Measurements of ecological patterns are often used as primary biological
indicators of river health. However, these patterns provide little
information about important stream ecosystem processes (eg the sources
and fate of energy and nutrients). The direct measurement of these
processes is considered fundamental to the determination of the
health of the stream and river ecosystems. Gross Primary productivity
and respiration provide measures of the amounts of organic carbon
produced and consumed within a creek system and thus provide a general
indicator stream metabolism.