Minimum shoreline restoration requirements to improve the ecological status of a north-eastern German glacial lowland lake in an urban landscape
Lorenz, Stefan; Pusch, Martin T.; Blaschke, Ulrike
published: Jun 1, 2015
ArtNo. ESP141018604004, Price: 29.00 €
Lakeshores suffer substantially from anthropogenic, hydromorphological degradation which affects habitat diversity and the diversity of benthic invertebrates colonizing the littoral zone. Therefore, in lakes subjected to multiple human uses, successful lakeshore restoration requires an adaptive restoration strategy targeting crucial habitat types for sensitive invertebrate groups that indicate a 'good' ecological status according to the EU Water Framework Directive. Hence, we studied the effects of crucial habitat structures, such as the reed belt and coarse woody debris (CWD), on invertebrate assemblages and ecological status. In order to assess the effect of a key human disturbance on those habitats, we generated waves by experimental boat passages and recorded wave heights behind reed belt patches of varying width. Based on critical shear stress values found in former studies that affect invertebrates, results showed that minimum reed belt widths of 27–32 m are needed to protect invertebrates from typical ship-induced wave action. Results from another field study showed that exposed CWD at shoreline sections with artificial shoreline protection by concrete walls and rip-rap indicated that the addition of CWD positively affected invertebrate communities at degraded lakeshore sections. When compared with previous assessments of ecological status, the ecological status already improved from 'moderate' to 'good' when the proportion of CWD among other littoral habitats reached 5% to 15%. Our study thus provides a general approach to estimate minimum restoration requirements depending on specific human pressures. Furthermore, we could demonstrate that even small proportions of specific littoral habitats at degraded shores significantly improve site-specific ecological status.