Survey of the Chemical Defence Potential of Diatoms: Screening of Fifty Species for α,β,γ,δ-unsaturated aldehydes

Abstract

In recent years a negative influence of diatom-derived alpha,beta,gamma,delta-unsaturated aldehydes (PUA) on the reproductive success of copepods and invertebrates has been suggested. Since adverse chemical properties of diatoms would question the traditional view of the marine food web, this defense mechanism has been investigated in detail, but the PUA-release by test organisms has only been determined in a few cases. The observed effects were nevertheless frequently discussed from a general point of view often leading to contradictory conclusions. We have examined the PUA-production of 51 diatom species (71 isolates) in order to provide a basis for the interpretation of laboratory and field results on the influence of diatom food on the reproductive success of their consumers. PUA-production is species and strain dependent. Thirty-six percent of the investigated species (38% of the cultivated isolates) release alpha,beta,gamma,delta-unsaturated aldehydes upon cell disruption in concentrations from 0.01 to 9.8 fmol per cell. Thalassiosira rotula and Thalassiosira pacifica, major spring-bloom forming diatoms isolated from Roscoff (Bretagne, English Channel, France) and Puget Sound (Washington, USA) were among the PUA-producing strains.

Exploring Valuable Lipids in Diatoms

“…Oxylipins that derived from the incorporation of oxygen into the carbon chains of PUFAs usually act as chemical mediators in many ecological and physiological processes in marine and freshwater diatoms (Wichard et al, 2005;Sieg et al, 2011). Around 30% of marine diatoms produce an array of oxylipin metabolites (Wichard et al, 2005;Sieg et al, 2011).…”

“…Around 30% of marine diatoms produce an array of oxylipin metabolites (Wichard et al, 2005;Sieg et al, 2011). Biosynthesis of oxylipins (Figure 1) is condition-dependent and immediately activated upon predation (D'ippolito et al, 2005;Cutignano et al, 2011;Nanjappa et al, 2014).…”

“…Particularly, oxylipin production starts by the oxidation action of iron non-heme enzymes lipoxygenases (LOXs) on the precursor PUFAs and membrane phospholipids upon loss of cell integrity (Orefice et al, 2015). A LOX provides a specific and precise incorporation of a hydroperoxide group into the carbon chains and mediate the further transformations, resulting in generation of a group of important oxylipins (Wichard et al, 2005).…”

Effect of food concentration and type of diet on Acartia survival and naupliar development

“…It is now well illustrated that not all diatom species per se are toxic, but even taxa lacking toxic metabolites can be insufficient to support copepod recruitment and development in mono-diet (Jones and Flynn 2005). While defence chemicals of diatoms can be diverse (Fontana et al 2007) and widely present (Wichard et al 2005) there are obviously species that lack the detrimental effects originally presumed for the entire taxon, and among these can be adequate and high quality food sources for copepods.…”

“…The diatom Thalassiosira weissflogii has been proved to constitute a high-quality food source for copepod development (Klein Breteler et al 2005), including Acartia tonsa (Støttrup and Jensen 1990;Jónasdottir and Kiørboe 1996). Investigation into the chemical defence potential of a wide range of diatom species detected polyunsaturated aldehyde release also in several species of the genus Thalassiosira including T. rotula and T. pacificus, but no PUA were found in T. weissflogii (Wichard et al 2005). Under N-saturated conditions, A. tonsa has been proved to ingest the diatom T. weissflogii preferentially over Emiliania huxleyi and Aureodinium pigmentosum, an alternative dinoflagellate food source, indicating selectivity for this diatom species in copepods especially under nutrient-sufficiency as may be found during early spring bloom conditions in the field (Jones et al 2002).…”