Potential Effluent Quality from Commercial Crawfish Ponds

Abstract

AbstractSeventeen commercial and two demonstration crawfish ponds in southern Louisiana that were either planted with rice Oryza sativa or a sorghum‐sudangrass hybrid (Sorghum bicolor × S. sudanese) or colonized with volunteer terrestrial or semiaquatic vegetation were evaluated for potential effluent quality. Nutrients and solids concentrations in potential crawfish pond effluents increased significantly in spring and summer from fall and winter levels. Potential effluent quality was poorest during the annual summer drawdown and is likely to have the greatest impact on receiving waterways. Total suspended solids and turbidity most frequently exceeded Louisiana water quality standards. Ponds with volunteer vegetation had significantly lower concentrations of chemical oxygen demand, turbidity, total suspended solids, total volatile suspended solids, and total Kjeldahl nitrogen than ponds with rice and sorghum‐sudangrass. Soluble reactive phosphorus, total phosphorus, total ammonia, nitrite, and nitrate were highest in ponds with sorghum‐sudangrass. Nutrient and solid concentrations were generally lower in ponds with volunteer vegetation, presumably as a result of nutrient uptake by aquatic macrophytes and reduced suspended sediment loads. Establishing limited stands of aquatic macrophytes inside crawfish ponds or using effluent to replenish water in adjacent ricefields may reduce the amount of suspended solids and nutrients entering receiving waters.