Detection and effects of harmful algal toxins in Scottish harbour seals and potential links to population decline
Highlights
- •
- We document exposure of Scottish harbour seals to both DA and PSP toxins.
- •
- We show evidence of immunomodulatory effects as a result of toxin exposure.
- •
- Exposure occurs through contaminated prey at potentially lethal levels.
- •
- Toxin exposure could be driving the harbour seal decline in specific regions.
Abstract
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.
Keywords
- Domoic acid (DA);
- Paralytic Shellfish Poisoning (PSP) toxins;
- HABs;
- Phoca vitulina;
- Marine mammal;
- Scotland
Copyright © 2015 Elsevier Ltd. All rights reserved.
