The Importance of Algae in a Shaded Headwater Stream as Food for an Abundant Caddisfly (Trichoptera)

Benthic algae are an important component of the diet of an abundant grazing insect, larval Neophylax aniqua (Trichoptera), in Bear Brook, New Hampshire, even though algal production represents an extremely small portion of the energy entering the stream. Analysis of larval gut contents showed that algae made up half of the food consumed by N. aniqua and supported an estimated 75% of their growth. The average density of algae in this shaded stream between mid-April and mid-July was approximately 4.6 ± 0.6 mg chlorophyll-a/m² (±1 SE). Algae were more abundant in gravel-covered areas (particle sizes -1 to -4 on phi scale) of stream bottom than in rock-covered areas (particle sizes -5 to -8 on phi scale).