Effects of Temperature, Growth Media, and Photoperiod on Growth and Toxin Production of Azadinium spinosum

Abstract

Azaspiracids (AZAs) are microalgal toxins that can accumulate in shellfish and lead to human intoxications. To facilitate their study and subsequent biomonitoring, purification from microalgae rather than shellfish is preferable; however, challenges remain with respect to maximizing toxin yields. The impacts of temperature, growth media, and photoperiod on cell densities and toxin production in Azadinium spinosum were investigated. Final cell densities were similar at 10 and 18 °C, while toxin cell quotas were higher (~3.5-fold) at 10 °C. A comparison of culture media showed higher cell densities and AZA cell quotas (2.5–5-fold) in f10k compared to f/2 and L1 media. Photoperiod also showed differences, with lower cell densities in the 8:16 L:D treatment, while toxin cell quotas were similar for 12:12 and 8:16 L:D treatments but slightly lower for the 16:8 L:D treatment. AZA1, -2, and -33 were detected during the exponential phase, while some known and new AZAs were only detected once the stationary phase was reached. These compounds were additionally detected in field water samples during an AZA event.

Distribution and abundance of azaspiracid-producing dinophyte species and their toxins in North Atlantic and North Sea waters in summer 2018

“…spinosum are able to cope with a wide range of environmental conditions. Temperature had the most significant impact on the growth of a North Sea strain and indicated higher growth rates at relatively high temperatures of 22˚C [66], however toxin production was significantly higher at lower temperatures [66,67]. Therefore, water temperatures of 13 to 17˚C, as observed in this study, are likely to be suboptimal for rapid cell division and formation of extensive Az.…”

“…Azadinium spinosum was found at almost all stations along the Irish south and west coast. This species was also detected at five stations (67)(68)(69)(70)(71) in the central North Sea, but was not…”

“…There may also be physiological reasons e.g., cell quotas of Azadinium spp. usually increase when growth is limited/stagnant [67,75]. The toxin profile of AZA-1, -2 and -33 is typical of Irish, Scottish and Shetland strains [46], which in phylogenetic trees form a well-supported ribotype (Ribotype A) [35].…”

Multiple New Strains of Amphidomataceae (Dinophyceae) from the North Atlantic Revealed a High Toxin Profile Variability of Azadinium spinosum and a New Non-Toxigenic Az. cf. spinosum

“…However, a number of minor AZA in Az. spinosum culture have been identified in dense stationary phase cultures only and thus are likely to be products of bacterial/chemical AZA degradation and not directly produced by the dinoflagellates [ 57 ]. Minor azaspiracids identified in the present study in ribotype A strains also include methylated AZA-1 and AZA-2 as well as phosphorylated forms of both AZA, and in some analyses of ribotype B strains phosphorylated AZA-11 and AZA-51 were detected.…”

“…A striking result of the multiple strain comparison is the enormous variability of AZA cell quota. Previous experimental studies show that the cell quota of a given strain may change in response to environmental conditions like temperature [ 57 , 60 , 61 ] or nutrient conditions [ 62 ]. However, here we used the same growth conditions for all strains.…”