Northern Gannets Morus bassanus as Indicators of Mercury Levels in the Marine Environment

• Main Author: Walsh, Paul M
• Format: Thesis
• Language: English
• Published: ProQuest Dissertations & Theses 1993
• Subjects: Fulmar; Grassholm; Fulmarus glacialis; North Atlantic; Northern Fulmar
• Online Access: http://theses.gla.ac.uk/75349/; http://theses.gla.ac.uk/75349/1/13815532.pdf

1. The use of seabirds as monitors of heavy metals in marine environments was reviewed. 2. Intra-population variables related to sampling of seabird feathers for mercury analysis were examined using data for Northern Gannets Morus bassarm and Shags Phalacrocorax aristotelis. 3. Feather of nestlings (including down) appeared to be the most useful, given that intra-population variation is less than for feathers of adults 4. The number and type of feathers analysed were less important for nestlings than for adults. 5. If adult feathers are to be mercury-analysed, pooled samples of small body- feathers are best. 6. Moulted body-feathers of adults are potentially useful (if pooled before analysis). 7. Geographical patterns of mercury concentrations were examined for feathers of adult and nestling Gannets and Shags, and for Gannet eggs. 8. Mercury concentrations in feathers (including down) of nestling Gannets showed ca. three- to four-fold variation in mean levels between North Atlantic colonies. Concentrations were highest in feathers from Littie Skellig (SW Ireland), followed by Grassholm (south Wales). 9. Feathers of adult Gannets showed much less clear-cut patterns than feathers of nestlings, but mercury concentrations were again highest in birds firom Grassholm (and, possibly, Aldemey in the Channel Islands). 10. Gannet eggs from British and Irish colonies showed similar patterns of mercury concentrations to feathers of nestling Gannets. 11. Feathers of nestling Shags showed similar patterns of mercury concentrations to nestling Gannets. 12. Patterns of mercury concentrations shown by Gannets and Shags may reflect a combination of localised anthropogenic inputs of mercury to coastal waters, and current-mediated inputs. 13. The possible role of variation in Gannet diet in influencing apparent pattems of mercury concentration is discussed, and remains a possible contributing factor. 14. The potential role of biological samples for detecting historical changes in global metal pollution is discussed, with particular reference to cadmium, mercury and lead. Mercury is the metal most amenable to such analysis. 15. Historical changes in mercury concentrations in north and northeast Atiantic seabirds were assessed using feather samples from museum specimens and live-sampled birds. Four out of five species, including Gannet, showed significant increases in plumage mercury concentrations since the mid 19th century; two Northern Fulmar Fulmarus glacialis populations showed significant decreases in mercury concentrations over the same period.