GARCIA (X.F.), GABEL (F.), HOCHMUTH (H.), BRAUNS (M.), SUKHODOLOV (A.), PUSCH (M.) 2007.- Do littoral habitats with high complexity mitigate the impact of ship-induced waves on benthic invertebrates. In: G. Nützmann (Ed.), Annual Report 2006, Leibniz-Institute für Gewässerökologie und Binnenfischerei, 24/2007, 99-108.
Ship-induced waves constitute a major threat to macroinvertebrates inhabiting littoral zones of lakes and rivers. However, factors influencing the dislodgment of invertebrates by waves were never addressed nor quantified. We investigated interactions between structural complexity of littoral habitats and wave-induced hydraulic disturbances on invertebrates. In an experimental wave tank, five species were exposed to waves of increasing shear stress (4.3 - 21.9 dyn/cm2) in five littoral habitat-types and in four different reed densities representing different levels of structural complexity.
The number of detached individuals depended significantly on the applied shear stress. Individual detachment rate averaged for the five species was significantly lower in habitats with a high degree of structural complexity, decreasing in the habitat sequence sand, coarse woody debris, stones, reed and roots and with increasing reed densities. Also, several significant species-specific effects were observed, as species-specific fixing or hiding capabilities matched specific physical habitat characteristics. Besides offering good fixing possibilities, the structural complexity also leads to a reduction of shear stress.
Consequently, adverse effects of ship and boat traffic on littoral invertebrate assemblages is drastically increased as soon as complex littoral habitats like tree roots or dense reed belts disappear by wave action or adverse lakeshore management practices.