Effect of activities associated with coastal reclamation on the macrobenthos community in coastal wetlands of the Yellow River Delta, China: A literature review and systematic assessment

Highlights

• The dominant species changed remarkably from Mollusca in the 1980s to Polychaeta, Crustacea, and Insecta after 2000.

• The species number and biomass decreased significantly under the comprehensive influence, but not under individuals.

• Reclamation intensity has an initially negative impact on the species number, biomass, abundance, and biodiversity indices.

• A suggested list of criteria has been prepared for future researchers to increase the quantity and quality of the data.

Abstract

Human activities such as seashore reclamation can have profound negative impacts on the macrobenthos of coastal wetlands. Using the Yellow River Delta as a case study, we conducted a thorough search of the literature to create a synthesis about the effects of reclamation processes. We found 31 publications that met our selection criteria, and we summarized their data to systematically quantify the impacts of reclamation on the dominant species, biomass, abundance, and biodiversity indices. We found that the dominant species changed remarkably, from Mollusca in the 1980s to Polychaeta, Crustacea, and Insecta (indicating a transition from a marine to a terrestrial environment) after 2000. The number of macrobenthos species in the community decreased by more than half from the 1980s to the 2010s and the effect sizes in the 2000s and 2010s both differed significantly from 0 (p < 0.01; t-test). Both the biomass and the abundance of the macrobenthos decreased significantly in the 2000s (p < 0.05 and p < 0.01, respectively; t-test), but not in the 2010s. The Margalef, Shannon-Wiener, and Pielou biodiversity indices did not differ significantly among four periods (from 1985 to 2015) or among the various reclamation activities. The number of species and biomass have decreased significantly under the comprehensive influence of seashore reclamation activities. Under individual reclamation activities, the number of species and their biomass decreased slightly but not significantly. The results of this research improve our understanding of the relationships among reclamation activities and the resulting changes in the macrobenthos community, thereby improving our ability to sustainably use these wetlands. We have prepared a suggested list of criteria to help future seashore reclamation researchers increase the quantity and quality of the data available to support future meta-analyses.

Introduction

The macrobenthos is a particularly important part of the biocenosis in coastal wetlands because these organisms play a key role in transferring energy and materials within the food web (Covich et al., 2004, Dauvin et al., 2006). Due to its ecological importance, obvious presence, high sensitivity to disturbance, and direct contact with sediments, the macrobenthos of coastal ecosystems is widely used as a tool to detect the environmental impacts of pollution and other consequences of reclamation activity (Buschbaum et al., 2012, Li et al., 2016), and has therefore been used to support ecologically sustainable marine management (e.g., Borja et al., 2000, Naser, 2011, Crippa et al., 2013, Nishijima et al., 2015).

The Yellow River Delta is the largest and youngest coastal wetland in the warm temperate zone of China. However, in recent years, the demands of urbanization and economic development have led to serious impacts on the delta's wetlands due to intensive land reclamation activities, which include the construction of ports and tidal embankments, oilfield exploitation, and the development of aquaculture. Such seashore reclamation activities are typically associated with both short- and long-term impacts that affect the characteristics and patterns of the macrobenthos community (Airoldi and Beck, 2007).

The responses of the macrobenthos community to seashore reclamation have been studied in Yellow River Delta wetland by means of field surveys and a range of experimental approaches. Most of these studies have focused on the responses of the macrobenthos during a specific period or at specific sites (Wang et al., 2008, Mao et al., 2011). Some have assessed the qualitative or quantitative impacts of specific reclamation activities on the macrobenthos community, such as protection of the shoreline by establishing Spartina alterniflora communities (Shen et al., 2009) and ecologically risky activities oilfield exploitation (Chen et al., 2012). This information is useful, but is restricted to point observations at the sampling sites, and therefore cannot provide the benefits of a comparative analysis of long-term time-series data. Walker et al. (2008) used field surveys and detected increased spatial variation of species diversity and biomass after reclamation. Song and Liu (2013) reviewed the impacts of reclamation activities on the ecosystem of estuarine delta wetlands, but did not quantitatively assess the influence on the macrobenthos. Some comparative surveys have indicated that a high-intensity of coastal reclamation contributed to a pronounced decline in species diversity and biomass (e.g., Yan et al., 2015). The distinctiveness of each delta and of each part of a large delta makes it important to perform quantitative comparisons to reveal long-term changes in the macrobenthos associated with coastal reclamation in a specific delta wetland.

In this paper, we systematically assessed the impacts of reclamation activities in the Yellow River Delta based on a literature review. We identified 31 studies that considered the long-term impacts of seashore reclamation activities on the delta's macrobenthos. Our goal was to answer three main questions: (1) Have seashore reclamation activities changed the dominant taxa since 1980 (the earliest data available)? (2) Did the seashore reclamation activities decrease the biomass, abundance, and biodiversity of the macrobenthos community? (3) Which reclamation activities had the greatest impact? Based on the results of our literature review, we have also created a list of suggested criteria that future seashore reclamation researchers should use to design their research in order to increase the quantity and quality of the data available to support future meta-analyses.