Publication Date:
2014-08-17
Description:
The actual estimates of carbon stocks beneath seagrass meadows worldwide are derived from few data, resulting in a tendency to generalize global carbon stocks from a very limited number of seagrass habitats. We surveyed Posidonia oceanica and Posidonia sinuosa meadows along depth-induced gradients of light availability to assess the variability in their sedimentary organic carbon (C org ) stocks and accretion rates. This study showed a 4-fold decrease in C org stocks from 2-4 m to 6-8 m depth P. sinuosa meadows (averaging 7.0 and 1.8 kg m -2 , respectively; top meter of sediment) and a 14- to 16-fold decrease from shallow (2 m) to deep (32 m) P. oceanica meadows (200 and 19 kg m -2 average, respectively; top 2.7 m of sediment). The average C org accretion rates in shallow P. sinuosa meadows were higher (10.5 g m -2 y -1 ) than in deeper meadows (2.1 g m -2 y -1 ). The reduction of sedimentary C org stocks and accretion rates along depth-related gradients of light reduction suggest that irradiance, controlling plant productivity, meadow density and sediment accretion rates, is a key environmental factor affecting C org storage potential of seagrasses. The results obtained highlighted the exceptional carbon storage capacity of P. oceanica meadows at Balearic Islands (Spain), containing the highest areal C org stocks of all seagrasses (estimated in up to 691-770 kg m -2 in 8-13 m-thick deposits). Seagrass communities are experiencing worldwide decline, and reduced irradiance (following e.g. eutrophication or sediment regime alterations) will lead to photo-acclimation responses (i.e. reduced plant productivity and shoot density), which may impact the carbon sequestration capacity of seagrasses.
Print ISSN:
0886-6236
Electronic ISSN:
1944-9224
Topics:
Biology
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Chemistry and Pharmacology
,
Geography
,
Geosciences
,
Physics
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