School Email Exchange

Do you tow nets at different depths, or just near the surface?  What are the differences at depth?

Posted on October 27 2012

Question submitted by Washingtonville High School

We have a net system called the MOCNESS that is being used for the first time in its present form aboard the Seamans.  The MOCNESS has separate nets that can be programmed to open and close at different times, allowing us to collect discrete samples at many different depths.

The four nets of the MOCNESS are put overboard before it is lowered into the water using the hydrowinch and the J-frame.

We are using this net system to test whether wind and wave action or epibionts (something that lives on the plastic) can draw the plastics floating on the surface deeper in the ocean.  We are collecting samples at 1, 3, 7 and 10 meters depth.  

When we count the number of pieces of plastic found in each net, we have found that in each set of tows the deepest net (10 m depth) has collected the fewest plastics and the shallowest net (1 m depth) has collected the most.

After the MOCNESS is brought back on deck, the cod ends of each net are placed in the buckets that will hold their contents.