Displacement of epifauna from seagrass blades by boat wake Melanie J. Bishop ⁎ Centre for Research on Ecological Impacts of Coastal Cities, Marine Ecology Laboratories A11, University of Sydney, NSW 2006, Australia Received 27 March 2007; received in revised form 23 October 2007; accepted 25 October 2007 Abstract Due to the increasing accessibility of waterways under coastal development, recreational boating is among the growing disturbances to seagrasses at the local scale. While previous studies indicate that in decreasing and fragmenting seagrass habitat, boating can impact the diverse faunal assemblages associated with this habitat, direct impacts of boat wake on phytal invertebrates have not been assessed. By sampling seagrass blades twice before, immediately after and 1 h after exposure to recreational boat wake, this study documented the displacement of macroinvertebrates from flapping seagrass blades. At wake-exposed sites, up to five-fold decreases in the total abundances of amphipods and polychaetes and two-fold deceases in taxon richness were evident from immediately before to immediately after the disturbance of wake. By contrast, at control sites, the abundance and richness of these taxa remained fairly unchanged during the study and in some cases even increased. Although many of the displaced taxa were mobile, additional sampling indicated that they did not completely recolonize seagrass patches within 1 h of the disturbance. Thus, in places where boat traffic is relatively frequent, permanent depression of abundances of macroinvertebrates in seagrass may occur. This is of concern given that macroinvertebrates fuel fisheries productivity. Thus, in areas with frequent and or intense boating activity, nursery functions of seagrass beds may be severely compromised. © 2007 Elsevier B.V. All rights reserved. Keywords: Boat wake; Epifauna; Invertebrate; Pulse disturbance; Seagrass 1. Introduction Seagrass beds are considered one of the most valuable coastal resources due to the many ecological services that they perform (Costanza et al., 1997). Seagrasses are important in nutrient cycling, acting as both a source and sink (Hemminga et al., 1991), and rank amongst the most productive coastal marine ecosystems worldwide (Fourqurean et al., 2001). In addition, seagrasses are of critical importance in supporting dense and diverse assemblages of fauna. The abundances and diversities of many faunal groups, including fish, clams, amphipods and polychaetes are much greater in seagrass beds than in adjacent unvegetated areas (Lewis, 1984; Orth et al., 1984; Summerson and Peterson, 1984; Turner and Kendall, 1999). Primarily as a result of human disturbance, seagrass meadows and the ecosystem functions they support are presently experiencing worldwide decline (Short and Wyllie-Echeverria, 1996; Hemminga and Duarte, 2000). While at large spatial scales, decline may be driven by Journal of Experimental Marine Biology and Ecology 354 (2008) 111 – 118 www.elsevier.com/locate/jembe ⁎ Present address: Department of Environmental Science and Institute for Water and Environmental Resource Management, University of Technology Sydney, PO Box 123, Broadway NSW 2007 Australia. Tel.: +61 2 9514 8406; fax: +61 2 9514 4079. E-mail address: Melanie.Bishop-1@uts.edu.au. 0022-0981/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2007.10.013