The Pacific geoduck Panopea generosa is the largest burrowing clam in the world and adults can live up to a meter below the sediment surface. To extract these clams, harvesters use pressurized water jets to dislodge surrounding sediments. This type of disturbance could have significant effects on the local benthic environment, but has been little examined. The present study was conducted on one intertidal and one subtidal plot to assess potential effects of commercial-scale geoduck harvesting on the sedimentary benthic environment and nearby eelgrass beds. Sediment samples were collected inside the impacted plots and at intervals up to 75 m away while eelgrass sampleswere collected adjacent to the impacted plots and at intervals up to 50maway, seasonally over 2 y.Harvest of the subtidal plot occurred at one year and mock harvest of the intertidal plot occurred after one preimpact sample. Sediment and infaunal qualities examined included: grain size, percent organics, total nitrogen, total organic carbon, sulfide content, redox potential, and infaunal community structure. Eelgrass parameters studied included shoot length, shoot density, and biomass. Sedimentation rates during harvesting were examined and compared with those of natural occurrence. Suspended sediments were increased by harvesting, but generally limited to the footprint of the harvested area, and were not greater than those created by wind/storm conditions. No changes were observed, however, in any of the measured sediment or infaunal variables on or near the harvested plot or in adjacent eelgrass. In addition, no significant response in eelgrass parameters was observed. This study indicated little effect of commercial geoduck harvesting practices beyond short-lived resuspension of sediment on the two harvested plots.
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Vol. 34 • No. 3