Population dynamics of natural colonies of <Emphasis Type="Italic">Aurelia</Emphasis> sp. scyphistomae in Tasmania,Australia |
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Authors: | Simon Willcox Natalie A Moltschaniwskyj Christine M Crawford |
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Institution: | (1) Marine Research Laboratories, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, PO Box 49, Sandy Bay, Hobart, Tasmania, Australia;(2) School of Aquaculture, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Locked Bag 1370, Launceston, Tasmania, Australia |
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Abstract: | The aim of this study was to identify potential environmental controls of the asexual phases of reproduction by measuring
the rates of asexual reproduction (budding and strobilation) and mortality in naturally occurring populations of Aurelia sp. scyphistomae at different spatial and temporal scales. The percentage cover, density of colonies of Aurelia sp. scyphistomae, and density of the population of two naturally occurring colonies of Aurelia sp. scyphistomae were examined over 2 years in southern Tasmania. Artificial substrates were also deployed to investigate
colony dynamics when density dependent effects were reduced. Clear spatial and temporal differences in the population dynamics
of the colonies were observed. Density dependent effects controlled budding and recruitment of new scyphistomae to the substrate
when populations were dense and space limiting. In contrast, environmental controls of budding and strobilation were more
apparent in a colony with significantly greater area of bare substrate and hence room for expansion. Water temperature and
rainfall (as a proxy for salinity) were linked to changes in population size. Annual and seasonal differences in population
dynamics were not observed in a colony limited by space but were apparent in a colony where space was not limited. When space
was removed as a limiting factor by deploying artificial substrates, a seasonal environmental effect on the rate of growth
of the colony was observed. These studies suggest that the growth, survival and reproduction of the sessile colonial phase
of Aurelia sp. is regulated by a combination of density dependent factors and environmental conditions, which are consequently important
to the formation of jellyfish blooms. |
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