Resistance to ship‐induced waves of benthic invertebrates in various littoral habitats

Abstract

Summary 1. Ship‐induced waves disturb benthic invertebrate assemblages colonizing 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 (0.43–2.19 N m−2). Mean number of detached individuals was recorded for five littoral habitats [coarse woody debris (CWD), reeds, sand, stones and tree roots], representing different levels of structural complexity as quantified by their fractal dimensions (FD). 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, CWD, stones, reeds and tree roots. 4. Consistent with their different morphologies and methods of attachment to substrates, the five species displayed differences in their response 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 FD 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.

Can biological invertebrate traits resolve effects of multiple stressors on running water ecosystems?

“…The a priori predictions of the effects of cargoship traffic addressed two potentially related stressors for riverine invertebrates: the importation of taxa from elsewhere (Ricciardi, Serrouya & Whoriskey, 1995;Tamburri, Wasson & Matsuda, 2002) and the production of disturbing waves (Petran, 1977). These stressors should affect trait categories favouring biological invasions (Statzner, Bonada & Dolédec, 2008b) or wave resistance (Gabel et al, 2008), respectively. Therefore, predicted that cargo-ship traffic should increase the frequency of trait categories that facilitate the foundation of new populations: long life cycles ( ‡semivoltine), several reproductive cycles per individual, reproduction by single individuals, hermaphroditism, bud production and ⁄ or ovoviviparity.…”

Ecology of freshwater shore zones

“…Structural complexity or high spatial heterogeneity is typically correlated with high densities (Lewin et al 2004;Kostylev et al 2005) or species richness (Moon 1934;Le Hir and Hily 2005;Kostylev et al 2005;Moschella et al 2005;Brauns et al 2007) of aquatic invertebrates. Just as with fish, structurally complex shore zones protect invertebrates from the damaging forces of waves (Gabel et al 2008). On the terrestrial side of the shore zone, Paetzold et al (2008b) found that channelization, which simplifies the structure of the shore zone, reduced abundance and richness of terrestrial arthropods, and some vertebrates preferentially use complex shore zones (e.g., Stickney et al 2002).…”

Three different patterns of how low-intensity waves can affect the energy budget of littoral fish: a mesocosm study

“…However, at high turbulence levels, prey capture success becomes hampered (MacKenzie et al 1994), leading to a domeshaped response of fish foraging success to turbulence. In an analogous context, waves in the littoral zone may increase the encounter rate of food items, with benthivorous fish reaping a particular benefit as macroinvertebrates are resuspended by waves (Gabel et al 2008), which may increase their conspicuity and accessibility to fish.…”