Abstract
Rongjiang River, the second largest river system in Guangdong Province, flows through the main urban areas of Jieyang and Shantou cities before reaching the South China Sea. Human activities in the surrounding area pose significant threats to this aquatic ecosystem. The ecological status (ES) of the benthic ecosystem of the Rongjiang River estuary has not yet been conducted using indices based on the macrobenthic fauna, which is important for evaluating environmental health. Here, we used four biotic indices (the AZTI’s Marine Biotic Index (AMBI) and Multivariate AZTI’s Marine Biotic Index (M-AMBI), and taxonomic distinctness indices (average taxonomic distinctness Δ+ and variations in taxonomic distinctness Λ+) to appraise the current ES of benthic communities in Rongjiang estuary. Samples were taken from 11 sampling sites located in six general regions: western aquaculture zones, aquaculture zones, Hanjiang River water channel, Shantou City, Shantou Port, and near the ocean. The benthic ecosystem of this estuary is greatly disturbed: the ES of the aquaculture zones and the sites near the Hanjiang River water channel, Shantou City, and close to the ocean was poorer compared with that of other areas; ES was also poorer in winter than in summer. Generalized linear models revealed that Shannon-Wiener index was negatively correlated with dissolved inorganic nitrogen (p < 0.01), M-AMBI was negatively correlated with temperature and dissolved inorganic nitrogen (p < 0.05 and p < 0.01, respectively), and Λ+ was negatively correlated with pH (p < 0.05). The AMBI, M-AMBI, Δ+, and Λ+ indices were suitable for assessing the ES of the benthic ecosystem in an anthropogenically disturbed estuary.
Highlights
With their complex hydrodynamics, estuaries have been important areas for human settlement, and they represent some of the most productive natural ecosystems on Earth (Costanza et al, 1997; Lotze et al, 2006; van der Linden et al, 2012)
dissolved inorganic nitrogen (DIN) and mean effects range-median (ERM) quotient (MERMQ) were lower in the aquaculture zones; in winter, DIN and MERMQ were higher in the aquaculture zones and areas near Shantou City
The robustness of results based on AZTI’s Marine Biotic Index (AMBI) and Multivariate AZTI’s Marine Biotic Index (M-AMBI) is reduced if only 1–3 taxa or individuals can be identified in a sample, or more than 20% of taxa in a sample are not assigned to an ecological groups (EGs) (Borja and Muxika 2005; Muxika et al, 2007)
Summary
Estuaries have been important areas for human settlement, and they represent some of the most productive natural ecosystems on Earth (Costanza et al, 1997; Lotze et al, 2006; van der Linden et al, 2012). Their health is key to the development of human society, but anthropogenic and natural stressors have increased estuarine ecosystem deterioration and biodiversity loss (Barbier et al, 2011; Gao et al, 2019; Hillman et al, 2020; Spreitzenbarth and Jeffs, 2021). Given the complex nature of biological systems, robust ES evaluations require the use of several biotic indices (Salas et al, 2006; Wetzel et al, 2012; Martinez-Haro et al, 2015)
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