Relationship Between Dam Construction and Red Tide Occurrence in Small Bays and the Seto Inland Sea, Japan with Considerations from the Gulf of Mexico
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Open Journal of Marine Science, 2013, 3, 201-211 http://dx.doi.org/10.4236/ojms.2013.34023 Published Online October 2013 (http://www.scirp.org/journal/ojms) Relationship between Dam Construction and Red Tide Occurrence in Small Bays and the Seto Inland Sea, Japan with Considerations from the Gulf of Mexico Kunio Ueda Department of Biological Resources Management, School of Environmental Science, The University of Shiga Prefecture, Hikone City, Japan Email: [email protected] Received August 19, 2013; revised September 21, 2013; accepted October 3, 2013 Copyright © 2013 Kunio Ueda. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT There are many papers on red tide occurrences and eutrophication. Here, we use these data to examine the relationship between dam construction and red tide occurrence in Kesennuma Bay, Dokai Bay and the small bays of the Seto Inland Sea, Japan. Here, for the first time, differences in mechanisms of red tide occurrences in these small bays are demon- strated. Mud overflowing from dams likely induces red tides in these areas as the mud flows out from the mouth of the rivers, is carried along the coast by the longshore current, and then enters and is deposited into small bays. Red tide is considered to be induced by the accumulation of mud and siltation. From data on the locations and year of red tide oc- currences in the Gulf of Mexico, the same mechanism as for the occurrence of red tide in small bays of Japan was found to be applicable. Keywords: Red Tide; Siltation; Dam Construction; Small Bays; Seto Inland Sea; Gulf of Mexico 1. Introduction caused by the overflow of fine particles of soils from the constructed dams causing siltation in bays. Red tide occurrences are a problem in coastal areas Several reports on red tide in Japan provide abundant worldwide, and red tides or harmful algal blooms are data [8-12]; however, these reports do not provide the toxic to fish and shellfish. There are many reports that analysis necessary to ascertain the causes of red tides. examine various aspects of these occurrences, especially Bays along the coast in Japan are vast, making it difficult the number, location and the causative algal species of for one or a group of researchers to collect and analyze the red tide blooms. Eutrophication specifically the trans- sufficient data to address the problem. Moreover, re- port of nitrogen, phosphorus and other nutrients from the search focused on one bay or one sea area is not suffi- drainage basin to the ocean, are considered to induce red cient for analyzing the causes of red tide occurrences. tide [1-6]. Much effort has been made to eliminate nutri- In my previous paper I demonstrated that there is a re- ent inputs from the basin by taking measures such as lationship between dam construction and red tide occur- increasing the implementation of sewer systems and de- rence in the larger bays of Japan [7] based on the chro- creasing the use of chemical fertilizers, but red tide oc- nology of red tide occurrences in these bays. Therefore, currences have not been able to be prevented until re- the chronology of red tide occurrences is very important cently, especially in Japan, as shown in my previous pa- for this analysis. Thus, it is important to collect and ana- per [7]. lyze data from various papers to be analyzed along with In a previous paper, I reported that there was a rela- the data collected by the International EMECS Center in tionship between red tide occurrences in four bays around order to identify causes of red tides [8-12]. Japan, Tokyo Bay, Ise Bay, Osaka Bay and the Ariake Red tides have historically been observed in small Sea, and dam construction on rivers flowing into these bays, such as Kesennuma Bay in Miyagi Prefecture, as bays [7]. Red tide occurred around the estuaries of the well as in the small bays of the Seto Inland Sea [8-12], rivers on which dams had been constructed. Based on and these small bays have no rivers with dams flowing this finding, it was considered that eutrophication was into them. In this paper, I investigate the relationship Copyright © 2013 SciRes. OJMS 202 K. UEDA between dam construction on rivers near Kesennuma Bay Sea (H), Suo-nada Sea (S), and Dokai Bay (D) were in- and in the Seto Inland Sea along with the red tide occur- vestigated in this paper (Figure 1). In these areas, the rence in these areas, and I compare these with red tide relationship between red tide occurrence and dam con- occurrences in the Gulf of Mexico reviewed by Magana struction was investigated. Results obtained in Kesen- et al. [13]. numa Bay, Dokai Bay, Suo-nada Sea and Harima-nada Sea from the chronology of red tide occurrences are 2. Materials and Methods shown as follows. Of the bays of Japan, Kesennuma Bay (K) and Dokai 3.1. Kesennuma Bay Bay (D) were researched in detail; the chronologies of red tide occurrences, including red tide severity and pe- The Kitakami River in Tohoku District has many dams riod of the red tide, were collected from the literature [8- as shown in Figure 2. Before 1934, the Kitakami River 10]. In the Seto Inland Sea of Japan, similar data on red flowed only into Sendai Bay, but the next year, the Kita- tide occurrences concerning the area and year of red tide kami River was separated into two branches (Figure 2): occurrences was collected by direct observation [11,12]. the Old Kitakami River which flows into Sendai Bay and Red tide occurrences have been reported worldwide, but the Kitakami River, which flows into Oppa Bay. The they are rare in the Gulf of Mexico, and the chronologi- location of dams constructed on the Kitakami River is cal red tide occurrence data reported by Magana et al. shown in Figure 2. [13] for the Gulf of Mexico was used for comparison. Based on a count of the number of days of red tide In the Seto Inland Sea, Harima-nada Sea (H), Suo- from the report of Ito et al. [8], the relationship between nada Sea (S), and Dokai Bay (D) were investigated in red tide occurrences in Kesennuma Bay and dam con- this paper (Figure 1). Information about dams in Japan struction on the Kitakami River system was developed was obtained from The Japan Dam Foundation website and is shown in Figure 3. Yuda Dam (A) was con structed [14], and the information about dams in the United States and Mexico was obtained from a website created by C. Abeyta [15] and from Wikipedia [16], respectively. Information about red tide occurrences in Kesennuma Bay was obtained from a paper by Ito et al. [8] on the relationship between water quality parameters and the occurrences and phytoplankton species of red tides in Kesennuma Bay. Information about red tide occurrences in Dokai Bay was obtained from papers by Yamada et al. [9,10]. Yamada et al. monitored the abundance of Skele- tonema tropicum, a species responsible for red tide in Dokai Bay from 1991 to 2006, and reported monthly cell density data along with temperature and eutrophic sub- stances, such as T-N, T-P and PO4-P. [9]. Information about red tide occurrences in the Seto Inland Sea was obtained from Setouti Net, which is part of the Enclosed Sea Net on the website created and maintained by the Ministry of the Environment [11,12]. The data sources are summarized in Table 1. 3. Results Figure 1. The areas investigated in this report are Kesen- numa Bay (K) in Tohoku District, Harima-nada Sea (H), Kesennuma Bay (K) in Tohoku District, Harima-nada Suo-nada Sea (S), and Dokai Bay (D) in Seto Inland Sea. Table 1. Source & year of data used in this paper. Bay Source & Year of Data Reference Areaa Kesennuma Bay & Sanriku Coast Ito et al. (1972-2003) & Miyagi Prefectural Government (1978-2011) [8,16] K Dokai Bay Yamada et al. (1991-2006) [9] D Harima-nada Sea Enclosed Sea Net (1960-2000) [11,12] H Suo-nada Sea Enclosed Sea Net (1960-2000) [11,12] S Gulf of Mexico Magana et al. (1968-2002) [13] - aAlphabets of the areas are showed in Figure 1. Copyright © 2013 SciRes. OJMS K. UEDA 203 in 1964. Shijyusida Dam (B) constructed in 1968 is con- sidered to be linked to red tide occurrences from 1972 to around 1980. Gosho Dam (C) constructed in 1981 is es- timated to be linked to red tide occurrences from 1984 to 1989. Ippoui Dam (E) and Irihata Dam (F) constructed in 1990 are estimated to be linked to red tide occurrences from 1994 to 1996. But Aratozawa Dam (G), which was constructed in 1998, was linked only to low red tide oc- currences observed after 2001 (Figure 3) compared with Ippoui Dam and Irihata Dam. 3.2. Dokai Bay Dokai Bay is located in Kyushu District (Figure 1) but is treated as being part of the Seto Inland Sea (Figure 4). Dokai Bay is considered to be influenced by the Suo- nada Sea. The river closest to Dokai Bay is Koya River in the Seto Inland Sea. There is a possibility that the dam built on Koya River affected the occurrence of S. tropicum in Dokai Bay. In 1990, the Yunohara (B) and Utsui (D) dams (Fig- ures 4 and 5) were completed on the Koya River.