Domoic acid production by Pseudo-nitzschia australis: Re-evaluating the role of macronutrient limitation on toxigenicity

William P Cochlan; Brian D Bill; Adrielle B Cailipan; Vera L Trainer

doi:10.1016/j.hal.2023.102431

Domoic acid production by Pseudo-nitzschia australis: Re-evaluating the role of macronutrient limitation on toxigenicity

Harmful Algae. 2023 Jun:125:102431. doi: 10.1016/j.hal.2023.102431. Epub 2023 Mar 22.

Authors

William P Cochlan¹, Brian D Bill², Adrielle B Cailipan³, Vera L Trainer⁴

Affiliations

¹ Estuary and Ocean Science Center, San Francisco State University, 3150 Paradise Drive, Tiburon, California, 94920-1205, United States of America. Electronic address: cochlan@sfsu.edu.
² Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd E, Seattle, WA 98112, United States of America.
³ Estuary and Ocean Science Center, San Francisco State University, 3150 Paradise Drive, Tiburon, California, 94920-1205, United States of America.
⁴ Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd E, Seattle, WA 98112, United States of America; Olympic Natural Resources Center, School of Environmental and Forest Sciences, University of Washington, Box 352100, Seattle, WA 98195, United States of America.

PMID: 37220984
DOI: 10.1016/j.hal.2023.102431

Abstract

The toxigenic diatom Pseudo-nitzschia australis (Frenguelli), isolated from the California Current System (CCS), was examined in unialgal laboratory cultures to evaluate domoic acid (DA) production and cellular growth as a response to macronutrient limitation. Toxic blooms of P. australis are common in the coastal waters of eastern boundary upwelling systems (EBUS), including those of the CCS off the west coast of the United States where limitation by macronutrients, specifically silicon as silicic acid [Si(OH)₄], or phosphorus as phosphate [PO₄^3-], has been suggested to increase the production of DA by these diatoms. This study used batch cultures grown under conditions of macronutrient sufficiency and limitation, expected during and after a natural upwelling event, to determine whether PO₄^3- or Si(OH)₄ deficiency enhances the production of DA and the expected risk of DA toxicity in natural coastal ecosystems. These controlled lab studies demonstrate that despite increases in cell-specific DA concentrations found during the nutrient-limited stationary phase, DA production rates did not increase due to either PO₄^3- or Si(OH)₄ limitation, and total DA production rates were statistically greater during the nutrient-replete, exponential growth phase compared to the nutrient-limited, stationary phase. In addition, the relative contribution of particulate DA (pDA) and dissolved DA (dDA) varied markedly with growth phase, where the contribution of pDA to total DA (pDA + dDA) declined from an average of 70% under P- and Si-replete conditions to 49% under P-limited conditions and 39% under Si-limited conditions. These laboratory results demonstrate that macronutrient sufficiency does not regulate the biosynthetic production of DA by this strain of P. australis. This finding, together with a comparative analysis of the various equations employed to estimate DA production, suggests that the current paradigm of increased toxigenicity due to macronutrient limitation be carefully re-examined, particularly when attempting to forecast the toxic threat of DA to coastal ecosystems as a function of macronutrient availability.

Keywords: Diatom; Domoic acid; HAB; Nutrient limitation; Pseudo-nitzschia australis.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Batch Cell Culture Techniques
Diatoms*
Ecosystem
Nutrients

Substances

domoic acid