It has been a few months since my last blog post here. Honestly I was super busy with prepping everything for the new field season going to conferences. And now here we are!
This year we wanted to start our measurements earlier than last year in Vobster Quay. There were two main questions we needed to answer first:
One of my biggest problem in the past weeks was measuring the size of Daphnia we have in Vobster Quay. That's very important to understand how they can affect the mixing during the vertical migration and their life stage. Daphnia usually live for 2 months reaching the maximum body length. So different sizes means different ages.
Unfortunately the microscope I have in the Water Quality Lab @UniBath in Civil Engineering wasn't that powerful and even using my Snapzoom microscope adapter didn't help that much. The image was too blurry and I couldn't use even the ruler!
Daphnia. Source: wikipedia.org
Coepods. Source: http://www.britannica.com/animal/copepod
Following the previous post about how to collect the zoo samples, we measured the zooplankton concentration during the day to verify that Daphnia is actually hiding during the day from predators (fishes). To do that, we collected samples during June more precisely on 25/06 @ 2.40pm and 5.30pm and on 30/06 @ 2.30pm.
After the deployment of our acoustic instrument to track the zooplankton migration Last week, we are currently collecting a lot of zooplankton samples during the day to understand the distribution of our Daphnia in Vobster Quay. And today I am going to explain how we are doing this.
ADCP with its frame on our boat
Last week we put down on the bottom of Vobster Quay the device shown in the figure above. The device is called ADCP and is an acoustic device that uses the same principles of a sonar or a fish-finder but it is actually much more advanced. It was firmly fastened to the aluminium frame and lowered with the three blue ropes from our boat.
Daphnia from Vobster Quay samples (mid-May)
Many people reading the post title will think: What the heck is a Daphnia? A Daphnia is a tiny zooplankton - the little organisms in lakes and oceans eaten by fishes - with an average length of 1/3 mm and is a species very common in fresh water bodies. All the images in the post are taken with a microscope from one of our samples collected in Vobster Quay in mid-May and the first one precisely shows a (dead) Daphnia. Since our microscope does not have a place to insert a specific microscope camera, I used the microscope adapter Snapzooms which is cheaper and very simple to use and smartphones offer nowadays as much resolution as microscope cameras. (more…)