Importance of bioturbators for biodiversity maintenance: indirect effects of fishing disturbance

The relative impact on macrofaunal diversity of 7 naturally co-occurring bioturbators has been examined in a benthic mesocosm experiment. The bioturbators chosen were selected because of their potential vulnerability to the disturbances associated with demersal trawling. The experiment was conducted...

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Published in:Marine ecology. Progress series (Halstenbek) 2004-07, Vol.275, p.1-10
Main Authors: Widdicombe, Stephen, Austen, Melanie C., Kendall, Michael A., Olsgard, Frode, Schaanning, Morten T., Dashfield, Sarah L., Needham, Hazel R.
Format: Article
Language:English
Subjects:
Amphiura chiajei
Animal and plant ecology
Animal communities
Animal, plant and microbial ecology
Aphrodita aculeata
Aquatic communities
Astarte sulcata
Biodiversity
Biological and medical sciences
Bioturbation
Brissopsis lyrifera
Burrowing
Calocaris macandreae
Community structure
Current density
Fundamental and applied biological sciences. Psychology
Marine
Nephtys caeca
Nuculana minuta
Sea water ecosystems
Sediments
Species
Species diversity
Synecology
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Summary:The relative impact on macrofaunal diversity of 7 naturally co-occurring bioturbators has been examined in a benthic mesocosm experiment. The bioturbators chosen were selected because of their potential vulnerability to the disturbances associated with demersal trawling. The experiment was conducted at the Solbergstrand mesocosm (Norwegian Institute for Water Research) using subtidal sediment collected from Bjørnehodebukta, a small sheltered bay in the Oslofjord. For 3 of the bioturbating species (Brissopsis lyrifera,Aphrodita aculeataandAmphiura chiajei) a positive, linear relationship was demonstrated between bioturbator abundance and measures of species richness (number of species and Margalef species richness). It was suggested that the presence of these bioturbating species increased oxygen penetration into the sediment, leading to an enhancement in the ability of benthic systems to process organic material. This had a beneficial effect on the associated fauna in terms of maintaining levels of diversity. ForNephtys caeca, highest species diversity was seen in the low abundance treatments. Predation byN. caecaon small polychaetes is proposed as a possible explanation of the lower diversity in high-density treatments. It is concluded thatB. lyrifera,A. aculeata,A. chiajeiandN. caecaare functionally similar with respect to setting the diversity of the associated macrobenthic community and may therefore fulfill the same role within the benthic ecosystem. The presence ofCalocaris macandreae,Nuculana minutaandAstarte sulcatahad no detectable effect on diversity. Trawling has been shown to reduce the abundance of bioturbating species, and the current study demonstrates important implications of this loss on the maintenance of diversity. In addition, the interactions between bioturbation, diversity and organic enrichment highlight the need for management of anthropogenic impacts within the coastal environment in a holistic way rather than by isolation.
ISSN:0171-8630
1616-1599
DOI:10.3354/meps275001