 |
| Titel |
Flow effects on benthic stream invertebrates and ecological processes |
| VerfasserIn |
Maja Koprivsek, Mitja Brilly |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250044784
|
|
|
|
|
|
| Zusammenfassung |
| Flow is the main abiotic factor in the streams. Flow affects the organisms in many direct and
indirect ways. The organisms are directly affected by various hydrodynamic forces and mass
transfer processes like drag forces, drift, shear stress, food and gases supply and washing
metabolites away. Indirect effects on the organisms are determining and distribution of the
particle size and structure of the substrate and determining the morphology of riverbeds. Flow
does not affect only on individual organism, but also on many ecological effects. To
expose just the most important: dispersal of the organisms, habitat use, resource
acquisition, competition and predator-prey interactions. Stream invertebrates are
adapted to the various flow conditions in many kinds of way. Some of them are
avoiding the high flow with living in a hyporeic zone, while the others are adapted to
flow with physical adaptations (the way of feeding, respiration, osmoregulation
and resistance to draught), morphological adaptations (dorsoventrally flattened
shape of organism, streamlined shape of organism, heterogeneous suckers, silk,
claws, swimming hair, bristles and ballast gravel) or with behaviour. As the flow
characteristics in a particular stream vary over a broad range of space and time scales, it is
necessary to measure accurately the velocity in places where the organisms are
present to determine the actual impact of flow on aquatic organisms. By measuring
the mean flow at individual vertical in a single cross-section, we cannot get any
information about the velocity situation close to the bottom of the riverbed where
the stream invertebrates are living. Just measuring the velocity near the bottom is
a major problem, as technologies for measuring the velocity and flow of natural
watercourses is not adapted to measure so close to the bottom. New researches in the last
two decades has shown that the thickness of laminar border layer of stones in the
stream is only a few 100 micrometers, what is not enough to make a shelter for
stream invertebrates. It serves as a shelter only for microorganisms, but the stream
invertebrates have to avoid the swift flow or adapt to flow with adaptations described
above. To understand what conditions are subject to aquatic organisms and how to
adapt, it is essential. Both, knowledge of fluid dynamics in natural watercourses and
ecology are needed to understand to what conditions the stream invertebrates are
exposed and how they cope with them. Some investigations of near bed flow will be
performed on the Glinšica stream. The acoustic Doppler velocimeter SonTek will
be adapted to measure so close to the bed as possible. It is expected we should
be able to measure the velocities just 0,5 cm above the bed surface. We intend to
measure the velocities on a natural and on a regulated reach and then compare the
results. |
|
|
|
|
|
|