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Identifying and interpreting 1) the timing of organic inputs and patterning of natural quality gradients to reaches along the river ecosystem, 2) strategic patterns adopted by consumer assemblages for processing organic matter available to the river system, and 3) process efficiencies associated with the utilization of energy throughout the continuum (p. 1). 9 According to the theory, river systems exhibit heterotrophy i 4 headwaters where shading and organic input are high, autotrop,y in mid reaches where insolation and temperatures increase, and h tero- trophy in lower reaches where increases in suspended material cause reduced light penetration. No works have specifically addressed the River Continuu Theory since its proposal although a wide range of studies have previously been done which address key elements of the theory and lend s pport to its relevance. . Fisher and Likens (1973) found that up to 99 percent of t e organic energy in a low order stream was of allochthonous orig'n. Minshall (1967) found similar heterotrophic conditions in a to order stream but suggested that primary production played a more imp rtant role in larger streams. Cummins discusses various aspects of he theory in a 1977 work. . The transitions between heterotrophy and autotrophy are controlled by a host of interacting factors including discharg rates and velocities, temperature, insolation, and organic and inorg nic . inputs (Cummins 1974). Thomas and O'Connell (1966) showed tha temperature and insolation are primary factors affecting Bros production but suggested that a combination of other factors, primarily allochthonous materials, control the net amount of p imary 0