Simulation of Vertical Limnological Gradients

ABSTRACT

A simple and inexpensive method of simulating vertical limnological gradients is described. Temperature and oxygen gradients can be created that are similar to those in temperate lakes during winter or summer stratification. Vertical stratification is created by moving a layer of cool, dense water across the bottom of a laboratory tank. The stratification is maintained due to the temperature-density relation of water. Hypoxia can be created by bubbling nitrogen gas to remove oxygen from the incoming water. Other vertical chemical gradients can be created in addition to those involving temperature and oxygen. Use of the method is illustrated by the reaction of benthic invertebrates to developing hypoxia such as might occur in a winterkill lake.