TY - JOUR
T1 - Non-additive increases in sediment stability are generated by macroinvertebrate species interactions in laboratory streams
AU - Albertson, Lindsey K.
AU - Cardinale, Bradley J.
AU - Sklar, Leonard S.
N1 - Funding Information:
We thank J. Byrnes, S. Cooper, T. Dunne, B. Fletcher, L. Harrison, K. Kulacki and C. Kurle for advice on study design, D. Herbst, L. Koenig, B. Lewis, B. Medhurst and M. Romanov for field assistance, and D. Viola for advice on statistical analyses. We would also like to thank the three anonymous reviewers who provided excellent comments on previous versions of this manuscript. A collection permit for macroinvertebrates was provided by the CA Department of Fish and Game. This work was supported by grants from the National Science Foundation (1110571), the Valentine Eastern Sierra Reserve, the Dawdy Fund for Hydrologic Science at SFSU, and UCSB’s Ecology, Evolution, and Marine Biology Department.
PY - 2014/8/7
Y1 - 2014/8/7
N2 - Previous studies have shown that biological structures such as plant roots can have large impacts on landscape morphodynamics, and that physical models that do not incorporate biology can generate qualitatively incorrect predictions of sediment transport. However, work to date has focused almost entirely on the impacts of single, usually dominant, species. Here we ask whether multiple, coexisting species of hydropsychid caddisfly larvae have different impacts on sediment mobility compared to single-species systems due to competitive interactions and niche differences. We manipulated the presence of two common species of net-spinning caddisfly (Ceratopsyche oslari, Arctopsyche californica) in laboratory mesocosms and measured how their silk filtration nets influence the critical shear stress required to initiate sediment grain motion when they were in monoculture versus polyculture. We found that critical shear stress increases nonadditively in polycultures where species were allowed to interact. Critical shear stress was 26% higher in multi-species assemblages compared to the average single-species monoculture, and 21% greater than levels of stability achieved by the species having the largest impact on sediment motion in monoculture. Supplementary behavioral experiments suggest the non-additive increase in critical shear stress may have occurred as competition among species led to shifts in the spatial distribution of the two populations and complementary habitat use. To explore the implications of these results for field conditions, we used results from the laboratory study to parameterize a common model of sediment transport. We then used this model to estimate potential bed movement in a natural stream for which we had measurements of channel geometry, grain size, and daily discharge. Although this extrapolation is speculative, it illustrates that multi-species impacts could be sufficiently large to reduce bedload sediment flux over annual time scales in streams where multiple species of caddisfly are present.
AB - Previous studies have shown that biological structures such as plant roots can have large impacts on landscape morphodynamics, and that physical models that do not incorporate biology can generate qualitatively incorrect predictions of sediment transport. However, work to date has focused almost entirely on the impacts of single, usually dominant, species. Here we ask whether multiple, coexisting species of hydropsychid caddisfly larvae have different impacts on sediment mobility compared to single-species systems due to competitive interactions and niche differences. We manipulated the presence of two common species of net-spinning caddisfly (Ceratopsyche oslari, Arctopsyche californica) in laboratory mesocosms and measured how their silk filtration nets influence the critical shear stress required to initiate sediment grain motion when they were in monoculture versus polyculture. We found that critical shear stress increases nonadditively in polycultures where species were allowed to interact. Critical shear stress was 26% higher in multi-species assemblages compared to the average single-species monoculture, and 21% greater than levels of stability achieved by the species having the largest impact on sediment motion in monoculture. Supplementary behavioral experiments suggest the non-additive increase in critical shear stress may have occurred as competition among species led to shifts in the spatial distribution of the two populations and complementary habitat use. To explore the implications of these results for field conditions, we used results from the laboratory study to parameterize a common model of sediment transport. We then used this model to estimate potential bed movement in a natural stream for which we had measurements of channel geometry, grain size, and daily discharge. Although this extrapolation is speculative, it illustrates that multi-species impacts could be sufficiently large to reduce bedload sediment flux over annual time scales in streams where multiple species of caddisfly are present.
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U2 - 10.1371/journal.pone.0103417
DO - 10.1371/journal.pone.0103417
M3 - Article
C2 - 25101964
AN - SCOPUS:84905460160
SN - 1932-6203
VL - 9
JO - PloS one
JF - PloS one
IS - 8
M1 - e103417
ER -