Zooplankton Tow Sample Analysis

We conducted our second indoor lab assignment on October 11, 2010. We analyzed the two plankton tow samples (surface and oblique) from the October 4, 2010 outdoor lab assignment. Surface tows were characterized by being able to see the net at the surface. Oblique tows were characterized by the net being at least 4 m below the surface. The objective of this lab was to utilize dissecting microscopes to assess the abundance of copepods from two milliliter (ml) water samples from surface and oblique plankton tow samples.


Copepods are vital marine organisms that prey on phytoplankton in coastal ecosystems. They serve as important prey items for shrimp, small fish species, and crabs.
The plankton samples were collected using bongo plankton net with 1 mm (500 µm) mesh and collection container attached in the middle. The bongo plankton net was towed behind the boat at a speed of 0.77 m/s. After each tow, the bongo net was brought aboard and the collection container was removed from the net. We used saltwater to wash the plankton samples from the collection container into separate containers labeled either “surface” or “oblique”.

In order to assess the abundance/ number of copepods per sample, 1 ml pipettes were used to remove a 1 ml water sample from the surface and oblique plankton tow samples. One water drop of the plankton samples were placed in 36 miniature squares of a water sample tray. Each tray was observed under a dissecting microscope. The number of copepods per miniature square was calculated for both plankton tow samples.

Both the surface and oblique plankton tow samples produced low numbers of copepods and other zooplankton.