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Diatoms of the intertidal environments of Willapa Bay, Washington, USA as a sea-level indicator

Hong, Isabel; Horton, Benjamin P.; Hawkes, Andrea D.; O'Donnell, Robert J.; Padgett, Jason S.; Dura, Tina; Engelhart, Simon E.

Diatoms of the intertidal environments of Willapa Bay, Washington, USA as a sea-level indicator Thumbnail


Isabel Hong

Benjamin P. Horton

Andrea D. Hawkes

Robert J. O'Donnell

Jason S. Padgett

Tina Dura


An understanding of the modern relationship between diatom species and elevation is a prerequisite for using fossil diatoms to reconstruct relative sea level (RSL). We described modern diatom distributions from seven transects covering unvegetated subtidal environments to forested uplands from four tidal wetland sites (Smith Creek, Bone River, Niawiakum River, and Naselle River) of Willapa Bay, Washington, USA. We compared our diatom dataset (320 species from 104 samples) to a series of environmental variables (elevation, grain-size, total organic carbon (TOCSOM), and porewater salinity) using hierarchical clustering and ordination. While no single variable consistently explains variations in diatom assemblages at every site, elevation, salinity, and substrate (mud fraction and TOCSOM) are variables affecting diatom distribution along our transects. Elevation was the major environmental control of diatom variability (explained 27–39% variance) at four transects (Bone River Transect 1, Niawiakum River Transect 2, Naselle River Transect 1 and 2). Salinity and substrate were the major environmental controls (explained 12–32% variance) of diatom variability at three transects (Niawiakum River Transect 1: salinity; Smith Creek Transect and Bone River Transect 2: TOCSOM). Analyses of a combined regional dataset of all transects suggest that elevation is the driver of regional diatom variability in Willapa Bay, with salinity and substrate co-varying along an elevation gradient. We identify species with narrow elevation tolerances that can serve as indicator species of specific environments. Despite the site-specific variability of our modern diatom distribution, the regional dataset provides an important dataset that can be used to reconstruct RSL in Willapa Bay.


Hong, I., Horton, B. P., Hawkes, A. D., O'Donnell, R. J., Padgett, J. S., Dura, T., & Engelhart, S. E. (2021). Diatoms of the intertidal environments of Willapa Bay, Washington, USA as a sea-level indicator. Marine Micropaleontology, 167, Article 102033.

Journal Article Type Article
Acceptance Date Jul 27, 2021
Online Publication Date Aug 11, 2021
Publication Date 2021-08
Deposit Date Aug 11, 2021
Publicly Available Date Aug 11, 2021
Journal Marine Micropaleontology
Print ISSN 0377-8398
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 167
Article Number 102033


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