A study of the impact of a pipeline construction on estuarine benthic invertebrate communities: Part 2. Recolonization by benthic invertebrates after 1 year and response of estuarine birds

The recovery of a benthic invertebrate community is further assessed, in this follow-up to a before/after impact study, 1 year after a pipeline construction at Clonakilty Bay, West Cork, Ireland. In addition, as the site is important for wintering wading birds, the study investigated the responses of estuarine bird species in the 18 months following the pipeline construction, including two winter periods. The polychaete Hediste diversicolor, having shown a good recovery 6 months after impact, exhibited greater numbers within the impact site after 1 year than existed before the pipeline construction. Their successful recolonization was most likely facilitated by high ragworm abundance in the surrounding areas. Scrobicularia plana, having been absent in samples taken 6 months after construction, showed a recovery after 1 year attributable mainly to settlement of juveniles, but with some evidence of passive or active dispersal by adults. Lower numbers, than the calculated expected number, of wading birds foraged within the impacted area during nearly all months of the first winter following the pipeline construction. The impacted area, however, held greater numbers of diurnally roosting birds than expected, the birds apparently taking advantage of the roughened sediment for shelter or to aid camouflage. The implications of habitat loss for foraging birds are therefore discussed, even when the impact, as in this study, was relatively limited and short term.