Sediment dredging influences the seasonal biomass and community composition of microphytobenthos on a sandy shoal

Melissa Millman Baustian; Emily J. Lain; James L. Pinckney; Stacy Calhoun-Grosch; Brian J. Roberts

doi:10.1016/j.ecss.2026.110198

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Sediment dredging influences the seasonal biomass and community composition of microphytobenthos on a sandy shoal

Melissa Millman Baustian·Emily J. Lain·James L. Pinckney·Stacy Calhoun-Grosch·Brian J. Roberts

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Abstract

Microphytobenthos on sand shoals of continental shelves support biogeochemical cycles and trophodynamics and can be affected by sediment dredging. Therefore, our goal was to assess seasonal (spring, summer, fall) microphytobenthic biomass and composition over two years (2021 and 2022) at three areas (reference, relic dredged pit, and new dredged pit) of Ship Shoal off the coast of Louisiana, USA. Surface sediment was collected for algal pigment analysis to estimate microphytobenthic biomass and community composition using high-performance liquid chromatography. The average seasonal biomass ranged from 0.2 to 16.7 μg chlorophyll a g dry sediment −1 across the three regions and was consistently high in the relic dredged pit, with peak biomass during summer 2022. All regions contained benthic diatoms, cyanobacteria, and green algae, with diatoms significantly higher in the reference shoal region compared to the other regions. Benthic cyanobacteria and green algae dominated the biomass in relic pit. Enhanced deposition of organic-rich material in the relic pit, likely drives high seasonal biomass and shifts the community to benthic cyanobacteria and green algae. New and active dredging may suppress biomass despite changes in community composition. Thus, dredging-related changes could impact the autotrophic base of the benthic food web and have potential cascading effects.

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Estuarine, Coastal, and Shelf Science Article

Source-reported bounding extent: 28.8° to 29° latitude; -91.125° to -90.5° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Melissa Millman Baustian, Emily J. Lain, James L. Pinckney, Stacy Calhoun-Grosch, Brian J. Roberts. 2026-08-18. Sediment dredging influences the seasonal biomass and community composition of microphytobenthos on a sandy shoal. https://doi.org/10.1016/j.ecss.2026.110198

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