Ecological and functional changes associated with long-term recovery from organic enrichment

• Published in: Marine ecology. Progress series (Halstenbek) Vol. 365; pp. 17 - 24
• Main Authors: Macleod, Catriona K., Moltschaniwskyj, Natalie A., Crawford, Christine M.
• Format: Journal Article
• Language: English
• Published: Inter-Research 18-08-2008
• Subjects: Animal communities; Biological taxonomies; Brackish; Fish culture; Freshwater; Larvae; Marine; Organic farming; Salmo salar; Sediments; Species; Sustainable agriculture; Synecology; Taxa; PSE, Australia, Tasmania
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps07534

The recovery of a soft sediment benthic invertebrate community from high levels of organic enrichment was evaluated after removal of farmed fish at an Atlantic salmonSalmo salarculture site in southeast Tasmania. Although the pattern of recovery followed established successional principles, after 36 mo neither communities under or at the edge of cages, nor communities 10 m from the edge of the cage, had attained a structure equivalent to that of the reference communities. In the first few months there was little evidence of recovery and the community was dominated by species characteristic of impacted conditions. After 12 mo the system had markedly improved, containing a diverse range of species with functional roles similar to those of the reference sites. Once the ecological function of the sediment was restored, subsequent changes in the community structure were relatively minor, simply reflecting the addition of rarer species with longer reproductive cycles and/or larval stages with a greater sensitivity to the negative effects of organic enrichment. These species may be significant where specific community changes, loss of diversity or the possibility of species extinction are the critical issues. However, restoration of system function may be a more useful indicator of generalized recovery from organic enrichment than of community equivalence.