High nutrients in the coastal area after heavy rain observed in the central Seto Inland Sea in July 2012
- PDF / 2,092,245 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 87 Downloads / 174 Views
SHORT CONTRIBUTION
High nutrients in the coastal area after heavy rain observed in the central Seto Inland Sea in July 2012 Kazuo Abe • Norihisa Nakagawa • Katsuyuki Abo Mutsumi Tsujino
•
Received: 30 October 2012 / Revised: 13 December 2012 / Accepted: 15 January 2013 / Published online: 5 February 2013 Ó The Oceanographic Society of Japan and Springer Japan 2013
Abstract Temporary enhancement of the nutrient concentrations in the coastal area was observed after heavy rain in the central Seto Inland Sea in July 2012. After passage of a stationary front accompanied by heavy rain, the river outflow was enhanced, and low salinity and high nutrient concentrations were detected near the mouths of rivers. The offshore salinity and nutrients increased and decreased, respectively, which suggested that a snapshot event, such as heavy rain, could influence the short-term variation of the coastal marine environmental conditions, such as the salinity and nutrient distributions. Keywords Nutrient Heavy rain Snapshot event Seto Inland Sea
1 Introduction The Seto Inland Sea is located in western Japan and surrounded by Honshu, Shikoku, and Kyushu Islands, with a length of approximately 450 km and 15–25 km from east to west and north to south, respectively (Fig. 1). The average and maximum water depths are approximately 31 and 200 m (Houyo and Naruto Straits), respectively. The marine environment of this sea has been affected by anthropogenic activities due to industrialization, and, historically, studies on environmental conservation have been important (e.g., Takeoka 2002). Recently, oligotrophication processes have developed (Yamamoto 2003), which are considered to influence the water productivity, including fishery activities. K. Abe (&) N. Nakagawa K. Abo M. Tsujino National Research Institute of Fisheries and Environment of Inland Sea, 2-17-5 Maruishi, Hatsukaichi 739-0452, Japan e-mail: [email protected]
Microorganisms related to primary production usually require macronutrients, and, in this sea, the main nutrient source has been considered to be of land origin through river transport; however, nutrients from the open ocean (Pacific Ocean) have been shown to contribute a significant amount to the nutrient content in the whole Seto Inland Sea (e.g., Fujiwara et al. 1997; Takeoka et al. 2002; Yanagi and Ishii 2004). From the point of view of the nutrient budget of this sea, nutrients from the open ocean should be an important component; however, the behavior of nutrients of land origin (river) should also be considered to be important because of its influence on the water quality, including the regional productivity of the onshore areas. The Hiuchi-Nada, BingoNada, and Bisan-Seto compose the central part of the Seto Inland Sea (Fig. 1). The Hiuchi Nada, a semi-enclosed bay, which is approximately 2,400 km2 with an average water depth of approximately 20 m, is located between the Shonai (Kagawa Prefecture) and Takanawa (Ehime Prefecture) Peninsulas. The western and eastern sides are the Kurushima (water de
Data Loading...
