Elsevier

Ocean & Coastal Management

Volume 128, August 2016, Pages 1-9
Ocean & Coastal Management

Ecological rehabilitation prediction of enhanced key-food-web offshore restoration technique by wall roughening

https://doi.org/10.1016/j.ocecoaman.2016.04.008Get rights and content

Highlights

  • Three techniques were proposed to enhance the key-food-web ecological restoration.

  • The effect of present enhanced restoration was evaluated by Ecopath model and ocean health index.

  • The maturity and health of the enhanced restoration ecosystems were improved comparing to the original ecosystem.

  • The enhanced technique with the integration of artificial reefs and hard slope roughing is the best.

Abstract

The enhanced key-food-web offshore restoration technique by wall roughening is proposed in this approach. Three kinds of wall roughening, i.e. artificial reefs, hard slope roughing and the integration of artificial reefs and hard slope roughing are applied to enhance the original key-food-web offshore restoration technique. The effects of ecological rehabilitation of the proposed enhanced key-food-web offshore restoration technique are predicted by the models of Ecopath model and ocean health index. The results indicate that the ecological rehabilitation of the enhanced key-food-web offshore restoration technique with different wall roughening is better than that of the original one. Among them, the enhanced key-food-web offshore restoration technique with the integration of artificial reefs and hard slope roughing is the best. After using it, the restored offshore ecosystem is the most mature, and the ocean health index is increased to 87.1 or 87.3 with respect to the case of 2% or 0.57% artificial reef for the conservative or optimistic analysis.

Introduction

Marine ecosystem is one of the most valuable human resources supplying a variety of benefit and servicing for human and other species (Shi et al., 2008). However, with expanding industrialization and urbanization such as wanton discharge of sewage from plants have caused water resources deterioration along vast coastline since late 1950s, and consequently marine ecosystems have been destroyed and degraded seriously (Chen and Uitto, 2003, Chen et al., 2012, Sun et al., 2013). The inshore ecosystem of Bohai Bay is no exception, and it is one of China's most pollution waters (Zhou et al., 2012). Therefore, it is urgent and significant to mitigate the degradation of Bohai Bay inshore ecosystem and make its structure and function recovered.

Previous ecological restoration methods are primarily classified into two categories. One is mainly ecological environment restoration, such as shoreline design technique, hard slope roughing (Moschella et al., 2005) and artificial reefs technique (Pitcher et al., 2002), to construct biological habitat and improve biotic living environment. These techniques contribute to an increment in the maturity of degraded ecosystem gradually. The other is biological population restoration, such as the quantitative biological food web proliferation technique (Zheng and You, 2014) and alien species introduction technique (Borsje et al., 2011), to enhance marine bio-resource and food web. These techniques help the restoration ecosystem achieve ecological balance and stability. However, these ecological restoration techniques only focus on one aspect of improving the biotic living environment or enhancing marine bio-resource and food web. In this paper, the original key food web technique is further enhanced by introducing wall surface roughening, which is an integration of increasing both biotic living environment and the species richness in restoration. The proposed method is benefit of both biotic living environment and species richness to improve the maturity and health of ecosystem comprehensively.

The key food web technique is to rebuild the key food web of restoration ecosystem by quantifying the trophic relationships of screening key species from the reference ecosystem. It is an effective restoration method, which avoids the risk of alien species invasion. The wall surface roughening technique is to increase roughness of onshore walls or revetments through engineering methods to provide artificial habitats for species spawning and feeding, similarly, to improve associated biota and water quality. Wall surface roughening is artificial reefs (ARs), hard slope roughing (HSR) and the integration of artificial reefs and hard slope roughing (ARHSR).

ARs are underwater structures which are deployed in underwater intentionally to imitate the features of natural reefs (Baine, 2001). The initial purpose of ARs is commercial fishing. With the pollution and degeneration of marine ecosystem, ARs has become been an important technique to rehabilitate degraded habitats and rich marine resources (Woo et al., 2014). ARs have achieved positive effect in restoring and rebuilding marine ecosystem (Rilov and Benayahu, 2000). ARs influences the environment over a spatial scale of tens to hundreds meters near the reef (Wilding and Sayer, 2002). The influences are the variations in nutrient cycling and transport (Falcao et al., 2007, Vicente et al., 2008) and sediment biogeochemistry (Alongi et al., 2008). This lead to the changes in the structures and richness of associated infaunal organisms (Langlois et al., 2006).

HSR is used to increase surface roughness through engineering methods. Roughness is peak-valley geometric shapes on offshore slope surface. Roughness is also important for sediment dynamics (Guillén et al., 2008). Rough surface performs as a wave dissipater to reduce the impacts on building infrastructure, and provides refuges for epibiotic species similarly (Nordstrom, 2014). HSR is obtained by engineering methods of making surface unevenness and planting vegetation on offshore slopes. The hybrid approach of combining unevenness or porous structure with ecological revetment is becoming popular.

In this study, three wall surface roughening techniques (ARs, HSR and ARHSR) are applied to enhance the restoration effect of key food web technique. The Ecopath model and ocean health index are used to analysis the maturity and health of the restoration ecosystem, respectively. The restoration effect and technical feasibility of the proposed enhanced technique is evaluated in the restoration of inshore marine ecosystem.

Section snippets

Study site and data sources

The restoration project is a part of a covered harbor, which is located at the first harbor of Tianjin Lin Gang Economic Zone (38°34′–40°15′N, 116°43′–118°04′E) of China (Fig. 1). The restored area is about 5 m in depth and 200 m along the shoreline and 60 m away from the land in horizontal plane.

The key food web technique enhanced by ARs, HSR and ARHSR is applied to restore the inshore marine ecosystem. Besides applying the ecological key food web restoration technique, the wall surface

Maturity assessment of ecosystem

The restoration effect of the key food web restoration technique with AR and HSR was evaluated with the maturity and health of ecosystem. The maturity of ecosystem is related to its stability, resilience and complexity. The higher of ecosystem stability, resilience and complexity is, the more mature is. The Ecopath model of EE1, EE2 and EE3 was established respectively.

Discussions

The proposed enhanced key-food-web offshore restoration technique is the enhanced technique with increasing the richness species and biotic living environment in restoration areas in order to recover the local healthy ecosystem before water body polluted. It considers the complicated, comprehensive and long-term impacts of ecosystem as it is established. The results of the Ecopath model and ocean health index showed that the restoration ecosystem has higher maturity and health than that of the

Conclusions

The ecological restoration of key-food-web restoration technique enhanced by three kinds of wall roughening techniques, i.e. artificial reefs (ARs), hard slope roughing (HSR) and the integration of artificial reefs and hard slope roughing (ARHSR) was studied in details. Three enhanced restoration ecosystems named EE1, EE2 and EE3 with respect to applying AR, HSR and ARHSR are studied, respectively. The Ecopath model and ocean health index were used to analysis and evaluate the maturity and

Acknowledgements

This study was supported by the key project in the Control and Management of National Polluted Water Bodies Of China (2014ZX07203-009).

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