledge that...) by staying at depth in a dormancy (diapause) state right before their final molt into adults. Dormancy means that every function of the organism is slowed down, no feeding takes place, and the only active behavior is, perhaps, a sluggish swimming to remain at depth.

Maybe you will be skeptical while you read me stating that little is known yet about the triggers controlling the entrance into and the exit from dormancy in C. finmarchicus. But... well, so it is !  Hence, as this species spends routinely more than half its life cycle down there, the EML has to broaden its interests to include the dormancy issue. And a promising approach to better understand dormancy makes use of the lipids stored in the so called "oil sac" of the copepods. The rationale is that lipids are a very efficient way of storing energy. Remember that while C. finmarchicus does not feed during dormancy, it spends most of its life cycle in that state. Thus, dormant individuals need huge amounts of energy reserves, which are in the form of lipids. Entrance into dormancy must be linked with the amount of lipid storage an individual managed to build up during its development. Indeed, you can see on this picture of a copepodid 5 of C. finmarchicus (the stage during which dormancy takes place) the impressive body volume occupied by the oil sac. When the diapause period approaches its end however, most of the lipid storage is used. Nevertheless, a certain amount of lipid still need to remain, in order to produce the gonadic tissue and the final molt. Exit from dormancy must be linked to the minimal amount of lipid required by these different steps of the final maturation.

Following these observations and deductions, the EML is now resolved to tackle the diapause issue. So be prepared to see soon model results during winter time !

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Photo by Phoebe Jekielek.

plant suprise!

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A few weeks ago, I transplanted several spider plants (genus Chlorophytum) into a spare pot we had in the lab. For soil, I used some of Dan's old compost (that we also had around the lab...).
I returned to the lab this week to find that we had some suprise guests growing out of the compost! It looks like they may be cucumber leaves (Cucumus sativis perhaps). I thought it was pretty cool.
 What's also neat is you can see that the plants are growing toward the sunlight to maximize utilization of the available energy. This phenomenon is known as phototropism. Phototropism is not to be confused with heliotropism, a mistake I made yesterday. (Heliotropism is the movement of a plant toward the direction of the sun over the course of a day, whereas phototropism is just growth toward sunlight in general).

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I think we're going to rotate the plant 180° to see if the leaves adjust and grow toward the sun. We'll take hourly photos to see how long it takes.... More on that soon.


Regime shift in the GoM

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       For the past two months, I have been interning with the EML. Mainly focusing on getting our Calanus finmarchicus model to work better; an investigation into the relationship between our model and the whale data revealed an interesting phenomenon. Below is a figure showing arrival dates (red line) versus departure dates (blue line) for Right Whales in Cape Cod Bay (CCB). 

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Interestingly, this figure shows that whales spent more time in CCB between 1998-2000 (an average of 103 days) versus time spent in CCB between 2002-2008 (just 41 days). Also, during the 1998-2000 time period, correlation plots (below) showing the strength of the relationship between the whale data and our model results in CCB show a strong correlation (the darker the color, the stronger the relationship with * symbols indicating a significant relationship). Plots showing the relationship after 2001 showed very little correlation. 

CCBbeforeandafter.jpg

Therefore, the relationship between our model and the whale data is significant during a time period when whales spent a lot of time in CCB. This regime shift is not a new discovery, and has, in fact, been linked to changes in zooplankton abundance, and ultimately changes in higher trophic levels (Pershing et al, 2005). It was very exciting to learn that this regime shift has been captured, at least partly, by our model. 


Works Cited:
Andrew J. Pershing, Charles H. Greene, Jack W. Jossi, Loretta O'Brien, Jon K.T. Brodziak, and Barbara A. Bailey. 2005. Interdecadal variability in the Gulf of Maine zooplankton community, with potential impacts on fish recruitment. ICES Journal of Marine Science: Journal du Conseil 2005 62(7): 1511-1523.

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