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  • Microbial transformation of jellyfish organic matter affects the nitrogen cycle in the marine water column - A Black Sea case study
    Tinta, Tinkara ...
    The increasing trend in jellyfish blooms that have been observed in some coastal areas around the world can have serious ecological consequences. In particular, the fate of jellyfish organic matter ... (jelly-OM), after the decay of jellyfish blooms, and their implications for marine biogeochemical cycles and ecosystem functioning, are still unclear. In order to study bacteria%jelly-OM interactions and the associated fate of the jelly-OM, we conducted two sets of short-term jelly-OM enrichment experiments using coastal and offshore ambient pelagic bacterial assemblages from the Black Sea, where the scyphozoan medusa Aurelia aurita blooms seasonally. The microbial transformation of the jelly-OM was followed using a stable 13C and 15N analyses of particulate jelly-OM together with standard organic and inorganic matter chemical analyses. The effect of the jelly-OM on the ambient bacterial community was investigated by following changes in bacterial abundance, growth rates, and community structure. The Black Sea's surface bacterial assemblages from both systems, coastal and offshore, responded rapidly to the jelly-OM enrichment, preferentially utilizing nitrogen-rich constituents of the jelly-OM, leaving carbon-enriched particulate OM (hypothetically recalcitrant) in the system. The end products of the bacteria-mediated jelly-OM degradation process, i.e. total dissolved nitrogen and ammonium, accumulated in the system, indicating possible implications for the nitrogen cycle. Despite the differences in the Black Sea's coastal and offshore seawater background nutrient concentrations and particulate OM quality, the nitrogen budget was very much the same in both studied systems, however there were differences in the bacterial community function/performance from these two environments. The addition of jelly-OM triggered different structural changes in the coastal and offshore ambient bacterial communities, suggesting that different bacterial groups were capable of utilizing jelly-OM. A comparison of the response of natural bacterial community to the jelly-OM and the bacterial transformation of the jelly-OM in different marine ecosystems indicates that the degree of bacterial growth rate and the rate of ammonium accumulation depend on the incidence of jellyfish occurrence, physiochemical environmental conditions, and possibly also on ambient bacterial community composition. Our study provides insights into the nature of bacteria-jelly-OM interactions, the processes and mechanisms of bacterial jelly-OM transformation, and the consequences for marine nitrogen (and carbon) cycle, as well as for the functioning of different coastal marine ecosystems.
    Source: Journal of experimental marine biology and ecology. - ISSN 0022-0981 (Vol. 475, 2016, str. 19-30)
    Type of material - article, component part
    Publish date - 2016
    Language - english
    COBISS.SI-ID - 3663183
    DOI

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