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Marine Ecology Progress Series

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MEPS 540:27-41 (2015)  -  DOI:

Impacts of physical disturbance on ecosystem structure in subtropical seagrass meadows

Amanda S. Bourque1,2,*, W. Judson Kenworthy3, James W. Fourqurean2

1Habitat Restoration Program, Biscayne National Park, National Park Service, Homestead, FL 33033, USA
2Marine Science Program, Department of Biological Sciences, and Southeast Environmental Research Center, Florida International University, Miami, FL 33199, USA
3109 Holly Lane, Beaufort, NC 28516, USA
*Corresponding author:

ABSTRACT: Soil disturbance, a key contributor to physical degradation in seagrass ecosystems, can lead to long-term changes in ecosystem function. We used a chronosequence of vessel grounding disturbances of different ages (0 yr, 1 yr, 3 yr, 4 yr, 5+ yr) as a model for soil disturbance to test hypotheses that disturbance alters primary producer communities, soil properties, biogeochemical processes, and infauna communities in seagrass ecosystems and that altered structure and processes will change following disturbance through seagrass bed development and ecosystem recovery. Disturbance involving excavated surface soils resulted in long-term loss of seagrass and macroalgae and stored organic carbon, nitrogen, and phosphorus. Disturbed sites were characterized by reductions in variables related to organic matter and inorganic nutrient content. Disturbance altered habitat quality for some taxa including amphipods, as evident from differences in invertebrate community structure. These impacts persisted in study sites for 5+ yr after the disturbance, likely because of physical and chemical soil modification accompanied by slow development of the seagrass community. We estimate that disturbance from 0.4 m deep excavations led to losses of 6.0 kg m-2 organic C (Corg), 0.4 kg m-2 N, and 0.03 kg m-2 P from the disturbed areas. First-order conservative estimates of scarring excavation rate in Miami-Dade County, Florida, USA, suggest potential annual fluxes of 1.1 × 106 kg Corg, 74000 kg N, and 5500 kg P from seagrass soils in the region. Our findings suggest that vessel grounding disturbances create complex and long-term resource losses that are undervalued by resource trustees.

KEY WORDS: Ecosystem function · Blue carbon · Nitrogen · Phosphorus · Infauna · Macroalgae · Biscayne National Park · Soil · Sediment

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Cite this article as: Bourque AS, Kenworthy WJ, Fourqurean JW (2015) Impacts of physical disturbance on ecosystem structure in subtropical seagrass meadows. Mar Ecol Prog Ser 540:27-41.

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