Data from: Trematode parasites exceed aquatic insect biomass in Oregon stream food webs

1) Although parasites are increasingly recognized for their ecosystem
roles, it is often assumed that free-living organisms dominate animal
biomass in most ecosystems and therefore provide the primary pathways for
energy transfer. 2) To examine the contributions of parasites to ecosystem
energetics in freshwater streams, we quantified the standing biomass of
trematodes and free-living organisms at nine sites in three streams in
western Oregon, USA. We then compared rates of biomass flow from snails
(Juga plicifera) into trematode parasites relative to aquatic vertebrate
predators (sculpin, cutthroat trout, and Pacific giant salamanders). 3)
The trematode parasite community had the fifth highest dry biomass density
among stream organisms (0.40 g m-2) and exceeded the combined biomass of
aquatic insects. Only host snails (3.88 g m-2), sculpin (1.11 g m-2),
trout (0.73 g m-2), and crayfish (0.43 g m-2) had a greater biomass. The
parasite 'extended phenotype', consisting of trematode plus
castrated host biomass, exceeded the individual biomass of every taxonomic
group other than snails. The substantial parasite biomass stemmed from the
high snail density and infection prevalence, and the large proportional
mass of infected hosts that consisted of trematode tissue (mean = 31% per
snail). 4) Estimates of yearly biomass transfer from snails into
trematodes were slightly higher than the combined estimate of snail
biomass transfer into the three vertebrate predators. Pacific giant
salamanders accounted for 90% of the snail biomass consumed by predators.
5) These results demonstrate that trematode parasites play
underappreciated roles in the ecosystem energetics of some freshwater
streams.