Investigations into the relationship between domoic acid and copepods in Scottish waters

This study investigated impacts of the algal toxin domoic acid (DA) on copepods in Scottish waters. Inspection of seasonal patterns revealed that several common copepods (Acartia spp. Dana, 1846, Calanus spp. Leach, 1816, Centropages spp. Krøyer, 1849, Pseudocalanus spp. Boeck, 1872, and Temora longicornis (Müller O.F., 1785)) regularly coexist with potentially toxic species from the diatom genus Pseudo-nitzschia H. Peragallo in H. Peragallo and M Peragallo, 1900. A short field study investigating the DA content of Calanus spp. at the Scottish Coastal Observatory site at Stonehaven recorded DA during every sampling event. The highest DA levels were associated with a July bloom (∼135000 cells L−1) of Pseudo-nitzschia cf. plurisecta Orive & Pérez-Aicua 2013. Several studies have previously investigated effects of ingested DA on copepods but information on effects of dissolved DA is lacking, therefore, simple exposure experiments were carried out to measure mortality of copepod species at ecologically relevant concentrations of dissolved DA. The highest concentrations tested (≥ 50 ng DA mL−1) decreased survival in Temora longicornis only; survival of other copepod species was unaffected. However, T. longicornis feeding on non-toxic algae in the presence of dissolved DA did not accumulate DA in their tissue. This study provides evidence of the potential for Calanus spp. to act as vectors for DA to higher trophic levels in Scottish waters.