大阪湾の栄養塩低下と直立構造物の潮間帯付着生物の分布変化

本研究は大阪湾沿岸の付着生物の調査を実施し，栄養塩低下と付着生物の分布の関連性を明らかにするために検討を行った．具体的には13年前に実施した調査地点を中心に調査を行った結果，生物相に大きな変化はなかったが，春季の海藻の種数は湾奥において増加しており，ワカメやクロフジツボ等の付着生物は環境勾配の変化に従って，湾奥に分布域を拡大していた．長期間のモニタリングデータを用いて大阪湾沿岸の水質変化を検討した結果，2000年からの栄養塩は減少していた．また，水質を用いて特徴的な生息分布を示した生物種に関し，Maxentを用いて分布に寄与する要因を解析した結果，栄養塩を主として透明度や塩分，護岸構造物の種類が寄与していると考えられた．大阪湾沿岸における栄養塩の低下は付着生物の分布に影響を及ぼしていることが示唆された．

To clarify the relationship between attached organisms and decreasing nutrients, we investigated attached organisms in the coastal area of Osaka Bay. There was no significant change in the biota, but the number of species of seaweeds in the spring increased in the inner part of the bay, and the number of attached animals in the summer increased south of inner part in Osaka Bay. In addition, the number of attached animal species increased south of inner part at Osaka Bay in summer. Some of the attached organisms have expanded their spatial distribution to the inner part of the Osaka bay. Water quality changes in the coastal areas of Osaka Bay were examined using long-term monitoring data. The results showed that nutrients in the coastal areas of Osaka Bay have decreased since 2000. Distribution of some species that showed characteristic habitat distributions, were analyzed the factors contributing to the distributions, and the results indicated that nutrients contributed to the spring distribution. The results suggest that low nutrient levels in coastal areas of Osaka Bay affect the distribution of attached organisms.

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