by Harriet Alexander, Woods Hole Oceanographic Institution
Harriet Alexander and Sarah Hurley pull a plankton net up
through the water from the side of the ship. (Colleen Durkin, WHOI)
The open ocean might be generally described as a nutrient-poor region, where small picophytoplankton are better able to acquire the things they need to grow than large phytoplankton, such as diatoms. As such, picophytoplankton tend to be numerically dominant over larger diatoms. However, there is mounting evidence that a confluence of events occasionally sparks a large bloom of these bigger phytoplankton in regions where they usually have a hard time growing. Imagine poppies suddenly blooming in the middle of the Sahara Desert.
|Everyone, including Harriet, was surprised by the color and smell|
of the phytoplankton that we captured. (Carly Buchwald, WHOI)
So, back to the unicorn.
Up until about a week ago, we had been traveling through the subtropical gyre, which is sparsely inhabited by large diatoms. The morning of April 17, I had been trying to snag a little bit more sleep, as I did not have any planned sampling that day. Suddenly, my roommate came and woke me, saying that we had found something interesting . I stumbled upstairs, slightly blurry-eyed to find everyone in a frenzy deploying a CTD at an unplanned station.
|Harriet sampled a small amount of "goo" to|
identify it. (Colleen Durkin, WHOI)
While everyone was gearing up for some on-the-spot sampling, we decided that a net tow might prove interesting. By dragging a net up and down through the water column we can capture and concentrate all the organisms larger than a certain size into a smaller volume. In this region, we might expect a typical net tow to contain a few animals and maybe some algae. When we recovered the net, it was full of (to use the scientific terminology) goo—greenish-yellowish-brownish goo, smelling strongly of sulfur. Gwenn Hennon and Colleen Durkin grabbed a sample to look at under the microscope and reported that we had, in fact, stumbled upon my unicorn—a huge bloom of diatoms.
My Ph.D. research is focused on trying to better understand the nutritional physiology of diatom growth in a nutrient-limited environment. By sampling the RNA (the genetic material being expressed) of the diatom community in the environment and in on-deck incubations, I will be able to create a metabolic fingerprint for the diatoms that are growing in the system. Coming across this large bloom of diatoms provides me with the opportunity to gauge what these organisms are doing and experiencing during such an event.
|Examination of the sample under a microscope revealed it to be|
a bloom of diatoms--large cells encased in glass-like shells. The
left photo shows how abundant these cells were and the left shows
a cell about to divide. (Colleen Durkin, WHOI)
This type of discovery is nearly impossible to make intentionally. Kind of like finding a unicorn.