Growth environment of diatoms in turbid water in the inner western part of Ariake Bay during winter
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To evaluate nutrient and light conditions as environmental factors that affect diatom growth in coastal areas of the inner western part of Ariake Bay, observations were conducted in the Kashima River and Shiota River estuary system. During high tide, nutrient concentrations increased between the upper and intermediate areas of the estuary due to river discharge. In these areas, cell densities of genus Skeletonema and Asteroplanus karianus tended to be high, reaching 22,350 and 6850 cells mL−1, respectively, whereas the euphotic depth (zeu)-to-water depth (z) ratios were low (0.1–0.3). In the lower estuary, where high salinities (> 28) were observed, zeu/z ratios were high (0.5–0.9) due to decreased turbidity, but nutrients were depleted. These results show that the diatom growth environment at high tide was characterized by low zeu/z ratios in the upper and intermediate areas of the estuary and low-nutrient conditions in the lower estuary. Time series observations in the lower estuary, performed to investigate the movement of water mass and variability in the growth environment with the tidal cycle, show a decrease in salinity during ebb tides and increases in nutrient concentrations and diatom cell densities, indicating movement of the water mass from the upper and intermediate areas to the lower estuary as the tide ebbs. Furthermore, the reduced water depth resulted in high zeu/z ratios. These results imply that nutrient and light conditions were improved in the lower estuary at low tide, and those better conditions made this area suitable for diatom growth.
KeywordsDiatom Winter bloom Nutrient Euphotic layer Light attenuation coefficient Ariake Bay
We thank Yuji Masuda (Saga Prefectural Genkai Fisheries Research and Development Center) and Taro Morikawa (Saga Prefectural Ariake Fisheries Research and Development Center) for their kind support in the sampling. We also thank Tadashi Matsubara (National Research Institute of Fisheries and Environment of Inland Sea, Japan Fisheries Research and Education Agency) and Yulina V. Hane (The University of Tokyo) for their constructive comments. This work was partially supported by the Japanese Fisheries Agency-aided project for addressing red tides and oxygen-depleted water mass.
- Caffrey JM, Chapin TP, Jannasch HW, Haskins JC (2007) High nutrient pulses, tidal mixing and biological response in a small California estuary: variability in nutrient concentrations from decadal to hourly time scales. Estuar Coast Shelf Sci 71:368–380. https://doi.org/10.1016/j.ecss.2006.08.015 CrossRefGoogle Scholar
- Kaeriyama H, Katsuki E, Otsubo M, Yamada M, Ichimi K, Tada K, Harrison PJ (2011) Effects of temperature and irradiance on growth of strains belonging to seven Skeletonema species isolated from Dokai Bay, southern Japan. Eur J Phycol 46:113–124. https://doi.org/10.1080/09670262.2011.565128 CrossRefGoogle Scholar
- Katano T, Yoshino K, Ito Y, Hayami Y (2013) Relationship between the number of cysts that germinate and the occurrence of red tides in the inner part of the Ariake Sea. Bull plankt Soc Jpn 61:8–14 (in Japanese with English abstract) Google Scholar
- Kiyomoto Y, Yamada K, Nakata H, Ishizaka J, Tanaka K, Okamura K, Kumagai K, Umeda T, Kino S (2008) Long-term increasing trend of transparency and its relationships to red tide outbreaks in Ariake Bay. Oceanogr Jpn 17:337–356 (in Japanese with English abstract) Google Scholar
- Matsubara T, Yoshida Y, Shuto T (2011) Trends in occurrence of phytoplankton in the Ariake Sea off Saga prefecture during a Porphyra (Nori) cultivation period (1989–2010). Bull Saga Prefect Ariake Fish Res Dev Cent 25:21–35 (in Japanese with English abstract) Google Scholar
- Matsubara T, Mine T, Ito S (2018) Population dynamics of harmful phytoplankton causing bleaching of cultured nori in the Shiota River Estuary in innermost Ariake Sea, Japan. Bull Coast Oceanogr 55:139–153 (in Japanese with English abstract) Google Scholar
- Nishikawa T (2011) Physiological ecology of the harmful diatom Eucampia zodiacus, a causative organism in the bleaching of aqucultured Porphyra thalli: mechanism of mass occurrences in recent year. Bull Hyogo Pref Tech Cent Agr Forest Fish (Fish Sec) 42:1–82 (in Japanese with English abstract) Google Scholar
- Shi F, McNabb P, Rhodes L, Holland P, Webb S, Adamson J, Immers A, Gooneratne R, Holland J (2012) The toxic effects of three dinoflagellate species from the genus Karenia on invertebrate larvae and finfish. New Zeal J Mar Freshw Res 46:149–165. https://doi.org/10.1080/00288330.2011.616210 CrossRefGoogle Scholar
- Shikata T, Matsubara T, Yoshida M, Sakamoto S, Yamaguchi M (2015) Effects of temperature, salinity, and photosynthetic photon flux density on the growth of the harmful diatom Asteroplanus karianus in the Ariake Sea, Japan. Fish Sci 81:1063–1069. https://doi.org/10.1007/s12562-015-0930-3 CrossRefGoogle Scholar
- Yamada M, Otsubo M, Tada K, Nakano Y, Matsubara T, IIda N, Endo Y, Montani S (2017) Species composition of the genus Skeletonema (Bacillariophyceae) in five Japanese coastal waters over the subtropics from the subarctic zone. Bull Jpn Soc Sci Fish 83:25–33. https://doi.org/10.2331/suisan.16-00040 (in Japanese with English abstract) CrossRefGoogle Scholar
- Yamaguchi A, Matsubara T, Masuda Y, Mine T, Ito S (2017) The role of a high nutrient and high chlorophyll water mass in the Kashima estuary on the dynamics of winter diatom blooms in coastal areas in the inner western part of Ariake Bay. Bull Coast Oceanogr 54:193–201 (in Japanese with English abstract) Google Scholar