Tag: stomach

NOAA Teacher at Sea: Natalie Macke
NOAA Ship: Oscar Dyson

We’re up to station #40 now and everyone certainly has their routine down.  One type of sampling I have yet to cover is the microscopic life; the base of the food web.  A look at the marine fisheries food web quickly reveals that in order to support the commercial fisheries as well as the vast number of marine mammals and ocean birds, there must be an abundance of phytoplankton and zooplankton available in the Bering Sea.  Evidence of this food chain is demonstrated by dissecting the stomach of a salmon.  The sample (in the picture below) revealed that the salmon had recently dined on euphaussids (commonly known as krill).   Before getting into how the zooplankton samples are collected, first let me go back and touch on the base of the food web; phytoplankton.  These samples are collected from the Niskin bottles on the CTD each cast.  The samples are preserved with formalin and will be brought back to the lab for further analysis.  Now, back to the critters..

At every sampling station on the side deck and immediately after each CTD cast, zooplankton net tows are completed.  There are three different tows being used for the BASIS survey. The first two are vertical tows where nets that are weighted are dropped to the seafloor and then brought back to the surface thus sampling a vertical water column. The pairovet, named from the fact that is was designed as a “pair of vertical egg tows” (designed to collect pelagic egg samples) has a netting mesh size of 150 microns.  The net is simply deployed with a weight on the bottom.  When it reaches the deepest part of the water column it is brought back to the surface collecting its’ sample.  Another similar net with a 168 micron mesh size is named the Juday.  Once either of these nets is brought to the deck, it is washed down and anything caught is captured in the cod end (the name for the PVC bucket at the bottom of the net).

The last type of tow that is completed for the BASIS survey uses the Bongo nets.  This tow is considered an oblique tow since the nets essentially are lowered to about 5m from the ocean bottom and towed for a certain length of time.  If you remember from the acoustics, in daylight hours the zooplankton migrate to the ocean bottom to hide from their prey.  Since our sampling is done in daylight hours, the deep sampling depth is where we expect to find the highest density of zooplankton sample.  The mesh sizes on the two nets of the Bongo are 335 and 505 microns.  This allows for sampling of zooplankton of different sizes.   The samples are collected on board and then taken back to the lab for analysis.  They are separated by species, counted and weighed.  Biomass and species composition is determined for each sample.  The majority of the zooplankton we have seen this cruise have been euphaussids and copepods of varying types.

So as August winds down and the school year gears up, my connection to the Internet is becoming more and more important.  Since my Oceanography class is with the Virtual High School, I have to essentially set up my virtual classroom in these upcoming days.  I’ll assume my esteemed colleagues will assist me in unpacking lab equipment back at home at my physical classroom. (Even though I know.. all my orders will mysteriously wind up in other labs, I’m assured they’ll be safely placed away.)

So I tracked down Vince Welton, our Electronic’s Technician for some help understanding why sometimes I can surf, and why sometimes I can’t….

Simple…

Our Internet connection is via the geostationary satellite GE 23 at 172 degrees East. This satellite transmits over most of the Pacific Ocean (see a coverage map).  Since this satellite is positioned on the equator, that means our receiver must look essentially due south for a signal.  When our ship is northbound, the mast and stack of the Oscar Dyson simply gets in the way.  Therefore… no Internet on northbound travels.

The Oscar Dyson also has access to two Iridium satellites for communication as well as the GE 23.   These are the SAT-B which can transmit both data and voice communications and the VSAT which only allows voice transmission.  The ship can access this set of orbiting satellites when the GE 23 is unavailable due to course of travel or weather conditions.

Yesterday, I got permission to stay on the trawl deck during one of our station trawls.  It was fun to be outside down with the net.  Jeanette helped do some taping which I hope to(during a few Internet-less days ahead) compile to a video for my classes.  Of course as fate would have it, our catch for the day (shown below) was not one for the record books or even worth remembering at all..  I guess that’s what the editing process is for hmmm…

In the Oceanography lab, we have started our primary productivity experiments and chlorophyll analysis so learning these new procedures has been interesting and given me lots of ideas for some research topics for Edelberg’s class.  All in all, I am enjoying watching, learning and doing science here in eastern Bering Sea.  One week left..