Secondary Production and Organic Matter Processing by Collector Macroinvetebrates in a Desert Stream

Secondary production (measured as dry mass) of collector macroinvertebrates of Sycamore Creek, Arizona, estimated by the size—frequency method, is 135 g°m—2°yr—1. This high rate of production is attributed to a long growing season, continuous reproduction, rapid life cycles of major taxa, and small size at maturity. Assimilation efficiency for selected collector taxa is estimated to be 7—14% and gross growth efficiency 2—11%. At mean standing stock (3 g/m2) collectors ingest 4.2 times their body mass per day. Ingestion exceeds gross primary production, dictating both fecal reingestion and rapid turnover of fine particulate organic matter in this desert stream.