A bat ray skates under the pedestrian bridge and into Lake Merritt. Since the implementation of Measure DD, which has allowed tidal flow to enter Lake Merritt, biodiversity in the lake has improved. Credit: Pete Rosos

Damon Tighe is no casual Lake Merritt visitor. The citizen scientist steps around picnickers, turns over rocks on the shore, and even wades through the water, his eyes alert for the smallest critters. One August afternoon five years ago, Tighe was on his knees near the boating center on the north side of the lake when he spotted a clump of mussels attached to the underside of a dock. When he looked closer, something moved. He pulled out a jar and coaxed the tiny animal inside and sealed it shut.

Back at his apartment not far from the lake, Tighe placed the wriggling creature on an empty asparagus tray from Trader Joe’s. He waited until it was dark, triggered a flash, and took the animal’s portrait. Its identity puzzled him, but after consulting a few naturalist websites and forums, Tighe identified it: Megasyllis nipponica, a marine segmented worm native to the waters around Japan. But what was it doing in the lake? How did it get there?

This year, Oaklanders will celebrate Lake Merritt’s 150th anniversary as the country’s first wildlife refuge. But the lake, once called the “Lake of 1,000 Smells,” has never quite been able to shake off its reputation as a polluted cesspool. Some people assume that the urban body of water is man-made, unnatural, and inhospitable to wildlife. Since the city was founded in 1852, the plants, animals, and other life that live in Lake Merritt have struggled with poor water quality and trash.  

However, its waters are far from empty. More than 600 species have been identified at Lake Merritt, including non-native lifeforms from all over the world. Among them are Tighe’s worm, and species that have not been found anywhere else on Earth.

Tighe is one member of a small community of naturalists who have been scouring the waters of Lake Merritt for decades, collecting and identifying the creatures lurking just beneath the surface. These professional and volunteer scientists have been telling the lake’s biological story, documenting what lives in the water and on the shores. In the process, they are helping retell Lake Merritt’s history through the organisms that inhabit it, revealing the lake’s beauty and, they hope, inspiring further restoration of the natural environment.

With dead man’s fingers and sea squirts in hand, naturalist Damon Tighe stands on a small rocky outcropping on the southern end of Lake Merritt. Credit: Pete Rosos

Invaders of a biodiverse tidal lagoon

Lake Merritt is not a man-made lake at all, but a tidal lagoon that formed 10,000 years ago at the end of the last Ice Age. Rising sea levels carried water from the Pacific Ocean inland, washing away ancient animals like giant ground sloths and saber tooth cats. The water settled and a tidal lagoon formed, connected to the Bay by a rivulet that carried a steady stream of saltwater and wildlife from the ocean. Natural creeks flushed freshwater from winter rains into the eastern edges of the lake, creating a brackish environment. 

Even before Oakland became a city, creatures began to arrive at Lake Merritt from all over the world, clinging to the bottom of boats docked at San Francisco Bay, and some boats that even traveled up the channel and into the lake. Homesick for the familiar wildlife of New England, settlers sent for railcars full of geese, Atlantic oysters, and striped bass, which rode across the country to California along the Trans-Continental Railroad and were introduced to the estuary. 

The San Francisco Bay is now home to at least 300 non-native species, according to Jim Carlton, who grew up studying Lake Merritt in Oakland as a high schooler and is now a leading expert on invasive species at Williams College. And the new species keep coming. “Not a year goes by that we don’t see something new in San Francisco Bay,” Carlton said.

Today, the lagoon remains connected to the Pacific Ocean through the same rivulet, now called the Lake Merritt Channel. Water from the Pacific Ocean flows into the Bay underneath the Golden Gate Bridge, toward the Alameda Waterway, and into the channel. These tidal flows carry all sorts of life under the I-880 Freeway, past Laney College, and underneath a green pedestrian bridge on the south side of Lake Merritt before delivering them into the lagoon.

Megasyllis nipponica, a marine worm native to Japan, now thrives in Lake Merritt. Credit: Damon Tighe

Recently, sea lions and river otters have found their way to the lagoon. Over the years, bat rays, salmon, sturgeon, jellyfish, and leopard sharks have navigated the channel into the lake. Fishermen still famously pull striped bass out of the lake’s deepest waters. And every year in the early fall, Lake Merritt will glow blue under a full moon thanks to dinoflagellates, tiny one-celled bioluminescent organisms. Even Lake Merritt’s most committed naturalists are surprised at the variety of life that call it home. 

“Within one day, I have seen organisms I never would have imagined in the lake. These giant spaghetti worms as thick as a human thumb with a giant gnarl of more or less arms at the top,” said Tighe. “I would only imagine this crazy foreign organism out of National Geographic in some tropical area, and there it is, stuck in the mud at Lake Merritt.”

Though the waters continue to teem with wildlife, Lake Merritt has not escaped the effects of urbanization. The most impactful invasive species were the American settlers who founded Oakland and built the city around the lake. In the mid-1800’s, Lake Merritt became Oakland’s toilet: creeks that once filtered water and hosted wildlife were converted to concrete drains that dumped stormwater into the lagoon and by 1884, 90% of the city’s sewage wound up in the waters. Wetland habitats gave way to busy streets, thousands of pounds of trash polluted the water, and the amount of dissolved oxygen, necessary for aquatic life to survive, tanked.

Polyorchis penicillatus, a jellyfish observed in Lake Merritt. Credit: Damon Tighe

‘Rewilding’ Lake Merritt

At some point in the early 2000s, Tighe joined a community nature walk around Lake Merritt hosted by Joel Peter, then the program manager for Measure DD, a $200 million bond measure approved by voters in 2002 to improve Lake Merritt, including projects intended to cleanse the lake’s waters. As they walked along the lake’s edge, Peter explained how Measure DD could “rewild” Lake Merritt by strengthening its connection to the Pacific Ocean. Tighe became fascinated with the idea that the critters in Lake Merritt could start thriving within a matter of years and new life would enter through the channel.

“I learned about the work being done to rewild Lake Merritt, to get rid of these obstacles that made the lake the cesspool everybody imagined it to be,” said Tighe. “After that walk, I started going down to the lake regularly, grabbing one or two critters, and documenting what organisms there are and seeing if they’re changing in the next few years,” Tighe said.

From 2003 until his retirement in 2012, Peter oversaw a number of improvements to Lake Merritt. Using Measure DD funds, the team installed storm drain filters to catch trash before it ended up in the water. They erected additional aeration fountains for a total of four to improve oxygenation levels in the water. Of particular significance was the effort to widen the Lake Merritt Channel at 10th and 12th streets to improve the tidal flow from the Bay. Twelfth Street, which borders the lagoon’s south side, was converted from a 12-lane freeway to a quieter four-lane boulevard with bike lanes. Natural habitats were restored, including a wetland area at Peralta Park on each side of the channel between 12th and 10th streets. Outside of the effort to improve water quality, Measure DD funds have also been used to renovate Children’s Fairyland, restore the boathouse, and construct the East Oakland Sports Center, among other improvements.

Illegal dumping remains a problem for the water quality, but the total trash volume has decreased. While a team from the Lake Merritt Institute empties about 20,000 pounds of trash each year from the lake, it’s far less than the 60,000 pounds of trash cleared in 2005. The storm drain filters have made a difference, as did Oakland’s ban on styrofoam containers in 2006 and the city’s 2007 plastic bag ban.

As diverse as the critters are, the trash that volunteers have pulled out of the lagoon is even more various. The bizarre smorgasbord of items removed from the lake include: a gerbil in a tiny casket, decapitated birds in a white pillowcase, a homemade crucifix, a briefcase stuffed with credit cards, a bag of human ashes (turned over to the coroner), an entire dumpster, love letters, a game of Mahjong, and hundreds of e-scooters. In 2018, it took a team half a day working with a truck and crane to extract a grand piano from the lake bottom. 

Naturalist and Rotary Nature Center Friends founder Katie Noonan has been keeping track of Lake Marritt water quality for years. Credit: Pete Rosos

Stunted water quality improvements

Though millions of Measure DD dollars have gone toward improving the water quality in Lake Merritt, the amount of dissolved oxygen in the water hasn’t increased. A 2015 study carried out by expert consultants for the city of Oakland found no improvement over a 10-year period.

The longest-spanning study of Lake Merritt’s water quality comes from Katie Noonan, a recently retired high school science teacher and long-time steward of Lake Merritt. Noonan and the biology students at Oakland Senior High School consistently measured the water quality since 1996, an effort Noonan has continued even after retirement in 2014 with a new crop of science teachers and the help of former students. Their research confirms that water quality has remained poor, even after Measure DD improvements around the lake. “There has been no detectable change in water quality, no increase in dissolved oxygen since that time,” Noonan said.

Sean Maher, a spokesperson for the city of Oakland, wrote in an email to The Oaklandside that more research needs to be done to determine the impact of Measure DD on the water quality in Lake Merritt, since the project to widen the 10th street channel was completed a year after the formal 2015 study.

The problem appears to lie with the 7th street tidal gates, essentially large doors that can open and close to allow different amounts of water to pass under the roadway and through the channel connecting Lake Merritt to the Bay. A wider channel should mean more tidal waters flushing the lake out and improving the dissolved oxygen concentration. But for years, Alameda County has kept the gates partially closed in order to regulate flooding. Rather than closing the gates when the risk of flooding is high and opening them when it isn’t, half of the gates have been permanently shut, preventing the constant flushing needed to improve the water quality.

“This restricts the water flow and puts us back into almost the same place we were before the Measure DD projects were built,” Peter said. “While the outlook right now is a bit dismal, these issues are certainly fixable, if there is the political will.” 

In response to the problem, Kristin Hathaway, the current manager of Measure DD implementation, hired hydrologist consultants a few months ago to develop a plan that would balance flood regulation and water quality. She anticipates hearing back about the plan in a few weeks and could make recommendations to the county to allow more water to flow into the lake.

Ficopomatus enigmaticus, an Australian tubeworm observed by Katie Noonan at the lake in 2019. Credit: Katie Noonan

Mysterious creatures, curious humans

In 1962, a 14-year-old Jim Carlton wandered away from his family picnic and onto the shore at Adam’s Point on the northern side of Lake Merritt where he stepped on something peculiar. He slipped what appeared to be a white, crumbling rock into a bag and took it home. With the help of the Rotary Nature Center, Carlton identified the object as a clump of tubeworms from thousands of miles away in the Pacific Ocean’s tropical South Seas. Pulled by the allure of faraway places, Carlton soon began spending his free time collecting anything that moved at Lake Merritt.

“At the time, nobody much knew what was in the lake,” Carlton said. For help with his identifications, he inquired with the California Academy of Sciences and zoologists at UC Berkeley. Soon, he was sending samples to experts around the world in letters that read, “Lake Merritt Biological Survey.” Some of the species had never been seen before. 

Carlton helped determine that Lake Merritt was “a real epicenter of invasions” of plant and animal species from around the world, and he went on to become one of the foremost experts in the global movement of species over the course of the last 1,000 years. “I stepped on some tube-worms and that led to a career,” Carlton said.

Naturalists like Tighe and Noonan have been carrying on Carlton’s work by identifying an ever-expanding number of species in Lake Merritt. While no comprehensive studies have been done comparing the biodiversity of Lake Merritt at different points in its history, the efforts of the citizen scientists help paint a picture of the changing wildlife.

Though the dissolved oxygen hasn’t improved much, the salinity of Lake Merritt has changed. When Carlton came back to survey the lake in 2016 with Dr. Andrew Chang, a scientist from the Smithsonian, they found that the balance of species in the water had shifted. It was a distinctly saltier body of water than it had been four decades ago, evidence of some tidal flushing at work. 

“The whole signature of the lake seemed to be much more marine, more salty. There were a lot more fully saltwater species than I had ever seen,” Carlton said of Lake Merritt in 2016. The saltwater Atlantic mud snails and Eastern oyster drills were rare sightings in the 1960s, but now they were everywhere in the lake. The new marine arrivals include colorful sea squirts like the star and chain tunicates, which are small invertebrate animals that live in colonies. Purple Bugula neritina, and abundant algae, has also recently arrived in the lake.

A yellow shore crab and striped bass swim past one of the Lake Merritt Underwater Observatory’s submersible robots in 2019.

To better understand Lake Merritt and its changing character, citizen scientists have organized a number of projects to document the species that call it home. Building off of Carlton’s work, Noonan started the Lake Merritt Citizen Monitoring Study in 2017 to sample species from the same shoreline sites that Carlton studied in 1966, including the Japanese Bubble Snail and the Australian tubeworm. Along with her ongoing work at the Rotary Nature Center, Noonan’s latest effort is a documentary celebrating Lake Merritt’s 150th anniversary as a wildlife refuge, which will be released in the fall.

In partnership with California Academy of Sciences, Tighe has organized three “bioblitzes” for the City Nature Challenge, bringing people together in workshops to identify massive numbers of species. Tighe brought DNA analysis into the mix in Barcode the Lake, a 2017 project to get the public to not only identify species based on their physical traits, but to also sequence their DNA.

Citizen scientists participating in these projects log their findings on iNaturalist, an app started by Ken-ichi Ueda in 2008 as part of his Masters thesis at UC Berkeley. Now, it’s among the world’s most popular nature apps, allowing people to record and identify lifeforms they observe. Currently, there are at least 8 iNaturalist projects focusing specifically on Lake Merritt.

Beginning in 2014, Noonan’s students built three underwater robotic vehicles called OpenROVs to take a more intimate look at the wildlife. Field notes from the Lake Merritt Underwater Observatory are published on National Geographic’s website. The excursions provide an honest view of the lagoon. On the one hand, they showcase the natural beauty and biodiversity of Oakland’s crown jewel. On full display are the crabs, invertebrates, colorful sponges, pipefish (a kind of seahorse), and striped bass that bring its waters to life. But there’s also the trash, overgrown by organisms and incorporated into the habitat. Along with the usual array of glass shards and hypodermic needles, Noonan’s students have discovered some disturbing oddities from the lake bottom including the wallet of a murder victim.

Antiopella barbarensis, a sea slug, observed by Damon Tighe near the eastern shore of Lake Merritt in 2016. Credit: Damon Tighe

Harmful past, hopeful future?

As many species as naturalists have identified at Lake Merritt in recent years, they have only scratched the surface of what there is to learn about the lagoon and by extension, the natural world and humans’ impact on it. 

“We barely understand what goes on at Lake Merritt, which is right under our noses everyday, let alone other biological areas being impacted by modernization and industrialization,” Tighe said. Urbanites tend to see nature as something that exists “out there,” far beyond the confines of our cities. But the efforts of naturalists like Tighe and Noonan bring our attention to the natural history unfolding in downtown Oakland. 

In the lake’s natural history, humans represent a tiny blip in time. Except for the indigenous people here before colonization, the human influence on the lake has been overwhelmingly harmful. 

“We can reflect on several generations of how people have interacted with the waters we call Lake Merritt: Exploitation, expansion, development, pollution, recognition, improvement and appreciation,” wrote Dr. Richard Bailey, who founded Lake Merritt Institute in 1992. Bailey urged Oaklanders to consider their relationship to Lake Merritt as a proxy for their relationship to the natural world writ large. “One thing is certain. The Lake will be here; how shall we relate to it?”

Like other coastal cities, Oakland faces rising sea levels, air pollution, population rise and the trash that comes with it, and a host of other challenges, many of which disproportionately impact the lives of people of color.

“Lake Merritt is a microcosm of what’s going to be happening up and down the coast,” Noonan said. But she is hopeful that Lake Merritt could be the point of inspiration for a new generation of environmental stewards.  

“Lake Merritt is the living room of Oakland. Thousands of people come by Lake Merritt every day, to picnic, to protest, and to enjoy nature,” Noonan said. For that reason, she believes it is an ideal place to educate people about the organisms that inhabit the lake and how we can protect their habitat from degradation. 

“My big hope is that Lake Merritt can inspire curiosity,” said Tighe. “That curiosity can make people better understand their interconnectedness with the environment and the ramifications of their actions on the world around them.”