Low parasite biomass in oligotrophic streams differs from previous estimates in aquatic ecosystems

Rachel E. Paseka

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Parasites may mediate ecosystem functioning through a number of direct and indirect mechanisms, but the importance of parasitism at the ecosystem scale is poorly understood. Measuring the density of free-living and parasitic consumers in units that are directly comparable provides a first step toward understanding the importance of parasitism to ecosystem processes. I sampled 2 streams in the New Jersey Pine Barrens seasonally for 1 y to measure the biomass density of all major consumer groups, including macroparasites infecting fish and macroinvertebrates. Parasites made up a small percentage of consumer biomass in Pine Barrens streams, representing just 0.00643 to 0.00733% of total consumer biomass annually. These low values contrast with higher estimates from other aquatic ecosystems, where parasite biomass exceeds that of some free-living consumers. The mean biomass densities of all consumer groups differed significantly between the 2 streams, perhaps because of stream characteristics, such as productivity or pH. Comparison of parasite biomass density in these 2 streams with that in 3 other types of aquatic ecosystems reveals substantial variation both within and among ecosystem types. Methodological differences among published studies complicate comparisons of parasite biomass across ecosystems. I reviewed the methods used in previous studies on parasite biomass and argue for a consistent and transparent method for future research. Comparing the biomass of free-living and parasitic consumers is a first step toward understanding the ecosystem-level importance of parasitism, but more work is needed to understand the specific mechanisms by which parasites influence ecosystem processes and the magnitude of parasite effects.

Original languageEnglish (US)
Pages (from-to)377-386
Number of pages10
JournalFreshwater Science
Issue number2
StatePublished - Jun 2017


  • Biomass density
  • Ecosystem functioning
  • Parasite ecology
  • Parasitism
  • Stream ecology


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