Ravikumar S, Gnanadesigan M, Ignatiammal S Thadedus Maria, Sumaya S
School of Marine Sciences, Department of Oceanography and Coastal Area Studies, Alagappa University, Thondi Campus, Thondi - 623409, India.
J Environ Biol. 2012 May;33(3):597-602.
Seasonal variations of population dynamics of free living nitrogen fixing bacteria, Azospirillum in relation to chemical parameters in Manakkudi mangrove ecosystem was assessed in root and rhizosphere soil samples of mangroves and mangrove associated plants. In rhizosphere soil and root samples, the counts of Azospirillum were recorded maximum in Acrostichum aureum as 8.63 +/- 0.92 x 10(4) and 115.48 +/- 17.36 x 10(4) CFU g(-1), respectively. The counts of Azospirillum in non-rhizosphere soil varied from 0.01 +/- 0.001 x 10(4) to 5.77 +/- 0.92 x 10(4) CFU g(-1) and found maximum in February and minimum in March and September. Azospirillum counts in water samples were found maximum (2.24 x 10(4) CFU l(-1)) in February. During seasonal variations maximum counts of Azospirillum were recorded during southwest monsoon season in Avicennia officinalis (1.40 x 10(4) CFU g(-1)) followed by Rhizophora mucronata (1.07 x 10(4) CFU g(-1)). The average maximum population density of Azospirillum counts was found during non monsoon season (9.73 x 10(4) CFU g(-1)) and the average maximum population density of Azospirillum counts was found with the mangrove associated root samples (13.73 x 10(4) CFU g(-1)). Of the selected isolates Azospirillum lipoferum (60%) was found to be predominant followed by Azospirillum brasilense (25%), Azospirillum irakense (5%), Azospirillum halopraeferens (5%) and Azospirillum amazonense (5%). Of the isolated species, A. halopraeferens exhibited better growth at 35 g l(-1) NaCl. The level of Fe, Cu, Zn and Mn were varied from 0.91 to 15.93 ppm. The level of Mn (12.13 ppm) was found maximum during non-monsoon of rhizosphere soil sample. Highest rainfall (192.80 mm) and atmospheric temperature (25.10 degrees C) were recorded during south west monsoon and non monsoon seasons. The increased population density was greatly influenced by the pH (r = +0.686). The present finding provides enough information on the nitrogen flow through biological process in Manakkudi mangrove ecosystem which can be useful for the effective implementation of mangrove management plan.
在马纳库迪红树林生态系统中，通过对红树林及其伴生植物的根和根际土壤样本进行分析，评估了自生固氮菌固氮螺菌种群动态的季节性变化及其与化学参数的关系。在根际土壤和根样本中，金毛狗脊根际土壤和根中的固氮螺菌数量最多，分别为8.63±0.92×10⁴和115.48±17.36×10⁴ CFU g⁻¹。非根际土壤中固氮螺菌数量在0.01±0.001×10⁴至5.77±0.92×10⁴ CFU g⁻¹之间变化，2月数量最多，3月和9月最少。水样中固氮螺菌数量在2月最多（2.24×10⁴ CFU l⁻¹）。在季节性变化期间，白骨壤西南季风季节固氮螺菌数量最多（1.40×10⁴ CFU g⁻¹），其次是红茄苳（1.07×10⁴ CFU g⁻¹）。固氮螺菌数量的平均最大种群密度出现在非季风季节（9.73×10⁴ CFU g⁻¹），与红树林伴生根样本中的平均最大种群密度（13.73×10⁴ CFU g⁻¹）相当。在所选择的分离菌株中，发现产脂固氮螺菌（60%）占主导地位，其次是巴西固氮螺菌（25%）、伊拉克固氮螺菌（5%）、嗜盐固氮螺菌（5%）和亚马逊固氮螺菌（5%）。在所分离的物种中，嗜盐固氮螺菌在35 g l⁻¹ NaCl浓度下生长较好。铁、铜、锌和锰的含量在0.91至15.93 ppm之间变化。根际土壤样本非季风期锰含量最高（12.13 ppm）。西南季风和非季风季节降雨量最高（192.80 mm），气温最高（25.10℃）。固氮螺菌种群密度的增加受pH值影响很大（r = +0.686）。本研究结果为马纳库迪红树林生态系统中氮通过生物过程的流动提供了足够信息，有助于有效实施红树林管理计划。
