The influence of seagrass beds on carbonate sediments in the Bahamas |
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| Institution: | 1. Department of Physics and Earth Sciences, School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany;2. Geochemistry and Hydrogeology Group, University of Bremen, PO Box 330440, 28334 Bremen, Germany;1. School of Earth and Ocean Sciences, University of Victoria, PO Box 1700 Stn CSC, Victoria, BC V8W 2Y2, Canada;2. Institute of Ocean Sciences, Fisheries & Oceans Canada, 9860 West Saanich Road, Sidney, BC V8L 4B2, Canada;1. Nelson Mandela University, Port Elizabeth, Eastern Cape, South Africa;2. University of the Western Cape, Bellville, Cape Town, South Africa |
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| Abstract: | Chemical variables were measured in calcium-carbonate-rich sediments inhabited by the dominant tropical seagrass, Thalassia testudinum, and in adjacent seagrass-free sediments at several locations in the Bahamas Islands. Pore-water alkalinity and pCO2 were consistently greater, while pH was consistently lower in sediment-pore waters within seagrass beds. The ammonium and molybdate-reactive phosphate concentrations in sediment-pore water were variable for vegetated, compared with unvegetated, sample locations.Thalassia testudinum can generate very large amounts of organic matter within calcium-carbonate-rich sediments. However, little of the organic matter is retained in the sediment and the effect of that organic matter on pore water chemical factors appears to be surprisingly small. These observations are markedly different from those for seagrass beds in high latitude clastic sediments and in Syringodium filiforme seagrass beds near San Salvador Island, where major influences of the seagrass beds on sediment chemistry have been observed. The generally coarser grain size of the carbonate sediments may be a primary factor contributing to these differences. |
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