Shipping in rivers can have substantial effects on local flow velocity conditions. With the expected increase in shipping in the near future, it is important to determine the effect of changing flow conditions on the potential occurrence of freshwater mussels and snail species. This study assessed 1) the effect of shipping on maximum flow velocities in the shore zone of rivers and 2) the upper flow velocity occurrences of native and alien freshwater mussels and snails. By combining these two datasets the potentially absent fraction of these species was determined. Subsequently, the impact of changed species composition on ecosystem services was assessed. Measurements of ship effects were performed in both impounded and free-flowing rivers, in traditional river training structures in the form of groins (see photo) and in the shore zone behind the novel longitudinal training dams.
Findings and Implications to practice
Highest effects on maximum flow velocity were found for freight ships in groin fields for both impounded and free-flowing rivers (54.0 and 73.7 cm.s-1, respectively). Under these flow conditions, the potentially occurring fraction of freshwater mussels and snails was reduced to 0.76 and 0.61 for groin fields in impounded and free-flowing rivers, respectively. The highest POFs were found inshore channels behind a longitudinal training dam in a free-flowing river. Shipping is associated with a shift of the mollusc species assemblage towards flow resistant species and could thereby affect ecosystem functioning and services.
- Koopman, R., Collas, F. P. L., Breure, A. M., Lenders, R., van der Velde, G., & Leuven, R. S. E. W. (2018). Predicting effects of ship-induced changes in flow velocity on native and alien molluscs in the littoral zone of lowland rivers. Aquatic Invasions, 13(4), 481–490. https://doi.org/10.3391/ai.2018.13.4.06.
Absence of freshwater mussels in Europe in relation to climate-related environmental factors
Longitudinal training dams decrease effects of navigation and increase the density of juvenile fish species in the littoral zones of the river Rhine.
Last modified: 19/06/2019