Relation Between Coral Distributions and Physical Variables in Sakiyama Bay, Iriomote Island, Japan

Abstract

2 東海大学 沖縄地域研究センター(〒907-1541 沖縄県八重山郡竹富町上原870-277) 3 正会員 (研)防災科学技術研究所 水・土砂防災研究部門(〒305-0006 茨城県つくば市天王台3-1) 4 東海大学 海洋学部海洋生物学科(〒424-8610 静岡県静岡市清水区折戸3-20-1) 西表島崎山湾におけるサンゴ分布と物理環境との関係を明らかにすることを目的として，調査研究を実 施した．まず，湾内72地点における群体形状別サンゴ被度分布と群集タイプ別サンゴ分布域の現地調査を 行い，次に，湾域の夏季と冬季の平均的な気象場における数値シミュレーションによる海洋流速場と土粒 子数分布の計算結果を解析し，現地調査で得られたサンゴ分布と比較した． 結果は，以下の通りである．1) サンゴ生育場所の底面流速が大きいほど，サンゴ被度が高い．また， 群集タイプにより，底面流速が異なる．2) サンゴ生育場所の土粒子数が多いほど，サンゴ被度が低い． また，土粒子数が多い場所では，主としてウミショウブが生育している．

Transport properties of soil particles in Sakiyamawan–Amitoriwan nature conservation area, Iriomote Island, Japan

“…2). The divisions reflected the distributions of reef-building coral (Murakami et al 2012;Shimokawa et al 2016) and E. acoroides (Murakami et al 2014;Nakase et al 2015), and each region has almost the same areal extent. For example, the west (11-14) and the east regions (15-17) of the Amitori bay correspond to the top of the reef slope (see also Fig.…”

“…These features are explainable mainly by seasonal differences in wind speed and direction, but the combination among seasonal differences in wind speed and direction, wind-driven current and topography is also important for them. For Amitori bay, we have conducted studies on the soil particle impact on coastal marine ecosystems such as corals (e.g., Murakami et al 2012;Shimokawa et al 2014bShimokawa et al , 2015Shimokawa et al , 2016Ukai et al 2015) and E. acoroides (e.g., Murakami et al 2014Murakami et al , 2015aNakase et al 2015Nakase et al , 2016. Those results provide the basic information about whether the control of soil input from the rivers should be done or not and how much it should be done.…”

“…Previous studies have shown that the distributions of reef-building corals (Murakami et al 2012;Shimokawa et al 2014bShimokawa et al , 2015Shimokawa et al , 2016Ukai et al 2015) and E. acoroides (Murakami et al 2014(Murakami et al , 2015aNakase et al 2015Nakase et al , 2016 are largely influenced by the environmental gradients and vary with location in the Sakiyama and Amitori bays. However, the impact of soil input from rivers on the coastal marine ecosystems has not been investigated thoroughly in the area, especially in Sakiyama bay.…”

Coral distribution and diversity in Sakiyamawan–Amitoriwan nature conservation area of Iriomote Island in Japan

“…We investigated the relationship between coral and E. acoroides distributions and physical fields since 2009 in this area (Shimokawa et al, 2016 for coral and E. acoroides distributions in Sakiyama Bay; Shimokawa et al, 2014aShimokawa et al, , 2015 for coral distributions in Amitori Bay; Nakase et al, , 2016 for E. acoroides distributions in the northwest region of Iriomote Island). A book including English versions of our previous studies written in Japanese was published in 2020 (Shimokawa et al eds., 2020).…”

“…Sakiyama and Amitori bays are adjacent, but their coral distributions differ significantly (Shimokawa et al, 2014a(Shimokawa et al, , 2016. This study investigates the differences in coral distribution and diversity between both bays from a diversity index and intermediate disturbance hypothesis…”