Distribution and Speciation of Dissolved Iron in Jiaozhou Bay (Yellow Sea, China)

Abstract

The distribution of total dissolved iron (DFe) and its chemical speciation were studied in vertical profiles of the shallow and semi-closed Jiaozhou Bay (JZB, China) during two contrasting periods: summer (July 19 th , 2011) and spring (May 10 th , 2012). Samples collected from the surface, middle and bottom layers were analyzed by competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-aCSV). The mean DFe concentration during the summer period (median 18.8 nM; average 20.7 nM) was higher than in the spring period (median 12.4 nM; average 16.9 nM), whereas the spatio-temporal variation in spring was larger than in summer. The DFe-values showed distinct regional and seasonal differences, ranging from 5.6 to 107 nM in spring period and 13.4 to 43.4 nM in summer period. In spring, the highest DFe-values were observed in the eastern coastal region, especially near an industrial area (up to 107 nM), whereas the DFe distribution in summer was relatively even. Due to a tide influence, the vertical variations in the DFe and L t in both seasons were not significant. On average, the L t concentration (one class of ligand was estimated in all samples), was higher in spring (35.2 ± 23.4 nM) than in summer (31.1 ± 10.3 nM). A statistically significant correlation was found between L t and DFe concentrations, it was higher for the summer period than for the spring period. The conditional stability constants (logK ′ ) of organic complexes with iron were weaker in spring (11.7 ± 0.3) than in summer (12.3 ± 0.3). The concentrations of L t were higher in comparison to DFe in all samples: the average [L t ]/[DFe] ratio in the spring and summer samples was 2.4 and 1.5, respectively. Speciation calculations showed that the DFe in the JZB existed predominantly (over 99.99%) in the form of strong organic complexes in both seasons.

Concentration, Spatial-Temporal Distribution, and Bioavailability of Dissolved Reactive Iron in Northern Coastal China Seawater

“…As DrFe was rarely studied in other areas, there was no comparison of DrFe. The TdFe results were comparable with those of East China Sea, Jiaozhou Bay, and Southern Yellow Sea (Table 3) [8,22,42], while iron contents from Sanggou Bay and two foreign coastal areas were much lower in comparison (Table 3). Table 3 shows that TdFe levels in seawater from sampling stations in the East China Sea were higher in spring than in autumn.…”

“…Iron fertilizing experiments in the high nutrient and low chlorophyll (HNLC) areas have indicated that adding iron can increase the growth of marine phytoplankton and influence local CO 2 absorption and nutrient consumption [6]. This further confirmed Martin's hypothesis from the 1990s [7] that the phenomenon of a high nutrient concentration but low biomass of phytoplankton in seawater was due to the low concentration of bioavailable iron [8]. However, iron limitations on phytoplankton growth may occur even though the total dissolved iron (TdFe) value is abundant; an example of this can be seen in Lake Kasumigaura of Japan, where iron concentrations were higher than those in oceanic waters while inorganic iron levels did not differ significantly [9].…”

Species, Spatial-Temporal Distribution, and Contamination Assessment of Trace Metals in Typical Mariculture Area of North China

“…To obtain more valuable experimental data, the total dissolved Fe concentration was determined and the relationship between Fe and TMs was further analyzed. The results showed that Fe concentrations were higher in Sishili Bay than in other areas (Nimmo et al, 1989;Su et al, 2016Su et al, , 2015Su et al, , 2017. The spatial distribution of the total dissolved Fe (annual average values) in the surface seawater of Sishili Bay is presented in Figure 8A.…”

“…As a mariculture area, it is very important to investigate the pollution level of seawater, especially the metal levels. Although various studies investigated TMs in seawater (Nimmo et al, 1989;Meng et al, 2008;Mao et al, 2009;Tian et al, 2009;Wang et al, 2012;Su et al, 2015Su et al, , 2016Su et al, , 2017Han et al, 2018), little information is available on the spatialtemporal distributions and species of TMs. However, studying the spatial-temporal distributions and species of TM is helpful to achieve a better understanding of the TM pollution degree in seawater and provides effective data support for aquaculture.…”

Towards the development of a new generation of whole‐cell bioreporters to sense iron bioavailability in oceanic systems—learning from the case ofSynechococcussp. PCC7002 iron bioreporter

“…; Su et al . ). In the boxplot representations, the box shows the second and the third quartile (from left to right), separated by a vertical line, which represents the median.…”