Peterson Grab

The Peterson grab samples seabed sediments and organisms. Seabed sediments and organisms can give an indication of the overall health of the sea-bottom with respect to the microbiology. This is very important as the seabed sediments and their contents are the source of our nutrients when we get upwelling.

o A rich, ocean/earthy smelling mud with lots of decomposers means that when we get upwelling currents across the seabed we have the potential to get large amounts of nutrients to the photic zone. This is when the phytoplankton go crazy and MULTIPLY.

o A black/dark rotten egg smelling bottom sediment that has very few organisms is an unhealthy seabed. This means that little nutrients will be available for upwelling. This makes the phytoplankton very sad and they don’t reproduce rapidly as above.

Setting and preparing to lower the Peterson Grab.

Once onboard the sampler is opened and the contents placed in a bucket.

The sediments are washed in a screen to get the organisms contained in the mud.

Small trays with pictures and descriptions are provided for each of the more common organisms.

Here’s a small brittle star.