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Results and problems of an "unsuccessful" benthos cage predation experiment (Western Baltic)
Arntz, W.E. (1977). Results and problems of an "unsuccessful" benthos cage predation experiment (Western Baltic), in: Keegan, B.F. et al. (Ed.) Biology of Benthic Organisms: 11th European Symposium on Marine Biology, Galway, October 1976. pp. 31-44
In: Keegan, B.F. et al. (Ed.) (1977). Biology of Benthic Organisms: 11th European Symposium on Marine Biology, Galway, October 1976. Pergamon Press: Oxford. ISBN 0-08-021378-2. XXXIII, 630 pp., more

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    VLIZ: Proceedings [25760]
Document type: Conference paper

Keywords
    Benthos; Experimental research; Submerged cages; Astarte elliptica (Brown, 1827) [WoRMS]; Asterias rubens Linnaeus, 1758 [WoRMS]; Capitella capitata (Fabricius, 1780) [WoRMS]; Carcinus maenas (Linnaeus, 1758) [WoRMS]; Diastylis rathkei (Krøyer, 1841) [WoRMS]; Mya truncata Linnaeus, 1758 [WoRMS]; Marine

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  • Arntz, W.E.

Abstract
    In the Protected Research Area of the Joint Research Programme "Interaction Sea-Sea Bottom" of Kiel University, at 20 m depth, a number of in situ macrobenthos experiments were carried out to follow up the establishment of a faunal community as well as specific community mechanisms like competition, displacement and predation. This paper deals with an experiment carried out in 9 benthos cages, each 1 m², between August 1972 and May 1974. Originally the cages were intended to provide data on the amount of predation by demersal fish (i.e. to show the development of a community that was not preyed upon by fish larger than 10 cm). Towards the end of the experiment however the fauna was no richer inside than outside the cages. One of the main reasons was that a "secondary hard bottom" in a muddy sand area attracts large numbers of starfish (Asterias rubens). The starfish, when young, enter the cages and prey upon the fauna much more heavily than on a "normal", 20 m depth, bottom. The same applies to the shorecrab, Carcinus maenas, which for lack of shelter does not normally appear at this depth and to gobies which were protected from large predators and thus appeared in unusually large numbers. Another reason was that drifting macroalgae caught on the cages and started decaying after a while, increasing 02 depletion and resulting in adverse H2S conditions. Apart from a number of useful experiences which were employed in designing a new experiment, the "unsuccessful" experiment yielded some results on the impact of oxygen decrease (which is a usual feature in the investigation area during late summer) on different faunal groups and species. While the mollusc populations collapsed with the exception of a few old specimens, mainly Mya truncata and Astarte elliptica, the polychaetes reacted in a very distinctive way. Some species were killed off whereas a few others (especially Capitella capitata) developed very well. With crustaceans (mostly Diastylis rathkei), as with the young stages of molluscs and polychaetes, predation, inside the cages, must be considered as having influenced the process of recolonization. Contrary to the original idea, this would give the benthic species even less chance to recover than under natural conditions.

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