Invading crayfish in a Michigan stream: Direct and indirect effects on periphyton and macroinvertebrates

Patrice M. Charlebois, Gary A. Lamberti

Research output: Contribution to journalArticlepeer-review


Crayfish are common inhabitants of North American streams and really species are undergoing human-assisted range expansions. We studied the effects of an introduced crayfish (Orconectes rusticus) on benthic macroinvertebrates and periphyton in a northern Michigan (USA) stream by 1) conducting a 46-d enclosure-exclosure experiment and 2) sampling benthic communities along a longitudinal gradient in crayfish density. In stream enclosures, crayfish reduced total macroinvertebrate densities by 47-58% and herbivore densities by 55-72% relative to exclosures. Over the course of the experiment, periphyton chlorophyll a increased by 48-70% in enclosures compared to an increase of only 8% in exclosures. Periphyton biomass, however, did not vary across treatments. Periphyton primary productivity increased 4-7 times in the presence of crayfish, probably because crayfish reduced grazer densities (indirect effect) and removed non-autotrophic components of the periphyton matrix (direct effect). The longitudinal survey supported experimental results. At sites along a crayfish density gradient occurring over 3 km of stream, periphyton chlorophyll a on rocks increased and macroinvertebrate density decreased with increasing crayfish density. These studies show that crayfish directly and indirectly affected the stream benthos, thereby producing responses at more than 1 trophic level. Some responses were consistent with a trophic cascade, but crayfish increased food web connectance by consuming periphyton. Therefore, crayfish can have complex, multi-trophic level effects on the food webs of invaded streams.

Original languageEnglish (US)
Pages (from-to)551-563
Number of pages13
JournalJournal of the North American Benthological Society
Issue number4
StatePublished - Dec 1996
Externally publishedYes


  • Orconectes rusticus
  • crayfish
  • enclosure-exclosure
  • exotic species
  • food webs
  • macroinvertebrates
  • periphyton
  • stream
  • trophic cascade

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science


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