Zebulon and Madeline Miller splashed water into the bug net in a shallow pool in Matadero Creek, gathering tiny aquatic insects. They carefully swished their nearly invisible finds into water in a plastic basin.
Tiny wriggling larva held fast to the plastic with suction-cup bottoms; swimmers half the length of a pinkie fingernail propelled with oar-like strokes. These lilliputian creatures provided a wealth of information about the creek's health last Friday, May 9. The presence or absence of the insects could indicate if something is afoul upstream -- pesticide runoff from neighboring lawns or illegally dumped cement, for example, said leaders of a creek-monitoring workshop.
Thirteen people ranging in age from single-digits to their 70s tested the creek shallows with thermometers, probes and test tubes as part of the Acterra Stewardship Program. The monitoring workshop coincided with the World Water Monitoring Challenge, which encouraged communities to keep track of the health of local waterways and to enter the information into a database.
Palo Alto's Matadero Creek is a prime candidate for monitoring. Winding along Page Mill Road, it traverses many different terrains. It comes down from the Santa Cruz Mountains and crosses into the flatland neighborhoods of Green Acres and Barron Park. It runs through Bol Park and the Ventura and Midtown neighborhoods before emptying into the Palo Alto Baylands near the Emily Renzel Wetlands and into San Francisco Bay. Along the way, it can pick up pollutants and trash that impact insects, plants and wildlife. At times, fish and other creatures have suddenly died off in the creek, with populations taking decades to recover, according to scientists.
Matadero's name alludes to its history. Called the Arroyo del Matadero, or slaughtering place, it was the site of a Spanish ranch in the 1830s and 1840s. In more recent times, it was subject to a chemical cleanup from the Superfund cleanup Hillview-Porter site in Stanford Research Park in 1994. A 1982 wheelchair-cleaner spill from the Palo Alto VA Healthcare System caused a die-off of tree frogs that took 20 years to rebound, according to longtime residents. Then 40 gallons of water containing copper and nickel leaked into a storm drain and the creek from Communications and Power Industries (CPI) in 2008. The creek earned the dubious honor of being on Save The Bay's list of the top 23 trashiest waterways in the Bay Area that same year. In 2010, 25 gallons of white roofing material washed into the creek from a Xerox/VMWare building after a rainstorm.
The most recent assault on the creek's health occurred after motor oil dumped on the creek bank went under the soil surface on Stanford land, Acterra Senior Ecologist Claire Elliott said.
But despite all of those environmental attacks, the creek has showed a remarkable ability to recover. During the monitoring event, Elliott and the resident volunteers tested the water for salt content, oxygen levels, temperature and turbidity -- murkiness that is a detriment to fish finding food -- and they looked for telltale critters. Stonefly and mayfly larvae are sensitive to pollution; black flies tolerate pollution , she said.
"What lives in the creek tells us a lot about the water quality. If there are only slugs and snails, and worms that are tolerant to pollution, then you know there's a problem," she added.
Scuds -- tiny crustaceans -- are somewhat tolerant to pollution. The volunteers found them during their monitoring that day, along with stoneflies and mayflies. The latter two are a good sign. Their presence showed the creek was clean, she said.
Simran Kadadi, 12, a Challenger School student, used a conductivity meter to test the water's ability to pass an electrical current. Conductivity in water is affected by inorganic dissolved solids such as chloride, sulfate, sodium and calcium. Salts, for example, are harmful in large quantities to freshwater creatures, Elliott said.
Conductivity can also indicate the geology of a creek or stream, she added. Waterways running through granite bedrock have a lower conductivity than those flowing through limestone and clay. But high-conductivity readings can also indicate industrial pollution or runoff from streets and parking lots, she said. An oil spill can also lower conductivity, indicating the presence of pollutants.
Kadadi added a chemical to a water sample she captured in a test tube. Depending on the water color change, the reading will tell her whether the water has low or high oxygen levels. Low oxygen is harmful to fish and other oxygen-using creatures, but overly high levels can also be harmful, Elliott said.
All of the readings taken last week indicated this location in Matadero Creek was clean. But vigilance is important, Elliott said. Acterra scientists and volunteers will test the location and others each month.
On Friday, volunteers emptied another catch from their net into the water basin, spying a water worm. They didn't find any hatchlings of the endangered steelhead trout nor any tadpoles or other vertebrates.
Just then, Jake Murphrey of the AmeriCorps and the Civilian Conservation Corps Watershed Stewards Project, lifted a heavy rock in the gravelly shallows and fished out a crawdad. The small green lobster-like creature wriggled its claws in Murphrey's grasp. It was the largest creature the group found that day and another sign of the Matadero's health.
Acterra monitors six creeks each month. Trained volunteers work on Matadero, Barron and Adobe creeks. Three other creek-monitoring events are open to new members of the public two times each month at San Francisquito, Stevens and Permanente creeks.
To sign up for a creek-monitoring event, residents can visit www.acterra.org and follow the link to Eventbrite. In addition, National River Cleanup Day takes place on May 17. More information is available at www.cleanacreek.org.