Elkhorn Slough is a really special place.  Our Marine Ecology class (CSU-Monterey Bay) went exploring in the slough and found some amazing critters!

About five miles upstream from the ocean, a railroad track cuts through the slough, trapping a section of the mudflat behind it.  Two bridges allow the area to fill with water during high tide, and empty as the tide recedes.

Here is the southern bridge during an outgoing tide:

In the stream, I found mussels ( Mytilus californianus ), oysters, orange sponges, tunicates, invasive orange-striped anemones ( Diadumene lineata ), and numerous other tiny animals.  As I inspected a rock, I found that it had dozens of spider-looking creatures!  They were pycnogonids, or sea spiders.  I didn’t get a good picture, but they looked something like this:

As I tried to pull them off the rock, I noticed they were linking their legs to other individuals and I got curious about what they might have on the ends of their legs that would allow them to cling to each other (and to rocks) so well.  Under the Foldscope, the secret was revealed: