|SREL Reprint #1842|
Effect of macroinvertebrates on detachment of bacteria
from biofilms in stream microcosms
JUDY L. MEYER
LAWRENCE J. SHIMKETS
Abstract. Transport patterns of bacteria in streams depend largely on processes
of detachment from and attachment to surfaces. Stream substrata are coated
with various microorganisms, including bacteria, embedded in a matrix of
extracellular material. These complex communities, called biofilms, may be
disrupted by movement and feeding activities of macroinvertebrates causing
bacterial cells to detach. Laboratory experiments were conducted to assess the
role of stream macroinvertebrates in detachment of bacteria from biofilms.
Marked bacteria that had a rare combination of antibiotic resistances were used
in microcosms as tracers of bacterial exchanges. The role of macroinvertebrates
in movement of bacteria from leaves to water was investigated by including
either mayfly, stonefly, or dragonfly nymphs or glass shrimp in microcosms. The
presence of macroinvertebrates did not alter bacterial exchange between
habitats. There were considerable variation among replicates for some
macroinvertebrate treatments, indicating invertebrates may cause large,
catastrophic releases of bacteria from biofilms on leaves or fecal pellets.
Alternatively, invertebrates may not be directly involved in these releases if
pulses of bacteria result from disintegration of fecal pellets. The effect of
invertebrate density on exchange was measured by varying mayfly nymph
density. No significant differences among densities were detected. The ability of
macroinvertebrates to serve as vectors for transfer of bacteria between leaf
packs was also investigated. Although transfer by invertebrates was detected in
some experiments, transfer was not consistently observed.
SREL Reprint #1842
Leff, L.G. and J.V. McArthur. 1994. Effect of macroinvertebrates on detachment of bacteria from biofilms in stream microcosms. Journal of the North American Benthological Society 13:74-79.