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Marine Ecology Progress Series

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MEPS 342:41-53 (2007)  -  doi:10.3354/meps342041

Biological recovery from organic enrichment: some systems cope better than others

Catriona K. Macleod1,2,*, Natalie A. Moltschaniwskyj2, Christine M. Crawford1, Susan E. Forbes1,3

1Marine Research Laboratories, Tasmanian Aquaculture & Fisheries Institute, and Aquafin CRC, University of Tasmania, Hobart, Tasmania 7001, Australia
2School of Aquaculture, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Launceston, Tasmania 7250, Australia
3Department of Environment & Heritage, Canberra, ACT 2601, Australia

ABSTRACT: This study examined the short-term recovery response at 2 salmon farms in southern Tasmania where organic loads were equivalent, but where background environmental conditions differed markedly. Although benthic communities at each of the farm locations showed good recovery over the 3 mo fallow period, community structure did not fully return to that observed under reference conditions at either location. At the Stringers Cove site the primary ecological functions of the background community were restored, but this was not the case at Creeses Mistake. These differences in recovery response were a direct reflection of background environmental conditions. Stringers Cove sediments had naturally high organic carbon content and as a result there was greater similarity in the ecological function of the unimpacted and impacted conditions at this location than at Creeses Mistake, where, under unimpacted conditions, the sediments had a very low organic content. In addition, the background fauna at Stringers Cove contained several species with reproductive strategies suited to rapid recruitment and well adapted for early recolonisation in organically enriched sediments. In contrast, the background fauna at Creeses Mistake not only changed more with the impacts of organic enrichment, but was less able to re-establish populations directly by immigration, needing to rely to a greater extent on remediation of the sediments by transitional species before being able to colonise. This has important implications for environmental management, as it suggests that the sediments in some areas have greater resilience to organic inputs.

KEY WORDS: Benthic recovery · Ecological function · Recolonisation · Organic enrichment · Resilience · Macrofauna · Salmon aquaculture

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