Bacterioplankton communities respond to cadmium (Cd) exposure in coastal water microcosms with high temporal variability.
Multiple anthropogenic disturbances to bacterial diversity have been investigated in coastal ecosystems, where temporal variability in bacterioplankton community has been considered as ubiquitous processes. However, far less is known about the temporal dynamics of bacterioplankton community responding to pollution disturbances such as toxic metals. We used coastal water microcosms perturbed with 0, 10, 100, and 1000 ?g L(-1) of cadmium (Cd) for two weeks to investigate temporal variability, Cd-induced patterns, and their interaction in coastal bacterioplankton community and to reveal whether bacterial community structure would reflect Cd gradient in temporal varying system. Our results showed that bacterioplankton community structure shifted along the Cd gradient consistently after 4-day incubation, although it exhibited some resistance to Cd at low concentration (10 ?g L(-1)). Arm race between temporal variability and Cd exposure was observed, and the temporal variability overwhelmed Cd-induced patterns in bacterial community. Temporal succession of bacterial community was correlated with pH, dissolved oxygen, NO3 (-)-N, NO2 (-)-N, PO4 (3-)-P, dissolved organic carbon, and chlorophyll a, and each of these parameters contributed more to community variance than Cd did. However, elevated Cd levels did decrease the temporal turnover rate of community. Furthermore, key taxa, affiliated to family Flavobacteriaceae, Rhodobacteraceae, Erythrobacteraceae, Piscirickettsiaceae, and Alteromonadaceae, showed high frequency of being associated with Cd level during two weeks. This study provides direct evidence that specific Cd-induced patterns in bacterioplankton community exist in highly varying manipulated coastal system. Future investigations on ecosystem-scale across longer temporal scales are needed to validate the observed pattern.