Multi-year measurements of carbon, nitrogen and phosphorus and sources of organic matter in the surface sediments of the Mirs Bay
大鹏湾表层沉积物中碳、氮、磷的多年调查结果和有机质来源分析

Based on the data obtained at 13 sites from 18 cruises of investigation from 1998 to 2006, the multi-year averaged spatial distributions and interannual variations of biogeochemical parameters, including carbon, nitrogen and phosphorus, in the surface sediments of the Mirs Bay were analyzed. The sources of organic matters in the sediments were identified on the basis of TOC/TN atomic ratios. It was shown that the hydrodynamics in the Mirs Bay only posed a weak impact on the distributions and variations of the biogeochemical parameters in the sediments. The concentrations of TOC, total nitrogen and total phosphorus were (17600±4600) mg·kg-1, (1738±446) mg·kg-1 and (562±89) mg·kg-1, respectively, which were higher than those in both the Pearl River Estuary and the Daya Bay. During the 9 years in investigation, the interannual variations of the concentrations of TOC, total carbon, total nitrogen and total phosphorus in the surface sediments witnessed an increasing trend, indicating a deterioration of the sediment environment in the bay as the rapid economic development and the continuous population increase in the peripheral areas that had brought in a mass of organic matters to the bay through many small rivers and surface runoffs. The TOC/TN atomic ratio was 12.4±2.5, in the range between those from marine planktons and land plants, suggesting that the organic matters in the sediments were a mixture from both sources of the terrestrial and the aquatic. The TOC/TN atomic ratio had undergone a trend of increase in the studied periods, showing a gradual increase of the terrestrial organic matters, relative to those from the aquatic sources, received by the bay.