Secondary production and trophic relationships in a spring invertebrate community

The invertebrate fauna of a shaded area of the Danish spring Rold Kilde was sampled for a year. There was a large input of allochthonous beech litter, and the water trickled between waterlogged beech leaves. Discharge was constant and temperature amplitudes were small. Primary consumer biomass and production were 3.24 g AFDM m−2 and 8.65 g AFDM m−2 yr−1 and were dominated by shredders (70 and 69%) and gathering collectors (29 and 30%). The seasonal variation in shredder biomass and production was considerably larger within each shredder species than within the total shredder population, implying a relatively uniform processing of energy during the year. The shredder community processed about half of the total leaf input. The primary consumer P : B̄ was as low as 2.67 yr−1 due to many species with long life cycles. Average P : B̄ for eight univoltine species and five semivoltine species was as low as 3.6 and 2.3 yr−1, mainly due to low rates of elimination. Invertebrate biomass and production in low‐order streams are compared, and it is concluded that streams with a shading canopy have a significantly lower mean biomass, production, and P : B̄ ratio than streams of similar order with reduced or no canopy.