Comparisons of the size, density and behavior of this jellyfish in three fjords (Lurefjorden, Sognefjorden and Halsafjorden) support the hypothesis that retention of P. periphylla is related to basin topography, light attenuation and photosensitivity. Furthermore, we hypothesize that the abundances of P. periphylla in Lurefjorden and Halsafjorden, but not in Sognefjorden, have been stimulated by increased light absorbance of water masses formed in the North Sea.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This is an electronic version of an article published in Journal of Plankton Research http://plankt.oxfordjournals.org/ and may be cited as: Sornes, T. A., Aksnes, D. L., Bamstedt, U., & Youngbluth, M. J. (2007). Causes for mass occurrences of the jellyfish Periphylla periphylla; an hypotheses that involves optically conditioned retention. Journal of Plankton Research, 29(2), 157-167.
Florida Atlantic University. Harbor Branch Oceanographic Institute contribution #1644.