Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Predicted trends towards more intense droughts are of particular significance for running water ecosystems, as the loss of critical stream habitat can provoke sudden changes in biodiversity and shifts in community structure. However, analysing ecological responses to the progressive loss of stream habitat requires a continuous disturbance gradient that can only be generated through large‐scale manipulations of streamflow.
In the first experiment of its kind, we used large artificial stream channels (mesocosms) as analogues of spring‐fed headwaters and simulated a gradient of drought intensity that encompassed flowing streams, disconnected pools, and dry streambeds. We used breakpoint analysis to analyse macroinvertebrate community responses to intensifying drought, and identify the taxa and compositional metrics sensitive to small changes in drought stress.
We detected breakpoints for >60% of taxa, signalling sudden population crashes or irruptions as drought intensified. Abrupt changes were most pronounced where riffle dewatering isolated pools. In the remnant wetted habitat, we observed a shift to larger body sizes across the community, primarily driven by irruptions of predatory midge larvae and coincident population collapses among prey species (worms and smaller midges).
Our results suggest that intense predation in confined, fragmented stream habitat can lead to unexpected changes in body sizes, challenging the conventional wisdom that droughts favour the small. Pool fragmentation might thus be the most critical stage of habitat loss during future droughts, as the point at which impacted rivers and streams begin to exhibit major shifts in fundamental food web properties.
In the first experiment of its kind, we used large artificial stream channels (mesocosms) as analogues of spring‐fed headwaters and simulated a gradient of drought intensity that encompassed flowing streams, disconnected pools, and dry streambeds. We used breakpoint analysis to analyse macroinvertebrate community responses to intensifying drought, and identify the taxa and compositional metrics sensitive to small changes in drought stress.
We detected breakpoints for >60% of taxa, signalling sudden population crashes or irruptions as drought intensified. Abrupt changes were most pronounced where riffle dewatering isolated pools. In the remnant wetted habitat, we observed a shift to larger body sizes across the community, primarily driven by irruptions of predatory midge larvae and coincident population collapses among prey species (worms and smaller midges).
Our results suggest that intense predation in confined, fragmented stream habitat can lead to unexpected changes in body sizes, challenging the conventional wisdom that droughts favour the small. Pool fragmentation might thus be the most critical stage of habitat loss during future droughts, as the point at which impacted rivers and streams begin to exhibit major shifts in fundamental food web properties.
Date Issued
2019-04-01
Date Acceptance
2018-12-20
Citation
Freshwater Biology, 2019, 64 (4), pp.750-760
ISSN
0046-5070
Publisher
Wiley
Start Page
750
End Page
760
Journal / Book Title
Freshwater Biology
Volume
64
Issue
4
Copyright Statement
© 2019 The Authors. Freshwater Biology Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium,
provided the original work is properly cited.
provided the original work is properly cited.
Sponsor
Natural Environment Research Council (NERC)
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000461212700011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
NE/J023736/1
Subjects
Science & Technology
Life Sciences & Biomedicine
Ecology
Marine & Freshwater Biology
Environmental Sciences & Ecology
disturbance gradient
drying
macroinvertebrates
predation
stream drought
CLIMATE-CHANGE
FOOD WEBS
COMMUNITIES
FLOW
RESILIENCE
REGRESSION
EVENTS
MACROINVERTEBRATES
RESTORATION
VARIABILITY
Publication Status
Published
Date Publish Online
2019-02-06