Are toxins from harmful algae a factor involved in the decline of harbour seal populations in Scotland?

• Main Author: Jensen, Silje-Kristin
• Other Authors: Hall, Ailsa Jane, Marine Alliance for Science and Technology for Scotland (MASTS)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of St Andrews 2015
• Subjects: QL737.P64J4; Harbor seal > Scotland; Seal populations > Scotland; Toxic marine algae > Scotland; harbor seal; harbour seal
• Online Access: http://hdl.handle.net/10023/7035

Firstly this study builds on the investigation initiated by Hall and Frame (2010), which found that Scottish harbour seals were exposed to domoic acid (DA), a potent natural neurotoxin produced by phytoplankton. Using the same sample collection technique to gather urine and faecal material from various populations around Scotland with differing population trajectories (Lonergan et al., 2007), the objective was to investigate not only exposure to DA, but also other groups of toxins such as paralytic shellfish poisoning (PSP) toxins and the lipophilic toxins okadaic acid (OA) and dinophysis toxins (DTXs). Toxins from harmful algae are thought to be potential causative factors in the ongoing harbour seal decline in some regions of Scotland (Hall and Frame, 2010). This investigation was initiated because Pseudo-nitzschia (which produces DA) in particular was found to be highly prevalent in the phytoplankton communities in Scotland (Fehling et al., 2004; Stobo et al., 2008) and indeed was first observed at increased concentrations at around the time the harbour seal populations were observed as declining (Lonergan et al., 2007; Stobo et al., 2008). Prior to 2000 harbour seal populations in Scotland were largely stable or increasing. In addition DA exposure has had a devastating effect on the California sea lions (CSL) from the US west coast, where morbidity and mass mortality has occurred as a result of exposure (Goldstein et al., 2008; Gulland et al., 2002; Lefebvre et al., 1999; Scholin et al., 2000). In addition to the toxin analysis in urine and faecal samples, blood samples were collected and health parameters such as white blood cell and differential cell counts were investigated. Plasma cortisol concentrations and parasite faecal egg counts were additionally investigated as parameters indicative of adrenal function and parasite burden. CSL exposed to DA have significantly lower blood cortisol levels and higher eosinophil counts (Gulland et al., 2012) so it was possible that these indicators of effects might ...