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Marine Ecology Progress Series

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MEPS 250:61-70 (2003)  -  doi:10.3354/meps250061

Effects of propeller scarring on macrofaunal use of the seagrass Thalassia testudinum

Amy V. Uhrin1,2,*, Jeff G. Holmquist1,3,4

1Department of Marine Science, University of Puerto Rico, Mayagüez Campus, PO Box 908, Lajas, Puerto Rico 00667, USA
2NOAA, National Ocean Service, Center for Coastal Fisheries and Habitat Research, 101 Pivers Island Road, Beaufort, North Carolina 28516, USA
3White Mountain Research Station, University of California, 3000 East Line Street, Bishop, California 93514, USA
4Marine Science Institute, University of California Santa Barbara, Star Route 1, PO Box 198, Mammoth Lakes, California 93546, USA

ABSTRACT: Propeller scarring within seagrass beds is common in shallow coastal waters. Scarring has the potential to fragment seagrass beds, resulting in habitat loss, decreased productivity, and the possibility for further erosion and degradation. We conducted a study in Thalassia testudinum beds in Puerto Rico to determine whether seagrass macrofauna are affected by this disturbance. Four sampling zones (propeller scar, seagrass-scar interface, homogeneous seagrass located 5 m from the scar, and homogeneous seagrass located 10 m from the scar) were compared among 10 replicate seagrass beds. Scarring modified faunal assemblages at the scale of the propeller scar; there was significantly lower total macrofaunal abundance and fewer species in scars. When individual taxa were considered, shrimp and mollusc abundances were lower in scars compared to the other sampling zones. Resident fish abundance was not significantly different among zones. Dominant shrimp species in scars differed from seagrass zones. Crabs and molluscs responded negatively to scarring as indicated by significantly lower densities of these 2 taxa up to 5 m from scars. The extent to which these results Œscale up¹ remains unknown and future studies should focus on larger, more intensely scarred areas.

KEY WORDS: Propeller scarring · Edge · Seagrass · Thalassia testudinum · Decapoda · Shrimp · Fish · Molluscs

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