Results tagged “Calanus finmarchicus”

RARGOM confirms 2012 was weird

RARGOM, the Regional Association for Research on the Gulf Of Maine, selected the 2012 ocean heatwave as its topic for this year's annual science meeting.  Due to my obsession with 2012 and inability to duck responsibility, I ended up organizing the meeting.  

The meeting was held on Tuesday in Portsmouth (NH, not England--maybe next year), and we had a huge turnout. I think this speaks to the impact that the 2012 event had on the collective psyche of the Gulf of Maine community.  We had a great series of talks and posters (here's the agenda  and hopefully, we'll get the talks up on the RARGOM website soon), and I think we're starting to get a picture of just how weird things have gotten in the Gulf of Maine. Here are a few themes that stuck out for me:

  • Causes of 2012: According to Ke Chen (WHOI), the 2012 heatwave was caused by the atmosphere and likely related to a strongly positive NAO.  Although 2012 stands out over the long-term history, according to our own Hillary Scannell (UMaine/GMRI), the current climate should produce 2012-like events about once every 10 years.
  • Impact on Calanus: Yes, our old friend Calanus made several appearances at the meeting, but mostly in the context of 2013.  Desiree Tommasi (GFDL), filling in for NOAA's Kevin Friedland who is being held hostage by the government shutdown, reported that they were not able to define a spring phytoplankton bloom for 2013 and that the total abundance of zooplankton caught by NOAA this spring was very, very low.  Jeff Runge's (UMaine/GMRI) found an opposite pattern in the western Gulf of Maine: Calanus was very abundant, but perhaps occurred later in the year.  Heather Koopman (UNCW) said that they had incredibly low Calanus abundances in the Bay of Fundy this year, and that right whales were scarce.Razorbill_iceland.jpg
  • Bad year for birds: The saddest stories from 2012 were about seabirds, especially puffins and razorbills.  Tony Diamond (UNB) and Thomas Robben described a dramatic shift in the distribution of razorbills during the winter of 2012/2013.  Razorbills were found regularly in Florida during the winter and there were many reports of dead razorbills up and down the coast (next time, I'll put Tony and his necropsy photos after lunch).  Tony's hypothesis is that the temperature caused a shift in the distribution of their prey (likely herring).  Puffins were also hit hard, and according to Steve Kress (Audubon/Cornell), the culprit was not a lack of prey, but the wrong kind of prey.  Although they sound tasty, butterfish are terrible food for baby puffins.  The fish are too wide for the babies to swallow (shown in this video), and islands where the adults were finding lots of butterfish had very poor chick survival.  
  • Not just the Gulf of Maine: Catherine Johnson (DFO, BIO) gave a great overview of the impact of the 2012 event on the Canadian shelf.  She describes many of the same impacts, including observations of butterfish and a subtropical fish called a blue runner in Newfoundland.
  • Lobsters and fish: Suzy Arnold from the Island Institute had a poster describing the synthesis from their workshop this summer.  Jenny Sun (GMRI) presented an analysis of the connections between the US and Canadian lobster markets. Kathy Mills (UMaine/GMRI) gave an overview of our 2012 lobster story, including our idea about seasonal predictions.  She is starting to weave this story into a broader vision of how to think about climate adaptation in fisheries.  Building on this view, Jonathan Labaree (GMRI) described how 2012 has made climate impacts a major concern among fishermen.

Fishermen's Forum

Greetings!  If you've visited this site before, you're probably aware that our lab has spent the past three July/Augusts cruising up and down the scenic coast of Maine, visiting coastal towns, gawking at amazing sealife, and gathering information on the zooplankton community under the speckled starlight of the summer sky.  Truly the good life.

It's one thing to spend your summers enjoying the Gulf of Maine, bobbing up and down, ogling skeleton shrimp under a microscope.  At the end of the day, however, we need to have something to show for our work.  There are many reasons to improve our understanding of the zooplankton community.  One such reason is so that we have better information on the migration patterns of planktivorous whales.  One of our main objectives has been to describe the feeding habitat of right whales, whose diet consists primary of the copepod Calanus finmarchicus.

This past weekend our lab and the biological oceanography lab presented some of the results of our cruises from 2008, 2009, and 2010 at the Maine Fishermen's Forum.  The forum is teeming with energy and activity, from seafood sampling to trade shows.  Thus I wondered to myself, as I found my way down a long, lonely hallway and up a grated stairway that led to our remote presentation room, How many people here will be interested in a talk with "Calanus finmarchicus" in the title?

After all, our time slot was competing with scallop farming, shrimp fishing, and "The Food Guys".

Not only was our talk well attended by an assortment of fishermen, managers, scientists, reporters, and others, but the array of questions that we received showed an impressive amount of interest, knowledge, and understanding of copepods and their ecological importance.  I doubt that there are many venues where a group of geeky scientists could talk about Calanus finmarchicus to such an eclectic audience, and receive such an enthusiastic response.

Nick Record, signing off.

The Twilight Series, part 2: what are those creatures?

Week 3 since the cruise, and the pieces of the puzzle are beginning to come into focus.  Cameron's incubation experiments indicate a presence we've not sensed since last year--the presence of diapausing copepods deep in the abyss.  As I typed earlier, I'm getting a similar signal in the laser data: an anomalously large aggregation of particles at just the size and depth we would expect to find C. finmarchicus.  Here is another view:

Diapause3D.jpg


While it is possible that this deep aggregation of particles is some mysterious, and as yet undiscovered presence in the gulf, the evidence points to one plausibility: if it quacks like a copepod, it's probably a copepod.

I returned to my personal microcomputer to plot up quasi-silhouettes from the lasers, showing these particles.  Here are the preliminary results:

WilkiFins.jpg
A glance at this image is far from conclusive, and it remains to demonstrate that the blobules we see are actually diapausing copepods.  I conjecture that they are indeed that, and I am presently taking steps to convince myself that I'm correct.

Nick Record, signing off.



The Twilight Series, part 1: Diapausers in Wilkinson Basin

With the thrill of the lobster molt wearing off, the time has come to crunch some numbers.  A few weeks ago--the 22nd of July, 2010 to be more precise--we spent a full day on our deep station in Wilkinson Basin.  For six relentless hours, we sampled profile after profile at the same station.  What began as a routine and sunny carefree day slowly morphed into grueling repetition, and as twilight descended upon us, so did the madness of tedium.  (I won't speak here of what that madness led to.)

cameroncopepods.jpeg

The driving motivation behind this long series of profiles was to capture the twilight transition in Wilkinson Basin.  Every night, an unfathomable host of plankton emerges from the depths of the world's ocean to feed at the surface under the cloak of darkness.  This transition occurs, for the most part, during the twilight hours--hence the name of this sampling series.  Our objective is to sort out some of the major players in this massive migration, and to pinpoint as well as we can their preferred depths.

Naturally, we are in the early stages of unraveling this depth-stratified tapestry of plankton, but some curious signals are already appearing.  The plot shown below is taken from a night sample, well after the sun has set.  On the left is a plot from our laser optical plankton counter.  It shows the depth concentration of each size class of plankton--divided by equivalent spherical diameter (ESD).  You can see that most of the critters we observed are near the surface, with the concentration tapering off around a depth of 20-40 meters.  What stands out is the strong signal at the size range 1000-2000 microns (1-2 mm) at depths below 120 meters.  I have labeled this "Diapausing finmarks"-- what I believe to be the copepod Calanus finmarchicus, gathered in large numbers in its deep hibernation.  This is something that we hope to confirm with the net tows.

It is interesting to note that, while we think of this species as a cold-water animal at the southern edge of its range here in the Gulf of Maine, it appears to be actively avoiding the coldest depths at this station.  The right-hand plot shows a temperature profile, with a classic Maine-intermediate-water signal. I've labeled that.  It's a cold layer that forms between two warmer layers in the ocean, due to a combination of processes.

The other curiosity to this temperature plot is the blip of warmer water around 50 meters depth.  This I've labeled with a question mark.  It appears in nearly all of our profiles, at the same depth, and I've since noticed it in other temperature profiles from the Gulf of Maine.  I have yet to find an explanation.  Thus, another mystery has bubbled up to the surface.


WilkiDeepE.jpg

PS in response to Pete's comment, I've posted some of the LOPC shapes on the LOPC blog: www.seascapemodeling.org/lopc/

Publications

Our lab has had a good month for publications.  Fred's paper on C. finmarchicus diapause, and the role of lipids, finally made it to press.  The paper appears in the Marine Ecology Progress Series, and can be found here.  The paper was submitted for review on the 4th of November, 2008--roughly 17 months ago.

Not all review experiences are as lengthy or arduous.  Our lab had three other papers accepted for publication this month.  Two of them were submitted earlier this year.  We will post an update when they make it to press.  Meanwhile, a list of our publications can be found on our welcome page, here.

Fred.jpg
Sample image from Fred's paper.  MEPS 403: 165-180.

October cruise: Nearshore - offshore zooplankton gradient

Our biological oceanography lab has a biweekly zooplankton time-series study collected from the Darling Marine Center in Walpole, Maine.  The study samples the zooplankton at two stations: one well within the Damariscotta estuary, and the other a few miles out.  At the nearshore station, we see an estuarine community, with a diverse collection of copepods and other zooplankton.  At the offshore station, depending on the time of year, the community is dominated by the large copepod, Calanus finmarchicus.  

These two communities are characteristic of two different marine ecosystems.  The big copepods in the oceanic system provide essential prey for pelagic species ranging from herring to right whales.  The smaller, more diverse estuarine system can serve as a nursery for larval fish.  The seascape modeling lab is interested in the processes that maintain the boundary between the two types of system.

In order to characterize the nearshore-offshore gradient, we ran a cruise on Thursday, taking profiles with the LOPC at fixed intervals of roughly 1 km (see map).  We're still feeding out and reeling the LOPC cable by hand, until we get the data logger fixed.  This can be tiresome, but thanks to ongoing splicing efforts (including some last-minute work before leaving the dock), it's effective.  We have a nice transect showing the shift in size distribution from the nearshore out towards the offshore.

Additionally, it was nice to be on the water on a brisk October day.  We got an early start, catching the sunrise ferry from Peaks Island, and we saw some fair wildlife, which, hopefully, Pete will share some pictures of in a later entry.

DMC20091001.jpg
Sampling stations (X).

LOPCdeployment.jpg
Reeling in the LOPC and cable.

Calanus finmarchicus diapause

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 !

CVoilsac.png
Photo by Phoebe Jekielek.

Cruise fauna: a whale's breakfast

Much of our sampling was directed toward characterizing the abundance and distribution of whale food.  This image shows a sample containing a few of the delicacies enjoyed by whales in the Gulf of Maine.  The large shrimp-looking animals are krill, enjoyed by minke, fin, and humpback whales, all of which we observed during our cruise (stay tuned for photos).  Among the smaller animals in the sample are copepods: the breakfast cereal of right whales.  If you've swum in Maine waters, you've probably swallowed many mouthfuls of them.

The favorite variety, Calanus finmarchicus (Finnmark copepods) occur in very high abundance in the deeper waters of the gulf.  We generally find them in waters deeper than 100 m.  This year, there seemed to be strangely low numbers of them in the waters south of the Penobscot, where we also saw a lot of bioluminescence.  Of course, we'll have to do the full analysis before we can be sure about these results.

Keep checking back for more wildlife photos from the cruise.

Krill1y.jpg
Copepods and krill from a net sample.

Forecast update

Our copepod forecasts are now appearing in habitat assessment reports produced by the Provincetown Center for Coastal Studies.  The PCCS runs cruises approximately weekly to characterize the prey resource for right whales in Cape Cod Bay.  Our forecasts include their samples from the previous week, coupling them with physical data to project into the upcoming week.

Here are a couple of our forecasts, with comparison to the actual data collected around the same time.

This plot shows a forecast for April 11th, for total copepodid zooplankton in the bay.
SEASCAPEapr11.png

This plot shows the distribution based on data collected on April 10th.
PCCSapr10.png
The higher concentration in the southern part of the bay matches fairly well, though our prediction put this patch further south than where it was observed.  Our forecast also predicted two strong patches near the tip of the cape, which didn't appear in the samples.  Note that the color bars are not quite the same in the two images.

This plot shows our forecast for April 15, for all copepodid zooplankton.
SEASCAPEapr15.jpg
Below is the distribution from the survey on April 14.
PCCSapr14.jpg
The spatial pattern of abundance matched well, with a low concentration in the northern part of Cape Cod Bay, and a higher concentration to the south.  As in the plots above, note that the color bars are not quite the same in the two images.

In both the forecasts and the sampled data, regions of zooplankton abundance were dominated by Calanus finmarchicus at this time of year, marking a shift from earlier in the year, when C.fin. was low, and Pseudocalanus spp. and Centropages spp. were higher.

Forecast 4/6/09

I created a new hindcast/forecast run. The key inputs are the satellite data (SST & chlorophyll), flow fields, and the PCCS zooplankton data.  The availability of the data changes throughout the  period. Here's what I used:
  • 1/1/2009-3/22/2009--FVCOM 2009 flow fields (high res), assimilating PCCS data
  • 3/22/2009-4/6/2009--climatological FVCOM fields (lower res), no assimilation
  • 4/6/2009-4/15/2009--climatological FVCOM fields, climatological satellite data
I mapped the adult abundances for Calanus, Pseudocalanus, and Centropages for the 10d assimilation windows and uploaded the images to Picassa.  You should be able to click through the figures.  Each figure contains three panels.  The two on the left are the initial conditions for the 10d period.  The leftmost is the initial guess (usually, the output from the previous 10d window).  The second, labeled "post" (for posterior) is the initial condition estimated by the EnKS algorithm.  The panel on the right is at the end of the 10d period.  OK, here are the images:

Calanus:

Pseudocalanus:

Centropages:


Some comments on the figures:
  • If the two initial conditions look the same, there was likely no PCCS cruise in that period
  • If the two initial conditions are similar, then the PCCS data and model agree well in that period
  • If the two initial conditions are wildly different, then the model required significant adjustment to reproduce the data.
We plan to try a few things to try to minimize the "case 3" situations.  In particular, using better parameters from Nick's genetic algorithm work, using BCs from our Gulf of Maine model (esp. for Calanus), and trying different analysis intervals.

Forecast: right whale arrival date in the Great South Channel

Our lab et al. published a series of papers in the latest issue of Marine Ecology Progress Series in which we explored linkages between copepod abundance and the migration patters of right whales.  Better knowledge of where and when right whales might show up can help prevent ship strikes and gear entanglements.  The full articles can be found here: 1 2 3.

One of our results was a strong correlation between the computed abundance of Calanus finmarchicus and the arrival date of right whales in the Great South Channel critical habitat.  Researchers have known for awhile that right whales use this habitat every year, but the factors that influence the timing of that usage are harder to pin down.  (Details on our computations, like how we calculate arrival date and C.fin. abundance, can be found in the papers.)

This correlation may have use as a forecasting tool.  The correlation spans the years 1998-2006.  By computing the C.fin. abundance for ensuing years, we can use a linear fit to produce a forecast for the arrival date in the Great South Channel (see figure).  Our prediction this year is for an early arrival date--right around now, in fact.  We also predicted an early arrival for 2007, and a late arrival for 2008.


ArrivalDate20090317.gif
Figure.  Top: correlation between computed C.fin. abundance and right
whale arrival day in the Great South Channel (R^2=0.7, p=0.01).  Red dots
show predicted values for 2009, with the most current prediction indicated
by text.  Bottom: our predictions for the 2009 arrival date.  As the year
progresses, we assimilate more data, and our prediction changes (see point
2 below).  The abrupt drop in late February is due to a modification in our
calculation (see point 4 below).



Caveats

There are a few caveats to this forecast.  I'll outline them here.

1) A linear regression is a simplification of the dynamics at play, and there is variability about the line.  Therefore, even though we give a specific arrival date, our forecasts should be taken as approximate.  It's better to think of them as "early", "average", or "late", rather than as occurring on a specific date.

2) Our models rely on satellite data, which is updated as the year progresses.  Therefore, our forecast changes as the year marches on (bottom plot in figure). It's similar to how the weather forecast gets better as next week gets closer.  This limits us somewhat, but our previous work has shown that satellite data from January and February generally provide enough data to get a significant correlation.

3) We check our forecasts against a whale arrival date that is calculated from survey data.  That is, real people looking for whales from boats and planes.  It takes a long time for that information to be processed and passed to us, so we haven't yet been able to check our 2007 and 2008 forecasts.  So, unlike the weather forecaster, we don't have the advantage of knowing what "today's weather" is.  Even though our 2009 forecasts tell us that right whales are arriving in the Great South Channel right around now, or possibly have arrived already, we may not be able to check that for awhile.

4) The nature of satellite data changes with technology.  For example, resolution has improved.  We've developed a new interpolation method that helps the satellite data to be consistent over many years.  The down side is that we had to re-run our experiment with all of the satellite data in this new format.  The good news is that the correlations persisted, though altered a little.

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