珠海夹洲岛无瓣海桑与秋茄群落对重金属吸附能力的比较研究

Comparative study of the heavy metal adsorption capacities of Sonneratia apetala and Kandelia candel communities on Jiazhou Island, Zhuhai, China

为了解外来红树植物无瓣海桑对重金属的吸附能力,以期为其科学引种和合理规划滩涂红树林造林提供科学依据,选取珠海夹洲岛两片恢复背景和林龄相同的无瓣海桑(Sonneratia apetala)和秋茄(Kandelia candel)人工林,比较研究裸滩和两种人工林土壤、两种红树植物体和林区内3种不同生活型底栖动物体内Cd、Pb、Cr、Cu、Zn的含量。结果发现:(1)无瓣海桑人工林土壤中仅Cr含量略低于秋茄人工林,其余4种重金属含量均高于秋茄人工林。(2)5种重金属在无瓣海桑体内含量的加权平均值大小排列为:Zn>Pb>Cu>Cr>Cd,而秋茄为:Zn>Cu>Cr>Pb>Cd。(3)无瓣海桑对Pb、Cu和Zn的累积量高于秋茄,而对Cd和Cr的累积量低于秋茄。(4)无瓣海桑对5种重金属的富集系数大小排序为:Pb>Cd>Cu>Zn>Cr,而秋茄为:Cd>Cu>Zn>Cr>Pb。无瓣海桑对Pb的富集能力最强,对Cr的富集能力最弱;而秋茄对Cd的富集能力较强,对Pb的富集能力最弱。(5)植食性褶痕相手蟹(Sesarma plicata)重金属的含量与红树植物叶子同一元素含量呈显著正相关(p<0.01),而底表类中国耳螺(Ellobium chinense)和底栖类褐蚶(Didimarca tenebricum)体内重金属的含量与林区土壤重金属的含量呈显著正相关(p<0.01)。这些表明了外来红树植物无瓣海桑对重金属的吸附能力明显不同于乡土红树植物秋茄,人工林区底栖动物体内重金属含量不仅与沉积环境中重金属含量有关,而且还与底栖动物自身的生活型和食性密切相关。

In order to provide a scientific basis for the introduction and rational planning of mangrove afforestation in intertidal regions, a study was undertaken to compare the heavy metal adsorption capacities of the exotic mangrove species Sonneratia apetala and an indigenous species Kandelia candel. The study region is located at Jiazhou in the Qi＇ao Island Mangrove Nature Reserve, Zhuhai, Guangdong Province, China. Six-year-old Sonneratia apetala and K. candel artificial mangroves with similar restoration backgrounds, and a naked tidal flat without vegetation and within 20 m of the forested areas, were selected as study sites. The Cd, Pb, Cr, Cu, and Zn contents in samples taken from the soil in the two plantations and the naked tidal flat, the two mangrove plant types, and three different macrofauna found in the mangrove plantations were compared. The results indicated that（1） the Cr content of the soil from the Sonneratia apetala plantation was only slightly lower than that of the soil from the K. candel plantation, and the contents of the other four heavy metals in the Sonneratia apetala plantation soil were higher than those in the K. candel plantation soil.（2） The weighted average value rank order for the five heavy metals in Sonneratia apetala soil was Zn〉 Pb 〉Cu 〉Cr〉 Cd, while the K. candel average value rank order was Zn 〉Cu 〉Cr 〉Pb 〉Cd.（3） The cumulative amounts of Pb, Cu, and Zn in Sonneratia apetala trees were higher than those in K. candel, while the cumulative amount of Cd and Cr in Sonneratia apetala were lesser than those in K. candel.（4） The accumulation index rank order for the five heavy metals in Sonneratia apetala was Pb 〉Cd 〉Cu 〉Zn 〉Cr, whereas in K. candel it was Cd 〉Cu〉 Zn〉 Cr〉 Pb. This showed that Sonneratia apetala strongly accumulated Pb, but was least able to take up Cr, whereas K. candel strongly accumulated Cd, but was least able to take up Pb.（5） The heavy metal content in herbivorous Sesarma plicata had a significant positive relationship with the heavy metal content in mangrove plant leaves（p〈 0.01）, while the heavy metal contents in bottom dwelling Ellobium chinense and benthic Didimarca tenebricum were significantly correlated with the heavy metal content in the forest soils（p〈 0.01）. These results illustrated that the heavy metal adsorption capacity of the exotic mangrove species Sonneratia apetala was quite different from that of the indigenous mangrove species K. candel. The heavy metal contents in the macrofauna were not only related to the heavy metal content of the sedimentary environment, but were also closely related to the life forms and feeding habits of the macrofauna.