Guest Columnist: Marilyn Browning Vogel, Professor, Diablo Valley College
The Peterson benthic grab
The Ocean 102 lab at Diablo Valley College in Pleasant Hill is a proper marine biological laboratory. It smells faintly of seaweed and formaldehyde, while fearsome, plastic versions of marine predators (sharks that happen to squeak) hang from the ceiling. A somewhat functional soldering iron sits on the counter in the supply room next to an open box of Girl Scout cookies. The Peterson benthic grab, a heavy jaw-like affair attached to a long rope sits in the supply room. Pity the TA who has forgotten to rinse it off since its last use at the various shoreline localities where Ocean 102 lab sections collect samples. As its name suggests, the Peterson benthic grab grabs the benthic, the benthic being the mud, rock and organisms that make up the bay floor. The benthic grab collects a known surface area of the sediment and allows oceanography students (or the marine scientists they hope to become) to tally the type and number of organisms found in that particular patch. After rinsing off the mud, Ocean 102 students will pluck out various species of worms, shrimp and clams that live on the bottom of the Bay, and mark them down on official laboratory tally sheets.
Nearly every semester, after sampling bay mud from Berkeley to Pittsburg, Ocean 102 students discover an astonishing surfeit of a tiny clam known as Potamocorbula Amurensis. One of the clam’s shells tends to be larger than the other, making it easy to identify according to its informal name, the ‘overbite clam’. Back in the lab, students will spend many hours assembling little piles of Potamocorbula shells, and learning the lessons it has to teach about how estuarine ecosystems work.
Dr. John Freytag is a professor of biology and director of the Diablo Valley College oceanography program. Dressed in flip-flops and a faded blue shirt, he is a proper marine biologist, on whom falls the task of turning Potamocorbula into a teachable moment. “With the sampling we do, it’s an interesting opportunity to look at snapshots of what’s happening in the Bay throughout the year, and we see fluctuations. There will be times particularly in the spring where we see a lot of dead or empty shells. If huge amounts of fresh water were allowed to flow through the Bay, it would effectively push Potamocorbula further west.”
Potamcorbula’s remarkable abundance is also a teachable moment about invasive species and community science. The clam arrived in the Bay sometime around 1986 as floating larvae in the ballast water of cargo ships arriving from Asia. (Potamocorbula is also referred to as the ‘Asian clam’.) The organism can tolerate a wide range of salinities and makes strident incursions deep into the Bay Delta, especially during times of drought, when freshwater outflows are absent.
“Some of the species that arrive in ballast water prove to be devastating,” Freytag explains to his students. “The estuary here is considered to be the most highly invaded estuary in the world, which is not a title you want to hold.”
Like many sessile, benthic organisms, Potamocorbula is a filter feeder, meaning that it sucks in water and harvests plankton caught in the intake. Due to its abundance, scientists estimate that Potamocorbula can currently filter feed on a volume of water equal the entire volume Suisun Bay, in one day. As it vacuums up the plankton that form the base of the food web, the clam has decimated native fish populations and changed some of the most basic characteristics of the bay ecosystem, ranging from the structure of the food web to the color and clarity of the water.
While its name is a mouthful, Potamocorbula is unfortunately inedible, even for many non-human consumers. Sturgeon feed on the clam but scientists have found that it can pass straight through the sturgeon digestive track, alive and well, landing wherever the tides or alimentary elimination will carry it. The clam does serve as a food source for ducks and even the native dungeness crab, which use the lip of the clam’s overbite to pry it apart.
The clam itself can eat a wider range of planktonic organisms than scientists had previously believed possible. In addition filtering microscopic algae out of the water column, Potoamocorbula also feeds on bacteria and tiny crustaceans known as copepods. A study in 1991 found that Potamocorbula had reduced populations of the three most common types of copepods by as much as 53-91%, and could consume as much at 8% of the juvenile population per day. It’s nothing personal, Potamocorbula also eats its own larvae, but not in quantities sufficient to overcome its ability to lay 45,000 – 220,000 eggs during a given breeding season, or as in the case of a drought, continuously throughout the year.
As Ocean 102 students tally their shells and learn about plankton, food webs and invasives, they seldom appreciate the historical role their laboratory course has played in the Potamocorbula saga. Dr. Bill Stevenson founded the Diablo Valley College Oceanography program and orchestrated its first training cruises in 1974. Later joined by his partner Dianna Matthias, Stevenson oversaw the lab sections and students that discovered some of the first Potamocorbula specimens ever observed in the San Francisco Bay. I spoke with them recently at their home in Martinez. “This was in 1986,” he told me. “It was three clams that the kids found that they couldn’t identify. It looked like a clam that had an overbite. One shell is bigger than the other. So I put some students on it, said ‘why don’t you kids research this?”
In the case of this particular invasion, the clam itself may have traveled faster through the Bay Delta ecosystem than news of its arrival. It wasn’t until two years later in 1988 that Stevenson and his students got word that that the U.S. Geological Survey (USGS) had identified a clam with an overbite that was taking over. After a few phone calls Stevenson realized that the DVC training cruise samples may have contained some of the first documented occurrences of the organism. “We went back through samples and found lots of them,” he says. Three Potamocorbula in the Suisun Bay benthic grab samples collected by DVC Oceanography students in October 1986 became the earliest documented occurrence of the organism at that locality. Ocean 102 data helped the USGS pinpoint Potamocorbula’s arrival and understand its immediate and devastating expansion.
As with many ecological threats to the Bay Delta, Potamocorbula’s invasion resulted from a Gordian knot of economic, environmental and logistical factors. From 1987 to 1992, California experienced its most severe drought since the 1930s. The year before the drought began had been a record year for rain. The San Francisco Estuary swelled with spring floods so powerful that they ripped out the existing benthic communities of the inner estuary and carried them out to sea. This was a one-two punch for the Bay. The floor of the upper estuary was a blank slate of benthic habitat, free for the taking.
One thing that keeps Potamocorbula in check is fresh water, which would have been in extremely short supply for the five years following the 1986 floods. With no freshwater flushing, Potamocorbula spread deep into the upper estuary. “The numbers early in the invasion were pretty surprising but we had no idea Potamocorbula would persist and become a member of the North Bay community,” wrote Dr. Jan Thompson in an email to me on the topic.
Thompson is a hydrodynamic engineer at the USGS in Menlo Park. She also has a degree in ecology and has studied Potamocorbula since its 1986 debut. “Essentially all of the bivalves in the Bay are exotics and they move around as salinity changes. Most of these bivalves are reasonably good at osmo-regulating, but none of them come close to Potamocorbula. There were no persistent populations of bivalves in the North Bay until it arrived.” This is to say that the natural variability of salinity in the Bay and Delta keeps the ecosystem in flux, theoretically fostering a much higher level of diversity. Static conditions, on the other hand, can favor takeover by a single organism.
Similar to a military campaign, once the line of defense was broken, the invaders poured in and took over. “It was amazing when I started going out in 1991,” Dianna Matthias told me. She had just begun teaching Ocean 102 and taking students on research cruises at the height of the 1987-92 drought. “Sometimes we’d bring up a bottom grab and think it was sand…. Each little grain was a tiny, tiny little clam. I mean, it was in the millions or billions even! At that time, I started figuring there was something going on and it didn’t look good.”
Limnologists sometimes describe clams, bivalves and other mollusks as ‘ecosystem engineers.’ Mollusks are called thus because they filter the water column, help link up the aquatic food web, and contribute shell material to benthic habitat. In ecosystems like the Chesapeake Bay, the loss of oyster beds has left the water column a murky, anoxic soup riddled with too many jellyfish. Potamocorbula’s re-engineering of the San Francisco estuary has created the opposite problem. The millions of invasive filter feeders now make the water too clear and the vast blooms of plankton that once nourished many species now mostly nourish just one: the overbite clam. The precipitous decline in native fish populations, especially in the early 2000s, was due to myriad factors, but Potomocorbula certainly contributed to the crash.
Thirty years later, Ocean 102 is still keeping an eye on Potamocorbula, along with the US Geological Survey and other agencies. Increased awareness of Potamocorbula’s effects helps policy makers protect habitat and endangered species like the Delta smelt. Environmental groups have begun calling for protection plans that manage Potamocorbula and other bivalves that threaten the smelt’s food supply. New Zealand, a nation known for its innovative approaches to protecting native species, got out in front by issuing a management plan for Potamocorbula back in 2001. Perhaps the most hopeful aspect of the Potamocorbula’s invasion is how little we know about the organism. The US Geological Survey’s Jan Thompson points out that while mechanisms for long distance transport of the bivalve are in place, Potamocorbula doesn’t seem to have taken to other west coast estuaries. These estuaries enjoy greater volumes and more natural cycles of freshwater flow compared to the San Francisco Estuary.
John Freytag is also optimistic, but as a teacher that’s kind of his job. This September, Ocean 102 surveys found a handful of Potamocorbula juveniles in their sediment samples but only a few full grown shells. Certain surveys over the last few semesters have similarly yielded only limited evidence of mature individuals. Whatever the next chapter, Ocean 102 will grab on to it.
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Hothouse Earth
By Ariel Rubissow Okamoto
Photo by Megan Nguyen
Nothing could be stranger than sitting in the dark with thousands of suits and heels, watching a parade of promises to decarbonize from companies and countries large and small, reeling from the beauties of big screen rainforests and indigenous necklaces, and getting all choked up.
It was day two of the September 2018 Global Climate Action Summit in San Francisco when I felt it.
At first I wondered if I was simply starstruck. Most of us labor away trying to fix one small corner of the planet or another without seeing the likes of Harrison Ford, Al Gore, Michael Bloomberg, Van Jones, Jerry Brown – or the ministers or mayors of dozens of cities and countries – in person, on stage and at times angry enough to spit. And between these luminaries a steady stream of CEOs, corporate sustainability officers, and pension fund managers promising percentages of renewables and profits in their portfolios dedicated to the climate cause by 2020-2050.
I tried to give every speaker my full attention: the young man of Vuntut Gwichin heritage from the edge of the Yukon’s Arctic National Wildlife Refuge who pleaded with us not to enter his sacred lands with our drills and dependencies; all the women – swathed in bright patterns and head-scarfs – who kept punching their hearts. “My uncle in Uganda would take 129 years to emit the same amount of carbon as an American would in one year,” said Oxfam’s Winnie Byanyima.
“Our janitors are shutting off the lights you leave on,” said Aida Cardenas, speaking about the frontline workers she trains, mostly immigrants, who are excited to be part of climate change solutions in their new country.
The men on the stage, strutting about in feathers and pinstripes, spoke of hopes and dreams, money and power. “The notion that you can either do good or do well is a myth we have to collectively bust,” said New Jersey Governor Phil Murphy whose state is investing heavily in offshore wind farms.
“Climate change isn’t just about risks, it’s about opportunities,” said Blackrock sustainable investment manager Brian Deese.
But it wasn’t all these fine speeches that started the butterflies. Halfway through the second day of testimonials, it was a slight white-haired woman wrapped in an azure pashmina that pricked my tears. One minute she was on the silver screen with Alec Baldwin and the next she taking a seat on stage. She talked about trees. How trees can solve 30% of our carbon reduction problem. How we have to stop whacking them back in the Amazon and start planting them everywhere else. I couldn’t help thinking of Dr. Seuss and his truffala trees. Jane Goodall, over 80, is as fierce as my Lorax. Or my daughter’s Avatar.
Analyzing my take home feeling from the event I realized it wasn’t the usual fear – killer storms, tidal waves, no food for my kids to eat on a half-baked planet – nor a newfound sense of hope – I’ve always thought nature will get along just fine without us. What I felt was relief. People were actually doing something. Doing a lot. And there was so much more we could do.
As we all pumped fists in the dark, as the presentations went on and on and on because so many people and businesses and countries wanted to STEP UP, I realized how swayed I had let myself be by the doomsday news mill.
“We must be like the river, “ said a boy from Bangladesh named Risalat Khan, who had noticed our Sierra watersheds from the plane. “We must cut through the mountain of obstacles. Let’s be the river!”
Or as Harrison Ford less poetically put it: “Let’s turn off our phones and roll up our sleeves and kick this monster’s ass.”
4th California Climate Change Assessment Blues
by Isaac Pearlman
Since California’s last state-led climate change assessment in 2012, the Golden State has experienced a litany of natural disasters. This includes four years of severe drought from 2012 to 2016, an almost non-existent Sierra Nevada snowpack in 2014-2015 costing $2.1 billion in economic losses, widespread Bay Area flooding from winter 2017 storms, and extremely large and damaging wildfires culminating with this year’s Mendocino Complex fire achieving the dubious distinction of the largest in state history. California’s most recent climate assessment, released August 27th, predicts that for the state and the Bay Area, we can expect even more in the future.
The California state government first began assessing climate impacts formally in 2006, due to an executive order by Governor Schwarzenegger. California’s latest iteration and its fourth overall, includes a dizzying array of 44 technical reports; three topical studies on climate justice, tribal and indigenous communities, and the coast and ocean; as well as nine region-specific analyses.
The results are alarming for our state’s future: an estimated four to five feet of sea level rise and loss of one to two-thirds of Southern California beaches by 2100, a 50 percent increase in wildfires over 25,000 acres, stronger and longer heat waves, and infrastructure like airports, wastewater treatment plants, rail and roadways increasingly likely to suffer flooding.
For the first time, California’s latest assessment dives into climate consequences on a regional level. Academics representing nine California regions spearheaded research and summarized the best available science on the variable heat, rain, flooding and extreme event consequences for their areas. For example, the highest local rate of sea level rise in the state is at the rapidly subsiding Humboldt Bay. In San Diego county, the most biodiverse in all of California, preserving its many fragile and endangered species is an urgent priority. Francesca Hopkins from UC Riverside found that the highest rate of childhood asthma in the state isn’t an urban smog-filled city but in the Imperial Valley, where toxic dust from Salton Sea disaster chokes communities – and will only become worse as higher temperatures and less water due to climate change dry and brittle the area.
According to the Bay Area Regional Report, since 1950 the Bay Area has already increased in temperature by 1.7 degrees Fahrenheit and local sea level is eight inches higher than it was one hundred years ago. Future climate will render the Bay Area less suitable for our evergreen redwood and fir forests, and more favorable for tolerant chaparral shrub land. The region’s seven million people and $750 billion economy (almost one-third of California’s total) is predicted to be increasingly beset by more “boom and bust” irregular wet and very dry years, punctuated by increasingly intense and damaging storms.
Unsurprisingly, according to the report the Bay Area’s intensifying housing and equity problems have a multiplier affect with climate change. As Bay Area housing spreads further north, south, and inland the result is higher transportation and energy needs for those with the fewest resources available to afford them; and acute disparity in climate vulnerability across Bay Area communities and populations.
“All Californians will likely endure more illness and be at greater risk of early death because of climate change,” bluntly states the statewide summary brochure for California’s climate assessment. “[However] vulnerable populations that already experience the greatest adverse health impacts will be disproportionately affected.”
“We’re much better at being reactive to a disaster than planning ahead,” said UC Berkeley professor and contributing author David Ackerly at a California Adaptation Forum panel in Sacramento on August 27th. “And it is vulnerable communities that suffer from those disasters. How much human suffering has to happen before it triggers the next round of activity?”
The assessment’s data is publicly available online at “Cal-adapt,” where Californians can explore projected impacts for their neighborhoods, towns, and regions.
DOWNLOAD the September 2016 Issue PDF
The results are alarming for our state’s future: an estimated four to five feet of sea level rise and loss of one to two-thirds of Southern California beaches by 2100, a 50 percent increase in wildfires over 25,000 acres, stronger and longer heat waves, and infrastructure like airports, wastewater treatment plants, rail and roadways increasingly likely to suffer flooding.