The relationship between seagrass ( Posidonia oceanica) decline and sulfide porewater concentration in carbonate sediments

• Published in: Estuarine, coastal and shelf science coastal and shelf science, 2007-07, Vol.73 (3), p.583-588
• Main Authors: Calleja, Maria Ll, Marbà, Núria, Duarte, Carlos M.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Brackish water ecosystems; carbonate sediments; Demecology; demographic plant dynamics; Fundamental and applied biological sciences. Psychology; hydrogen sulfide; Marine; Plants and fungi; Posidonia oceanica; seagrass; sulphate reduction rate; Synecology
• ISSN: 0272-7714; 1096-0015
• DOI: 10.1016/j.ecss.2007.02.016

In this study we test the hypothesized negative relationship between seagrass status and porewater hydrogen sulfide (H 2S) levels, through a comparative analysis within a range of seven Posidonia oceanica meadows growing over carbonate sediments in the NW Mediterranean Sea around Mallorca Island. The studied meadows range from meadows growing on sediments with very low sulfide porewater concentrations (4.6 μM) to those growing over higher sulfide conditions (33.5 μM). Organic matter content, sulfate reduction rates and sulfide porewater concentrations in the sediments were determined concurrently with the assessment of demographic plant dynamics (specific mortality and net population growth rates). Sulfide porewater concentration increased with increasing organic matter content in the sediment, while net population growth decreased significantly with low increases of sulfide concentrations. Our results confirm the previously suspected vulnerability of seagrass meadows growing on carbonate sediments to increased sulfide levels. An excess of 10 μmols H 2S L −1 porewater is identified to already conduce P. oceanica meadows to decline, which this study identifies, particularly, as strongly sensitive to sulfides. The results reported here suggest that even moderate increases in organic carbon inputs may lead to enhancement of dissolved sulfides and may be an important factor for seagrass status in these iron-depleted carbonate sediments from the Mediterranean Sea.