Ask a biologist what the single-best indicator of the environmental health of an area is and you’ll likely get this answer: creeks.
Creeks are a landscape’s lifeblood. They are also where most of its pollutants wind up.
With this in mind, a group of staff members and volunteers with the Morro Bay National Estuary Program pulled on hip waders one recent morning and climbed down into a secluded stretch of Los Osos Creek in the Los Osos Oaks State Reserve for a morning of intensive creek monitoring.
Los Osos Creek is one of 10 creeks that are monitored within the Morro Bay watershed. The information these surveys generate is a vital tool for state and local regulators and resource managers alike.
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Creek monitoring is environmental science at its most basic. Meticulous work that is sometimes tedious, sometimes strenuous — lots of stooping and bending over — but is ultimately fascinating.
I know. I was one of the volunteers who participated in the Los Osos Creek monitoring. We monitored 150 meters, or nearly 500 feet, of the creek. I ended the day astonished at the number of different ways the health of a creek can be measured.
Looking for bugs
It is springtime, and that means macroinvertebrates were our quarry. Macroinvertebrates are insects large enough to be seen with the naked eye.
Some of these species spend the larval stages of their lives in creeks during spring. They are one of several indicators of the creek’s health, explained Adrienne Harris, the estuary program’s director.
“Knowing the health of the streams is important to the estuary program because they ultimately feed into Morro Bay,” she said.
A broad diversity of macroinvertebrate life is a sign of a healthy creek, Harris said. Some of these larval bugs can tolerate pesticides well; others cannot. Some like muddy creek beds; others need creek beds free of mud, with lots of big cobble.
Annie Gillespie, the program’s energetic monitoring manager, is in charge of the effort. She has undergone extensive training to ensure that the data collected meets scientific research standards.
That morning, we clambered down into the creek and entered a magical world of babbling water, dappled light and towering oaks and sycamores. We deposited our gear on the creek bank.
Our first job was collecting water samples. These are analyzed for a variety of qualities, including temperature, clarity and salinity.
“We do the water-quality sampling first before we muddy up the water by walking in it,” Gillespie said.
We then broke up into two teams. Volunteers B.K. Richard and Josh Troyer worked their way upstream, marking the creek at regular intervals with lettered flags.
They used bug nets to gather up insect larvae at regular intervals. They also measured how shaded the creek is and whether it is straight or sinuous.
“It’s a more natural pattern to have a creek meander,” Gillespie said. “This creek doesn’t meander much so that means it was probably straightened out at one time.”
The second team consisted of me, Harris and Gillespie. Our job was to analyze the characteristics of the streambed, or substrate as scientists call it.
Using the grid laid out by Richard and Troyer, we monitored 21 locations. At each stop, we took a long list of measurements and observations.
How wide is the creek? How deep is it? Is the surface of the water riffled or smooth? How big are the rocks in the creek bed? Are they rough or slimy? How much leaf litter and algae growth is there? How prone are the banks to erosion?
The answers to all of those questions were recorded on standardized forms that will be sent to the state’s Surface Water Ambient Monitoring Program, where the findings will be entered into a huge database.
After the monitoring was done, we slogged back to the starting point for the event everyone was waiting for. The contents of the bug nets were dumped out into sieves.
The mesh at the bottom of the sieves crawled with insect life ranging from beetles to small specks of larvae. Gillespie identified the bulk of the squirming mass as caddis fly, mayfly and black fly larvae.
Missing were what Gillespie calls large predators, such as stoneflies and dragonflies. The main reason for this is the fact that the creek bed here is too muddy and lacks the kind of large cobble those bugs like, she said.
We placed the contents of the bug nets into plastic bottles. Alcohol would later be added as a preservative and the bottles shipped to a laboratory in Idaho for detailed analysis.
Lab analysis is necessary in order to get an exact picture of the insects present. The difference between species at this larval stage sometimes comes down to how many legs the bug has or the shape of its mandible, Gillespie explained.
The lab will give the samples a ranking between 1 and 100 to indicate its biodiversity. Last year, the lab gave this section of Los Osos Creek a grade of 41, which falls in the “fair” category. Overall, the creeks in the Morro Bay watershed get a ranking of 63, in the “good” category.
The wealth of data generated by these surveys will inform the decisions made by government regulators, such as the state Department of Fish and Game, and resource management groups, like the estuary program.
“Creek monitoring helps us decide where we want to do projects in the future and whether the current projects we have are effective,” Harris said.
As a nonprofit group, the estuary program relies on volunteers. Between 18 and 20 volunteers typically participate in creek monitoring. They range from Cal Poly students to retirees.
Not all monitoring work is as time-consuming as macroinvertebrate sampling, which takes four to five hours to complete. Other sampling is done in an hour or two and is not so physically demanding, Harris said.
But some volunteers, such as nature enthusiast Richard, prefer the longer monitoring sessions. “This is fun because it lets me spend more time in the creek,” he said.
HOW YOU CAN HELP THE ESTUARY PROGRAM
To find out more about volunteering with the Morro Bay National Estuary Program, go to www.mbnep.org/get-involved/ or call 772-3834.