贵州草海光合有效辐射衰减特征及影响因素研究

Study on attenuation characteristics and influencing factors of photosynthetically active radiation in Caohai Lake,Guizhou Province

水下光环境对湖泊生态系统具有重要影响,是限制沉水植物生长、发育的重要因素,研究光合有效辐射衰减特征对湖泊沉水植物恢复具有重要指导意义。于2022年3~8月对草海水下光合有效辐射(PAR)时空分布进行调查,研究了光合有效辐射衰减系数(K d(PAR))与总悬浮物(TSS)、无机悬浮物(ISS)、有机悬浮物(OSS)、叶绿素a(Chl.a)和有色可溶性有机物(CDOM)等光衰减物质的关系,以及真光层深层(Z_(eu))的时空分布特征。结果表明:草海春夏季K_(d)(PAR)平均值为(2.90±1.12)m^(-1),Z_(eu)平均值为(1.84±0.69)m;光衰减因子TSS、ISS、OSS、Chl.a浓度和CDOM(380)吸收系数分别为(20.11±4.76)mg/L、(8.68±4.91)mg/L、(11.66±12.43)mg/L、(21.88±8.49)mg/m^(3)和(3.11±0.68)m^(-1);草海K_(d)(PAR)北部水域高于南部;草海水体K_(d)(PAR)与TSS(P<0.01)、ISS(P<0.01)和浊度(P<0.001)相关性显著,与Chl.a相关性不显著;春季影响草海K_(d)(PAR)的主导因子是ISS,夏季影响草海K_(d)(PAR)的因子是由ISS和CDOM共同主导,以春夏季整体来看,影响草海K_(d)(PAR)的因子是由ISS和Chl.a共同主导,这主要是由于草海水生植被衰退后风浪等导致沉积物再悬浮的缘故,且CDOM和Chl.a浓度的增加也是影响K_(d)(PAR)的关键因子;草海Z_(eu)平均值大于水深平均值,说明草海水体总体光环境有利于沉水植物生长发育,但是草海水体悬浮物质含量较高,其遮蔽可能导致沉水植物生长发育受阻,这也许是草海降低水位后沉水植物恢复不理想的一个重要原因。

The underwater light environment has an important influence on lake ecosystem and is an important factor limiting the growth and development of submerged plants.Studying the attenuation characteristics of photosynthetically active radiation(PAR)is of guiding significance for the recovery of submerged plants in lakes.This study investigated the spatial and temporal characteristics of PAR in Caohai Lake from March to August in 2022.The relationship between diffuse attenuation coefficients of photosynthetically active radiation(K_(d)(PAR))and total suspended solid(TSS),inorganic suspended solid(ISS),organic suspended solid(OSS),chlorophyll-a(Chl.a)and chromophoric dissolved organic matter(CDOM)were studied.The results showed that the average K_(d)(PAR)during the period from spring to summer was(2.90±1.12)m^(-1),and the average of Z_(eu) was(1.84±0.69)m.The concentration of TSS,ISS,OSS,Chl.a and CDOM absorption coefficient was(20.11±4.76)mg/L,(8.68±4.91)mg/L,(11.66±12.43)mg/L,(21.88±8.49)mg/m ^(3) and(3.11±0.68)m^(-1),respectively.In Caohai Lake,K_(d)(PAR)in northern waters was greater than that in southern waters.The K_(d)(PAR)was significantly correlated with TSS(P<0.01),ISS(P<0.01)and turbidity(P<0.001),but was not significantly correlated with Chl.a(P>0.05).The dominant factor affecting K_(d)(PAR)in Caohai Lake in spring was ISS,and the factors in summer were dominated by ISS and CDOM.Taking the spring and summer as a whole,the factors affecting K_(d)(PAR)were dominated by ISS and Chl.a.,indicating that the dominant factor of K_(d)(PAR)in Caohai Lake was suspended material,which was mainly due to sediment resuspension caused by wind and waves after the decline of aquatic plants.In addition,the increase of CDOM and Chl.a concentration were also key factors affecting K_(d)(PAR).In this waterbody,average value of euphotic depth(Z_(eu))was greater than the average of water depth,indicating that the light environment was favorable to the growth and development of submerged plants.However,water suspended material content was high in Caohai Lake,and its coverage can limit growth and development of submerged plants,which may be an important reason for the unsatisfactory recovery of submerged plants after lowering water level.