Science Results : Daily Update

Daily Update | Current SEA Research

June 18, 2010

By Giora Proskurowski

While our major focus is on plastic marine debris (on this trip we've also seen one or two tar balls per tow), we are also interested in what else is in the nets. In order to characterize the net tows, the sample is processed following a standardized protocol that SEA has developed over the past 40 years of taking undergraduates to sea: the contents of the net are rinsed into the cod end jar and placed in a bucket, the bucket is moved to the sink inside the lab, and the fun begins.

All large plant and algae material (such as Sargassum) are removed, along with all gelatinous and small fish that are larger than 2 cm in length. Certain organisms – including Halobates (the only marine insect), myctophids (lantern fish), and cephalopods (squid) – which SEA has been studying in collaboration with researchers around the world, are recorded and preserved. A representative dollop of the biomass is subsampled and taken to the microscope where the diversity is determined by identifying, to the family level, the first 100 organisms encountered.

The plastic pieces are removed, counted, rinsed with deionized water, and then dried in metal tins for storage. Any tar pieces are counted, described, photographed, and frozen in clean aluminum foil pouches for geochemical analysis at the Woods Hole Oceanographic Institution by Robert Nelson.

Lastly, a sample of the surface seawater is taken during the tow and analyzed for nutrients (nitrate, nitrite, and phosphate) and chlorophyll-a (a measure of plant productivity). All of this information is recorded on a data sheet along with the details of the deployment, including time the net entered and was removed from the water, wind and weather data, tow speed, and tow length in kilometers.

I'm sure I've skipped over a lot of the fine details, but that is an impressive amount of new information collected – four times a day, every day. The talent and dedication of this group of volunteers (as well as the teaching and management skills of SEA scientists Juliet Alla, David Murphy, and Skye Moret) is demonstrated by the fact that they all learned every aspect of this procedure within the first week. The lab is humming right along, and we'll soon have to stop and do a neuston tow to feed the beast.