Long-Term Temporal and Spatial Distribution of Coliform Bacteria in Jiaozhou Bay Associated With Human Activities and Environmental Governance

Abstract

Coliform bacteria (CB) can be used as an indicator of seawater quality. Long-term monitoring of seawater quality based on CB abundance is lacking in Jiaozhou Bay. In this study, CB abundance in surface seawater of 12 different stations in Jiaozhou Bay was investigated by culturing method. The results showed that: (1) the abundance of CB showed a decreasing tendency during the investigation. During 2004–2007, 2008–2013, and 2014–2017, the average CB abundance decreased significantly, forming a “three stages phenomenon”; (2) the average CB abundance in the first half of the year was lower than that in the second half; (3) the CB abundance in Jiaozhou Bay was spatially heterogeneous. The maximum average CB abundance was observed in the estuary area, and followed by the bay mouth area, the outer bay area, and the inner bay area. The highest abundance may be associated with sewage discharge related to human activities; (4) the abundance of CB was most positively correlated with the concentration of ammonium salt and nitrate, while most negatively correlated with salinity; (5) the years 2007 (2008) and 2013 (2014) were time points of the “three stages phenomenon.” These time points coincide with environmental governance actions, indicating that the actions have played a prominent role in improving seawater quality. Long-term survey of CB can not only serve as an indicator of seawater quality, but also provide a basis for the development of environmental governance strategies and pollution control.

Seasonal and spatial variations of Synechococcus in abundance, pigment types, and genetic diversity in a temperate semi-enclosed bay

“…Type 1 was more abundant in summer at stations A5 and C1 with low salinity of 27.23 and 29.47, respectively ( Figure 3 ). Low salinity in the inner bay was mainly attributed to freshwater discharge and summer rainfall ( Cui et al, 2021 ). Lower salinity and higher temperature seemed to be favorable for the higher growth rate of type 1 Synechococcus in the inner bay in summer.…”

“…More than 10 small rivers enter the bay and become the major sources of external nutrient input. Freshwater discharge exhibits seasonal fluctuation with the highest discharge in summer and the lowest discharge in spring and winter ( Cui et al, 2021 ). Connected with the Yellow Sea and surrounded by Qingdao City (population > 10 million), Jiaozhou Bay is affected by both natural and anthropogenic factors, such as East Asian monsoon, Yellow Sea Water Mass, seasonal freshwater inflow, half-day tidal exchange with the open sea ( Feng et al, 2018 ) and rapid economic development, aquaculture, and pollutions from the land.…”

“…Connected with the Yellow Sea and surrounded by Qingdao City (population > 10 million), Jiaozhou Bay is affected by both natural and anthropogenic factors, such as East Asian monsoon, Yellow Sea Water Mass, seasonal freshwater inflow, half-day tidal exchange with the open sea ( Feng et al, 2018 ) and rapid economic development, aquaculture, and pollutions from the land. Due to the interaction between natural changes and human activities, as well as long-term monitoring and systematic investigation, Jiaozhou Bay has become a “model” bay of temperate coastal ecosystem for ecological investigation ( Zhao et al, 2020 ; Cui et al, 2021 ).…”