Displacement of epifauna from seagrass blades by boat wake

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. (C) 2007 Elsevier B.V. All rights reserved.