Environmental change in Jiaozhou Bay recorded by nutrient components in sediments.
Inorganic or bulk organic chemical indicators, including organic carbon (OC), total nitrogen, organic nitrogen (ON), fixed ammonium (N(fix)), exchangeable ammonium, exchangeable nitrate, organic phosphorus (OP), inorganic phosphorus (IP), and biogenic silica (BSi), were examined in a 3-m core collected in Jiaozhou Bay (JZB) to decipher how the environment has changed during the preceding two centuries of increasing anthropogenic influence in this region. Concentrations of BSi, OC, and OP reveal overall increases to ca.30 cm ( approximately 1984), then decreased toward the surface, probably reflecting a decrease in the productivity of overlying waters since 1984. Aquaculture might play an important role in the decrease of nutrient elements in the upper layers recorded in sediments. The decreased molar BSi/OC ratios upcore may be due to a change in dominance from large- to small-sized diatoms, as shown in other research. However, the shift may also be related to changes from heavily-silicified to lightly-silicified diatoms or to non-siliceous forms such as dinoflagellates. ON concentrations increased towards the surface sediment, which is most likely consistent with the increase in fertilizer application and wastewater discharge. Concentrations of IP, total P, and N(fix) all decreased conspicuously upcore at 41 cm depth ( approximately 1977), and were largely consistent with the decrease in rainfall and freshwater discharge to JZB. Our data suggest that the environment has significantly changed since the 1980s. Anthropogenic activities in the watersheds may exert a substantial influence on carbon cycling processes in estuaries and potentially the coastal ocean.
Liu
Su Mei
SM
Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China. sumeiliu@ouc.edu.cn
Zhu
Bing De
BD
Zhang
Jing
J
Wu
Ying
Y
Liu
Guang Shan
GS
Deng
Bing
B
Zhao
Mei-Xun
MX
Liu
Guan Qun
GQ
Du
Jin Zhou
JZ
Ren
Jing Ling
JL
Zhang
Gui Ling
GL
D000818:Animals; D017756:Aquaculture; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000032:analysis*; D017672:Nitrogen Compounds / Q000032:analysis*; D010755:Organophosphates / Q000032:analysis*; D013997:Time Factors
D017672:Nitrogen Compounds; D010755:Organophosphates; C121815:triisopropyl phosphite