Beneath the Ocean Floor

Ponar grab before being deployed (photo by Harvey Walsh/NOAA)

Now that our cruise track has taken us into the Gulf of Maine, we are deploying a ponar grab,  a piece of gear that collects sediment samples from the ocean floor.  The jaws of a ponar grab sink several inches into the sediment, and when the grab is pulled to the surface the jaws close, capturing the sediment samples.

Alison (University of Rhode Island) collects samples from the surface of the sediments to identify what microeukaryotes (small plants and animals invisible to the naked eye) are living there.  The first step is scraping collections from the surface layer of the sediment.

Sediment sample with layer of algae, microeukaryotes, and a brittle star (photo by Alison Cleary/URI)

Back in the lab, Alison will then use a process called DNA probing that allows her to identify the different organisms present in a single sample.  What’s living on the bottom can then be compared to what planktonic krill eat; birds, fish, and whales in turn eat krill.

Krill collected with a Bongo net.

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