Threshold Responses in the Taxonomic and Functional Structure of Fish Assemblages to Land Use and Water Quality: A Case Study from the Taizi River

Abstract

Biological functional traits help to understand specific stressors that are ignored intaxonomic data analysis. A combination of biological functional traits and taxonomic data ishelpful in determining specific stressors which are of significance for fish conservation and riverbasin management. In the current study, the Taizi River was used as a case study to understand therelationships between the taxonomic and functional structure of fish and land use and waterquality, in addition to determining the thresholds of these stressors. The results showed thattaxonomic structure was significantly affected by the proportion of urban land and specificconductivity levels, while functional metrics were influenced by the proportions of farmland andforest. Threshold indicator taxa analysis found that Phoxinus lagowskii, Barbatula barbatula nuda,Odontobutis obscura, and Cobitis granoei had negative threshold responses along the gradients ofurban developments and specific conductivity. There was a significant change in fish taxonomiccomposition when the proportion of urban land exceeded a threshold of 2.6–3.1%, or specificconductivity exceeded a threshold of 369.5–484.5 μS/cm. Three functional features—habitatpreference, tolerance to disturbances, and spawning traits—showed threshold responses to theproportion of farmland and forest. The abundance of sensitive species should be monitored as partof watershed management, as sensitive species exhibit an earlier and stronger response to stressorsthan other functional metrics. Sensitive species had a positive threshold response to the proportionof forest at 80.1%. These species exhibited a negative threshold response to the proportion offarmland at 13.3%. The results of the current study suggest that the taxonomic and functionalstructure of fish assemblages are affected by land use and water quality. These parameters shouldbe integrated into routine monitoring for fish conservation and river basin management in the TaiziRiver. In addition, corresponding measures for improving river habitat and water quality shouldbe implemented according to the thresholds of these parameters.

Land-Use Change Impacts from Sustainable Hydropower Production in EU28 Region: An Empirical Analysis

“…In particular, a 1% improvement in institutional quality declines the land-use change by 0.050%. This outcome is consistent with prior research [68][69][70] which points out that institutional quality encourages a decrease in land-use change. This suggests that the growth of government effectiveness and alignment with highly efficient applications could lead to a decline in the land-use change in EU13 underdeveloped countries.…”

Threshold responses of riverine fish communities to land use conversion across regions of the world

“…Abrupt shifts in the composition of fish communities are the result of species‐level responses to land conversion (Rhodes et al., 2008; Zhang et al., 2019). We found that fish communities in disparate biogeographic regions of the world showed marked consistency in patterns of species turnover that occurred at comparable or lower threshold levels of urbanization (1–10 times lower; Table 1) compared to agricultural land use.…”

“…Evidence for threshold responses of riverine fish communities to land use change remain primarily limited to catchment‐level scales (Paul & Meyer, 2001); whereas investigations at larger biogeographic scales are scarce (Clapcott et al., 2012; Daniel et al., 2015; Feld, 2013). Catchment studies have reported threshold values ranging up to 50% agricultural land use, beyond which fundamental shifts in fish community structure and biodiversity (e.g., species richness and index of biotic integrity) were observed (e.g., Allan, 2004; Feld, 2013; Kovalenko et al., 2014; Zhang et al., 2019). Threshold responses of fish community structure to urban land use appear less variable, and generally occur at lower levels ranging from 5% to 25% (e.g., Clapcott, Young, Goodwin, & Leathwick, 2010; Dahm et al., 2013; King, Baker, Kazyak, & Weller, 2011; Lisi et al., 2018).…”

Effects of Land Use on Stream Water Quality in the Rapidly Urbanized Areas: A Multiscale Analysis

“…The negative hydrological effects caused by this particular land use form are mainly manifested by reduced soil infiltration and increased surface runoff, as well as increased sediment and sources of pollutants [10,11]. From a long-term perspective, the regional urbanization process is usually accompanied by the degradation of surface water quality and aquatic ecosystems [12][13][14]. For streams, the common pollutants, e.g., nitrogen, phosphorus and heavy metals, usually increased significantly with rapid urbanization, and it has been suggested that stream water quality and aquatic ecosystems might be damaged if the proportion of impervious surfaces in watersheds reach 10%-15% [15][16][17][18].…”