クメ　マナブ   Manabu Kume   久米　学    所属   石巻専修大学  理工学部    職種   准教授
言語種別	英語
発行・発表の年月	2014/05
形態種別	研究論文（学術雑誌）
査読	査読あり
標題	Terrestrialization alters organic matter dynamics and habitat quality for freshwater mussels (Unionoida) in floodplain backwaters
執筆形態	未選択
掲載誌名	Freshwater Biology
出版社・発行元	WILEY-BLACKWELL
巻・号・頁	59(5),pp.1026-1038
著者・共著者	Junjiro N. Negishi,Kotaro Katsuki,Manabu Kume,Shigeya Nagayama,Yuichi Kayaba
概要	Anthropogenically induced reduction in flood inundation frequency often leads to terrestrialisation, which accompanies establishment and expansions of tree cover on areas formerly with little or no trees. We tested hypotheses that terrestrialisation degrades habitat for freshwater mussels (Unionoida: Unio douglasiae nipponensis and Lanceolaria grayana) by changing the organic matter (OM) dynamics in floodplain backwaters. Stable isotope composition of seston, periphyton, fine and coarse benthic particulate OM (FBPOM and CBPOM) and mussel tissues was measured to understand OM dynamics and food webs in 14 backwaters in the middle segment of the Kiso River, Japan. Isotope ratios, C:N ratio and chlorophyll a as a proxy of food resource characteristics and the frequency of hypoxia were related to mussel growth rates. delta C-13 of seston, periphyton and FBPOM was low at sites with lower inundation frequency (a greater degree of terrestrialisation), whereas such a trend was not observed for CBPOM (i.e. riparian leaf litter). Mussels fed exclusively on seston or mixtures of seston and periphyton with their delta C-13 tracking fluctuations in food resources. Sestonic delta C-13 differences were attributed to changes in dominant carbon origin from predominantly river-borne to autochthonous sources, while periphytic delta C-13 differences were possibly caused by a varying level of dependence on respiratory CO2. FBPOM-delta C-13 differences were associated with a greater contribution of CBPOM to the FBPOM pool in infrequently flooded backwaters. Variability in mussel growth was more closely related to hypoxia than food resource characteristics. We inferred that terrestrialisation changes quality of seston and benthic detritus and degrades habitat conditions largely by accumulating riparian leaf litter in the benthic detrital pool and increasing the frequency of hypoxia. The removal of riparian trees may temporarily improve habitat condition in backwaters heavily affected by terrestrialisation. However, ecological integrity in the long run requires the recovery of the process that suppresses terrestrialisation, which includes restoration of incised channels and flood pulses.
DOI	10.1111/fwb.12325
ISSN	0046-5070/1365-2427