A simple reciprocating apparatus for maintaining long-term turbidity in biological experiments

Andrew Sutherland

Limnol. Oceanogr. Methods 4:49-57 (2006) | DOI: 10.4319/lom.2006.4.49

ABSTRACT: Elevated turbidity adversely affects the behavior, physiology, and distribution of marine and freshwater organisms. Although laboratory turbidity studies vary in topic, scope, and design, they all require an experimental apparatus with the ability to maintain constant sediment concentrations (or turbidities) for extended periods of time. Here, I describe a low-cost alternative to more complex systems, a reciprocating apparatus that uses motor-driven paddles and compressed air to keep fine sediment in suspension for extended periods of time in at least 20 tanks simultaneously. With this apparatus, suspended sediment levels, ranging from 25 to 500 mg/L, were maintained within 90% to 95% of initial values for 7 days. In addition, because sediment was kept in suspension using a very slow curtain of air bubbles, this apparatus did not induce a stress response in test organisms, as measured by stress hormone concentration.