Ultimate biochemical oxygen demand in semi-intensively managed shrimp pond waters

Abstract

Three independent studies were conducted to quantify ultimate biochemical oxygen demand (UBOD) and the corresponding decomposition rate constant for production pond (average 21.5 ha each) waters and effluents on six semi-intensively managed marine shrimp ( Litopenaeus vannamei) farms in Honduras. Samples were collected during the rainy season in studies 1–3 and during the dry season only in Study 1. Pond water samples were collected during the culture period and/or at harvest. The dry season 30-d biochemical oxygen demand (BOD 30) of pond waters across all farms was 26% lower and UBOD was 54% lower, but the decomposition rate constant was more than twice as great as during the rainy season. During the dry season, biochemical oxygen demand was nearly completely expressed after 30 d of incubation whereas during the rainy season BOD was about 65% expressed after 31 d of incubation and the correlation between BOD 31 and UBOD was less strong compared to the dry season. Water quality variables were correlated with measures of BOD during rainy and dry seasons, but only the correlation between chlorophyll a and BOD measures was predictive. In studies 2 and 3, BOD after 88–94 d of incubation was expressed almost completely and corresponded closely with computed UBOD. No significant differences in UBOD were detected in pond samples taken after 30, 61, or 71 (harvest) d of grow out in study 3. Mean decomposition rate constant ranged from 0.054 to 0.071 d −1 in studies 1–3 (rainy season), compared to 0.123 d −1 in Study 1 (dry season).