Without knowing what the foundation looked like, we cannot measure what is being lost.
Beneath the surface of the Salish Sea, trillions of glass-shelled organisms have been quietly sustaining a fifth of Earth's photosynthesis — yet no one had ever taken a full accounting of them. Canadian researchers have now compiled the first comprehensive inventory of the sea's 924 diatom species, drawing on more than two centuries of fragmented records to establish a baseline that science has long needed but never achieved. In a region home to nine million people and mounting industrial pressure, this quiet act of cataloguing becomes something larger: a way of knowing what exists before it is lost, and a foundation for measuring what comes next.
- A critical gap in marine science has persisted for over 200 years — no one had ever assembled a complete picture of which diatom species inhabit the Salish Sea, leaving the microscopic foundation of the entire food web undocumented.
- The stakes are high: diatoms drive 20% of global photosynthesis and act as early-warning indicators, meaning any undetected collapse in their diversity could silently unravel ecosystems supporting shorebirds, shellfish, fish, and whales.
- Rapid urbanization, industrial expansion, and heavy shipping traffic are already stressing the Salish Sea, yet without a baseline, scientists and policymakers had no way to measure what was being damaged or lost.
- A team of Canadian researchers has now closed that gap, integrating 11,469 historical and new records through old literature, microscopy, molecular sequencing, and community science to produce a checklist of 924 diatom taxa.
- The dataset is now in the hands of researchers and policymakers, enabling real-time detection of ecosystem shifts — and arriving in direct response to the United Nations' Plankton Manifesto calling for exactly this kind of foundational marine research.
Somewhere beneath the surface of the Salish Sea, trillions of microscopic organisms with glass-like shells are quietly performing roughly one-fifth of all photosynthesis on Earth. These are diatoms — single-celled algae that form the invisible foundation of the marine food web — and until now, no one had ever compiled a complete inventory of which species actually inhabit these waters.
A team of Canadian researchers has changed that. Their new checklist, published in the Biodiversity Data Journal, identifies 924 distinct diatom taxa drawn from 11,469 records spanning more than two centuries. It is the first comprehensive baseline of its kind for the Salish Sea, the body of water bordering British Columbia and Washington State — and it fills a gap that scientists had long recognized as critical.
The Salish Sea is far from pristine wilderness. Nine million people live along its shores, and the region faces mounting pressure from urbanization, industrial activity, and marine shipping. Diatoms respond quickly to shifts in water quality, temperature, and pollution, making them reliable early-warning indicators of ecosystem stress. Without knowing what the diatom community looked like before these pressures intensified, it was nearly impossible to measure what was being lost.
The research is a form of scientific archaeology. Historical diatom records from the region date to the 1800s, but they were scattered and incomplete. Ph.D. student Andrew Simon of the University of Alberta describes how the Salish Sea had been extensively studied for its larger marine life while its primary producers — the organisms at the very base of the food chain — remained poorly documented. The new checklist pulls those fragments together, integrating old literature, microscope analysis, and molecular sequencing contributed by both academic researchers and community scientists.
The work also answers a global call. The United Nations recently released the Plankton Manifesto, urging the scientific community to strengthen plankton research and build monitoring atlases to address climate change, biodiversity loss, and pollution. The Salish Sea checklist stands as a direct response — and a proof of concept that collaboration between institutions and community scientists can produce the kind of foundational knowledge the moment demands.
With the dataset now available to researchers and policymakers, the real work begins: detecting shifts in diatom communities, assessing whether the ecosystem is holding or fraying, and measuring change against a baseline that, for the first time, actually exists.
Somewhere in the waters of the Salish Sea, invisible to anyone looking down from a boat or shore, trillions of microscopic organisms are quietly doing the work that keeps the entire ocean alive. These are diatoms—single-celled algae with glass-like shells—and they are responsible for roughly one-fifth of all photosynthesis happening on Earth. Yet until recently, no one had bothered to make a complete inventory of which diatom species actually live in these waters, or how many there are.
That gap has just been closed. A team of Canadian researchers has compiled the first comprehensive checklist of diatoms in the Salish Sea, the body of water that borders British Columbia and Washington State. The list contains 924 distinct diatom taxa, drawn from 11,469 records spanning more than two centuries. The work appears in the Biodiversity Data Journal and represents something scientists have long recognized as essential but never quite managed to accomplish: a baseline against which to measure change.
The Salish Sea is not a remote corner of the ocean. It is home to roughly nine million people. The region is experiencing rapid urbanization, industrial expansion, and heavy marine shipping traffic. These pressures are real and mounting. Yet without knowing what the microscopic foundation of the food web looked like before these changes accelerated, it is nearly impossible to understand what is being lost or damaged. Diatoms respond quickly to shifts in water quality, pollution, and temperature. They are, in the language of ecology, early-warning indicators. If something is going wrong in the Salish Sea, the diatoms will show it first.
The research effort itself is a kind of archaeology. Historical records of diatoms in the region date back to the 1800s, but those early inventories were scattered and incomplete. Throughout the twentieth and twenty-first centuries, surveys came and went, leaving gaps. Andrew Simon, a Ph.D. student at the University of Alberta and one of the study's lead researchers, describes the problem plainly: the Salish Sea had been studied extensively for its larger marine life, but the history of research on its primary producers—the organisms at the very bottom of the food chain—had remained fragmented. No one had ever tried to pull all the pieces together.
The new checklist does exactly that. It integrates old literature, new microscope analysis, and molecular sequencing data contributed by academic researchers and community scientists working over many years. Mark Webber, a resident diatomist at IMERSS, one of the organizations behind the work, emphasizes what this means in practical terms: diatoms are vital to everything that lives in the sea, from shorebirds and shellfish to fish and whales. Without understanding the baseline of diatom diversity, it is impossible to understand how changes in that baseline will ripple outward through the entire web of life.
The timing of this work aligns with a broader global push. The United Nations recently released the Plankton Manifesto, calling on the scientific community to strengthen research on these microscopic organisms and develop comprehensive atlases to monitor marine ecosystem health. The manifesto frames plankton research as essential to addressing climate change, biodiversity loss, and pollution. The Salish Sea checklist is a direct response to that call—a proof of concept that sustained collaboration between community scientists and research institutions can bridge the gap between observation and technology, between local knowledge and scientific rigor.
What happens next is the real work. The checklist and dataset are now available to researchers and policymakers tasked with environmental assessments of the region. As the team continues to refine and analyze the data, they will be able to detect shifts in diatom communities that signal broader changes in the ecosystem. They will be able to answer questions about whether the Salish Sea is becoming healthier or sicker, whether interventions are working, whether the food web is holding or fraying. For the first time, they will have a clear picture of what was there before, and a way to measure what comes next.
Notable Quotes
The Salish Sea has long been studied for its rich marine biodiversity. Yet, until now, the history of research on its primary producers has been fragmented, and we have lacked a consolidated baseline record.— Andrew Simon, Ph.D. student at the University of Alberta and study researcher
Diatoms are vital to the health of countless organisms—from shorebirds and shellfish to fish and mammals. This baseline provides a reference point for understanding changes that could ripple across the entire web of life.— Mark Webber, resident diatomist at IMERSS
The Hearth Conversation Another angle on the story
Why does it matter that we now have a list of 924 diatom species? Couldn't we just monitor water quality directly?
Water quality tests tell you what's in the water right now. Diatoms tell you what the water has been like, and how fast things are changing. They're living sensors. If the diatom community shifts, it means something fundamental has shifted.
But they're invisible. Most people will never know these organisms exist.
That's exactly the problem. We've built our understanding of the ocean around the things we can see—fish, whales, kelp forests. But those things eat diatoms. If the diatoms disappear or change, everything else collapses. We just can't see it happening until it's too late.
So this checklist is like a before picture?
Exactly. For two hundred years, people have been studying the Salish Sea, but no one ever said, "Here's what the foundation looks like." Now we have that picture. In ten years, we can take another picture and see what's different.
What would a bad change look like?
Pollution-tolerant species replacing sensitive ones. Invasive diatoms outcompeting native ones. Sudden drops in diversity. Any of those would mean the ecosystem is under stress. And because diatoms respond so quickly, we'd know about it before the fish populations crashed.
And this was done by combining old records with new research?
Yes. Some of the data goes back to the 1800s. But it was scattered across different studies, different researchers, different institutions. No one had ever consolidated it. That's what makes this baseline so powerful—it's not just new data. It's the full historical record, finally in one place.