MEPS 308:61-78 (2006)  -  doi:10.3354/meps308061

Effects of physical disturbance on infaunal and epifaunal assemblages in subtropical, intertidal seagrass beds

Greg A. Skilleter1,*, Bronwyn Cameron1, Yuri Zharikov1, David Boland1, Daryl P. McPhee1,2

1Marine and Estuarine Ecology Unit, School of Integrative Biology, University of Queensland, Brisbane, Queensland 4072, Australia
2Present address: Environmental Management Centre, School of Geography, Planning and Architecture, University of Queensland, Brisbane, Queensland 4072, Australia

ABSTRACT: We assessed the impact of large-scale commercial and recreational harvesting of polychaete worms Marphysa spp. on macrobenthic assemblages in a subtropical estuary in Queensland, Australia, by examining: (1) the spatial extent of harvesting activities and the rate of recovery of the seagrass habitat over an 18 to 20 mo period; (2) the recovery of infauna in and around commercial pits of known age; (3) the indirect effects of physical disturbance from trampling and deposition of sediments during harvesting on epibenthos in areas adjacent to commercial and recreational pits; (4) impacts of potential indirect effects through manipulative experimentation. Harvesting caused a loss of seagrass, changes to the topography and compaction of the sediments associated with the creation of walls around commercial pits, and the deposition of rubble dug from within the pit. The walls and rubble were still evident after 18 to 20 mo, but comprised only a small proportion of the total area on the intertidal banks. There was a shift from an intertidal area dominated by Zostera capricorni to one with a mixture of Z. capricorni, Halophila spp. and Halodule uninervis, but there was no overall decline in the biomass of seagrass in these areas. There were distinct impacts from harvesting on the abundance of benthic infauna, especially amphipods, polychaetes and gastropods, and these effects were still detectable after 4 mo of potential recovery. After 12 mo, there were no detectable differences in the abundances of these infauna between dug areas and reference areas, which suggested that infauna had recovered from impacts of harvesting; however, an extensive bloom of toxic fireweed Lyngbya majuscula may have masked any remaining impacts. There were no detectable impacts of harvesting on epifauna living in the seagrass immediately around commercial or recreational pits.

KEY WORDS: Bait harvesting · Physical disturbance · Intertidal Zostera · Macrofauna

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