Detection and effects of harmful algal toxins in Scottish harbour seals and potential links to population decline

Silje-Kristin Jensen, Jean-Pierre Lacaze, Guillaume Hermann, Joanna Kershaw, Andrew Brownlow, Andrew Turner, Ailsa Jane Hall

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Over the past 15 years or so, several Scottish harbour seal (Phoca vitulina) populations have declined in abundance and several factors have been considered as possible causes, including toxins from harmful algae. Here we explore whether a link could be established between two groups of toxins, domoic acid (DA) and saxitoxins (STXs), and the decline in the harbour seal populations in Scotland. We document the first evidence that harbour seals are exposed to both DA and STXs from consuming contaminated fish. Both groups of toxins were found in urine and faeces sampled from live captured (n = 162) and stranded animals (n = 23) and in faecal samples collected from seal haul-out sites (n = 214) between 2008 and 2013. The proportion of positive samples and the toxins levels measured in the excreta were significantly higher in areas where harbour seal abundance is in decline. There is also evidence that DA has immunomodulatory effects in harbour seals, including lymphocytopenia and monocytosis. Scottish harbour seals are exposed to DA and STXs through contaminated prey at potentially lethal levels and with this evidence we suggest that exposure to these toxins are likely to be important factors driving the harbour seal decline in some regions of Scotland.
Original languageEnglish
Pages (from-to)1-14
Number of pages14
Early online date9 Feb 2015
Publication statusPublished - Apr 2015


  • Domoic acid (DA)
  • Paralytic Shellfish Poisoning (PSP) toxins
  • HABs
  • Phoca vitulina
  • Marine mammal
  • Scotland


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