engleski

Role of temperature increase on bacterial carbon flux towards higher trophic levels in the Adriatic Sea

Mediterranean Sea (including Adriatic Sea) has been identified as a ‘hotspot’ for climate change, with prediction of the increase in water temperature of 2-4oC over next few decades. Being mainly oligotrophic, and strongly phosphorus limited, Adriatic Sea is characterised by important role of microbial food web in production and transfer of biomass and energy towards higher trophic levels. We hypothesized that predicted rise in temperature of 3oC in the near future may be resulted with increase of bacterial production and bacterial losses to grazers which could significantly enlarged trophic base for metazoans. This empirical study is based on combined ‘space-for-time-substitution’ analysis and experimental approach (in situ grazing experiments performed). ‘Space-for-time-substitution’ analysis includes 3583 data sets of seawater temperature, salinity, inorganic nutrients (P, N, Si), bacterial abundance, HNF abundance and bacterial production, collected at 75 sampling sites located all over the central and south Adriatic Sea during the 2014-2016 period. Grazing on bacteria and bacterial carbon flux towards higher trophic levels were studied by 36 in situ experiments, which were performed on the monthly bases at three sites in the central Adriatic, covering temperature range from 10.26oC to 25.07oC. Results showed that predicted temperature increase of 3oC in the near future, as a result of global warming, could cause a significant increase in bacterial growth at temperatures lower than 16o C (during the colder winter-spring period, as well as in the deeper layers). Furthermore, temperature increase of 3oC, could double the grazing on bacteria by their predators, and could increase the proportion of bacterial production transferred to metazoan food web by 42%. Therefore, it is expected that global warming may further strengthen the role of microbial food web in a carbon cycle in the Adriatic Sea.

Temperature increase ; Bacterial carbon flux ; Adriatice Sea

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