Macroinvertebrates

Observer: Eloise Bacher

Date: 21 September, 2008

Time: 1440-1515

Location: Mill Stream, near library.

Weather: Overcast, drizzling a little, warm.

It's raining now, but at first it was simply overcast. I went into the Mill Stream with the intention of looking for macroinvertebrates to see if I could determine the health of the stream. I didn't have high hopes because of what we talked about on Friday, that the bottom of the stream is concrete. The main organism I found were these pure black, smallish snails that didn't have the best grip on the rocks (they were falling off as I lifted the rock out of the water). There were at least a dozen of them on each rock I picked up, and I could see more in the water. There was another type of snail, with greenish yellow shells that were smooth and kind of bulbous. There were less of these, but there were a bunch of their shells, empty, in a little pile on the side of the stream where it gets sandy/silty and very shallow and even gentler. There were also these clusters of tiny rocks, which are either Caddisfly or Stonefly larva, can't remember which right now. Either way, it's a good sign. The water feels pretty warm, however, and it doesn't flow very fast in this location. Which reminds me...I was visiting with a dog a few minutes before this observation and her owner said that they had seen a Nutria here before, in this part of the stream. Is it possible that there are Nutria here? I've seen Muskrats in urbanized areas in Portland, so I wouldn't be surprised to see one of those here, but I'm going to keep my eyes open for either of these animals.

*Photo (Caddisfly Larva) courtesy of http://www.troutnut.com/im_underwater/picture_235_medium.jpg