Degradation of the Adriatic medusa Aurelia sp. by ambient bacteria
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The decomposition of jellyfish after major bloom events results in the release of large amounts of nutrients, which can significantly alter nutrient and oxygen dynamics in the surrounding environment. The response of the ambient bacterial community to decomposing jellyfish biomass was evaluated in two marine ecosystems, the Gulf of Trieste (northern Adriatic Sea) and Big Lake (Mljet Island, southern Adriatic Sea). The major difference between these two ecosystems is that Aurelia sp. medusae occur throughout the year in the oligotrophic Big Lake, whereas in the mesotrophic Gulf of Trieste, they occur only seasonally and often as blooms. Addition of homogenized jellyfish to enclosed bottles containing ambient water from each of these systems triggered considerable changes in the bacterial community dynamics and in the nutrient regime. The high concentrations of protein, dissolved organic phosphorous (DOP), and PO4 3− immediately after homogenate addition stimulated increase in bacterial abundance and production rate, coupled with NH4 + accumulation in both ecosystems. Our preliminary results of the bacterial community structure, as determined with denaturing gradient gel electrophoresis, indicated differences in the bacterial community response between the two ecosystems. Despite divergence in the bacterial community responses to jellyfish homogenate, increased bacterial biomass and growth rates in both distinctive marine systems indicate potentially significant effects of decaying jellyfish blooms on microbial plankton.
KeywordsAurelia sp. Decomposition Nutrients Bacterioplankton Jellyfish
This research was financed by the Ministry of Higher Education, Science and Technology of the R Slovenia (P1-0237), and bilateral cooperation with the Ministry of Science, Education and Sport of the Croatia. We are grateful to the Mljet National Park authorities for their hospitality during field work. Also thanks to A. Benović, D. Lučić, V. Onofri, J. Forte, and T. Makovec for their help in field work. We are grateful to anonymous reviewers for their critical and valuable comments on the manuscript.
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