Effects of hydrodynamic disturbances on biodegradation of tetrabromobisphenol A in water-sediment systems

Tetrabromobisphenol A (TBBPA) is an emerging contaminant and exists widely in river and lake systems due to its widespread use. In natural water-sediment systems, hydrodynamic disturbances always exist. However, few studies have investigated the mechanism of TBBPA biodegradation under the influence of water disturbances. In this paper, using a specialized type of racetrack-style flumes, the TBBPA biodegradation in water-sediment systems was studied under the influence of three typical hydrodynamic disturbances. The results of 5-week experiments showed that strong hydrodynamic disturbances greatly accelerate the TBBPA biodegradation rate of the water-sediment systems. The half-lives (T_1/2) under static condition (SC) were approximately 40.2 days, and the T_1/2 was reduced to 16.0 days under strong hydrodynamic condition (SHC). Furthermore, the physicochemical properties and corresponding bacterial communities under these conditions were investigated to help explain the TBBPA biodegradation mechanism. The results showed that strong currents could promote dissolved oxygen (DO) levels, increase nutrient concentrations, and reduce the bacterial diversity in the sediment. Meanwhile, due to the increase in DO and nutrient concentrations, the aerobic bacterial genera conducting TBBPA biodegradation showed rapid growth with strong water disturbances, while the growth of anaerobic bacterial genera was inhibited. Citrobacter, which was the most dominant degrading bacterial genus (0.6%-14.9% in water and 3.5%-17.4% in sediment), was closely related to water disturbances and may be linked to enhanced TBBPA biodegradation. Other minor degrading bacterial genera, such as Bacillus, Sphingomonas, Anaeromyxobacter, Geobacter, Clostridium, and Flavobacterium, were also found in these water-sediment systems. The findings from this study showed the importance of considering hydrodynamic disturbance in understanding TBBPA biodegradation in aquatic environments.

"Swimming against the current": Behavioral data of B etta splendens during an escape and avoidance task with water flows as the aversive stimulus

This paper describes the behavioral data of an experiment in which water flows (WFs) were first used as replacement of the traditional electric shocks to test free-operant avoidance in Betta splendens (Hurtado-Parrado et al. 2019 https://doi.org/10.1016/j.beproc.2018.10.021). WFs with a duration of 10 s each were delivered with 30-s flow-flow (F–F) and response-flow (R–F) intervals in a custom-made shuttle tank. Fish escaped or avoided the WFs by changing compartments. Crossings during the WFs, interrupted the flows, were automatically scored as escape (Esc), and initiated a new R–F interval. Crossings that occurred during R–F or F–F intervals were scored as avoidance responses and also reset the R–F interval. We compared the effect of adding a warning stimulus - curtains of air bubbles - to the last 5 s of the R–F interval; i.e., signaled versus unsignaled avoidance. A unique development of the WFs procedure, and thus the data here described, is that crossings were further differentiated into subcategories; namely, early avoidance (EA) if a crossing occurred during the first 25 s of the R–F interval; late avoidance (LA) if a crossing occurred during the last 5 s of the R–F interval; and Flow-Flow avoidance (FF) if a crossing occurred anytime during the F–F interval. Here we present the data of six bettas across the different phases of the experiment; namely, baseline (BL - no WFs programmed), signaled avoidance (SA – warning stimulus scheduled), and unsignaled avoidance (UA - no warning stimulus scheduled). The dataset available at the Open Science Framework (OSF) repository (http://doi.org/10.17605/OSF.IO/FMHXD (Hurtado-Parrado et al., 2019)) includes for each fish and per 20-min daily session the total number of crossings; frequency of each type of crossing (Esc, EA, LA, FF); total WF frequency and duration, the total time spent in each compartment, and an index of preference for each compartment based on the proportion of time spent in the tank's compartments.

Aversive control of Betta splendens behavior using water disturbances: Effects of signaled and unsignaled free-operant avoidance and escape contingencies

The vast majority of research on aversive control of behavior using animal models employs electric-shock based procedures with avian and mammalian species. Notwithstanding that pragmatic aspects explain this prominence in the field, there is still a need for testing well-established facts about shock-based aversive control using other, perhaps more ecologically valid or biologically relevant, forms of stimulation with other species. Following up on an observation that water disturbances appear to be aversive to Betta splendens (bettas), we developed a preparation for studying free-operant avoidance with this species in which water flows (WFs) replaced electric shocks. Fish changed compartments in a shuttle tank to escape or avoid 10-s WFs, which were delivered with 30-s flow-flow and response-flow intervals. We tested the effect of adding a warning stimulus (curtains of air bubbles) to the last 5 s of the response-flow interval (i.e., signaled avoidance) on the bettas' temporal distribution of crossings and swimming patterns. Escape was the predominant response, which importantly reduced the exposure to the WFs. Avoidance responses rarely exceeded the frequency of escape. The warning stimulus did not produce the expected postponement of responses to the last segment of the response-flow interval. Distinctive swimming patterns emerged, dissipated, and reappeared during baseline and treatment conditions. These findings confirm the aversive function of WFs for bettas and expand the generality of negative reinforcement phenomena using non-shock-based procedures with a less-frequently studied species. Further developments of the WFs paradigm show promise for replicating other aversive control phenomena (e.g., punishment), and analyzing spatiotemporal patterns produced by aversive contingencies.