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Ecosystem significance of crayfishes and stonerollers



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J N Am Benthol Soc 2003 22 3 423 441 q 2003 by The North American Benthological Society Ecosystem significance of crayfishes and stonerollers in a prairie stream functional differences between co occurring omnivores MICHELLE A EVANS WHITE1 AND WALTER K DODDS Division of Biology Kansas State University Manhattan Kansas 66506 USA MATT R WHILES Department of Zoology Southern Illinois University Carbondale Illinois 62901 6501 USA Abstract The ecosystem significance of crayfishes Orconectes nais Faxon and O neglectus Faxon and central stoneroller minnows Campostoma anomalum Rafinesque was examined in a tallgrass prairie stream by estimating the trophic basis of production and consumption for each species Annual ash free dry mass production and production to biomass ratios of C anomalum 260 mg m22 y21 1 3 were lower than that of O nais 719 mg m22 y21 2 4 and O neglectus 508 mg m22 y21 2 1 Gut content analysis revealed no significant differences in the percentages of the various food items ingested by O nais and O neglectus indicating they were functionally similar with respect to the types of organic matter processed in this system We found a significant difference among seasons in the of invertebrates in C anomalum guts p 5 0 0001 and the of algae in Orconectes spp guts p 5 0 005 indicating the importance of measuring resource use throughout the growing season Leaves contributed most to Orconectes spp annual production 45 followed by animal matter 30 algae 19 and amorphous detritus 6 Algae contributed most to C anomalum production 47 followed by amorphous detritus 30 animal matter 21 and leaves 2 Orconectes spp consumed more leaf litter filamentous green algae and macroinvertebrates than C anomalum whereas C anomalum consumed more diatoms Crayfish and central stonerollers are both omnivores that function as important consumers and processors of algae and detritus in this tallgrass prairie stream but each focuses on slightly different types of similar resources Key words tents Orconectes central stonerollers omnivory growth rate secondary production gut con Crayfish and central stonerollers Campostoma anomalum Rafinesque are widespread and abundant benthic omnivores in North American streams Momot 1984 Matthews et al 1987 These organisms often co occur in midwestern streams in the United States and are thought to consume similar food resources However few comparative data exist on the functional role of these 2 omnivores within the same stream system Crayfish can play important roles in structuring benthic macroinvertebrate and algal communities Creed 1994 Charlebois and Lamberti 1996 Parkyn et al 1997 as well as in organic matter processing and energy flow Huryn and Wallace 1987 Whitledge and Rabeni 1997 An examination of the trophic basis of production Winner of the WILDCO Student Award for the Best Oral Presentation in Basic Research at the 49th Annual NABS Meeting La Crosse Wisconsin 2 7 June 2001 Present address Department of Biological Sciences University of Notre Dame Notre Dame Indiana 46556 USA E mail mevanswh nd edu 1 of crayfish in a Missouri stream indicated that animal 29 51 and detrital 32 56 material contributed the most to secondary production followed by algae 14 18 Whitledge and Rabeni 1997 In addition Whitledge and Rabeni 1997 found crayfish were important consumers of animal matter detritus and algae when compared to other invertebrates in this system Similar information on the role of C anomalum in organic matter processing and energy flow is lacking even though these fish can be extremely abundant in small and medium sized streams and sometimes dominate the fish community both numerically and in terms of biomass Schmulbach 1953 Lennon and Parker 1960 Beets 1979 Matthews et al 1987 Studies of C anomalum have focused primarily on its ability to structure benthic algal communities and to reduce algal biomass in prairie and Ozark mountain streams Power et al 1985 1988 Gelwick and Matthews 1992 1997 but see Vaughn et al 1993 In addition to algae C anomalum also ingests animal matter and a signif 423 424 M A EVANS WHITE icant amount of detritus Kraatz 1923 Fowler and Taber 1985 Burkhead 1980 However the relative importance of these food sources to C anomalum production is not known In addition few investigators have measured C anomalum growth rates Schmulbach 1953 Lotrich 1973 or secondary production Lotrich 1973 in a way that can be compared among streams and among different components of stream communities e g macroinvertebrates Recent investigations in a prairie stream provided comparative data for the roles of crayfish and C anomalum in material processing Dodds et al 2000 quantified N cycling in Kings Creek a tallgrass prairie stream located on Konza Prairie Biological Station KPBS and found that crayfish Orconectes spp played a more significant role than other stream macroinvertebrates and C anomalum in algal and detrital N processing However this experiment spanned only 2 mo of the growing season April and May In a related study natural abundance isotope data 15N and 13C collected over many seasons from the same stream suggested that crayfishes might be more dependent than C anomalum upon algal and detrital resources for growth Evans White et al 2001 The objective of our study was to compare the ecosystem significance of Orconectes spp and C anomalum in Kings Creek by estimating the trophic basis of their production and comparing consumption of food resources We addressed 2 component objectives 1 to estimate Orconectes spp and C anomalum biomass growth and production in Kings Creek over 1 growing season and 2 to determine food sources used by each omnivore in Kings Creek by examining gut contents of Orconectes spp and C anomalum We predicted that algal and detrital food sources would be more important to the production of crayfish than C anomalum given previous evidence from natural abundance d15N and d13C studies In addition we predicted crayfishes because of their apparently higher biomass in this stream would be more significant than C anomalum as processors of algae and detritus Methods Study area Kings Creek drains 1059 ha of KPBS a tallgrass prairie preserve located in the Flint Hills ET AL Volume 22 region of northeastern Kansas Fig 1 The availability of detrital and algal resources to consumers in Kings Creek depends upon the composition of the riparian vegetation which has 3 distinct zones Grasses and forbs dominate the riparian zones of headwater


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