[Ecological characteristics of phytoplankton in Shenzhen Bay].

Based on the data of surface phytoplankton investigated by Hong Kong Environmental Protection Department in Shenzhen Bay in 2006, variation characteristics of phytoplankton communities and the relationship between the phytoplankton diversity indices and environmental factors were analyzed in the present paper. Results showed that a total of 27 genera and 34 species of phytoplankton were identified. Of these, 18 were diatoms (52.94%), 10 were dinoflagellates (29.41%), 6 were from other minor groups (17.65%). The cell abundance was estimated to be from 2.13 x 10(6) to 4.15 x 10(6) cells/L, with an average of 2.92 x 10(6) cells/L. The maximum cell abundance appeared in the autumn (October), followed in spring (May). The cell abundance showed double abundance peaks annually. The cell abundance of phytoplankton decreased from the middle bay to the bay mouth. In the marine area, the diversity index of the phytoplankton ranged from 0.76 to 2.52; the evenness of phytoplankton ranged from 0.29 to 0.74; the diversity and evenness of phytoplankton community were rather low, which indicated that the relative abundances of the species diverged from evenness, phytoplankton community were not steady, and only few dominant species increased rapidly. The species richness index ranged from 0.57 to 2.17, the high eutrophic water body caused the species richness index declined. Better relationship was found between phytoplankton diversity indices and nutrient, salinity, dissolved oxygen.

[Status analysis of nutrients and eutrophication assessment in Shenzhen coastal waters].

Based on the field data of Shenzhen coastal water quality in 2002-2007, variation characteristics of nutrients including NH4+ -N, NO3- -N, NO2- -N, PO4(3-) -P and DIN were presented. And the correlationships between nutrients and pH, salinity were also investigated. Furthermore, eutrophication index (E), organic pollution index (A) and potential eutrophication were employed to assess the eutrophication degree of Shenzhen coastal waters. Results show that the nutrient levels of east coast are higher than that of west coast. And the peak year of nutrients are 2002 and 2006. The average concentrations of PO4(3-) -P and DIN are 0.007 mg/L and 0.078 mg/L for Shenzhen east coast while 0.090 mg/L and 1.544 mg/L for west coast. Nutrients in Shenzhen coastal waters have negative correlations with pH and salinity. The N/P ratios are all far more than 16 indicating that Shenzhen coast belongs to seriously P-limiting water. Eutrophication degree of Shenzhen east coast is far lower than that of west coast, and the average eutrophication index of east coast is 0.11 while 42.15 for west coast. Furthermore, west coast is classified as P-limiting moderate level potential eutrophication area and even as P-limiting potential eutrophication level.

[Environmental biogeochemical significance of nitrogen in Jiaozhou Bay sediments].

The geochemical characteristics of nitrogen forms in different grain size sediments of Jiaozhou Bay were investigated employing the sequential extraction technique. Results showed that the transferable nitrogen in Jiaozhou Bay sediments can be divided into four forms, ion exchangeable form (IEF-N), weak acid extractable form (WAEF-N), strong alkaline extractable form (SAEF-N) and strong oxidant extractable form (SOEF-N). The percentages of nitrogen forms for transferable nitrogen in different grain size sediments were different. Generally, for all grain size sediments, the SOEF-N was the primary form accounted for 35.38%, 44.38% and 58.69% of transferable nitrogen for fine, medium and coarse sediments. And for medium and coarse grain size sediment, SAEF-N was the dominant inorganic nitrogen accounted for 26.31% and 25.85%, respectively. And for fine-grained sediments, IEF-N was the primary inorganic nitrogen accounted for 27.67% of transferable nitrogen. The correlation analysis showed that generally, nitrogen was positive correlated with fine and medium grain size but negative correlated with coarse sediments. In addition, nitrogen in different grain size sediments had also positive correlations with phytoplankton abundance, chlorophyll-a and NO3- concentrations of overlying water. The results showed that sediments had great influences on element concentrations of overlying water, and on the other side, it also illustrated that sedimentary nitrogen was an excellent indicator of hypereutrophication and had essential environmental significance.

[Sediment record of phosphorus and the primary study of its bioavailability in Jiaozhou Bay sediments].

The geochemical characteristics of phosphorus forms in different grain size sediments, the influencing factors as well as the bioavailability of phosphorus in Jiaozhou Bay were investigated employing the sequential extraction method. The results showed that inorganic phosphorus was the dominant form of total phosphorus and organic phosphorus was only the minor part. The detrital carbonate-bound phosphorus was the largest part of total phosphorus. The grain size, organic carbon, temperature, pH and etc. are the main controlling factors of phosphorus in sediments. Except for Ca-P, most of other phosphorus forms contents increased as the grain size decreased. The bioavailability research showed that the bioavailable phosphorus was mainly the exchangeable phosphorus, phosphorus bound to Al and Fe and organic phosphorus. Moreover, the potential bioavailable phosphorus proportion in total phosphorus increased as the grain size decreased. The bioavailable phosphorus in different grain size sediments has positive correlationship with phytoplankton abundance and phosphate in overlying water.

[Phosphorus and its environmental marker function in Jiaozhou Bay sediments].

Phosphorus is a key biogenic element and plays an essential role in global biogeochemical cycles. The geochemical characteristics of phosphorus as well as the controlling factors and the environmental marker function in Jiaozhou Bay sediments were presented. The different forms of sedimentary phosphorus were studied in three sediment cores, which are forms of inorganic phosphorus, exchangeable phosphorus, phosphorus bound to Al-Fe, and calcium, occluded phosphorus as well as total phosphorus and organic phosphorus, respectively. The vertical profiles of various forms of phosphorus in response to 210Pb chronological studies of sediment cores were investigated in order to reveal sedimentary environment changes. The results showed that inorganic phosphorus was the dominant form of total phosphorus and organic phosphorus was only the minor part. The detrital carbonate-bound phosphorus was the largest part of total phosphorus. The concentrations and burial fluxes of phosphorus were controlled by source and environmental factors including pH, salinity, temperature and grain size of sediments etc. Moreover, the analysis of OC/OP ratios suggested that the terrestrial inputs were the dominant source of Jiaozhou Bay sediments. The sedimentation fluxes of phosphorus increased in the past two decades, as a result, the pollution was still serious from the 1980 to 2000. But the state has greatly improved since 2000. The Fe-P, Al-P and Oc-P have close relationships with the degree of pollution and may act as good indicators for environment pollution in Jiaozhou Bay.

[Effects of heavy metal (copper and cadmium) coupled with Ulca pertusa on marine inorganic carbon system in simulated experiments].

Simulated experiments coupled with ocean biota dynamics were performed in laboratory. In these experiments, effects of heavy metal (copper and cadmium) coupled with Ulca pertusa on marine inorganic carbon system and CO2 fluxes were investigated. The results indicated that concentration changes (delta) of components in carbon dioxide system with time scale were correlated with the concentrations and kinds of heavy metal. In copper groups and cadmium groups (0.1 micromol x L(-1) and 1 micromol x L(-1)), DIC HCO3- and PCO2 significantly decreased comparing to the control experiment data( p = 0.01). However, when the heavy metal infusions were higher than the "critical concentration", the above mentioned parameters increased with time scale and their increments followed the uptrend with increasing heavy metal concentrations. The "critical concentration" in copper groups was much lower than that in cadmium groups, which attributed to the tolerance diversity of Ulca pertusa to copper and cadmium. Furthermore, CO2 fluxes under the influences of heavy metal were also regularly changed with time. Sea waters with low infusions of heavy metal represented as sinks to the atmosphere CO2. These sinks would probably convert into CO2 sources after a period of time. Sea waters with comparatively high amount of heavy metal were always to be CO2 sources, and their release fluxes of CO2 augmented along with the increasing infusions of heavy metal.