Characteristics of the ratio of dissolved cadmium to phosphate in subtropical coastal waters of Ishigaki Island, Okinawa, Japan

• Published in: Journal of oceanography Vol. 67; no. 2; pp. 241 - 248
• Main Authors: Abe, Kazuo, Fukuoka, Kouki, Shimoda, Toru
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01-04-2011; Springer Nature B.V
• Subjects: Cadmium; Carbon dioxide; Chemical analysis; Chemical oceanography; Coastal waters; Coastal zone; Coasts; Dissolution; Earth and Environmental Science; Earth Sciences; Environmental conditions; Freshwater & Marine Ecology; Manganese; Marine; Oceanography; Phosphates; Phytoplankton; Salinity; Seawater; Short Contribution; Water analysis; Water temperature; Ishigaki Island; ISEW, Japan, Nansei-shoto, Okinawa; Ishigaki Island; Cd/PO; Subtropical water; Cadmium–phosphate plot; ratio
• ISSN: 0916-8370; 1573-868X
• DOI: 10.1007/s10872-011-0014-7

The ratio of dissolved cadmium (Cd) to phosphate (PO
4
) in the subtropical coastal area of Ishigaki Island, Okinawa, Japan, was investigated. Twenty vertical seawater samplings were carried out once a month from May 2008 to January 2010. In order to examine how the Cd/PO
4
ratio in seawater varies with the oceanographic conditions (i.e., the water temperature–salinity characteristics), the water masses at the study sites were classified into two types: group 1 with a water temperature of >25°C and a salinity range of 34.0–34.4, and group 2 with a water temperature of <25°C and a salinity of >34.4. A different phytoplankton assemblage was observed in each water mass defined. Different Cd/PO
4
ratios were obtained for the two water mass types, due to the differences between the types in terms of the environmental conditions such as the water temperature–salinity (
T
–
S
) characteristics and phytoplankton assemblages, as well as possible variations in the concentrations of dissolved iron, zinc, manganese, and CO
2
in seawater in each water mass.