Detecting Differences in the Gulf of Maine

This past weekend found us crossing Georges Bank and crossing over into the Gulf of Maine.  While crossing the shoal portion of Georges, we caught a couple of juvenile fish from the Gadidae family, possibly either cod or haddock.

gadidae juvenile

A juvenile fish of the Gadidae family, possibly a cod or haddock. (Credit: Jerry Prezioso, NEFSC/NOAA)

The first one was spotted by our student volunteer, Katy McGinness, as she was washing the sample from one of the plankton nets. We nicknamed it “Katy’s Cod” in her honor!

Katy McGinness discovers juvenile fish in bongo net

Katy McGinness, the student volunteer who discovered the juvenile fish while washing the sample from the bongo net. (Credit: Jerry Prezioso, NEFSC/NOAA)

We have also been coming across increasing numbers of the copepod Calanus finmarchicus, which one of our scientists, Chris Taylor, is freezing in liquid nitrogen to be analyzed ashore for signs of environmental stress.

Chris Taylor with live Calanus copepods

Chris Taylor, a scientist from NEFSC Narragansett Lab, with a bucket full of live Calanus copepods washed from the bongo net. (Credit: Jerry Prezioso, NEFSC/NOAA)

Chris has also been involved in obtaining data from one of our newest instruments, a LISST,  (Laser In-Situ Scattering and Transmissometry), which is an optical sensor using laser diffraction to determine the size spectrum and concentration of particles encountered in the water column when we do our rosette water bottle casts. Strapped to the bottom of the cage housing the Niskin sampling bottles, this instrument bounces its laser beams off of particles that pass between its optical ports, measuring, and counting them, and then storing this data in its memory for downloading at the end of the day.

particle measuring instrument

The LISST particle-measuring instrument, mounted under the sampling bottles, in the rosette sampler. (Credit: Jerry Prezioso, NEFSC/NOAA)

By Sunday afternoon we had completed all our Georges Bank stations and moved on into the Gulf of Maine.  Here we are seeing an increased amount of structure to the water column temperature, salinity, chlorophyll, and light measurements made by our instruments.   In the shallow, well-mixed areas of Georges Bank, the water column was pretty homogenous from top to bottom, but not so in the deeper Gulf of Maine area.  Here, there are distinct layers of water of varying temperatures and salinities at various distances below the surface.   At this time of year, many Gulf of Maine stations have a thermocline or demarcation line where warmer, less dense water sits on a layer of cooler, denser water.  Interestingly, the interface between these two water masses seems to be where the phytoplankton hang out, literally buoyed up by that denser layer, as shown by the fluorometer on our submersible instrument package.

Hefferan steers Deleware II

NOAA Corps Officer Shannon Hefferan steers the Delaware II from the outside helm station towards a cluster of balloons which were recovered from the water by the crew. (Credit: Jerry Prezioso, NEFSC/NOAA)

Sometimes the Delaware II does oceanographic litter patrol as well as scientific research.  Several days ago a cluster of balloons was removed from the water by the Delaware II as it was enroute to Georges Bank.  Ingestion of floating plastic debris contributes to the deaths of many loggerhead and leatherback turtles, species that feed on jellyfish.   Such recovery operations provide the Delaware’s NOAA Corp Officers and crew practice in maneuvering the vessel and an opportunity to make the waters a bit safer for these protected species. Now, with eight working days remaining in our cruise schedule, the Delaware II is striving to sample the remaining Gulf of Maine area, and if we have enough time, to conduct some comparisons of two different types of plankton sampling gear before we return home to Woods Hole.

Jerry Prezioso
Chief Scientist
DE 1105 EcoMon/NASA/ODU Cruise

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