On the first morning of the Coastal Science Camp, between dip netting and seining at the estuary, we tried sampling beneath the seabed using a little coring device which I seem to have to forgotten the name of.
Usually, they can see the little holes in the seabed where the benthic macrofauna live, but not this time. All the sediment pouring into the Mississippi Sound from this spring’s swollen rivers had made the waters too turbid to see through. So we were coring blind.
The corer is simply a metal (stainless steel) barrel with a rubber piston inside. The piston is connected to a handle at the top with metal rod. To sample, you put the tip of the barrel at the sediment-water interface and push the barrel into the sediment at the same time holding the handle steady to keep the piston from moving into the sediment. Holding the piston steady provides a little suction on the inside of the barrel, which helps the barrel move into the sediment, and keeps the sediment in the barrel when you pull it out. However, it does help to put your hand on the bottom of the barrel as soon as possible to keep the sediment from falling out, even if that means sticking your hand into the sediment itself.
Once you’ve recovered the sediment, you extrude it into a sieve. Sometimes you can see a little layering in the extruding sediment, but we did not take the time to try to interpret it since our focus was on finding benthic fauna.
The sieve’s mesh is pretty coarse, so anything sand sized or smaller is washed out as you gently rock it back and forth in the water. We did not find much. Mostly small pebbles. Without being able to see the seabed our sampling pattern was pretty random.
The more persistent groups (the class had been broken into groups of two or three) did find a couple things, including a polychaete, which is a segmented worm.
They also turned up a small, clawed, lobster-like organism:
We also found the burrow of an unknown organism, surrounded by a clayey cast. It looked very much like some of the fossilized burrow casts we saw at Coon Creek.
This type of sampling was not everyone’s cup of tea, however. Fortunately, the water was shallow and warm, so a good time was had by all.
