Interactive effects of Russian olive and the common carp on linked stream-riparian food webs

Interactive effects of Russian olive and the common carp on linked stream-riparian food webs Kaleb K. Heinrich 1,2 and Colden V. Baxter 2 1 Department of Biology, University of Mary Hardin-Baylor, Belton, Texas 2 Department of Biological Sciences, Idaho State University, Pocatello, Idaho

Multiple invaders Biological invasions continue to increase Non-native, invasive species effects on other non-native species are lacking Multiple invaders maybe involved in a variety of complex interactions

Invasional meltdown hypothesis The process by which a group of nonindigenous species facilitate one another s invasion (Simberloff and Von Holle 1999)

Ecological Stoichiometry Nutrient recycling by a consumer depends on imbalance between its nutrient content and its food Invasive species effects via changes in nutrient stoichiometry has received little attention

Deep Creek International Biological Program (IBP) Site Deep Creek Dr. G. W. Minshall

Russian olive invasion 1971 2006 2014 Photo credit: G. W. Minshall

Russian olive invasion 1971 2006 Minshall 1978 Bioscience

Russian olive invasion at Deep Creek

Deep Creek 1992 2011 Russian olive cover ~3X increase

Reduces N limitation of stream primary producers Increases DON by 37%, increased load & export DeCant 2008

Increases litter inputs 25X Decomposes 35% slower than native litter Few native stream animals eat it ( mismatch ) 4X increase in benthic storage, then export ~15% decrease in ecosystem efficiency

Carp invasion Deep Creek

Carp increase subsequent Russian olive invasion F [1,12] = 7.82, P = 0.02 IACUC Protocol 707 ~4X increase in carp density Photo: C. V. Baxter

Carp consume and assimilate Russian olive On average, Russian olive made up ~40% of gut contents (n=63) ~1/3 of carp tissue derived from Russian olive (δ 13 C and δ 2 H analysis) Common carp pharyngeal teeth

Bioenergetic analysis of carp Demand: 1 Carp requires 2.0-3.2 g AFDM/day (Huisman 1976, Lupatsch et al. 1998) 1200 g AFDM/day to sustain 70s population 3500 g AFDM/day to sustain current carp population Availability: 1970-71 1800 g AFDM/day 2007-08 12200 g AFDM/day (calculated from Mineau et al. 2012) 1970s

Carp exclusion experiment Carp exclusion (n=7) Control (n=7) Primary producer biomass, organic matter, macrophytes

Subsidized carp effects: F [1,12] = 6.91, P = 0.02

Subsidized carp effects: F [1,12] = 5.41, P = 0.04 F [1,12] = 5.52, P = 0.04

Carp excretion experiment Carp held in coolers NH 4, SRP, TDN, TDP, total N, and total P Comparison of carp with variable amounts of Russian olive in gut (Deep Creek) Compared with carp that do not consume Russian olive (Deep Creek vs. Portneuf River)

Subsidized carp effects: P = 0.008, F [1,18] = 8.849 R 2 = 0.50, P < 0.001

Subsidized carp effects: N:P ratio of recycled material was higher for carp that consumed Russian olive F [1,18] = 8.85, P = 0.008

Consequences for nutrient dynamics?

Consequences for nutrient dynamics? Amplify the spiraling and export of N from streams?

Another dimension:

Large scale Russian olive removal Large scale carp manipulation

Photo credits: Hannah Harris

Summary Current carp population could not be supported without Russian olive inputs Subsidized carp are reducing chlorophyll-a, organic matter, and macrophytes Carp consuming RO are excreting more N

Multiple invasive species interact Consequences for aquatic-terrestrial ecosystem Understanding synergistic consequences of invaders, should inform adaptive management

Acknowledgements Dr. G. W. Minshall Dr. J. Hood & Dr. M. Mineau ISU Stream Ecology Center UMHB Science Education Resource Center Field and lab assistance: C. Baxter, T. Gardner, A. Bell, N. Tillotson, J. Cornell, M. Schenk, R. Blackadar, H. Harris, K. Behn, M. K. Ventura, D. Larson, M. Lyon, A. Eckersell, L. Denny, S. Collins, M. Mozneb, N. Nelson, M. Blackhorse, S. Hennings, E. Richins, D. Huber, R. Burrow, M. Heinrich, and A. Heinrich