TheJiaozhouBayischaracterizedbyheavyeutrophicationthatisassociatedwithintensiveanthropogenicactivities.FourcoresedimentsfromtheJiaozhouBayareanalyzedusingbulktechnologies,includingsedimentarytotalorganiccarbon(TOC),totalnitrogen(TN),thestablecarbon(δ~(13)C)andnitrogen(δ~(15)N)isotopiccompositiontoobtainthecomprehensiveunderstandingofthesourceandcompositionofsedimentaryorganicmatterandfurthershedlightontheenvironmentalchangesoftheJiaozhouBayonacentennialtimescale.ResultssuggestthattheTOCandTNconcentrationsincreaseintheuppercore,havingindicatedaprobableeutrophicationprocesssincethe1920sintheinnerbayandthe2000sinthebaymouth.TheTOCandTNconcentrationsoutsidethebayhavealsochangedsince1916owingtothevariationofterrigenousinput.ConsideringTOC/TNratio,δ~(13)Candδ~(15)N,itcanbeconcludedthereisamixtureofterrigenousandmarineorganicmattersourcesinthestudyarea.Asimpletwoend-member(terrigenousandmarine)mixingmodelusingδ~(13)Cindicatsthat45%–79%ofTOCintheJiaozhouBayisfromthemarinesource.TheenvironmentalchangesoftheJiaozhouBayarerecordedbygeochemicalproxies,whichareinfluencedbytheintensiveanthropogenicactivities(e.g.,extensiveuseoffertilizers,anddischargeofsewage)andclimatechanges(e.g.,rainfall).
