Friday, February 27, 2009

Lake Core Investigation

Hi our names are Amelia, Brittany, Jessica, and Madison. We are from Parkers Prairie High School. We are doing an investigation on diatoms in 8th grade Earth Science. For this investigation we are using a core sample 90 cm deep in Lake Adley.

Question: How many different kinds of diatoms are found at 30 and 90 cm from the surface of the core.

Variables Changed: Depth sample was taken at.
Variables Measured: Kinds of diatoms.
Controls: Core, amount of sediment taken for slide, and procedure.


  1. First we will take a core sample with a toothpick from 30 cm deep.
  2. Put sample on slide and add a drop of water, then put a cover slip on top.
  3. Then view the slide under a compound microscope and look for kinds of diatoms. (mark this in notebook.
  4. Take the same steps at 90 cm deep.


  • core/core sample
  • toothpick
  • slide
  • cover slip
  • compound microscope
  • water
  • diatom sheet
  • pipette


Diatoms found at 30 cm deep

  • Navicula/Pinnularia
  • Fragellaria
  • Cymbella
  • Aulacoseira
  • Amphora
  • Cyclotella

Diatoms found at 90 cm deep

  • Cyclotella
  • Asterionella
  • Hantzchia/Nitzchia
  • Melosiera
  • Navicula/Pinnularia
  • Synedra


Claim: There are mostly different diatoms at 30 and 90 cm, but some are the same. We found about the same number of different diatoms at each site.

Evidence: We found 7 kinds of diatoms at 30 cm. They are the following. Navicula/Pinnularia, Cyclotella, Aulacoseira, Cymbella, Amphora, Asterionella, & Fragellaria. At 90 cm we found Navicula/Pinnularia, Hantzchia,Nitzschia, Cyclotella, Melosiera, Synedra, & Asterionella. We found three diatoms consisting in both sites. They were Cyclotella, Asterionella, & Navicula/Pinnularia.

Reasoning: We believe that the reason we found three of the same diatoms at both sites is because those three diatoms can live in multiple environments. The reason there are different ones found at 30 and not 90 cm could be because the water environment was different when 90 cm was the top of the lake bottom.

Further Questions

1) How long ago was 90 cm deep on the core the surface.?

2) How are different diatoms formed?

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