Ecological rehabilitation prediction of enhanced key-food-web offshore restoration technique by wall roughening
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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2020, Ocean and Coastal ManagementCitation Excerpt :Recently, the study of ARs has shifted to a more integrated multidisciplinary approach (Becker et al., 2018; Lima et al., 2019a) with the goal of understanding the communities that colonize these structures and the associated socioeconomic impacts (Schaffer and Lawley, 2012; Hooper et al., 2015; Macusi et al., 2017). Various studies have integrated ecological and socioeconomic information to create protocols and guidelines for management policies of this reef type (Brochier et al., 2015; Techera and Chandler, 2015; Guan et al., 2016; Tolentino-Zondervan et al., 2018). Initiatives like the National Artificial Reef Plan of USA (NOAA Fisheries, 2019), Australia's Oceans Policy (Australian Government, 2019), and the EU Water Framework Directive (Fabi et al., 2011) have emphasized comprehensive management of aquatic environments, including guidelines about the strategic use of low-impact, integrative ARs (Murray, 1994; Kim, 2001; Kheawwongjan and Kim, 2012).
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2019, Marine Environmental ResearchCitation Excerpt :Other studies have dealt with questions related to flow fields (Kim et al., 2014; Liu and Su, 2013; Liu et al., 2013; Miao et al., 2007), improvement of artificial structures (Kim et al., 2016; López et al., 2016), fractal-based models of habitats (Hsui and Wang, 2013; Lan et al., 2008) and submersion analysis of the artificial structures on the ocean floor (Yun and Kim, 2018). During this period (2001–2018), publications that covered socio-environmental aspects focused on artificial reefs as potential fishing and underwater tourism areas (Belhassen et al., 2017; Edney and Spennemann, 2015), and as mechanisms to restore aquatic environments (Chai et al., 2014; Guan et al., 2016). The use of artificial reefs as habitat and breeding sites focused mainly on biota behavior (Kimura and Munehara, 2010; Orchard et al., 2018), showing that this can influence grouping and displacement of economically important species (Maufroy et al., 2015; Taylor et al., 2018).
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