Phytoplankton productivity and community structure variations over the last 160 years in the East China Sea coast in response to natural and human-induced environmental changes

Abstract

Eutrophication has caused drastic changes to the marine ecosystem of the East China Sea during the past decades. However, there is relatively sparse evidence of historical changes, as well as the explicit effects of climatic changes and anthropogenic activities on the primary productivity of marine coastal ecosystems. In this study, surface and core sediments from the Zhejiang-Fujian coastal mud area, East China Sea coast, were analyzed using the bulk and molecular biomarkers. The results showed that ecosystem changes were characterized by increased phytoplankton productivity and a fluctuant transition from blooms mostly dominated by diatoms to red tide events dominated by dinoflagellates. Variations from the early 1850s to the early 2010s can be divided into a nature-dominated period (the early 1850s–1960s) and a human-impacted period (1960s–the early 2010s). Particularly, natural forcing such as heavy floods (e.g. 1998, 1954, and 1931) in the whole of the Yangtze River catchment, variations in the intensity of East Asia Monsoon, and strengthened or weakened Kuroshio intrusion/positive or negative Pacific Decadal Oscillation phase in the coastal mud area have substantially affected the phytoplankton productivity and community structure during the nature-dominated period. In contrast, changes in nutrient supply and compositions were more apparent during the human-impacted period, which could have been because of increased fertilizer usage, discharges of industrial wastewater and domestic sewage, and large-scale human projects (e.g. Danjiangkou Reservoir and Three Gorges Dam) in the Yangtze River drainage area, leading to significant phytoplankton productivity and community structure variations in the coastal mud area system of East China Sea.

The Globalization of Cultural Eutrophication in the Coastal Ocean: Causes and Consequences

“…Riverine inputs of N have been increasing since the 1960s (Zhou et al, 2008;Chen et al, 2019). Despite the Three Gorges Dam, which began storing water in 2013, inputs of DIN from the Changjiang increased by nearly an order of magnitude from 0.220 × 10 9 kg N yr −1 in 1970 to 2.0 × 10 9 kg N yr −1 in 2012 (Tong et al, 2015;Lin et al, 2017;Strokal et al, 2020).…”

“…Blooms of other potentially toxic dinoflagellates (Karodinium veneficum, Karenia mikimotoi, K. veneficum, Alexandrium tamarense, A. catenella, and Heterosigma akashiwo) have also been observed (Lu et al, 2014;Zhou et al, 2015;Wang Y.-F. et al, 2018). Toxic dinoflagellate blooms have resulted in millions of dollars of lost fish landings (Tang et al, 2006;Zhou et al, 2008;Li et al, 2014;Mackey et al, 2017;Glibert et al, 2018;Chen et al, 2019).…”

Effects of pollution on marine organisms

“…Long‐term responses of phytoplankton communities to wastewater, nutrient, and climate factors were documented in the Arabian Gulf of Kuwait (Devlin et al, 2019) and in the East China Sea (Chen, Liu, Xu, & Li, 2019). Three macroalgae taxa ( Ceramium spp., Corallina spp.…”

Multiple lipid biomarkers record organic matter sources and paleoenvironmental changes in the East China Sea coast over the past 160 years

“…All analyses were conducted at the Qingdao Institute of Marine Geology, Qingdao, China, and appropriate laboratory standards were maintained. The complete sample set has been previously studied for long-chain n-alkanes, free FAs, brassicasterol, dinosterol, and GDGTs (Chen et al, 2017(Chen et al, , 2018a(Chen et al, , 2018b(Chen et al, , 2019), which will be discussed further in the succeeding sections.…”

“…dam construction, soil conservation, land reclamation, agricultural plantations, anthropogenic nutrient input, dust storms, eutrophication) and climatic events (e.g. East Asian Monsoon, Kuroshio/Pacific Decadal Oscillation intensity, and flood events) were the predominant controls on historical changes in OM input, phytoplankton productivity/community structure, sea surface temperature (SST) in the ECS inner shelf, and continental temperature and humidity in the mid-lower Yangtze River basin over the last 160 years (Chen et al, 2017(Chen et al, , 2018a(Chen et al, , 2018b(Chen et al, , 2019. We undertook further analyses of the composition and distribution of various lipid biomarkers, including hydrocarbons, alcohols, and FAs, in core sediments from the inner shelf of the ECS.…”