Metals and biogenic elements were analyzed from surface sediments and a 100 cm core collected from Jiaozhou Bay in July 2009, to determine how the environment has changed over the past 90 years due to increasing anthropogenic influences in this region. High concentrations of biogenic silica （BSi） represented the dominance of diatoms in the bay. Most metals were lower than the marine sediment quality guidelines; however, Hg, Zn, and Mn were at polluted levels. The vertical profiles of biogenic elements and metals in the sediment core suggest that the most significant environmental changes occurred since the 1990s, and three stages could be defined： （1） before 1950, characterized by low concentrations of biogenic elements and metals; （2） between 1950 and 1990, displaying an obvious increase of rig and a slow increase ofbiogenic elements; （3） after 1990, reflected by a significant increase of total organic carbon （TOG）, total nitrogen （TN）, total phosphate （TP）, and most metals, but a decrease of BSi. Correlation and principal component analyses indicated that most metals originated from lithogenic sources, industrial and domestic discharges as well as maricultural activities.
Three surveys were carried out in Pearl River Estuary and adjacent coastal area in May, August, and November, 2013, to investigate the temporal and spatial variations of abundance of phycoerythrin-rich Synechococcus(PE-rich SYN) and phycocyanin-rich Synechococcus(PC-rich SYN). The effects of environmental factors on the alternation of the different Synechococcus groups were also elucidated. PE-rich SYN was detected in three surveys, whereas PC-rich SYN was detected in May and August, but not in November. The highest abundances of PE-rich SYN and PC-rich SYN were recorded in August and May, with mean values of 74.17×103 and 189.92×103 cells m L-1, respectively. From May to November, the relative abundance of PE-rich SYN increased, whereas that of PC-rich SYN declined. PE-rich and PC-rich SYN presented similar horizontal distributions with high abundance in the southern estuary in May, and in the western estuary in August. The abundances of PE-rich and PC-rich SYN were high at 27–32℃and salinity of 10–20. PC-rich SYN was not detected at < 24℃, and PC:PE-rich SYN decreased in abundance with salinity increase. When less than 20 mg L-1, suspended particulate matter(SPM) was helpful for Synechococcus growth. PE-rich SYN decreased in abundance when the concentration of dissolved inorganic nitrogen increased in May and November, and the concentration of phosphate increased in November. However, PC-rich SYN abundance and nutrients showed no correlation. Principal component analysis and regression analysis indicated that PE-rich SYN significantly correlated with the principal components that were affected by environmental factors.
The growth and alkaline phosphatase activity（APA） of two raphidophyceae species Chattonella marina and Heterosigma akashiwo were investigated in response to P-limitation and subsequent addition of dissolved inorganic phosphorus（DIP, Na H2PO4） and two dissolved organic phosphorus（DOP） compounds： guanosine 5-monophosphate（GMP） and triethyl phosphate（TEP）. APA levels increased greatly after P-starvation as the decrease of the cellular phosphorus quotes（Qp）. C. marina responded to P-limitation quickly and strongly, with 10-fold increase in APA within 24 hr after P-starvation. The larger difference between maximal and minimal QP values in C. marina indicated its high capacity in P storage. APA of H. akashiwo was maximally enlarged about 2.5 times at 48 hr of P-starvation. After the addition of nutrients, cell numbers of C. marina increased in all treatments including the P-free culture, demonstrating the higher endurance of C. marina to P-limitation. However, those of H. akashiwo increased only in DIP and GMP cultures. APA increased only after the addition of the monophosphate ester GMP. The results suggest that quick responses of C. marina to P-limitation, high capacity in P storage as well as endurance for P-depletion provide this species an ecological advantage in phytoplankton community competition under DIP-limited conditions.
Metals and biogenic elements were analyzed from surface sediments of sixteen stations and a 32 cm core collected from Zhifu Bay in July 2009.High concentrations of biogenic silica（BSi）reflected the high diatom productivity in the Bay.Meanwhile,total organic carbon（TOC）in Zhifu Bay was mainly from terrestrial sources.All metals were lower than the marine sediment quality guidelines.Based on the vertical profiles of biogenic elements,there was a clear increase of TOC,total nitrogen（TN）,and total phosphate（TP）between1985 and 2000.TN concentrations decreased after the start of the operation of the sewage treatment plant in 1998;however TOC and BSi remained at high levels.Metal concentrations showed a general increase from the bottom to the top of the core.Most anthropogenic metals reached a maximum during 1996 and 2000,and decreased after the startup of the sewage plant;however,they have increased again recently.The results from correlation analysis and principal component analysis show that industrial pollution is the main source of Cd,Cr,Cu,Ni,Pb and Zn contamination in Zhifu Bay,and Yantai Port and ship transportation also contribute a lot to Cd,Cu,Hg,and Pb pollution.
