Introduction
Oysters are known filter feeders and can play a role as consumers of bioflocs in integrated farming with other species (IMTA system). However, the tolerance of these bivalves to the high levels of total suspended solids (TSS) characteristic of cultures in biofloc systems is not known. Thus, the aim of the present study was to evaluate the biological responses of the oyster Crassostrea gasar when exposed to different concentrations of total suspended solids in biofloc culture systems, based on behavioral and biochemical analyses.
Methodology
Oysters with an initial weight of 54.18 ± 13.45g; height of 68.2 ± 4.44 mm; length of 50.4 ± 3.50 mm and width of 24.1 ± 5.02 mm and were cultivated for 28 days in 100L tanks. Four treatments were studied. Phyto: control treatment supplied daily with the microalgae Chaetoceros muelleri at a concentration of 16 x 104 cel/ml; Low BFT treatment – with maintenance of approximately 100 mg/l of TSS; Medium BFT treatment – maintained above 100 to 200 mg/l TSS; High BFT treatment – maintained above 200 mg/l TSS, each with 4 replicates.
The oyster valve activity was monitored using Hall effect sensors according to the methodology of Guterres et al. (2020). The total antioxidant capacity against peroxyl radicals (ACAP) was determined according to the methodology of (Amado et al., 2009).
Results
The use of aperture sensors indicated that there was a significant difference between treatments. The BFT High treatment had a shorter valve opening time, followed by the BFT Medium, BFT Low and control (Fito) treatments (Table 1). Table 1 shows the frequency (%) with which oysters open their valves and were classified as "Closed", "Slightly Open", Open and "Fully Open" (Table 1).
Regarding the total antioxidant capacity against peroxyl radicals (ACAP), there was a significant difference between treatments at the end of the experiment. The BFT High treatment showed a larger average area than the Fito, while the BFT Low and BFT Medium treatments showed no differences between the other treatments (Figure 1).