Senilia senilis (Linnaeus, 1758), a biogenic archive of environmental conditions on the Banc d'Arguin (Mauritania)
Lavaud, R.; Thébault, J.; Lorrain, A.; van der Geest, M.; Chauvaud, L. (2013). Senilia senilis (Linnaeus, 1758), a biogenic archive of environmental conditions on the Banc d'Arguin (Mauritania). J. Sea Res. 76: 61-72. dx.doi.org/10.1016/j.seares.2012.11.003
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101; e-ISSN 1873-1414, more
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| Author keywords |
Bivalve; Sclerochronology; Oxygen isotopes; Barium; Uranium |
| Authors | | Top |
- Lavaud, R.
- Thébault, J.
- Lorrain, A.
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- van der Geest, M., more
- Chauvaud, L.
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| Abstract |
Environmental archives are useful tools for describing past and current climate variations and they provide an opportunity to assess the anthropogenic contribution in coastal ecological changes. Along the West African coast, few studies have focused on such archives in coastal ecosystems. The bloody cockle Senilia senilis, an intertidal bivalve mollusk species, is widely distributed from Western Sahara to Angola, and has been harvested by humans over thousands of years. Therefore, this species appears to be a good candidate for assessing past variations of key environmental parameters such as temperature, primary production, and Saharan dust advection within West African coastal ecosystems. In the present paper, we focused (i) on the identification of growth rhythms of S. senilis shells in Mauritania (Banc d'Arguin), and (ii) on the potential of these shells as (paleo-)environmental archives. The method we used combined environmental survey, sclerochronology, and geochemical analyses of aragonite samples. We showed that microgrowth line formation was controlled by a tidal forcing, leading to the formation of two lines per lunar day. Brightness and thickness of these microgrowth lines progressively decreased from spring to neap tides (fortnightly cycle). Lunar daily growth rates displayed strong seasonal variations, with highest values (>300 mu m per lunar day) recorded in summer. The oxygen isotope composition of S. senilis shells (delta O-18(aragonite)) accurately tracked seawater temperature seasonal variations, with a precision of 0.8 degrees C. Finally, we discussed the opportunity to use Ba:Ca ratio in shells as a proxy for primary production or for Saharan dust transport. We also hypothesized that either Canary Currentvariations or, more probably, massive aerosol transfers from Sahara to the Atlantic Ocean could control uranium availability in coastal waters and explain the occurrence of U:Ca peaks within S. senilis shells. |
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