title: [Characteristics of diffuse attenuation coefficient of underwater irradiance in the lakes in the middle and lower reaches of Yangtze river ].
abstract: Based on the underwater irradiance profile measurement and water samples collection in September, October 2007 in Lake Donghu, Lake Liangzi and Lake Honghu, and in April in 2010 in Lake Kuileihu, the diffuse attenuation coefficient and the dominant attenuation factors were analyzed. The ranges of diffuse attenuation coefficient and total suspended solid (TSS), organic suspended solid (OSS), inorganic suspended solid (ISS), chlorophyll a (Chla), and dissolved organic carbon (DOC) concentration varied less in Lake Donghu and Lake Kuileihu than in Lake liangzi and Lake Honghu. The regression analysis showed that ISS was the dominant affecting factor of transparency in Lake Donghu and Lake Kuileihu, but ISS and OSS jointly controlled the transparency in Lake Liangzi and Lake Honghu. The diffuse attenuation coefficient minimum occurred near 580 nm. At around 675 nm, the diffuse attenuation coefficient peak was due to phytoplankton absorption, especially at sites with high pigment concentration. The euphotic depth was less than the mean water depth in Lake Donghu, suggesting that the submerged aquatic vegetation (SAV) can not grow in the present underwater light climate. However, the euphotic depth was larger than the mean water depth in other three lakes showing that the underwater light climate can meet the light requirements for the growth of SAV. The regression analysis showed that ISS was the dominant affecting factor of PAR attenuation in Lake Donghu and Lake Kuileihu, but ISS, OSS and Chla jointly controlled PAR attenuation in lake Liangzi and lake Honghu. The significant correlation between the beam attenuatin coefficient at 750 nm and PAR difffuse attenuation coefficient showed that the particles scattering significantly contributed to underwater irradiance attenuation.
authors.affiliation: Chinese Academy of Sciences, Nanjing, China. szq19850518@126.com
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Shi
authors.forename: Yun-Lin
authors.initials: YL
authors.lastname: Zhang
authors.forename: Ming-Zhu
authors.initials: MZ
authors.lastname: Wang
authors.forename: Xiao-Han
authors.initials: XH
authors.lastname: Liu
mesh_terms: D002681:China; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D056890:Eukaryota / Q000254:growth & development / Q000378:metabolism; D005618:Fresh Water; D060106:Lakes; D009391:Nephelometry and Turbidimetry; D010316:Particle Size; D045483:Rivers; D012542:Scattering, Radiation; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D014873:Water Pollutants; D002734:Chlorophyll; D000077194:Chlorophyll A