Relationship between Salinity and Nutrients in the Subsurface Layer in the Suruga Bay

Author： Iwata Tatsuya Shinomura Yoshiko Natori Yuta Igarashi Yasumasa Sohrin Rumi Suzuki Yoshimi

ISSN： 0916-8370

Source： Journal of Oceanography, Vol.61, Iss.4, 2005-08, pp. : 721-732

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Abstract

We investigated the water structure and nutrient distribution in the Suruga Bay from April 2000 to July 2002, especially the Offshore Water, which occupies a large part of the bay. The maximum salinity in the upper 200 m varied between 34.49 and 34.71, indicating a temporal change in the influence of Kuroshio Water on the Offshore Water. Seasonal variation in nutrient concentrations was largest from surface to 50 m. On the other hand, the variance in nutrient concentrations within each season was largest in the subsurface layer of 100–300 m in spring, summer and fall. In the Offshore Water, the change of nutrients was negatively correlated with that of salinity in each season. This suggests that an increasing intrusion of saline water brings about a lower nutrient concentration in the Offshore Water. Likewise, negative correlations were observed between the change of the maximum salinity and chlorophyll a (∆ [chl.a-int])/nutrients integrated in the upper 200 m. ∆[chl.a-int] was significantly correlated with the changes of nitrate and phosphorus, but there were no significant correlations between ∆[chl.a-int] and the change of silicate. These results suggest that the concentrations of chlorophyll a and nutrients in the Offshore Water were decreased due to the increasing intrusion of Kuroshio Water. The Offshore Water is likely to be related to the regulation of primary production by nitrate.