広島湾における水中懸濁物と大型褐藻クロメの葉上堆積物との光吸収特性の比較

海水中の懸濁物と，海藻の葉上堆積物は，ともに藻体表面に到達する光を質的かつ量的に変化させ，海藻の生産力に多大な影響を及ぼす。本研究では内湾域である広島湾における大型褐藻クロメの葉上堆積物とクロメ群落直近の海水中の懸濁物について，両者の光吸収係数を統一的手法（QFT法）に基づいて把握し，その特性を比較した。懸濁物と堆積物の全体の光吸収特性に明瞭な差は認められず，葉上堆積物の多くが沈降した懸濁物によって構成されていたことが推察された。懸濁物・堆積物ともに，デトリタスや微細藻類など多様な要素により構成されており，光合成有効波長域（400-700nm）のうち，短波長側の光は微細藻類の色素以外のデトリタスなどが，長波長側の光は微細藻類の光合成色素が吸収し，それぞれクロメの光吸収に大きく影響すると考えられた。

Light is the primary limiting factor for macroalgal production. Understanding not only the quantity but also the quality of light reaching algal thalli is important to the success of algal recovery and sustainability. This study explores the optical properties of accumulated matter on the thalli of Ecklonia kurome and suspended matter in the water surrounding an Ecklonia bed in Hiroshima Bay, based on spectral absorption coefficient estimated by the quantitative filter technique (QFT) method.

According to the experiments, minimal difference of optical properties between suspended matter and accumulated matter was recognized. It is assumed that suspended matter in the water formed the accumulated matter on the thalli of E. kurome. Both suspended matter and accumulated matter were composed of multiple components, various kinds of microalgae, detritus and inorganic matter. In the wavelength-specific photosynthetically active radiation (400-700nm), detritus and inorganic matter formed the primary absorber of blue light, while microalgal pigments was the primary absorber of red light. Each absorber in suspended and accumulated matter might attenuate specific wavelength and change the quality of light reaching the thalli of E. kurome.