Benthic community history in the Changjiang (Yangtze River) mega-delta: Damming, urbanization, and environmental control

Abstract

The coastal environment of the Changjiang delta has been influenced by recent anthropogenic activities such as dam construction and increased sewage and fertilizer inputs. Previous work examined the compositional shift of marine plankton to assess ecological impacts of these activities on marine ecosystems in the Changjiang discharge area. Here we used benthic marine ostracodes collected in the Changjiang estuary and the adjacent East China Sea in the 1980s and the 2010s, respectively, to investigate temporal changes of the benthic community and controlling factors for the benthic fauna. Our results revealed more shoreward distribution of some well-known offshore ostracode species in the 2010s compared with the 1980s and a relatively more important role for environmental processes (e.g., bottom-water temperature, bottom-water salinity, and eutrophic conditions of surface water) than spatial processes (e.g., the flow of ocean currents) in structuring ostracode compositions. The temporal changes in the ostracode community are likely attributable to the combined effects of reduced fresh water and sediment discharge and eutrophic conditions of the Changjiang due to the many dams constructed along the Changjiang and population expansion in the Changjiang Basin. Results of redundancy analysis and variation partitioning suggest that ocean currents facilitated environmental filtering of ostracode species such that they could disperse to preferred environmental conditions. These findings highlight the potential uses of marine microfossils to better understand ecological impacts on benthic ecosystems in vulnerable Asian mega-deltas and provide insights into the integration of metacommunity concepts in disentangling dynamics of marine benthic communities.

Persistent eutrophication and hypoxia in the coastal ocean

“…It was first detected in 1959 (~1800 km 2 ) and developed into an extensive area exceeding 2 × 10 4 km 2 by 2016 (Figure S4d) (Zhu et al, 2017). The minimum DO concentration off the Changjiang Estuary shows a stepwise reduction at a rate of 0.05 mg L -1 yr -1 since the 1980s, which has probably led to a meiobenthic faunal shift (Cheung et al, 2019). A weak but statistically significant negative correlation is found between the DO minima and hypoxic areas (R=0.66, p<0.01; Figure 4c).…”

[Retracted] Protection and Inheritance of Traditional Culture in Urbanization Construction Based on Genetic Algorithm under the Concept of Environmental Protection

“…Guo et al proposed that in the process of traditional urbanization, due to the lack of restraint mechanism for the protection and development conditions of rural cultural resources and the lack of attention to the scientific development of rural culture, rural culture is distorted and distorted, and the value of rural culture is greatly reduced [ 7 ]. Cheung et al proposed that in the process of improving the appearance of villages, urbanization and ecological civilization, national unity, follow-up industry cultivation, spiritual civilization construction of farmers and herdsmen, and improvement of urban cultural connotation should be mutually promoted to reflect the characteristics [ 8 ]. Yang et al proposed that the common development of urban and rural areas is an important premise and fundamental policy to narrow the economic and social gaps between urban and rural areas, and it is also the best choice to solve the contradictions and problems between urban and rural areas at present and in the future [ 9 ].…”

Holocene ostracods (Crustacea) from a whale-fall excavation site from the Chao Phraya delta, Central Thailand

“…Modern distribution: Japan (Tanaka et al 2019); China , 1990Cheung et al 2019); Hong Kong (Brady 1869;Hong et al 2017Hong et al , 2019; Central Vietnam (Tan et al 2021). Mae Khlong estuary, NW Gulf of Thailand, Thailand (Montenegro et al 2004); Klong Thom, Krabi, Andaman estuary, Thailand (Yamada et al 2014).…”