GABEL (F.), GARCIA (X.F.), BRAUNS (M.), SUKHODOLOV (A.), LESZINSKI (M.), PUSCH (M.) 2008.- Resistance to ship-induced waves of benthic invertebrates in various littoral habitats. Freshwater Biology (in press).

Abstract

1. Ship-induced waves disturb benthic invertebrate assemblages colonising littoral zones of lakes and rivers. However, the impact of ship-induced waves on invertebrates has rarely been quantified, and the influencing factors have not been addressed.

2. In an experimental wave tank, five benthic invertebrate species, Bithynia tentaculata, Calopteryx splendens, Dikerogammarus villosus, Gammarus roeseli and Laccophilus hyalinus, were exposed to waves of increasing shear stress (0.43 to 2.19 N m-2). Mean number of detached individuals was recorded for five littoral habitats (coarse woody debris, reeds, tree roots, sand and stones), representing different levels of structural complexity as quantified by their fractal dimensions.

3. Results showed that detachment of invertebrates was significantly related to shear stress in all habitats except tree roots. Detachments averaged for the five species were significantly lower in habitats with a high degree of structural complexity, decreasing in the habitat sequence: sand, coarse woody debris, stones, reeds and tree roots.

4. Consistent with their different morphologies and methods of attachment to substrates, the five species displayed difference in their responses to hydraulic stress that were dependent on habitat.

5. The increasing sheltering effect of structural habitat complexity was mirrored by increasing dissipation of the kinetic energy of waves; i.e. the fractal dimension of the habitat was positively correlated with shear stress reduction due to the flow resistance of the habitat.

6. Network habitats such as tree roots provided the best sheltering conditions against hydraulic disturbance, because they combined good refuge availability for all studied invertebrate species and maximal dissipation of kinetic wave energy. Consequently, persistent anthropogenic impacts, such as lakeshore modification or long-term exposure to ship-induced waves, which cause disappearance of complex littoral habitats such as tree roots or dense reed belts, will drastically increase the adverse effects of boating and ship traffic on littoral invertebrate assemblages.

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