Recovery of lotic macroinvertebrate communities from disturbance |
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Authors: | J Bruce Wallace |
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Institution: | (1) Department of Entomology, University of Georgia, 30602 Athens, Georgia, USA |
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Abstract: | Ecosystem disturbances produce changes in macrobenthic community structure (abundances, biomass, and production) that persist
for a few weeks to many decades. Examples of disturbances with extremely long-term effects on benthic communities include
contamination by persistent toxic agents, physical changes in habitats, and altered energy inputs. Stream size, retention,
and local geomorphology may ameliorate the influence of disturbances on invertebrates. Disturbances can alter food webs and
may select for favorable genotypes (e.g., insecticidal resistance). Introductions of pesticides into lotic ecosystems, which
do not result in major physical changes within habitats, illustrate several factors that influence invertebrate recovery time
from disturbance. These include: (1) magnitude of original contamination, toxicity, and extent of continued use; (2) spatial
scale of the disturbance; (3) persistence of the pesticide; (4) timing of the contamination in relation to the life history
stages of the organisms; (5) vagility of populations influenced by pesticides; and (6) position within the drainage network.
The ability of macroinvertebrates to recolonize denuded stream habitats may vary greatly depending on regional life histories,
dispersal abilities, and position within the stream network (e.g., headwaters vs larger rivers). Although downstream drift
is the most frequently cited mechanism of invertebrate recolonization following disturbance in middle- and larger-order streams,
evidence is presented that shows aerial recolonization to be potentially important in headwater streams. There is an apparent
stochastic element operating for aerial recolonization, depending on the timing of disturbance and flight periods of various
taxa. Available evidence indicates that recolonization of invertebrate taxa without an aerial adult stage requires longer
periods of time than for those that possess winged, terrestrial adult stages (i.e., most insects). Innovative, manipulative
experiments are needed in order to address recolonization mechanisms of animals inhabiting streams that differ in size, latitude,
disturbance frequency and magnitude, as well as the potential influence of early colonists on successional sequences of species
following disturbance. |
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Keywords: | Macroinvertebrates Communities Recovery Disturbance |
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