【作者】 冯建祥；

【导师】 林光辉； 高亚辉；

【作者基本信息】 厦门大学 ， 水生生物学， 2013， 博士

【摘要】 红树林因其高的初级生产力和生境异质性支持了红树林生态系统丰富的生物多样性和复杂的食物网结构,而以前的研究显示互花米草入侵红树林生态系统后可能会对底栖动物食物源造成显著影响,从而改变了红树林湿地生态系统食物网关系。然而,至今未见互花米草入侵如何影响红树林周边水域浮游动物和游泳动物食物来源的研究报道。本博士论文研究利用稳定同位素技术系统分析了互花米草入侵对福建漳江口(N23°55.719’,E117°26.436’)红树林周边水域内浮游动物和游泳动物的食物来源,并跟踪了三个红树林生态系统中利用本地红树植物替代互花米草过程中大型底栖动物群落结构和主要物种食物源的变化,主要结果和结论如下：(1)漳江口周边水体叶绿素a含量表现出较大的时空变化,在夏季和春季最高,而冬季最低,并于盐度之间存在显著负相关关系。冬季颗粒有机物(POM)组成相对稳定,自近岸到近海处,陆源红树植物平均贡献度下降(30.6%—24.1%),而海源浮游植物的平均贡献度逐渐升高(23%—28%),本地源底栖微藻的平均贡献度在33%—35%之间,而互花米草的平均贡献度低于15%。夏季POM组成变化较大,近岸处红树植物的平均贡献度高达62.1%,近海处平均贡献度也达到33.5%,海源浮游植物(Phytoplankton)(10.9%-20.9%)、底栖微藻(BMA)(21.4%—31.4%)和入侵种互花米草(5.7%—10.7%)的平均贡献度均随近岸到近海呈上升趋势。总体来讲,本地红树植物和底栖微藻及海源浮游植物是漳江口颗粒有机物的主要贡献者,而入侵种互花米草对POM组成的贡献度较低,平均低于15%,贡献范围最高也低于40%。(2)漳江口浮游动物总密度在不同季节之间表现出显著差异,夏季最高,冬季最低。浮游动物的有机碳来源方面,冬季陆源红树植物对浮游动物贡献较小,低于21%,POM和BMA的平均贡献度在24—34%之间变化,而互花米草平均贡献度在15%—35%之间。夏季浮游动物有机碳来源变化较大,近岸处陆源红树植物的平均贡献度高达65.6%,但随近岸到近海处下降至14.5%,POM和BMA的平均贡献度在14%—28%之间变化,入侵种互花米草平均贡献度范围也较广,在4%—45%之间变化。浮游动物主要有机碳来源是本地源的红树植物和底栖微藻等,但互花米草也能对浮游动物的有机碳来源比例造成显著影响,平均贡献度低于50%,考虑其贡献比例范围,最高可达59%,成为浮游动物主要食物源。(3)福建漳江口潮沟内采集到的鱼类主要有碎屑食性的前鳞鲻(Osteomugil ophuyseni),杂食性的拟矛尾复鰕虎鱼(Parachaeturichthys polynerna),七丝鲚(Coilia grayii)和黄鳍鲷(Sparus latus)以及肉食性的花鲈(Lateolabrax japonicus)和尖吻蛇鳗(Ophichthus apicalis)等6种。对这些鱼类组织的稳定同位素分析结果显示,互花米草对6种鱼类的有机碳源贡献度,除对黄鳍鲷的贡献度最低值为28%(28—57%)之外,对其它5种鱼类的有机碳贡献度最低均在50%以上,表明互花米草已经同化入本地食物网,成为高营养层次的鱼类的主要有机碳源。6种鱼类中,只有黄鳍鲷表现出稳定同位素值与个体体长之间显著相关性：个体小于10cm的黄鳍鲷的δ13C和δ15N值分别比个体大于10cm的黄鳍鲷高出5.99‰和3.4‰；小个体黄鳍鲷高的营养级位置表明其捕食特性,而随着个体生长,其食性发生转变,主要碳源也由互花米草转变为微藻。(4)对福建湄洲湾(N25°14.552’,E118°53.314’)、闽江口(N26°01.934’,E119°37.707’)和漳江口大洲岛三地互花米草及1年秋茄修复样地大型底栖动物群落结构进行了调查,发现前期物理处理手段和红树种植对大型底栖动物的群落结构造成了影响,主要是改变了底上生活型甲壳类和腹足类的密度和生物量,底下生活型多毛类密度和生物量并未受到影响,小个体生物更易于适应新环境。对大洲岛互花米草、1年修复秋茄样地、10年秋茄林和40年秋茄成熟林内底栖动物群落结构和多样性水平的比较结果显示：各多样性指数在个样地之间均无显著差异,但底栖动物群落组成可能受到了修复过程的影响。四个样地之间总密度虽未表现出显著差异(P>0.05),但10年秋茄林内多毛类密度最高,而软体动物密度最低(P<0.05)。总生物量方面,10年秋茄林总生物量最低,显著低于互花米草(P<0.05),而与1年修复样地和40年成熟秋茄林之间差异不显著(均为P>0.05)。(5)利用稳定同位素技术比较湄洲湾、闽江口和大洲岛互花米草及不同修复年份秋茄林内底栖动物食物来源,结果表明：红树替代互花米草前期工程处理并未改变其食物源,1年修复样地内底栖动物有机碳源依旧以互花米草为主；随修复年份增加,互花米草对底栖动物的食物贡献水平逐渐下降,但修复10年后,林内底栖动物食物源组成与40年成熟林之间仍有差异,表明红树林替代互花米草修复过程中底栖动物食物源改变较为缓慢。不同摄食类型的底栖动物食物源变化对秋茄替代互花米草修复过程响应的时间存在差异,植食性物种的食物源随秋茄修复互花米草在3年左右已有较大变化,随着修复进行,互花米草在6年修复秋茄林内平均碳源贡献度可以降至50%以下；而底栖碎屑食性的腹足类和蟹类在3年修复秋茄林内互花米草来源有机物质对其有机碳源贡献依旧为100%,在6年秋茄林内碎屑食性侧足厚蟹中来自互花米草的有机碳降低至70%以下。综上,互花米草入侵红树林生态系统后不仅对大型底栖动物的食物源造成了影响,也改变了周边水体中浮游动物和游泳动物的有机碳来源；利用本土红树植物替代控制互花米草可以修复大型底栖动物群落结构及其食物源,使其由单一碳源向多有机碳来源转变,增加了食物多样性程度,虽然修复的过程较为缓慢,但表明了该方法控制互花米草的合理性及可行性。更多还原

【Abstract】 Mangrove ecosystems can support high biodiversity and complicated trophic structure due to its high primary production and habitat heterogeneity, but previous studies have shown that the invasion Spartina alterniflora into mangrove wetlands could significantly change the food sources of benthic macro-invertebrates. However, there is still no study on such effect of S. alterniflora invasion on zooplankton and nekton communities. In this dissertation research, I investigated possible effects of S. alterniflora invasion on the organic carbon sources of aquatic animals in the adjacent water of mangrove including zooplankton and nekton. I also monitored changes in the structure of macrofaunal community and food sources of main macro-invertebrates species in the invased S. alterniflora stands following replacement by native mangrove species Kandelia obovata. The main results of these studies could be summarized as follows:(1) The chlorophyll a (Chi a) concentration of water in Zhangjiangkou Estuary (N23°55.719’, E117°26.436’) demonstrated large spatial-temporal variations. The highest Chi a concentrations were found in summer or spring, while the lowest values occurred in winter. A negative relationship existed between Chi a concentration and salinity (P<0.05). In winter, the compositions of particulate organic matter (POM) remained relatively stable, and the average contribution from mangrove carbon to POM decreased from30.6%to24.1%the upstream to offshore areas, while the contribution from marine phytoplankton increased from23%to28%. Benthic microalgae (BMA) averagely contributed33%-35%to the POM and the average contribution from invasive S. alterniflora was less than15%. In summer, the compositions of POM showed much larger variations. The average contribution of mangrove carbon ranged from62.1%in the upstream area to33.5%in the offshore area. Contrary to the mangrove carbon, the average contributions from marine phytoplankton (10.9%-20.9%), BMA (21.4%-31.4%) and invasive S. alterniflora (5.7%-10.7%) increased from the upstream to offshore areas. In general, the autochthonous materials including mangrove and BMA were the major carbon sources for the POM, while the invasive S. alterniflora showed much less contribution to the POM even when considering the variation range of different sources.(2) Total density of zooplankton showed significant seasonal variations (P<0.05). The highest density was found in summer while the lowest in winter. The stable isotopic analyses of zooplankton and autotroph species indicated that, in winter, mangrove forests contributed less than21%to the organic carbon of zooplankton, while the total contribution from POM and BMA ranged from15%to35%and from the S. alterniflora varied between15%-35%. The carbon sources of zooplankton demonstrated large spatial variations in summer. The average contribution from terrestrial mangrove was as high as65.6%in the upstream area, but it decreased greatly from the upstream to offshore areas, where the average contribution from mangrove was only14.5%. The average contribution from POM and BMA varied from14%to28%, while the average contribution from S. alterniflora ranged broadly from4%to45%. Major carbon sources to the zooplankton were autochthonous carbon from the mangrove forests and POM/BMA. While considering the variation range of different sources, S. alterniflora could also be the major contributor to organic carbon of zooplankton.(3) I analyzed the stable carbon and nitrogen isotope ratios of six common fish species, including detritus feeding Osteomugil ophuyseni, omnivorous Coilia grayii, Parachaeturichthys polynern and Sparus latus and carnivorous Lateolabrax japonicas and Ophichthus apicalis, in the tidal creek of Zhangjiang Estuaryto assess the relative nutritional contributions from invasive S. altemiflora and native autotrophs. The results indicated that S. alterniflora was a major contributor to all fish species. For S. latus, the minimum proportion of carbon sources from S. altemiflora was28%. For the other species, S. alterniflora contributed at least50%of organic carbon to them. Among the above6fish species, only S. Latus showed significantly negative correlation between carbon isotope ratio and its body length, demonstrating the transference of main food sources and trophic levels during growth. (4) The benthic macrofaunal community in S. alterniflora and1year restored K. obovata forest were investigated in Meizhou Bay (N25°14.552’, E118°53.314’), Minjiang Estuary (N26°01.934’, E119°37.707’) and Dazhou island. Results indicated that the preliminary physical treatment and plantation activities significantly changed the benthic community. The density and biomass of large-sized epifauna including crustacean and gastropod were impacted by the preliminary treatment, while no such effect were found on the infaunal Polychaeta, demonstrating that the small-sized organisms could be adapted to the change of habitat rapidly. The community structure and biodiversity of benthic macrofauna in S. alterniflora,1year restored K. obovata,10years K. obovata forest and40years mature K. obovata forest were compared in Dazhou island. Although no significant differences were found for the biodiversity indexes among4habitats, the community structure might be impacted by the restoration. Total density showed no significant differences among different habitats (P>0.05), but the10years K. Obovata forest had highest density of Polychaeta and lowest density of mollusk.10years K. obovata also had lower total biomass than S. alterniflora (P<0.05), but no significant differences were found between the other habitats.(5) Based on the stable isotope analyses, the variations of food sources of main gastropod and crab species in S. alterniflora and K. obovata with different ages were investigated in Meizhou Bay, Minjiang Estuary and Dazhou Island. The preliminary engineering activities did not change the food sources of macro-invertebrates, while the major carbon source for gastropod and crab species came from the remains of S. alterniflora. The relative carbon contribution from S. alternifolra to macro-invertebrates decreased with the age of K. obovata forest. However, obvious discrepancy still existed between the10year old K. obovata forest between40year old mature K. obovata forest, suggesting that it take a long period for the restoration of food source of macro-invertebrates in mangrove forests following the invasion of S. alterniflora. Furthermore, macrofaunal species with different feeding types showed different change in their food sources in response to the restoration of mangrove. The food sources of herbivorous gastropods and crab species already changed significantly in3year old K. obovata forest and their carbon contribution from S. alternifora decreased to less than50%in6year K. obovata forest. However, the detritus-feeding invertebrates did not change their food sources and derived most100%organic carbon from S. alterniflora in3year old K. obovata forest. The carbon sources from S. alterniflora to detritivorous H. latimera decreased to less than70%in6years K. obovata forest, indicating that these kind of species need at least5-6years to begin obvious change in their food sources.In general, the invasive S. alterniflroa also significantly changed the food sources of zooplankton and nekton. However, the restoration using native mangrove species to control the S. alterniflroa could restore the benthic macrofaunal community and food sources of macro-invertebrates. Although the restoration takes a long time, it feasible and beneficial to use this method to controle the spread the S. alterniflora and reverse the ecological effect.更多还原