Plankton Race: Marine Bio 101 Homework, Week 4, Part 2

For Marine Biology, I had to design a plankton which had adaptations for buoyancy and drag that we discussed in class and get it to take as long as possible to sink to the bottom of a tank of water.

The water had to be 12 inches deep.

The plankton could not be bigger than 3 inches long on its longest side.  Mine was about 2.5 inches long on its longest body side. 

The body was a sponge, which was a flat body plan.  The sponge had air pockets, an adaptation for buoyancy which some real plankton have.  It also had spikes made of bamboo skewers (another adaptation which increases buoyancy).

To test the design, you hold it in the water so it is just sumberged, then let go.  (You don't just drop it into the water.) 

It floated.

So I attached some flagella-like structures made of fishing line and beads.  I also added some screws to the sponge with a rubber band to give it some mass. 

It went straight to the bottom in less than 2 seconds. 

Next, I removed some beads and made the flagella shorter.  I figured that would cut down the drag a bit.

That helped it to sink somewhat slower. It took approximately 3 seconds.

It still needed something. 

Next, I attached a cloth parachute to it (a drag increasing adaptation, similar to the body plan of jellyfish). 

That slowed it down, but not enough.

I added streamers (less than 3 inches long) (also to increase drag.)  And then a second set of streamers.

Now it just sank.  Fast.

I cut the streamers shorter.  That helped a little bit, but not enough.

So next I added some vaseline to the bottom of the sponge to mimic lipid or fat pockets that some real plankton have.  This increased the buoyancy enough that my plankton slowly sank to the bottom of the tank. 

At this point, my parents helped me by timing it and shooting video.  Unfortunately, my mom's camera did something really weird, and it lost the audio of me explaining the project, so I am typing this up instead. 

It wouldn't download either, showing up as only a still photo, but it ran on mom's camera.  She used another camera to video the video so I could upload it.  Sorry if the video quality is not the best, but you can pretty much make out my dad's phone that he used as a timer. 

I did several tests of the final plankton.  The best time I had was 10.2 seconds, and the next best was 9.7 seconds.