魚投入実験池でみられたフェオ色素組成の特徴と底泥への沈降

抄録

Pheopigments concentrations in sestons, settling materials and bottom muds in experiment ponds were measured by HPLC. Pyropheophytin a (pptn-a) as well as pheophytin a (ptn-a), chlorophyll a(chl-a) and pyrochlorophyll a(pchl-a) were identified by using a LC/MS method. An increase of pptn-a and a decrease of pheophorbide a(pbd-a) in sestons were observed in the ponds with abundant gold fish (Carrasius auratus). This tendency was also observed in settling materials and bottom muds in the experiment ponds. The decomposition process of chl-a was suggested to be chl-a → ptn-a → pbd-a (demetalation followed by dephytylation) in the ponds without gold fish where a large amount of zooplankton was observed. On the other hand chi-a → pchl-a → pptn-a (decarbomethoxylation followed by demetalation) seemed to be the main decomposition process in the ponds with abundant gold fish with a small amount of zooplankton. Zooplankton and fish may play an important role in the dephytyl process and the decarbomethoxy process, respectively. Pheopigments concentrations in surface sediments were different between Tokyo Bay, Onjuku Reservoir and Lake Imbanuma. The pyropheophorbide a (pphd-a) concentration was high in the sediment of Tokyo Bay where settling particles would take the longest time to reach the surface sediments. High percentage of chl-a was observed in the surface sediment of Lake Imbanuma, which was a shallow eutrophic lake, and undecomposed phytoplanktons were recognized on the surface sediment.