A new, consolidated checklist of diatoms—a major group of photosynthetic microalgae—has been compiled for the Salish Sea, northeast Pacific, by a team of Canadian scientists. Integrating historical records with new reports, this first comprehensive baseline establishes a foundation for assessing diatom diversity in the region. As primary producers at the base of marine food webs, diatoms are key indicators of environmental change, providing critical insight into the health and resilience of the Salish Sea bioregion. The checklist is now published in the open-access Biodiversity Data Journal.

Though invisible to the naked eye, the ecological importance of phytoplankton continues to be underestimated. Recently, the UN Global Compact released "The Plankton Manifesto," highlighting how these microscopic organisms are crucial for addressing the "triple planetary crisis" of climate change, biodiversity loss, and pollution. Diatoms, a major group of photosynthetic microalgae, are particularly powerful in driving roughly 20% of global photosynthesis and forming the very base of marine food webs.

Yet despite their monumental importance, microalgal ecosystems remain largely unexplored and poorly mapped. That is why a recent major scientific undertaking in the Northeast Pacific is so significant.

Diatom records of the Salish Sea bioregion have historically been fragmentary, dating back to early inventories in the 1800s, and with only scattered surveys filling the gap across the 20th and 21st centuries. As Andrew Simon, PhD student at the University of Alberta, president of IMERSS, and one of the study's researchers, puts it: "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."

Now, for the first time, researchers have taken a significant step toward closing that gap. A team of Canadian researchers — Mark Webber (University of Victoria; IMERSS), Elaine Humphrey (UVic; IMERSS), Arjan van Asselt (IMERSS), Alice Chang (UBC), Evan Morian (Hakai Institute; UBC), and Andrew Simon (IMERSS; University of Alberta) — has published a new checklist of 924 diatom taxa alongside a curated dataset of 11,469 records in the open-access journal Biodiversity Data Journal, providing a long-needed foundation for environmental monitoring across this region of the northeast Pacific Ocean.

This dataset also directly answers a key recommendation from the UN Plankton Manifesto, which urges the scientific community to strengthen plankton research and develop comprehensive plankton atlases to biomonitor the health of marine ecosystems.

The Salish Sea — the traditional territory of the Coast Salish peoples — is home to roughly nine million people and is experiencing rapid growth in urbanization, industrial activity, and marine shipping. Because diatom populations respond quickly to changes in water quality and environmental conditions, they serve as highly effective early-warning bioindicators for shifts in ecosystem health and pollution levels.

Without a clear picture of what the base of the food web looks like today, it is impossible to understand the impact of tomorrow's environmental changes.

"We are fortunate to have had a dedicated group of academic researchers and community scientists contribute to this work over many years," says Mark Webber, IMERSS' resident diatomist. "Drawing from the literature, microscope analysis, and molecular sequencing, we now have a better picture of the diatoms present in the Salish Sea. 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."

The UN Plankton Manifesto stresses that understanding and managing plankton communities can unlock "Plankton-Based Solutions" to support fisheries, clean waters, and climate change mitigation.

Our work demonstrates how sustained collaboration between community scientists and research institutes can bridge these gaps, through partnering community expertise and observation with access to microscopy and molecular technologies,

- the team concludes.

The new checklist and dataset will support researchers and policymakers in environmental assessments of the Salish Sea, as the team continues to refine and analyze the data to support ongoing regional research.

Original source

Webber M, Humphrey E, van Asselt A, Chang A, Morien E, Simon ADF (2026) Diatoms (Bacillariophyta) of the Salish Sea, Northeast Pacific: annotated checklist and new species reports. Biodiversity Data Journal 14: e189060. https://doi.org/10.3897/BDJ.14.e189060

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About Institute for Multidisciplinary Ecological Research in the Salish Sea (IMERSS)

IMERSS, or the Institute for Multidisciplinary Ecological Research in the Salish Sea, is a non-profit society based in Galiano Island, British Columbia, Canada. IMERSS joins scientific researchers, citizen scientists, and Indigenous communities to conduct multidisciplinary ecological research, monitor biodiversity and the environment, and communicate results to better understand and respond to change in the Salish Sea bioregion.