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Marine Ecology Progress Series

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MEPS 508:1-15 (2014)  -  DOI:

Dominant macrobenthic populations experience sustained impacts from annual disposal of fine sediments on sandy beaches

Lisa M. Manning1,3, Charles H. Peterson1,*, Melanie J. Bishop2

1University of North Carolina at Chapel Hill, Institute of Marine Sciences, Morehead City, North Carolina 28557, USA
2Department of Biological Sciences, Macquarie University, New South Wales 2109, Australia
3Present address: National Oceanic and Atmospheric Administration, 1315 East-West Highway, SSMC3, Silver Spring, Maryland 20910, USA
*Corresponding author:

ABSTRACT: Despite increasing use of dredged materials as beach fill to protect coastal property and public beaches from storm damage, knowledge of how this practice affects sandy beach ecosystems remains poor. We coupled field monitoring of 2 successive beach disposal events with mesocosm experiments to assess mechanisms of ecological effects of fine sediment disposal. Macrobenthic sampling on Topsail Island, North Carolina, revealed that disposal of dredge spoils transformed beach grain sizes from medium to fine sand. Water sampling documented substantially elevated surf-zone turbidity during and occasionally after sediment deposition. When disposal occurred before spring invertebrate recruitment to the beach, it negatively influenced recruitment of the mole crab Emerita talpoida and the amphipod Parahaustorius longimerus. When disposal followed recruitment, it affected abundances of the bean clam Donax variabilis and 3 species of haustoriid amphipods negatively, and abundance of the spionid polychaete Scolelepis squamata positively. Effects lasted for the full warm season, and suppressions of invertebrate abundances were repeated across successive annual disposal events. In mesocosms, turbidity matching that induced in the field slowed growth of clams and modified habitat choices by predatory fishes. Hence, annual disposal of fine-grained dredge spoils on these sandy beaches maintained depressed abundances of 5 of 6 macroinvertebrate prey of shorebird and surf fish, without sustaining elevated volumes of beach sediments as long as a year. Implementation of disposal projects before the beginning of the seasonal recruitment of benthos resulted in fewer negative impacts on abundance than disposal projects conducted after the recruitment season, probably reflecting a more universal risk from burial and  suffocation.

KEY WORDS: Beach nourishment · Coastal erosion · Fine sediment disposal · Sandy beach · Sea-level rise · Soft sediments · Surf fish · Turbidity

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Cite this article as: Manning LM, Peterson CH, Bishop MJ (2014) Dominant macrobenthic populations experience sustained impacts from annual disposal of fine sediments on sandy beaches. Mar Ecol Prog Ser 508:1-15.

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