ORCID
0000-0003-3316-3124 (Ladds)
Document Type
Article
Publication Date
2026
DOI
10.1016/j.hal.2026.103209
Publication Title
Harmful Algae
Volume
160
Pages
103209 (8 pp.)
Abstract
While harmful algal blooms (HABs) are prominent occurrences in coastal zones where microplastic concentrations are maximal, the manner in which microplastics may influence food webs and HABs is poorly understood. This study explored how polystyrene microplastics affected copepod grazing of the saxitoxin-synthesizing harmful dinoflagellate, Alexandrium catenella, as well as a non-toxic dinoflagellate, Gymnodinium aureolum. Experiments were performed using multiple densities of microplastics (250 – 10,000 mL–¹) of differing sizes (4 and 10 µm), as well as multiple densities of microalgae in microplates. The addition of 10 µm microplastics at densities of 1000 – 10,000 beads mL–¹ consistently and significantly reduced grazing on A. catenella while 10,000 beads mL–¹ (10 µm diameter) consistently and significantly increased grazing on G. aureolum (p < 0.05 for all). The addition of 4 µm beads (10,000 beads mL–¹) did not alter grazing on A. catenella but did mitigate grazing disruption caused by 10 µm beads when offered as a mixture of bead sizes. When A. catenella and G. aureolum were combined, the addition of 10 µm beads led to grazing rates on G. aureolum that were five-fold greater than A. catenella. In contrast, the algal mixture without bead additions yielded enhanced grazing on G. aureolum while grazing on A. catenella was unchanged compared to mono-algal treatments. Microplastics 10 µm and smaller are poorly studied but likely have disproportionate interactions with lower levels of marine food webs. This study highlights potential co-stressor effects of HABs and microplastics on zooplankton grazers which could combine to promote HABs.
Rights
© 2026 The Authors
This is an open access article under the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.
Data Availability
Article states: "https://doi.org/10.5061/dryad.hhmgqnkwb (Data in this manuscript are available at .)"
Original Publication Citation
Ladds, M., & Gobler, C. (2026). Microplastics suppress copepod grazing of the harmful algal bloom-forming dinoflagellate, Alexandrium catenella. Harmful Algae, 160, Article 103209. https://doi.org/10.1016/j.hal.2026.103209
Repository Citation
Ladds, Megan and Gobler, Christopher, "Microplastics Suppress Copepod Grazing of the Harmful Algal Bloom-Forming Dinoflagellate, Alexandrium catenella" (2026). OES Faculty Publications. 587.
https://digitalcommons.odu.edu/oeas_fac_pubs/587
Appendix. Supplementary materials
Included in
Algae Commons, Oceanography Commons, Public Health Commons, Terrestrial and Aquatic Ecology Commons