Qubin Qin

1 Introduction Freshwater introduced by river inflow plays a critical role in estuarine and coastal systems. It modifies buoyancy forces and establishes salinity gradients, thereby regulating estuarine circulation and mixing, and influencing flushing conditions (Dyer, 1997; MacCready & Geyer, 2010; Sheldon & Alber, 2006).

1. Introduction Hypoxia and anoxia are phenomena characterized by dissolved oxygen (DO) levels falling below 2 g O2 m−3 and reaching zero, respectively. Persistent seasonal hypoxia occurs in many stratified or partially mixed estuaries and shelf regions worldwide [1,2,3,4]. It causes water degradation, which is harmful to living resources, kills fish, and causes the deterioration of water quality [1,4].

Acknowledgments The authors acknowledge William & Mary Research Computing (https://www.wm.edu/it/rc) for providing computational resources and technical support that have contributed to the results reported within this paper. The authors thank Todd Egerton for providing cell abundance data of M. polykrikoides, Ross Vennell and Kimberly S. Reece for useful discussion in the model development, and Yizhen Li, Alexandria Hounshell, and Dongxiao Yin for proofreading the manuscript.