Meeting Data from the Sea with Data from the Sky

Sunrise seen from the bridge of the Delaware II. (Photo by Harvey Walsh/NOAA.)

We’ve had several beautiful days offshore!  Clear skies are good news for another sampling objective of our cruise.

The Climate Variability on the East Coast (CLiVEC) scientists on board are collecting lots of water to study primary productivity,  phytoplankton communities, and the carbon cycle along the east coast continental shelf. One goal of their research is ground-truthing data collected by satellites.

Antonio (NASA) and Pete (ODU) filter water in the wet lab. (Photo by Harvey Walsh/NOAA.)

To do this, we collect water samples at times when the satellites are passing over us estimating the amount of chlorophyll and organic carbon in the surface waters around the ship. Antonio (NASA), Mike (NASA), Pete (Old Dominion University- ODU), and CJ (ODU) process water samples on board, which involves filtering lots of water in the ship’s wet lab. The data from their water surface samples were collected while the satellites passed overhead and should be similar to the data collected at the same time by the satellite. This particularly true on cloud free days we we have direct comparison of satellite and water measurements.

Rosette sampler over the side of the Delaware II. (Photo by Harvey Walsh/NOAA.)

We use a rosette sampler with twelve 10-liter bottles to collect water from the surface to the ocean floor. The rosette sampler has a Conductivity, Temperature, and Depth (CTD) probe attached to it that is similar to the bongo net’s CTD, except with more instruments. The main one we are using on this cruise is the fluorometer, which estimates the amount of chlorophyll in the water column. Where there is chlorophyll, there are phytoplankton, the main providers of primary production in the ocean. Phytoplankton are at the base of the food web for many of the zooplankton and ichthyoplankton we collect in our bongo nets. As I said earlier, the CLiVEC scientists are interested in primary productivity and the phytoplankton community. With real-time data coming into the dry lab we are able to trigger the bottles on the rosette to collect water when we seen a spike in the green line on the computer screen.  That spike indicates maximum chlorophyll levels, where there should be lots of phytoplankton.

As the CTD gives us readings on the levels of chlorophyll in the water, we know exactly when to collect samples that will give us the most phytoplankton. (Photo by Harvey Walsh/NOAA.)

When the rosette comes back on deck, everyone is eager to fill their bottles and get back to work in the lab. From a single inshore station, we will filer about 10 gallons of seawater, and from offshore we might filter as much as 20 gallons.

Antonio, Mike, and CJ fill their carboys with seawater for further sampling. (Photo by Harvey Walsh/NOAA.)

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