大亚湾湿地底栖微藻对氮素的吸收存储及影响因素探究

Study on nitrogen uptake and storage of benthic microalgae and itsinfluencing factors in Daya Bay wetlands

为探讨不同类型湿地表层沉积物中底栖微藻对氮素的吸收存储能力及其影响因素,于2017年3月(枯水期)和8月(丰水期)分别采集大亚湾光滩湿地(T1)、河口湿地(T2)和红树林湿地(T3)表层沉积物底栖微藻样品,并进行了反复冻融实验。研究结果表明,大亚湾滨海湿地表层沉积物中的底栖微藻丰度具有显著的时空差异,温度、营养盐和沉积物粒径可能是影响底栖微藻生长繁殖的主要因素。不同季节比较发现,底栖微藻的氮累积存储能力表现为枯水期强于丰水期,主要由于丰水期较高温度和强光照引起的过度干燥和光刺激,限制了底栖微藻的生长繁殖。河口湿地丰富的营养物质能促进底栖微藻的生长繁殖,致使在淡澳河河口湿地叶绿素含量最高,底栖微藻丰度也最大。底栖微藻胞内溶解无机氮(DIN)含量表现为T2(河口湿地)>T1(光滩湿地)>T3(红树林湿地)的空间分布特征,这与其生物量的时空分布特征相一致(P<0.01),并且底栖微藻对氨氮(NH_(4)-N)有较强的累积存储能力,胞内氨氮(IC-NH_(4))占胞内无机氮(IC-DIN)高达90.4%。底栖微藻IC-DIN占整个沉积物氮库的24.2%,其中约20.0%的NH_(4)-N、17.6%的NO_(3)-N和16.0%的NO_(2)-N被吸收累积在底栖微藻细胞内。整体上,大亚湾湿地沉积物底栖微藻的氮素累积能力受营养负荷的影响,且NH_(4)-N负荷越高,底栖微藻对氮的吸收存储能力越强,能有效降低近岸富营养化水平。

In order to investigate the nitrogen absorption and storage capacity of benthic microalgae on surface sediments of different types of wetlands and its influencing factors,samples of benthic microalgae were collected from surface sediments of barren wetland(T1),estuarine wetland(T2)and mangrove wetland(T3)of Daya Bay in March and August 2017,and repeated freeze-thaw experiments were conducted.The results showed that the spatial and temporal distribution of the abundance of benthic microalgae varied significantly,and temperature,nutrients and sediment particle size were main factors affecting the growth and propagation of benthic microalgae in the Daya Bay coastal wetland.It was found that the nitrogen accumulation and storage capacity of benthic microalgae was stronger in dry season than in wet season,which was mainly due to excessive dryness and photostimulation caused by higher temperature and strong light.Excessive dryness and photostimulation could restrict the growth and reproduction of benthic microalgae.The abundant nutrients in estuary wetland promoted the growth and reproduction of benthic microalgae,resulting in the highest chlorophyll content and the maximum abundance of benthic microalgae in T2 Dan'ao river estuary wetland.The intracellular DIN content of benthic microalgae showed the spatial distribution characteristics of T2>T1>T3,which was consistent with the distribution characteristics of microalgae abundance(P<0.01),and the benthic microalgae had a strong accumulation capacity of NH_(4)-N,accounting for about 90.4%of IC-DIN.Generally,IC-DIN of benthic microalgae accounted for 24.2%of the total sediment nitrogen pool,and about 20.0%of NH_(4)-N,17.6%of NO_(3)-N and 16.0%of NO_(2)-N were stored in benthic microalgae cells.The nitrogen accumulation capacity of benthic microalgae in Daya Bay wetland was affected by nutrient load,and the higher the NH_(4)-N load was,the stronger the nitrogen absorption and storage capacity of benthic microalgae was,which could effectively alleviate the nearshore eutrophication level.