Ecological characteristics of a typical coastal artificial shoreline considering the key drivers involved

Abstract

The loss of natural shorelines has been accelerated by the construction of artificial shorelines in recent years, which is a serious threat to intertidal biodiversity and makes the ecological construction of artificial shorelines increasingly urgent, yet the mechanisms of regulating intertidal biodiversity using artificial structures are still poorly understood. In this study, the different fates and causes of the ecological effects of the two artificial seawalls were investigated in detail. We conducted on-site sampling and surveys on the water quality, wave conditions, and organisms around seawalls of different types of structures, and quantified the hydrodynamic strength distribution of the seawall walls through field experiments, while introducing numerical simulation methods to reproduce the flow field characteristics near the seawalls. The results show that the differences in the ecological effects of the investigated artificial seawalls are mainly due to flow (including wave-induced flow) rather than water quality, or other factors. Although the cavity structure of the seawall surface contributes to biodiversity, it is also the presence of this large and complex cavity structure that leads to local flow field heterogeneity in the seawall, which enhances fluid wall shear and makes it more difficult for intertidal organisms to attach and even causes a decrease in their surface biomass. However, in terms of ecosystem health, seawalls with more complex structures provide a more stable community structure, so we believe that they are more ecologically sound. In ecological shoreline construction, flow field heterogeneity should be taken into account as an important driver of biotic community assemblages on artificial coastlines. How to reconcile structural complexity with the resulting flow field heterogeneity should be an important part of ecological engineering construction. Our study provides new insights into the ecological construction of artificial shorelines.