Surficial Corg stocks of Z. noltei were reduced by 4-fold by intense harvesting.
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Greater loss of Corg stocks in intensively than in non-intensively harvested areas.
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Loss of surficial Corg stock (sediment and biomass) ranged from 165 to 678 g C · m−2.
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Effect of clam harvesting on surficial Corg stocks increased over the growing season.
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Seagrass cover increased after the growing season in intensively harvested areas.
Abstract
Seagrass carbon stocks are vulnerable to physical disturbance. We assessed the effect of clam harvesting on the organic carbon (Corg) stocks in surface sediments in four intertidal Zostera noltei meadows on the Iberian Atlantic coast (Spain and Portugal), by comparing undisturbed and harvested areas. We also monitored the spatial cover of the meadows throughout the growing season. Sedimentary Corg content and Corg stocks were about four times lower in intensively harvested areas than in control areas, but there were not differences between areas with low harvesting pressure and control areas. Reductions of 53–85% in sedimentary Corg stocks of Z. noltei meadows were caused by intensive clam harvesting. The effect of intensive clam harvesting on Corg stocks increased throughout the growing season, but the area covered by the seagrass increased from 21 to 37%, suggesting rapid recovery of seagrass canopies and potential recovery of sedimentary Corg stocks.
