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Elevated trace elements in sediments and seagrasses at CO2 seeps
A K Mishra1, R Santos2, J M Hall-Spencer3
1Centre for Marine Sciences, University of Algarve, Campus de Gambelas, Faro, 8005-139, Portugal; School of Biological and Marine Sciences, University of Plymouth, Plymouth, PL48A, UK.
Marine Environmental Research
|November 18, 2019
Summary
Seagrasses near marine carbon dioxide (CO2) seeps can accumulate high levels of trace metals like cadmium. Metal toxicity explains why seagrass abundance varies at these unique environments.
Area of Science:
- Marine Biology
- Environmental Chemistry
- Geochemistry
Background:
- Seagrasses thrive near shallow marine carbon dioxide (CO2) seeps.
- These environments offer unique opportunities to study trace metal accumulation in marine ecosystems.
- Understanding metal dynamics is crucial for seagrass health and biodiversity.
Purpose of the Study:
- To quantify trace metal (Cd, Cu, Hg, Ni, Pb, Zn) concentrations in sediments and seagrasses at CO2 seeps and reference sites.
- To assess the potential adverse effects of elevated metal levels on marine biota.
- To investigate the relationship between metal bioavailability, toxicity, and seagrass abundance at CO2 seeps.
Main Methods:
- Field sampling of sediments and seagrass tissues (Posidonia oceanica, Cymodocea nodosa) at six Mediterranean CO2 seeps and six reference sites.
- Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for trace metal analysis.
- Comparison of metal concentrations between seep and reference sites, and assessment against established toxicity thresholds.
Main Results:
- Elevated concentrations of certain trace metals, notably cadmium (up to 43x higher), were found in seep sediments.
- Metal levels at three seeps (Vulcano, Ischia, Paleochori) were predicted to be harmful to marine life.
- Seagrasses exhibited higher tissue concentrations of Zn and Ni (Posidonia oceanica) and Zn (Cymodocea nodosa), particularly in roots, despite varying sediment metal levels.
- High copper levels in Ischia seep sediments did not correlate with high copper in the abundant seagrass found there.
Conclusions:
- Trace metal contamination is a significant factor at some marine CO2 seeps.
- Seagrass abundance at CO2 seeps is influenced by the bioavailability and toxicity of specific trace elements.
- Variations in metal accumulation and effects help explain differential seagrass distribution in these geochemically active zones.
