Oakland Watershed Rangers Assess the Health of Lake Merritt
Watershed Rangers in Teacher Lily Gee’s class at Lincoln Elementary School in Oakland had the opportunity to walk from their school to Lake Merritt to learn more about this special, brackish water habitat. Volunteers from Rotary Nature Center Friends (RNCF) helped our young scientists to test lake water quality using special scientific tools, and to observe plankton under microscopes.
“We love partnering with KIDS for the BAY. These relationships help to make our work more widespread and robust.”
David Wofford, Rotary Nature Center Friends Co-Chair
Students arrived at the Lake Merritt amphitheater on a bright, clear afternoon, eager to start the day’s activities. RNCF Co-Chair Katie Noonan gave a talk about the history of Lake Merritt and its first stewards. “Can anyone tell me who were the first stewards of Lake Merritt?” she asked. “The Ohlone People!” Bruk exclaimed. “Ms. Sabreena taught us all about the Ohlone People in our KIDS for the BAY! Program.” Katie replied, “This land was occupied and taken care of by the Ohlone People long before a lot of people from Europe arrived and forced them off their land. We want to keep talking about and honoring the Ohlone People for their past and present stewardship of this important habitat.”
Katie also spoke about Lake Merritt’s geographical changes over time. “During the Ice Age, there was a lot of ice at both of the Earth’s poles. The sea-level was a lot lower, and this region looked very different. In that time, this area was a huge marshland! Do you think the plants and animals that lived here thousands of years ago were the same ones that live at Lake Merritt today?” asked Katie. “No!” exclaimed Zoe. “I think the animals that used to live here went extinct because of climate change and because people built houses in their habitat.”
“It’s so meaningful to have taught hundreds of classes of students about Lake Merritt with Katie over the last seven years. Some of them are starting their first and second years of University now. One of them is a member of Nature Center Friends’ Board of Directors. It’s inspiring to see this work come full-circle.”
David Wofford, Rotary Nature Center Friends Co-Chair
Greater Farallones Naturalist and self-described Plankton Enthusiast Janai Southworth helped the young KftB scientists get a closer look at microscopic phytoplankton and zooplankton from Lake Merritt. “Who can tell me what plankton are?” asked Janai. “Tiny fish?” suggested Gabriel. “Like algae, but smaller!” said Carter. “We define plankton with a three-part definition. The first part is, plankton are alive. The second, plankton is in the water. Third, plankton are drifters.”
Janai explained the difference between phytoplankton and zooplankton. “Phytoplankton can photosynthesize and make their food from the sun’s energy, just like plants! Zooplankton must consume other organisms to survive.” Students took turns observing tiny plankton in water samples collected from Lake Merritt under a large field microscope with an iPhone attachment for easier viewing. Students experimented with adjusting the dials to focus the scientific instrument and observe the microscopic creatures.
Testing Water Quality
“What do you think the water quality is in Lake Merritt?” asked Katie. “Not so good,” Emily replied. “At my station, we are going to assess the five key indicators of lake health (Temperature, Dissolved Oxygen, pH, Conductivity and Salinity, and Turbidity). These are Lake Merritt’s vital signs. When you go to the doctor and she checks your blood pressure and listens to your heart, she is checking to see if you’re healthy. We’re going to be collecting scientific data to assess the water quality of Lake Merritt and to check that this special place is healthy. Why do you think it’s important for us to monitor lake health?” asked Katie. “If the vital signs are bad, it means the lake is unhealthy and the animals that live at Lake Merritt might get sick,” said Benjamin. “That’s right! In 2022, blooms of harmful algae caused the oxygen to drop to almost 0, suffocating hundreds of fish that lived in the lake,” Katie explained.
“What kind of an ecosystem is Lake Merritt?” Gabriel’s hand shot into the air. “An estuary!” he exclaimed. “An estuary is a place where different types of water meet,” added Bruk. “What kind of water do estuaries have?” asked Katie. “Brackish water,” replied Idris. “Lake Merritt experiences big swings in salinity. After a big storm with lots of rain, the water is fresher and the salinity is lower. In the middle of summer, when the weather is hot and there’s lots of evaporation happening and there hasn’t been any rain, the water will be saltier and Lake Merritt’s salinity will be higher. What do you think it is today?” asked Katie. “I think the water in Lake Merritt will be fresher and the salinity will be lower, because the weather is colder and we just had lots of rain,” said Ayden. “I agree with you,” said Katie. “We’re going to test the salinity of Lake Merritt today, to see if we’re right.”
Each pair of students used a hydrometer, a scientific instrument for measuring water salinity. Katie poured water samples from Lake Merritt, collected that morning, into each hydrometer for students to measure. Each pair shouted out the number on their hydrometer representing the salinity level. “Our hydrometer says 22!” said Phoebe. Bruk said, “We got 21!” Angelica said, “I think it’s somewhere between 21 and 22.” Students discussed amongst themselves and agreed on an average result. Florence recorded the salinity of Lake Merritt’s water on the Water Quality Report Card, where the previous group had already recorded measurements for temperature and dissolved oxygen. Students felt empowered to collect scientific data and take up their important roles as stewards of this special watershed habitat.
Discovering the Birds of Lake Merritt
David distributed bird guides to help students identify some of the lake’s avian residents. “Did you know that Lake Merritt was designated as a bird sanctuary over 150 years ago?” asked David. Students spotted snowy egrets wading through the shallows in search of food, ring-billed gulls perched on nearby benches and signposts, flocks of American coots floating lazily on the lake’s surface. They also observed ruddy ducks and double-crested cormorants. Students marveled at the biodiversity of the feathered residents of Lake Merritt.
David also spoke to students about the Oakland estuary watershed. “Can you point to the top of the watershed?” Students pointed to the top of the East Bay hills in this distance. “When rain falls on top of those hills, where does it go?” asked David. “The water flows down the mountain in creeks and streams, and eventually drains into Lake Merritt,” said Emily.
At the end of the day, students reviewed Lake Merrit’s ‘Water Quality Report Card’ to assess the data they collected. As a class group, students determined that Lake Merritt’s water quality was healthy after all, thanks to the care and attention of the Rotary Nature Center Friends, and the scientists and naturalists who volunteer their time and energy to care for this special ecosystem. Our young scientists left Lake Merritt feeling equipped and empowered to collect data and draw scientific conclusions about the health of their local lake, and take up their important roles as stewards of this special watershed habitat.