Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment,we were able to identify the source of OM in these sediments.The stable carbon isotope values of Bohai Bay sediments were between-22.94‰ and-23.90‰,while those of riverine sediments were from-24.45‰ to-32.50‰.Marine algae were the main source of OM in Bohai Bay sediments.However,lacustrine algae were the main source of riverine sediments,not terrestrial OM.The nitrogen isotopes in Bohai Bay sediments decreased in eastward direction,with increasing distance from the coastline,which suggested a higher degree of impact from human activities along the coast. Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter (OM), and for identifying OM from different types of plants. By analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment, we were able to identify the source of OM in these sediments. stable carbon isotope values ​​of Bohai Bay sediments were between-22.94 ‰ and-23.90 ‰, while those of riverine sediments were from -24.45 ‰ to-32.50 ‰. Marine algae were the main source of OM in Bohai Bay sediments. Host, lacustrine algae were the main source of riverine sediments, not terrestrial OM. Nitrogen isotopes in Bohai Bay sediments decreased in eastward direction, with increasing distance from the coastline, which suggested a higher degree of impact from human activities along the coast.