Quantification, extractability and stability of dissolved domoic acid within marine dissolved organic matter

Abstract

The widespread diatom Pseudo-nitzschia can produce domoic acid (DA). DA is a compound with well described neurotoxic effects on vertebrates including humans known as amnesic shellfish poisoning (ASP) syndrome. It has also been suggested to serve as an organic ligand that binds to iron and copper. By binding these trace elements, DA may increase their solubility and bioavailability. In order to serve this function, DA has to be excreted and reabsorbed by the cells. Only few records of dissolved domoic acid (dDA) concentrations in the ocean exist. To accomplish quantification by ultra performance liquid chromatography (UPLC), samples have to be pre-concentrated and desalted using solid-phase extraction, a procedure commonly applied for dissolved organic matter. Our major goals were to quantify dDA in a basin-wide assessment in the East Atlantic Ocean, to determine extraction efficiencies for complexed and uncomplexed dDA, and to assess whether domoic acid is represented by its molecular formula in direct-infusion high resolution mass spectrometry. Our results showed that dDA was extracted almost quantitatively and occurred ubiquitously in the ocean surface but also in deeper (and older) water, indicating surprisingly high stability in seawater. The maximum concentration measured was 173 pmol L −1 and the average molar dDA carbon yield was 7.7 ppm. Both carbon yield and dDA concentration decreased with increasing water depth. Providing quantification of dDA in the water column, we seek to improve our understanding of toxic bloom dynamics and the mechanistic understanding of DA production.

First Evidence of the Toxin Domoic Acid in Antarctic Diatom Species

“…The current study is consistent with a large-scale study in the transect of the east Atlantic Ocean, detecting dissolved DA in the Southern Ocean [ 29 ]. The highest dissolved DA concentration was found around the equator; dissolved DA was detectable in all surface water samples as south as 70° S [ 29 ]. This knowledge adds to the pivotal importance of studying DA presence and impact in global as well as Antactic ecosystems.…”

Mathematical chromatography deciphers the molecular fingerprints of dissolved organic matter

“…Since chromatograms of DOM represent unresolved humps, the abundance of single analytes cannot easily be deduced. 13,18 Instead, complex mass spectra in broadly eluting fractions must be analysed. However, the visual analysis of raw data is overburdened by the large number of spectra, and statistical analyses capable of extracting information from direct infusion datasets (such as principal component analysis) require unfolding of the multidimensional data.…”

Molecular underpinnings and biogeochemical consequences of enhanced diatom growth in a warming Southern Ocean

“…A search for DA biosynthesis transcripts (Brunson et al 2018) did not yield strong evidence for expression of the DA biosynthesis gene cluster in this experiment (Table S1; Table S2). However, a few studies have reported DA production in the SO (Silver et al 2010; Geuer et al 2019), but the temporal, spatial and environmental factors that elicit DA production remain unclear. Further work is required to investigate whether resident Pseudo-nitzschia can produce the toxin under conditions not examined in our study, or if DA producing Pseudo-nitzschia are likely to migrate into a warmer SO.…”