Synergy between shading and herbivory triggers macrophyte loss and regime shifts in aquatic systems

TY - JOUR

T1 - Synergy between shading and herbivory triggers macrophyte loss and regime shifts in aquatic systems

AU - Hidding, Bert

AU - Bakker, Elisabeth S.

AU - Hootsmans, Michiel J. M.

AU - Hilt, Sabine

N1 - 6022, AqE; Data Archiving: no data model study

PY - 2016

Y1 - 2016

N2 - Macrophytes play a keystone role in shallow aquatic ecosystems. In lakes, macrophytes stabilize clear-water conditions with high biodiversity and their decline can cause a shift to a turbid state with lower biodiversity. Various mechanisms have been suggested as triggers of macrophyte collapse. Herbivory by waterfowl and fish seems to be one of the obvious factors, but the response of macrophytes to herbivory is ambiguous. We hypothesized that herbivory alone does not typically cause macrophyte collapse, but that shading from periphyton can enhance the effect of herbivores. Shading of macrophytes is supposed to increase with eutrophication due to changes in the top–down control cascading from fish via macroinvertebrates to periphyton. We elaborated on this idea by fitting a macrophyte growth model with different herbivore grazing and periphyton shading scenarios. In addition, we performed a meta-analysis on existing experimental herbivore exclosure studies with respect to periphyton growth. The model supported our proposed hypothesis and the reviewed field studies appeared to point in the same direction. We suggest that a significant herbivore impact may indicate a reduced resilience of vegetation to eutrophication, making it an early warning signal for an imminent macrophyte collapse leading to a sudden shift of the system to turbid conditions.

AB - Macrophytes play a keystone role in shallow aquatic ecosystems. In lakes, macrophytes stabilize clear-water conditions with high biodiversity and their decline can cause a shift to a turbid state with lower biodiversity. Various mechanisms have been suggested as triggers of macrophyte collapse. Herbivory by waterfowl and fish seems to be one of the obvious factors, but the response of macrophytes to herbivory is ambiguous. We hypothesized that herbivory alone does not typically cause macrophyte collapse, but that shading from periphyton can enhance the effect of herbivores. Shading of macrophytes is supposed to increase with eutrophication due to changes in the top–down control cascading from fish via macroinvertebrates to periphyton. We elaborated on this idea by fitting a macrophyte growth model with different herbivore grazing and periphyton shading scenarios. In addition, we performed a meta-analysis on existing experimental herbivore exclosure studies with respect to periphyton growth. The model supported our proposed hypothesis and the reviewed field studies appeared to point in the same direction. We suggest that a significant herbivore impact may indicate a reduced resilience of vegetation to eutrophication, making it an early warning signal for an imminent macrophyte collapse leading to a sudden shift of the system to turbid conditions.

KW - international

U2 - 10.1111/oik.03104

DO - 10.1111/oik.03104

M3 - Article

SN - 1600-0706

VL - 125

SP - 1489

EP - 1495

JO - Oikos

JF - Oikos

IS - 10

ER -