Tag Archives: zooplankton

Microscope: Compound and Dissecting

01/27/2016 Eric Hanson Leave a comment

I’ve spent a lot of time in front of a microscope either chasing around a micro invertebrate to analyzing a histological stain for Q/A. During lab courses in school I was always the one person that was good at following around single celled organisms so everyone could get a glimpse at it.

When working at the Desert Studies Center, Zzyzx, CA on the Mohave Tui Chub project, I spent huge amounts of time in front of a stereo dissecting microscope counting zooplankton. It was very tedious work, but a really fun way to explore a world invisible to the naked eye.

At Caris Lifesciences, working in the immunohistochemistry (IHC) lab required immense amounts of microscopy work. We had really nice stereo compound microscopes that every single slide went through. When I was making tissue micro-arrays (TMA) I had to quality control (QC) all kinds of tissue to make sure they would work for use in the TMA. I also spent a lot of time looking at each of our IHC stains to make sure they stained properly and the stainer machines were still staining with the intensity we were looking for. In order for a slide to leave the lab and get in front of a pathologist, it had to go through our internal quality analysis (Q/A) team.

Skills

Zooplankton Counting and Classification

01/20/2016 Eric Hanson Leave a comment

My primary function while participating in the life history study of the Mohave Tui Chub was zooplankton counting. This was the first year of the field project, with several more years of study scheduled. During this phase of the project, we were developing a deeper understanding of the environment the chub lived in. We also did extensive water sampling and created micro habitats called mescosms. If you would like to read the dessertation paper Sujan Henkanaththegedara wrote about the Mohave Tui Chub, please see it here.

zooplankton1 — Conochilidae family – Rotifers

We collected zooplankton utilizing the horizontal water sampler which allowed us to get a representative sample at various depths across the waters were were testing. Once the water sample was collected, the invertebrates were strained out and placed in a sugar-formalin solution. Sugar formalin was chosen due to it’s similar osmostic characteristics to the saline environment they were taken out of.

zooplanktoncounts — Zooplankton counting station. The pink vials contain sugar-formalin and lots of invertebrates

The samples were than aliquoted out and a several mL sample was dumped in a zooplankton counting wheel. The wheel consists of a non-continuous circular line inset in a clear plastic dish. It is then placed under a dissecting scope and you start counting and classifying the zooplankton as you go around the wheel. We did this four times for each sample.

When we found an interesting or unknown specimen, we would take it over to a compound microscope on a glass slide. This allowed for much greater magnification so we could further classify the zooplankton.

For the study, we were not interested in classifying individuals down to the species, but instead got them all down to the family. Most of the samples contained many rotifers, and even on occasion we found some of the aquatic invertebrates such as water mites and chironomidae spp.

These photographs were taken through a compound microscope on a glass slide. I love using the Image-Based Key to the Zooplankton of North America, and recommend it’s use if you ever need to get down to the family of zooplankton you’re looking at. After that, a comprehensive key can be used to get to the species, but you’ll want to have several individuals for dissection, and a really good microscope.

Skills

Horizontal Water Sampling

01/09/2016 Eric Hanson Leave a comment

This sampling technique is great for surveying various depths in a body of water. You lower the opened horizontal cylinder down into the water at the depth you want to sample and let loose a weight. The weight travels down the string that hits a switch which closes the ends (through a rubber elastic band). This technique is great for giving you a representative sample at a specific depth. The design of the contraption is pretty much always similar to these.

While I was studying the life history of the Mohave Tui Chub in California, we used this technique to survey the zooplankton distribution in Lake Tuende and MC Spring.

Lake Tuende at the Desert Studies Center

Learning Through Life