Drew School

San Francisco

Sally Dickinson's Marine Science Class

Excerpts from the Drew School Newsletter

Exploring Old Mill Creek: The Adventures of a Marine Science Class

By Lissie Gormley

This past semester of Marine Science has been focused on the ecology of the San Francisco Bay watershed.  Several of our field trips in this class have been to three sites along Old Mill Creek.  Old Mill creek was sort of our microcosm.  It was the place where we put most of what we leaned and discussed in class into practice.

Old Mill creek runs from up on Mt. Tamalpais down through Mill Valley to empty into Richardson Bay.  Up on Mt. Tam, it merges with Cascade Creek, and later it joins with Arroyo Corte Madera del Presidio.  It is one of the creeks cared for by the Mill Valley Stream Keepers.  Supposedly Old Mill Creek is home to steelhead trout, but we never saw any.

The first site we visited (in chronological order), was Old Mill Park.  It is –Obviously—a park.  There are homes in it, and a playground.  It is filled with towering redwoods.  Old Mill Creek is very shallow here, and it is hard to believe that any fish could live here.  Perhaps the Creek will be deeper in the spring.  There is a playground, with swings.  There are also houses, and a road.  The creek dips under a bridge, and runs over cement.  A pipe comes out, over the creek.

When testing Old Mill Creek we worked with two representative from The Bay Institute who helped us out, John parody and Chris Choo.  The first day we used simple tests:  you filled the test tube with creek water, and then dropped a pill in.  The water changed color.  The second time we went to Old Mill Park, though, we used fancy tests.  These involved powders and various gizmos, but they were much more accurate.

“The Whole Foods Parking Lot” is not technically where we went.  We went to the very back of the parking lot across the street from the Whole Foods Parking Lot.  The name stuck.

The creek flows under a bridge.  On the one side is a sort of gooky, green water, with plants growing out of it, a pipe, and some trash.  On the other side the water is clearer, with more movement.  You can actually see some sort of small fish in the water.  The water flows over stone about the size of your thumb.  There are homes on one side of the bank, here and blackberry bushes.

I did not visit the Mt. Tam site personally.  This description was given to me by my friend, Andrew Nusbaum.  On the drive up, the class passed ritzy houses that looked out of place.  They came to a dirt road, and followed the dirt road to a clearing.  Somewhere in this area they parked.  Across the road from where they parked was a gorge, or trough.  At the bottom was Old Mill Creek.  The class went upstream from where they parked.  The place where they tested had blackberries growing all over the place.  The water pooled in one spot so that it “looked like a Jacuzzi.”

We tested for several things at each site: 1. Dissolved oxygen, which is necessary for the organisms (such as fish) in the water to breathe, 2. Nitrates and Phosphates.  These are also necessary for life, but they can also be toxic in large amounts, causing algal blooms which use up dissolved oxygen and suffocate other creatures.  3. pH, or acidity.  Different organisms can only live within a certain pH range, usually somewhere between 6.4 and 8.4.  (Water should be 7, neutral.  The smaller the number, the more acidic the solution.  The larger the number the more basic the solution.  Acids are things like lemon juice, and bases can be found in soaps.  It has to do with hydrogen ions, but let’s not get too carried away…).  4. We looked at indicator species, in the form of different kinds of insects.  An indicator species can tell you how healthy the stream is in general.  Insects can tell you how much pollution was present in the area in the recent past, because certain insects can tolerate only so much pollution.  5. Water temperature.  Temperature is important not just because organisms need certain temperatures to survive, but because lower temperatures help water retain dissolved oxygen.  The warmer the water, the less dissolved oxygen it will hold.  (6. We also tested for bacteria and pesticides, and had good results there.)

There is too much data to fit neatly into this article.  Suffice it to say that Old Mill Creek is a fairly healthy creek.  The different parameters are all around where they should be, and the insects are not too worrisome.  A little more insect diversity at the Whole Food Parking Lot and Mt. Tam would be more reassuring, but there do not seem to be any current health problems for Old Mill Creek.

I think that studying Old Mill Creek was one of the greatest things we have done in this class.  It gives us—the students—a chance to apply what we are learning to the real world (something students are always demanding of their teachers:  How will this matter in my life?).  It allowed us to do the test, see what the results were, and then figure out what it meant, and why they were what they were.

Non-Charismatic Microphauna

            A lot of people do not know that California is home to two very special endangered species.  These are the California clapper rail and the salt marsh harvest Mouse.  They live in salt marshes, and are in serious danger due to the rapid development of their homes into…Our homes, and malls, and so on.  Not a pleasant experience.  Dr. Tina Swanson of The Bay Institute was kind enough to tell us her thoughts on the subject of endangered species:

            “When most people think about endangered species, they tend to think of either the large ‘important’ species like bald eagles, grey whales and grizzly bears (which they generally agree should be protected) or small ‘insignificant’ species like the sail darter (a fish), checkerspot butterfly, or the delta smelt (for which many people question the need for protection if that protection is inconvenient, expensive, or disrupts development, water use or agriculture).  I think the most important concept that people should understand about endangered species is that ALL species are important, not just the ‘charismatic megafauna’ (as some scientists sometimes refer to large, publicly appealing, usually furry animals).

            “The reason is that every species (including us),” Tina continues, “is part of a larger community of organisms—loss of one species changes the entire system and in some cases can jeopardize the continued existence of many other species in the ecosystem.  For example, many plant species that are in danger of extinction are in trouble because the insect species upon which they relied for pollination have been eliminated or their populations reduced.  A very famous ecologist, in response to a question about why it was important to protect a particular species in an ecosystem, once said ‘It’s because everything is connected to everything else.’”

            Since the biggest threat to the salt marsh harvest mouse and the California clapper rail is the destruction of their habitat, the simplest way to solve the problem would be to stop destroying it, and replace some of it.  Easier said than done.  When asked what she wished more people would DO to take care of wetlands and endangered species, Dr. Swanson said:

            “The first best thing people can do is to become better informed about the issues and about the species and habitats in their neighborhood, county, state and country.  Informed people are more likely to think about the consequences of their actions—both at the individual and community levels.  For example, people who understand the importance of wetlands and aquatic habitat do not dump their trash in creeks and they understand the problems with building a housing development along a riverbank.

            “Next, informed people should become engaged in their communities, local watershed groups, and local (or statewide or national) government, educating others and arguing for the importance of species and habitat protection.  Right now, the commitment of the national government to protect endangered species and to provide the types of habitat protection and management that will be necessary to prevent more species from becoming endangered is not very strong.  It will take an active, informed public to convince the government that species and habitat protection is important and that we cannot slack off on our efforts.  For species and their ecosystems, extinction is forever—there are no second chances.” 

(untitled) A.M.S.

I am hunter.

I soar over mountains and

Tear through clouds.

I am harvester.

I rustle through leaves and

Dart under shadows.

I am wader.

I whisper through shallows

And stab at reflections.

I am swimmer.

I wriggle against currents and

Jump to catch the dawn.

I am dreamer.

I step into water and let it knock me down.

I hold out my arms and soar over ocean and forest.

The water crashes against me and I am

Mermaid, dolphin, otter, osprey.

I am dreamer.

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