The State Key Laboratory of Marine Environmental Science (MEL) of Xiamen University is hosting the Fourth Xiamen Symposium on Marine Environmental Sciences (XMAS-IV). The symposium is going to be held at the Science and Arts Center, Xiamen University (Siming Campus) on Jan. 6-9, 2019, with the overarching theme of The Changing Ocean Environment: From a Multidisciplinary Perspective. The symposium features 33 sessions and workshops. Five keynote speakers are: Chris Bowler, Eileen Hofmann, John A. Church, Jack Middleburg and Kenneth Johnson. During the symposium, the best student posters will be selected and be announced at the conclusion of the symposium on Jan. 9. Other events includes Special Reception for Early Career Scientists, Meet the Editor, Women in Science Salon, Student Poster Lightning Talks and Mentoring Workshop. Attendees can visit the research vessel Tan Kah KEE, which is the first global class general-purpose oceanographic research vessel owned by Xiamen University. To learn more about XMAS-IV please visit https://mel.xmu.edu.cn/conference/4xmas/.