DEVELOPMENT OF A CONTINUOUS-FLOW RENEWAL SYSTEM FOR SEDIMENT TOXICITYTESTING

Development of a flow-through system for sediment toxicity testing has been difficult in part because of problems associated with the precis ion, and subsequent expense, necessary to create a pump that accuratel y delivers small amounts of overlying water. This article describes a novel continuous flow-through apparatus designed to quantitatively and continuously deliver small amounts of overlying water to individual t est chambers. This system uses a series of motor-driven pistons, simil ar to bicycle pumps, to accurately (similar to 5% variability) deliver small amounts of overlying water (<0.1 ml/min) to individual beakers. The system can deliver more than 3.5 L of replacement fluid in a 24-h period from a single outlet hose. Different solutions can be simultan eously delivered to selected beakers, allowing researchers to study ef fects of water quality parameters on sediment toxicity. Materials for the system are affordable, but construction requires technical assista nce. Detailed schematics to aid in construction of this system are ava ilable on the Internet at http://www.clemson.edu/entox or from the cor responding author. Water quality and the growth and survival of Chiron omus riparius in clean sediments were tested under conditions of conti nuously and intermittently renewed overlying water. Both methods of re newal maintained acceptable average dissolved oxygen levels (>70% of s aturation), but an average daily range of 0.685 and 1.67 mg/L dissolve d oxygen in continuous and intermittent renewal systems, respectively, was observed. No differences were observed in midge survival between continuous and intermittent renewal, but there was a 33% decrease in g rowth (dry weight) of C. riparius in test chambers subjected to interm ittent renewal.