Effect of UV-B radiation on the feeding behavior of the rotifer Brachionus plicatilis

Effect of UV - B radiation on the feeding behaviour of marine zooplankton is important to assessing the health harm of marine ecosystem due to the gradually enhanced UV - B radiation in air. However, there are a few studies on this topic. The feeding behavior of the rotifer, Brachionus plicatilis, under the treatment of UV - B radiation on five species of microalgae, i. e. , Chlorella sp. , Tetraselmis chuii, Isochrysis galbana Park 8701, Chaetoceros muelleri Lermumerman, and Nitzschia clostertum, was studied. The results showed that the filtering and feeding rates of the rotifer decreased significantly with the dose increase of UV - B radiation when fed with five species of microalgae respectively （ P 〈 0.05 ） which indicates UV - B radiation inhibits the feeding activities of the rotifer on microalage. The mixed culture experiments shows the rotifer preferred to feed Chlorella sp. , then C. muelleri, L galbana, N. clostertum and T. chuii in turn if without UV - B radiation. Under the highest dose of UV - B radiation treatment （2.70 kJ/m^2）, the rotifer preferred to feed C. muelleri, then Chlorella sp. , N. clostertum, L galbana and T. chuii in turn. Chlorella sp. , L galbana and C. muelleri became the more favorite foods of the rotifer while T. chuii and N. clostertum became less favorite foods. The change of feeding rate and feeding selectivity of zooplankton driven by the enhanced UV - B radiation will lead to the change in the structure of phytoplankton community.

The effect of the causative algae of large-scale HAB in the East China Sea on egg hatching of Argopecten irradians, and population growth of Brachionus plicatilis and Moina mongolica

The impacts of Prorocentrum donghaiense Lu and Alexandrium catenella Balech, causative species of the large-scale HAB in the East China Sea, were studied under laboratory conditions. According to bloom densities, the effects of monocuhure and mixture of the two species were examined on the egg-hatching success ofArgopecten irradiarts Lamarck, and the population growth of Brachionus plicatilis MUller and Moina mongolica Daday. The results showed that monocuhure of A. catenella had a significant inhibition on the egg hatching success of A. irradians, and the population growth of B. plicatilis and M. mongolica. The median effective densities （ED50） inhibiting the egg hatching success of A. irradhms for 24 h and the population growth of B. plicatilis and M. mongolica for 96 h were 800, 630, and 2 400 cells/cm^3 , respectively. Monoculture of P. dongha/ense has no such inhibitory effect on the egg hatching success of A. irradians; P. donghaiense at lower suitable densities could sustain the population growth of B. plicatilis （ 1 × 10^4 ～ 3 ×10^4 cells/cm^3 ） and M. mongolica （2 × 10^4～5 ×10^4 cells/cm^3 ） ; P. donghaiense at higher densities had significantly adverse effect on the population growth of B. plicatilis （4 × 10^4 ～ 10×10^4 cells/cm^3 ） and M. mongolica （ 10 ×10^4 cells/cm^3）. When the two algae were mixed according to bloom densities, P. donghaiense at suitable densities to some extent could decrease the toxicity of A. catenella to B. plicatilis and M. mongolica. The results indicated that the large-scale HAB in the East China Sea could have adverse effect on zooplankton, and might further influence the marine ecosystem, especially when there was also Alexandrium bloom.

Effects of two polybrominated diphenyl ethers(BDE-47,BDE-209) on the swimming behavior, population growth and reproduction of the rotifer Brachionus plicatilis

Polybrominated diphenyl ethers（PBDEs） are new kinds of persistent organic pollutants（POPs） and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE（BDE-47）and deca-BDE（BDE-209） were applied, and their toxic effects on the swimming behavior,population growth and reproduction of Brachionus plicatilis were investigated. The results showed that：（1） The actual concentrations of BDE-47 and-209 in the seawater phase measured by GC–MS（Gas Chromatography-Mass Spectrometer） were much lower than their nominal concentrations.（2） In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 is more toxic than BDE-209.（3） Both BDE-47 and-209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females（OF/NOF）, the ratio of mictic females/amictic females（MF/AF）, resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and-209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately.

井盐水培育轮虫过程中碳酸钙浓度过饱和的危害及防控方法的研究

为探究自然海水、井盐水混合自然海水两种水体下轮虫产量差别,提高轮虫的单产水平,找到限制轮虫产量的环境影响因子,试验选择盘锦光合蟹业有限公司三角洲基地12排5个自然海水轮虫池塘和18排5个自然海水与井盐水混合的轮虫池塘进行调查,井盐水的量占总量的比例≥50%,连续监测15 d水温、pH值的变化,定期测定水体的理化指标,包括碱度、盐度、钙离子,计算晶型CaCO_(3)·H_(2)O临界突变的饱和度指数,并跟踪记录各池轮虫总产量。结果显示,对比自然海水池塘,井盐水混合池塘更易发生水质突变,且突变次数明显增多,平均自然海水为0.4±0.49次,井盐水混合池塘为2.6±0.49次。井盐水混合池塘碱度普遍较高,平均(4.18±0.10)mmol/L,自然海水为(2.63±0.22)mmol/L。添加井盐水的池塘,轮虫产量显著低于正常轮虫池(P<0.01),平均每亩产量低25万kg左右。研究结果显示,在轮虫池大量混合井盐水会使水体突变增多,最终导致轮虫大量减产。

乳酸菌联合小球藻对褶皱臂尾轮虫种群增长的影响

为研究乳酸菌联合小球藻(Chlorella vulgaris)对褶皱臂尾轮虫(Brachionus plicatilis)种群增长的影响,以盘锦光合蟹业有限公司轮虫池冬卵孵化的轮虫为试验对象,以小球藻为轮虫基础饵料并添加不同浓度的微生态制剂乳酸菌(Lactic acid bacteria,LAB),设置乳酸菌的浓度梯度为0(对照组)、1×10^(8) cells/mL、2×10^(8) cells/mL、5×10^(8) cells/mL、10×10^(8) cells/mL,连续观察4d,对轮虫种群密度、抱卵率和平均增长率等进行统计。结果表明,在轮虫种群密度起始相同的情况下,添加适宜浓度的乳酸菌处理组轮虫最大种群密度、抱卵率和平均增长率是同时期对照组的3倍、3倍和5倍(P<0.05),且能有效降低培养水体pH使其在轮虫生长适宜范围内。结果表明以小球藻为轮虫基础饵料,添加一定浓度的乳酸菌有利于褶皱臂尾轮虫的生长繁殖,可以提高轮虫的种群数量,促进种群增长。