Wednesday November 11th marked the first glider deployment for this years Antarctic field season. We couldn't of asked for better weather, it was a balmy 30 degrees, clear sunny skies and flat calm seas. We journeyed out to Station E and after surveying the water depth in the area, we decided it was a good spot to splash RU25. After she completed a few short missions it was time for her journey to begin. The main mission is to obtain a battery curve for this glider in preparation for her flight to Rothera later in the season. However, we will also be running the CTD and optics puck and collecting some science. Enjoy the photos!
Posts Tagged ‘biology’
Yesterday (Tuesday) was our first sampling day here at station. We would have gone Monday but if the wind is blowing over 20 knots they don't want us out on the water. Which is fine by us, no one wants to feed the fishy! So since the winds had laid down it was time to head out on our trusty zodiac 'Bruiser'. As you can see Bruiser is kind of a beast! The good news is that since it's such a heavy boat it would take an Orca to flip it, so hopefully I will have better luck here than I did in the Azores! Anyway back to the science, we have two main goals while sampling, first is the lowering of our bio-optics cage and second is collecting seawater samples. Yesterday we lowered our optics cage to 60m and collected water in Niskin bottles at 50, 25 and 10m and then two surface samples. Once we have what we need it's time to head back to the lab and filter the samples. As you can see we have a lovely filtration system setup. We use 25mm filters and filter the seawater in incriminates of 100ml until we see pigment on the filters. Right now since the water is so clear there is not a lot of activity so we have to filter more water. This will change as the weather warms and the water livens up as we head deeper into the Antarctic summer. We follow this process twice, once for chlorophyll samples and a second time for HPLC samples. Once we have the filters we store them in either the deep freeze or in liquid nitrogen. And that's a wrap!
Tonight marks the hurtle over a gigantic milestone in gooseneck barnacle research. From the basement of Mabel Smith Douglass Library, Brian and I finally conquered the barnacle JPEGS, capturing their size in a pixel-to-pixel ratio using the the ruler tool in the Photoshop program. We measured the theoretical, tangential diameter of the glider at the point closest to the sample barnacle, and then measured either the height or the width of the sample barnacle itself. Pretty simple.
The tricky part for us was figuring out how to successfully convert pixel measurements into millimeters. Luckily, there are conversion tools floating around the web, waiting to be found by a pair of eager researchers like Brian and myself. We fished for a bit, and decided to go with a .org site (...based on the mythical legitimacy of the .org genre of websites). The website we chose can be found here. Just put in your pixel measurements, and voila: mm, cm, km, whatever.
By using a proportions formula, that we hope we've set up correctly (...remember, we're biologists, not mathematicians!), we scaled 2 barnacles and a large cluster situated near the front segment of the glider, on the "R" side of the vehicle.
Here is an example of the formula we used (all measurements in millimeters):
Theoretical Glider Diameter/Actual Glider Diameter = Actual Barnacle Height/Theoretical Barnacle Height
"Theoretical" values represent the pixel measurements taken from the JPEG converted to millimeters. The value in bold was the one we were searching for.
We were surprised by the accuracy of the conversion. Our first test subject, Barnacle 1, measured a height - from first visible point of peduncle (stalk) to tip of cirri (featherlike feeding apparatus) - of 43.14 mm after conversion.
Our barnacle books have told us that a full grown Lepas anatifera can clock in at around 40 mm! So, Barnacle 1 can be assumed to be a full grown parasite, secreting disulfide fluids with adult-sized vigilance and malice.
The cluster, comprised of 15 visible barnacles, measured 90.58 mm from top to bottom, slightly off-kilter, but helpful. The cluster takes up approximately a little less than half of the glider's diameter (212. 725 mm).
Our third specimen, Barnacle 2, was the sample from which we measured the average height and width of the capitula (flowerhead, or plated body) of the barnacles. The height of B2 was just shy of 30 mm (28.22 mm), and the width was 24.11 mm. The measurements for B2 are interesting because this barnacle rests on (or rather sinisterly cements itself to) the frontmost ring of the vehicle, the width of which is only 15 mm across in actual measurement. So, the capitula of Barnacle 2 is actually both wider and taller than the ring it rests on. The height of B2's capitula (28.22 mm) compared with the total height Barnacle 1, is about half of B1's entire length from tip of stalk to tip of cirri. Just interesting.
The specific measurements themselves, of course, are of vital importance. But, the main point we're trying to make here is: most of barnacles on the glider are full-grown, which means that they were probably residing on the glider itself for around 2 weeks before the photos were taken in the Azores. They also fit within size range suggested for a full-grown barnacle of the Lepas species.
Thanks, Sage, for showing us how to use the Photoshop ruler tool!
Amanda and Brian