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Temporal variability in heavy metal content, shell morphology, and intersex in Littorina littorea (Mollusca: Gastropoda) along the Scheldt estuary (The Netherlands)
Malbas, S.A. (2002). Temporal variability in heavy metal content, shell morphology, and intersex in Littorina littorea (Mollusca: Gastropoda) along the Scheldt estuary (The Netherlands). MSc Thesis. Universiteit Antwerpen (RUCA)/Vrije Universiteit Brussel (VUB): Brussel. VIII, 85 pp.

Thesis info:
    Vrije Universiteit Brussel; Faculteit Wetenschappen; Vakgroep Biologie; Ecological Marine Management Programme (ECOMAMA), more

Available in Author 
    VLIZ: Non-open access 140938
Document type: Dissertation

Keywords
    Animal morphology; Heavy metals; Imposex; Temporal variations; Tributyltin; Littorina littorea (Linnaeus, 1758) [WoRMS]; ANE, Netherlands, Oosterschelde [Marine Regions]; ANE, Netherlands, Westerschelde [Marine Regions]; Marine

Author  Top 
  • Malbas, S.A.

Abstract
    Samples of Littorina littorea were collected from six stations along the western Scheldt estuary on November 18, 2001. Additional samples were gathered from three sampling sites in the eastern Scheldt on December 23, 2001. The shell morphology, as well as the total weight and the body weights were determined and the animals were sexed. Intersex and sterility were determined in female periwinkles, whereas penis shedding incidence was determined in the male individuals. In addition, heavy metals such as Silver, Aluminum, Arsenic, Calcium, Cadmium, Cobalt, Chromium, Copper, Iron, Manganese, Nickel, Lead, and Zinc were measured in their soft tissues using inductively coupled plasma atomic emission spectrophotometry (ICP-AES). The current morphological results more or less agree with previous studies performed along the same study area, showing that the variation was not randomly distributed. However, as shown from our data, salinity and metal pollution alone cannot explain the morphological structuring, as animals from the most polluted and least saline like sites seem to attain comparable shell sizes compared to animals that live on less polluted environments. The highest intersex incidence was observed in Borsele, the site closest to the harbor of Vlissingen where TBT levels were expected to be high, probably due to the presence of boats bigger than 25 m. Similarly, sterility percentage followed intersex patterns whereby the number of sterile females was highest in those areas that had the highest ISI values. However, the highest ISI value observed in the present study (Borsele = 0.882) was lower than what has been observed in the same area in a 1998 survey (ISI = 1.26), and was even much lower than those recorded in some heavily polluted German ports (ISI >3.0). The metal gradients, which are known to exist in the western Scheldt, were also found in the present study. Our results further revealed that the eastern Scheldt is relatively clean compared to the western Scheldt as manifested by the metal levels detected in the animals' soft tissues. However, in comparison with a previously performed heavy metal survey (1998) in L. littorea at the same study area, tissue heavy metal levels have increased. Further more, a correlation was observed between heavy metals and the morphology of female L. littorea, an indication of a possible influence of heavy metal pollution on the morphology of female L. littorea

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